ContentsFactors in disease preventionand control ................................................. 4 Body soundness and livability......................4 Adequate nutrition......................................4 Suitable environment..................................4 Prevention, eradication, and control of transmissible diseases...............................5 Sanitation program................................5 Disinfection..........................................6 Practices to maintain health and prevent disease.............................................7Bacterial diseases .................................... 7 Pasteurellosis...............................................7 Rhinitis (snuffles)..................................7 Pneumonia............................................8 Pyometra...............................................8 Orchitis.................................................9 Otitis media..........................................9 Subcutaneous abscesses..........................9 Septicemia.............................................9 Enteritis......................................................9 Enterotoxemia.......................................9 Mucoid enteropathy............................10 Tyzzer’s disease....................................10 Coccidiosis..........................................11 Listeriosis..................................................11 Necrobacillosis..........................................11 Salmonellosis.............................................12 Staphylococcosis........................................12 Mastitis...............................................13 Conjunctivitis (weepy eye)..................13 Treponematosis (vent disease)....................13 Hutch burn...............................................14 Pseudotuberculosis....................................14 Tularemia..................................................14Viral diseases ..........................................15 Myxomatosis.............................................15 Rabbit pox................................................16 Fibroma....................................................16 Herpes virus infection...............................16 Rabbit papilloma.......................................16 Oral papilloma..........................................16 Viral enteric diseases..................................17 Viral hemorrhagic disease..........................17Fungal diseases .......................................18Parasitic diseases ..................................19 Prevention and control..............................19 External parasites.......................................20 Ear mites.............................................20 Fur mites.............................................20 Cuterebrid flies....................................20 Fleas and ticks.....................................21 Internal parasites.......................................21 Coccidiosis..........................................21 Encephalitozoonosis............................22 Toxoplasmosis.....................................23 Roundworms......................................23 Tapeworms..........................................24Nutritional diseases ..............................25 Pregnancy toxemia....................................25 Vitamin A deficiency.................................25 Vitamin E deficiency.................................25Hereditary diseases ...............................26 Glaucoma..................................................26 Malocclusion.............................................26 Splay leg and ataxia...................................26Miscellaneous ...........................................27 Cannibalism..............................................27 Heat prostration........................................27 Broken back..............................................27 Sore hocks.................................................28 Tumors......................................................28 Fur eating and hairballs.............................28 Coprophagy..............................................29 Yellow fat..................................................29 Winter breeding depression.......................29How to pack and ship specimensfor laboratory diagnosis .....................29 Shipping dead animals..............................29 Accompanying information.......................30
Domestication of the Euro‑pean rabbit probably occurred inmonasteries during the MiddleAges. By the middle of the 17thcentury, rabbits were commonlyraised in England and continen‑tal Europe. Oryctolagus cuniculus,one of the more successful mam‑mals of the world, is both pro‑lific and adaptable. Most of the fancy breeds weredeveloped within the past100 years, and only since theearly 1900s have rabbits beenraised domestically in the UnitedStates. The first commercialcolonies were started in southernCalifornia. Meat rationing dur‑ing World War II gave the infantindustry a push. Today, approximately200,000 people are engaged insome phase of the rabbit businessin the United States, and animalsare produced in every state. Meatprocessors serving major citiesmarket more than 10 millionpounds of rabbit meat annually.Over the years, the breeds havebeen improved from the long,rangy, low‑meat‑yield type to thecompact, blocky animal of today. The offspring of one doeyield more than 120 pounds ofmeat per year, and 200 poundsper doe is not unlikely in thefuture. Feed required to pro‑duce 1 pound of meat has beenreduced from about 6 pounds to3.5 or 4 pounds. During the past 10 years, therabbit industry has expandedconsiderably. It may not, as yet,have reached the popularity itexperienced during WorldWar II. But the nutritionalqualities of rabbit meat aremaking rabbit more acceptable,and production is increasing. Rabbit raising has continuedto be a backyard or part‑timebusiness. However, the size ofthe herds has expanded from afew does to the current averagerabbit herd of 20 does, and it isnot uncommon to see herds of300–500 breeding does. Commercial rabbitries aver‑aging fewer than 30 rabbits percage per year (sent to market)find it very difficult to show aprofit. Typically, the profitablecommercial number is morethan 40 rabbits per cage per year. As in all facets of agriculture,the profits from rabbit raisingdepend a great deal on manage‑ment and market. If an area hasa steady demand for rabbit meatand a stable processor, the rab‑bit farmer can net a reasonableprofit and add to the familyincome.Domestic Rabbits: Diseases and ParasitesN.M. Patton, K.W. Hagen, J.R. Gorham, and R.E. FlattNephi M. Patton, director emeritus,Rabbit Research Center, Oregon StateUniversity; Karl W. Hagen (deceased),bacteriologist, and John R. Gorham,veterinarian, Agricultural Research Ser‑vice, U.S. Department of Agriculture,Pullman, Washington; and Ronald E.Flatt (deceased), veterinarian, Depart‑ment of Veterinary Pathology, IowaState University. Revised in 2007 byJohn Harkness, professor emeritus,Mississippi State University. Thispublication is a revision of USDAAgriculture Handbook 490, originallypublished in 1976. It was preparedwith the support and permission of theAgricultural Research Service.
The difference between profitand loss often comes down toa person’s ability to master thehusbandry and disease controltechniques necessary for success.The only rabbit that willreturn a profit to its owner is ahealthy one. This publication isdesigned to help ranchers recog‑nize the more common rabbitdiseases and to know when pro‑fessional advice is needed. Dis‑eases are classified according tomajor cause—bacterial, viral,nutritional, hereditary, fungal,and miscellaneous (includingpoisoning, tumors, and vices).Factors in diseaseprevention andcontrol Factors conducive to goodhealth include body soundnessand livability; adequate nutri‑tion; suitable environment; andprevention, eradication, and con‑trol of transmissible diseases.Body soundnessand livability Sound, vigorous rabbits arenecessary both as quality meatproducts and as replacementstock. Carefully examine thebackground of animals saved forbreeding so that recognizabledefects are not perpetuated. Ahealthy, mature breeder—onethat has a history of several littersshowing fast development, goodreproduction, high livability ofthe young, and relative freedomfrom disease—is a better sourceof replacement stock than arabbit that does not show thesetraits. Healthy, well‑framed, well‑fleshed mature does producinglitters containing from 8–12 liveyoung, with low mortality at8 weeks, good feed conversion,and high weights are potentialsources of breeding stock. Care‑fully examine each individualselected for breeding. Look fordefects and general health, andeliminate animals that deviatefrom normal. Through rigidapplication of this practice, aprofitable, high-producing herdcan be established.Adequate nutrition Feeding is the most importanthusbandry technique in therabbitry and should be done byan experienced person. Mostdisease and potential diseaseproblems are discovered duringfeeding time. Some disease prob‑lems can be corrected by chang‑ing the amount or type of feed. Much has been learned in thepast few years concerning rab‑bit nutrition. Diets that producegood growth in poultry andswine are disastrous in rabbits.Rabbits are foraging animals thatlive on grasses and seeds in thewild. Their digestive system andits microbes do not adapt well tohigh-energy, cereal‑grain diets. In fact, diets high in starchand carbohydrates often causediarrhea and death in fryerrabbits. A simple change to adiet higher in fiber and lower inenergy gives adequate growthwithout the risk of entericdisease. On the other hand, does needadequate energy for reproduc‑tion, which may not be pro‑vided by diets extremely high infiber. Progressive rabbit raisersnow feed two diets, one to thegrowing fryers and another tothe producing does. A simplediet that provides good health,growth, and production is pre‑ferred but often difficult to findbecause the needs of the variousclasses of rabbits are considerablydifferent. Inadequate nutrition is acostly problem. A general declinein health may increase suscepti‑bility to diseases, which can leadto large monetary losses. Inaddition, young rabbits growslowly if the doe has inadequatemilk or they do not get enoughfeed. Thus, feeding is a criti‑cal element in successful rabbitraising.Suitable environment The term “environment”includes every factor that influ‑ences a rabbit’s life. Some ofthese factors are hutch size andlocation, nearness to other ani‑mals, dryness, temperature, ven‑tilation, amount of light, shelterdesign, availability of water, andgeneral management. Carefulexamination and control of theenvironment are essential foreffective disease prevention.
Prevention,eradication, andcontrol of transmissiblediseases If disease prevention has failedand transmissible diseases areestablished in a rabbitry, highmortality may lead to businessfailure. Growers commonlyencounter pasteurellosis, earmange, and coccidiosis. Theseinfectious diseases usually areintroduced by contact withinfected rabbits or by contami‑nated mechanical carriers. Pasteurellosis and liver coc‑cidiosis are important diseasesspread by contact. Adult rabbitsare the most important contactcarriers. An animal may seem torecover from a disease but stillshed infectious organisms in itsfeces, urine, or in dropletsexhaled while breathing. Intro‑ducing new stock directly to aherd or exhibiting animals atshows and fairs increases the riskof disease outbreaks. Keep newor exhibition animals in a specialisolation section of the colonyuntil you are reasonably certainthey are disease‑free. This quar‑antine period usually is at least2 weeks. Carriers of disease often arenot recognized because theyseem healthy. Tests to pinpointwhich animals are carriers arenot always practicable. Liver coc‑cidiosis is found when the fryeris dressed out for market, toolate to trace back to the doe thatproduced it. Bacterial culturesof the nasal cavity may showthe presence of Pasteurella, butcultures usually cost too much tobe used routinely. Mechanical transmission ofdisease occurs when the infec‑tious agent is carried accidentallyfrom place to place. People arethe chief offenders. The growerwho treats a sick animal andthen moves on to check or countnewborn young can be animportant carrier of respiratoryinfection and coccidiosis. Feedsalespeople, service representa‑tives, rabbit buyers, and otherswho have visited other rabbitriesmay be sources of infection.Avoid visiting other rabbitrieswhere disease is present. Theseexamples might seem extreme,but they happen repeatedly andare definite factors in introduc‑tion of disease. Dogs, cats, birds,and rodents have been incrimi‑nated in carrying diseases to rab‑bits and should be kept out ofthe rabbitry. Insects also shouldbe controlled. When disease prevention fails,you must consider how to con‑trol and eliminate the disease.When liver coccidiosis isinvolved, the adult carrier maybe freed from infection by che‑motherapy, but improved man‑agement practices are the onlyway to eliminate the disease fromthe herd. In some cases, it may be nec‑essary to depopulate to eliminatea disease. The time betweendepopulation and repopulationwith clean, healthy animalsdepends on many factors. Envi‑ronment plays an important partin the time interval involved.Sanitation program A constant sanitation pro‑gram is an important part ofdisease prevention. Cleanliness isrequired to establish and main‑tain a safe environment in whichanimals can live and reproduce.Elimination of disease carriers ismost important. Environmental factors mustbe considered in any sanitationprogram. Unfavorable environ‑mental factors lower animals’resistance to disease and facilitatethe spread of infection. Particu‑larly important are hutch andshelter construction and mainte‑nance (Figure 1, next page). Easeof cleaning, a supply of cleanwater, and space for rodent‑prooffeed storage are important.Proper drainage is another factor.Provide for water runoff fromthe rabbitry area. Constructhutches so that individual unitsmay be removed for disinfecting.Adjust the number of animalsper unit based on the area andthe environment. Water should be fresh, clean,and protected from contamina‑tion by urine, fecal matter, andfeeds. It is important to cleanwater containers frequently. Feed contaminated with fecesmay act as a mechanical car‑rier for infection. Protecting thefeed from contamination by theuse of properly designed andwell‑constructed feed hoppersis necessary in any good sanita‑tion program. Clean feedersperiodically.
Good feed utilization andwaste removal are important indisease prevention. Feed scat‑tered about the rabbitry attractsinsects, mice, rats, and birds—allpotential carriers of disease. Storebulk feed properly. In small rab‑bitries or where large quantitiesof bulk feed are not stored, metalgarbage cans with tight lids aregood feed-storage containers.Disinfection Disinfection refers to the kill‑ing of infectious agents such asbacteria, viruses, and parasites.To facilitate the use of disinfec‑tants, all equipment and otherconstruction should be as simpleand easy to clean as possible. Fecal matter and other organicmaterial protect disease‑producing bacteria, viruses,and parasites and nullify theeffectiveness of even the mostefficient disinfectants. Thoroughscraping and washing shouldprecede disinfection. A solution of sodiumhypochlorite (bleach) is botheffective and economical for dis‑infecting cages, nest boxes, andancillary equipment. Make thesolution by adding an ounce ofbleach to a quart of water. Placethe solution in a spray bottle andspray it on the equipment to besanitized. Cages generally are sprayedafter rabbits are sent to marketand before the next occupantsarrive. Spray feeders and water‑ing devices at the same time.Clean and wash nest boxesbefore spraying with the solu‑tion. You can soak or rinseremovable equipment in thehypochlorite solution. There areno disadvantages to using thismethod of sanitation except thatcoccidial oocysts might not bekilled. Another disinfectant usedby some rabbit breeders is lyewater. One 13-ounce can of lyeis enough to make 15 gallons ofcleaning and disinfecting solu‑tion. For large ranches, it isadvisable to buy the lye in theform of caustic soda. Eachpound makes about 20 gallonsof solution. Heating is advisablebut not necessary. In addition toacting as a disinfectant, lye cutsgrease and partly dissolves andpenetrates fecal material. Use of lye has some disad‑vantages. Concentrated lye is apoison and damages aluminumpaints and clothing. The lyemay be slightly irritating to thehands and face of the operator.Consequently, take precautionsto avoid excessive exposure ofthe skin during the disinfectingprocess. Keep containers of lyetightly covered. Some ranchers use steamunder pressure to clean anddisinfect pens and equipment.When using steam, first soakcaked fecal material with water.Use of a good cleansing com‑pound, followed by steam, cleansand disinfects satisfactorily. Sunlight is a potent disinfec‑tant if equipment is very cleanand sufficient exposure time isallowed. A cement slab exposedto the direct rays of the sun is agood place to disinfect movableequipment.Figure 1.—Shed construction suitable for mild climates.
Flaming or burning cages witha propane torch to remove hairdoes not sanitize the cagebecause the wires are not heatedto a sufficient temperature todestroy the organisms. Be carefulnot to singe rabbits when burn‑ing hair. This procedure also is afire hazard.Practices to maintainhealth and preventdisease Successful growers practicegood sanitation and manage‑ment, feed an adequate diet ofsimple ingredients, and give theiranimals plenty of fresh water. It is important to inspect allanimals in the herd each day.When you first notice sickrabbits, immediately try todetermine the cause. The follow‑ing course of action is suggested:1. Mark or note pens that con‑tain sick animals.2. Isolate sick animals. If pos‑sible, keep them in roomsor buildings separate fromhealthy rabbits.3. Care for the sick animal onlyafter all other rabbits in theherd have been cared for to pre‑vent carrying infection fromsick to healthy rabbits. Be sureto wash hands and disinfectboots after caring for sickanimals. Clean and disinfectany equipment moved froman area where there are sickanimals to the pens containinghealthy animals.4. If you cannot determine thecause of the trouble quickly,send a few typically sickrabbits to a diagnostic labora‑tory or your local veterinarian.5. Destroy all hopelessly sickanimals and bury or burn alldead animals. Open disposalpits are not recommended.6. Clean and disinfect all pensbefore placing new rabbits inthem.Bacterial diseasesPasteurellosis “Pasteurellosis” is the designa‑tion for all diseases associatedwith Pasteurella multocida. Thedisease manifestations are variedand include rhinitis (snuffles),pneumonia, pyometra, orchi‑tis, otitis media, conjunctivitis,subcutaneous abscesses, andsepticemia.Rhinitis (snuffles) The mucous membranes ofthe nasal sinuses become infectedby bacteria from inspired air orby direct contact with infectedanimals or contaminated objects.The clinical disease is character‑ized by nasal sounds and by acatarrhal (mucus or pus) nasaldischarge (Figure 2). The extentto which the infection spreadsinto the lower respiratory pas‑sages depends on the virulence(invasiveness) of the bacteria andthe susceptibility of the animal.If the disease is confined to theupper passages, the first signs aresneezing followed by a nasal dis‑charge. The inner aspects of therabbit’s forepaws may be cakedwith exudate because of attemptsFigure 2.—Adult showing signs of snuffles. Note discharge from nose. (Thelarge dewlap is normal on this animal.)
to wipe the exudate away fromthe nose. Pasteurella bacteria often arefound in the nasal sinuses ofhealthy‑looking rabbits. Stressresulting from extremes of tem‑perature, high humidity, highammonia levels, travel, preg‑nancy, and lactation is a primaryfactor in the development ofsnuffles. Treatment of snuffles has notproven to be economically effec‑tive in commercial rabbitries. Byusing broad-spectrum antibiot‑ics such as oxytetracycline orchlortetracycline, the symptomsmight be alleviated. However,the animal often remains a car‑rier of P. multocida and is ableto infect offspring and cagedneighbors. Fluoroquinolones (e.g., Bay‑tril) may be used in individualrabbits. Antibiotic combina‑tions have been used to reducesymptoms in pet rabbits withsome success. Antimicrobialresidues might remain in thetreated rabbits’ meat for days orweeks, making the meat unus‑able for human consumption.Penicillin use may cause fatalenterotoxemias. If the nasal discharge regresses,take care not to stress the rabbit.It should not be used as abreeder. The next stress period(e.g., kindling, lactation, heatwave) very likely will cause thesymptoms to reappear. Vaccineshave not proven to be effec‑tive. The only effective methodof control is strict culling. If arabbit has a nasal discharge ormatted paws or sneezes on 2consecutive days, cull it from theherd. If you are not sure whetherto cull a rabbit, “when in doubt,cull it out.” In addition to a strict cullingprogram, good ventilation mustbe provided to control snuffles.There is a direct correlationbetween the level of ammoniain a rabbitry and the amount ofrespiratory disease. An effectivemanure removal system and10–20 air changes per hour arenecessary to reduce the ammoniato an acceptable level.Pneumonia Upper respiratory disease(snuffles) may spread to thelungs and cause pneumonia.Rabbit mortality surveys revealpneumonia to be present in25 percent of the animals exam‑ined; it is the greatest singlecause of death in mature ani‑mals. Signs of pneumonia aredepression, labored breathing,bluish eye color in albinos, and anasal discharge. The body tem‑perature usually is above normal. Gross lesions of the lungsappear as red consolidated areas,sunken purple areas, andabscesses. The consolidatedlesions most often are in theanterior lobes of the lungs(Figure 3). A catarrhal exudate isfound in the air passages.Abscesses appear with thin,fibrous capsules close to thesurface of the lungs. Sometimesthere are adhesions between thewall of the chest cavity and thelungs. Pneumonia rarely is treated inrabbitries as it usually is apostmortem diagnosis. Broad‑spectrum antibiotics have beenused with some degree of successwith pet and show rabbits.Pyometra “Pyometra” means pus in theuterus. The walls of the uterususually are dilated, and the organis filled with pus. Affectedfemales will not produce and,therefore, are culled and oftenslaughtered. Pyometra resultsfrom the introduction of Pasteu-rella bacteria into the uterus dur‑ing mating and may be tracedto a single buck with a chronicinfection of the testicles. It alsocan occur as a retrograde infec‑tion from the vagina. Does that are nasal‑positivefor P. multocida often are vaginal-positive for the same bacteria,especially if the doe has a nasaldischarge. The vagina is thoughtto be contaminated during theFigure 3.—Gross appearance ofrabbit lungs, showing consolidationdue to Pasteurella bacteria.
normal practice of coprophagy(eating their own feces; seepage 29) or during the kindling(birth) process. Treatment of pyometra sel‑dom is attempted because thedisease usually is not noticeduntil the female is slaughtered.Successful treatment is unlikely.Pets sometimes can be saved byan ovariohysterectomy.Orchitis Orchitis is an infection of thetesticles. The testicle becomesenlarged and usually contains anabscess. Pus can be seen whenthe testicle is cut open. Some‑times infection is limited to themembranes covering the penis, acondition called balanoposthitis. Balanoposthitis appears as areddening and swelling of themembrane covering the penis,and a white exudate (pus) ispresent on these membranes. Asdescribed above, the infection istransmitted to does by infectedbucks during breeding. Treatment seldom isattempted; however, balanopos-thitis may be treated by applyingantibiotic ointment containingpenicillin or other suitable anti‑biotics to the penis.Otitis media Middle ear infection of one orboth ears causes filling of thetympanic cavity with a purulentexudate. If the process spreads tothe inner ear, the equilibrium ofthe animal is disturbed, and headtilt or wryneck results (Figure 4).Although the Pasteurella organ‑ism is sensitive to certain antibi‑otics, treatment generally is noteffective because of the isolatedlocation of the infection.Subcutaneous abscesses Pasteurella may cause abscessesin many organs, but abscesses areespecially evident when theyoccur in the subcutaneous tissue.These appear as soft swellingsunder the skin. Treatment con‑sists of opening and draining theabscess and administration ofsystemic antibiotics.Septicemia This form of pasteurello‑sis usually is an overwhelm‑ing blood stream infection ofshort duration without clinicalsigns, resulting in death. Tis‑sue changes are limited to a fewhemorrhagic areas on the heartand pericardium, swelling of thespleen, and slight congestion ofthe upper digestive tract. Thelack of clinical signs and shortduration do not allow time forsuitable treatment.Enteritis “Enteritis” is a group designa‑tion much like “pasteurellosis.”Any diarrheal‑type disease thatkills rabbits generally is placedin this grouping. In the past, thegroup designation often has beencalled “enteritis complex,” asmany different symptoms wereobserved, but the one unifyingfactor was death as the finalresult of the syndrome. Morerecently, specific diseases havebeen described; they are dis‑cussed below.Enterotoxemia Enterotoxemia is an explo‑sive diarrheal disease of youngrabbits 4–8 weeks of age. Rab‑bits often are observed to benormal one day and dead thenext with or without evidenceof diarrhea. This acute death isdue to a deadly toxin producedby the bacteria Clostridium spi-roforme. Young rabbits die in24–48 hours; occasionally adultand junior breeders are affected,and they may live as long as96 hours. Penicillin used to treatrabbits may also cause the diseaseby altering the gut bacteria. The typical lesions of entero‑toxemia seen at necropsy are afluid‑filled intestine that is cov‑ered with petechial hemorrhages.The hemorrhage is most apt tobe observed in the cecum. Thecausative agent, C. spiroforme,can be isolated on blood agar,but it is an anaerobic bacte‑rium and must be grown underanaerobic conditions. DiagnosisFigure 4.—Wryneck resulting from amiddle and inner ear infection.
10of this disease is accomplished bydemonstrating the iota‑like toxinin the intestinal contents or bystaining and microscopic exami‑nation for the distinctive bacteriain centrifuged cecal content. Amouse bioassay test or an intra-dermal test in guinea pig skincommonly is used to detect thetoxin. Little is known about thetransmission of the organism,but it has been shown that rab‑bits do not have this organism aspart of their normal microflora.The type of diet seems to be afactor in the development of thedisease. Diets high in fiberreduce the incidence of thedisease. The addition of hay orstraw to a low‑fiber diet is ben‑eficial. Antibiotics used in thefeed or water give temporaryremission of symptoms, but thedisease recurs once they areremoved unless the diet has beenchanged.Mucoid enteropathy This uncommon enteric dis‑ease affects rabbits of any ageand is a chronic type of diarrheaor constipation. Rabbits livefor several days and sometimesseveral weeks with this disease.However, they will not eat andthey sit hunched in the cage andgrind their teeth as if in pain.They sometimes look bloatedand often are crouched near thewater supply (Figure 5). The etiology of this disease isunknown, but one commonfinding in almost all cases isconstipation. Impaction of thececum and/or terminal part ofthe small intestine is observed atnecropsy in about 75 percent ofthe cases. Along with the findingof a gelatinous‑type of mucusin the colon, this leads to thediagnosis of mucoid enteropathy.Other lesions observed duringa postmortem examination aregeneralized dehydration andexcess water in the stomach. Thislatter finding causes a “splash” or“water bottle” sound when theseanimals are rocked to and froclose to one’s ear. The impaction often can bepalpated through the abdominalwall on young fryer rabbits, buttreatment is not very successful.By the time the disease is recog‑nized, the rabbit seldom can besaved. Rehydration with electro‑lytes sometimes is beneficial. Theaddition of excess salt to theration occasionally helps stopan outbreak. Salt added to thefeed seems to increase waterconsumption and decrease theincidence of the disease. Add‑ing salt to the drinking wateror salt spools in the cage is notbeneficial.Tyzzer’s disease Tyzzer’s disease was firstdescribed in Japanese waltzingmice, but since has been foundin a variety of animals, including(uncommonly) rabbits. Clos-tridium piliformes is the causativeorganism. Signs of the acute form seenin weanling animals are diarrhea,listlessness, lack of appetite, anddehydration, followed by deathwithin 72 hours. Lesions includeedema, hemorrhage, and necro‑sis in the wall of the cecum andfocal necrosis in the liver andheart (Figure 6). The organismsare found in cells near necroticareas, and the demonstration oftypical bacteria within the cell isessential to diagnosis. AnimalsFigure 5.—This rabbit has mucoidenteropathy. Note feces on hind feet,rough fur coat, hunched posture, andsquinty eyes.Figure 6.—Tyzzer’s disease. This rabbitdied acutely with diarrhea. At autopsy,focal areas of cell death (arrows) wereseen in the liver. Photograph courtesy ofAcademic Press and Co., New York.
11surviving the acute stage mightlive to adulthood but fail to growat a normal rate. Transmission of Tyzzer’s dis‑ease is by direct contact withfecal-contaminated feed andbedding. Some form of stress,such as overcrowding orextremes in temperature, is nec‑essary for initiating the condi‑tion in nature. Antibiotics reduce the effectof the disease in mice, but drugsseem to be of little value in rab‑bits. The best alternative is pre‑vention through strict sanitation,especially daily thoroughremoval of fecal material fromthe cage floor. Because this seemsto be a highly transmissible dis‑ease, the only way to treat severeoutbreaks is to depopulate andrepopulate with disease‑freerabbits.Coccidiosis Coccidiosis is one of theenteric diseases. The etiologicagents are protozoan parasitesthat attack the liver or intestines.This disease is discussed under“Internal parasites,” page 21.Listeriosis Listeria monocytogenes causesa rare septicemic infection inyoung rabbits, a meningo‑encephalitis in adults, and metri‑tis and fetal mortality in preg‑nant does. Pregnant females anddoes that recently have deliveredyoung are most susceptible.The organisms are ingested orinhaled. In septicemia, death can occursuddenly without previous ill‑ness. Generally the rabbit isdepressed, weak, has a nasaldischarge, and may have con‑vulsions. Nervous system signsinclude incoordination, loss ofequilibrium, and rolling move‑ments. These signs may persistfor several days or weeks, andcomplete recovery is rare. Sickpregnant animals have a puru‑lent metritis, lose weight, andmay abort. Survivors generallyare useless for breeding becauseof uterine damage and pyometra(pus within the uterus). The most consistent lesion atnecropsy is liver necrosis. Thelesions consist of a few pinpointfoci to almost complete stud‑ding of the liver. The mesentericlymph nodes may be enlargedand reddened. In cases of metri‑tis, the uterine wall is thickened,the mucous membrane may becovered with a grayish exudate,and the fetuses are decomposedor mummified. When infectedfetuses are retained in the uterus,severe metritis develops. Due to their tolerance by rab‑bits and their specific mode ofaction, antibiotics of the tetra‑cycline group are the best drugsfor treating listeriosis. In treat‑ing pregnant rabbits, antibioticsprobably will not prevent fetaldeath, and females saved byantibiotics may be sterile as aresult of the infection. The mosteffective prevention of losses isimmediate isolation of diseasedpregnant animals.Necrobacillosis Fusobacterium necrophorum,an anaerobic bacterium infarm animals, is considered asecondary invader rather than aprimary cause of disease. Lesions first appear on thelower lip, which becomes swol‑len, purplish, and painful to thetouch. Later, small abscesses areseen that contain a thick, puru‑lent material. These abscessesare enclosed in a tough, fibrouscapsule, with little tendency torupture and drain. The diseaseprogresses to ulceration andnecrosis of the skin and subcu‑taneous tissues in the face, head,and neck. When the liver andlungs become involved, the ani‑mal becomes emaciated and diesafter several weeks. Inadequate sanitation in therabbitry, especially dirty cages,is prerequisite to this disease.When scratches, bite wounds, orskin wounds become contami‑nated with feces containing theetiologic agent, necrobacillosisis most likely to occur. The bac‑teria are sensitive to exposure toaerobic conditions and will notlive long when exposed to air(oxygen). When the disease is recog‑nized and treated in its earlystages, recovery is usual; whenthere is extensive ulcerationand abscessation, death ensues.The organism is sensitive tosome antibiotics, includingmetronidazole.
12Salmonellosis Naturally occurring Salmo-nella infections are uncommonin domestic rabbits. Salmonellaorganisms are spread easily byfecal contamination, and a singleinfected animal can quicklyinfect a whole colony. Rabbitsalso can become infected byhuman caretakers, as Salmonellabacteria occur in humans as well. Salmonellosis in rabbits gen‑erally is caused by Salmonellatyphimurium or S. enteritidis,but S. pullorum also has beenisolated. All members of thesalmonellae group are aerobic,gram‑negative bacteria. Inrabbits, the disease is char‑acterized by septicemia andrapid death, with diarrhea andabortion commonly observed.When outbreaks occur, theyoften are explosive, with highmorbidity and mortality. Mortal‑ity is highest in young rabbitsand pregnant does. Bacteria areshed in the feces of carrier rab‑bits and clinically ill animals. Infection usually takes placeby the oral route, and signsappear after 3–6 days. The firstsigns are listlessness, ruffled haircoat, loss of appetite, anddiarrhea. Later, the respirationrate increases, and body temper‑ature may rise. In its acute form,the disease progresses rapidly todeath. In the chronic form, theremay be no signs of illness otherthan a transient diarrhea. The most prominent lesionsfound at necropsy are in theliver, spleen, mesenteric lymphnodes, lungs, and intestine.Hemorrhagic and ulcerativechanges are present in the intes‑tine. The liver and spleen usuallyare enlarged and contain pin‑point, pale areas of necrosis. Thelymph nodes may be soft, hem‑orrhagic, and enlarged. Survivingrabbits become carriers and mayshed bacteria in their feces inter‑mittently for a long time. Streptomycin and other anti‑biotics have been used effectivelyagainst Salmonella. Animalstreated with chlortetracyclinerespond to the medication, butmay continue to excreteorganisms in their feces longafter treatment. Pigeons, spar‑rows, and wild rodents havebeen shown to be reservoirs ofSalmonella. Protect stored feedand bedding from these possiblecarriers.Staphylococcosis Staphylococcus aureus causessepticemic infections andabscesses in numerous organs,including the subcutaneous tis‑sue, lungs, kidneys, and heart.This organism is known espe‑cially for causing infection inthe mammary glands of nursingdoes. The breasts become swol‑len, hot, and may become blu‑ish, accounting for the alternatename “blue‑breast.” Cutaneous lesions in younganimals appear as small abscessesand later develop into firm case‑ous nodules (Figure 7). Theseabscesses usually are found onthe lower abdomen, on the inneraspects of the forelegs, and onthe lower jaw. Small, white nod‑ules also may be found in thelungs and heart. The Staphylo-coccus organism also may causebronchopneumonia. The lungsare consolidated, with numer‑ous necrotic lesions. The bron‑chi and trachea may contain amucopurulent exudate. Bacteria enter the skinthrough broken or abraded areasfollowing birth; transmissionoccurs from mother to young.Staphylococci live in the nasalpassages of rabbits, and the closeFigure 7.—Cutaneous abscesses onyoung rabbit caused by Staphylo-coccus.➔➔➔➔
13contact associated with kindlingand nursing offers opportunitiesfor both direct contact and aero‑sol transmission. Mastitis results from inva‑sion of the milk glands by thedisease‑producing bacteria. Theglands and teats become redand swollen and may advance toblue‑black tissues, which arewarm to the touch. The doemay refuse to nurse her youngand generally loses her appetite.Young from does with mastitisshould not be fostered to othernursing does because the diseasemight be transmitted to the fos‑ter doe. Mastitis also may resultfrom abrasions to the teats orinsufficient removal of milkwhen too few young are left withthe doe or when the young areweaned too soon. The septicemic form of staph‑ylococcosis results in peracutedeath in young rabbits, primarilythose still in the nest box. Deathis so rapid that few if any lesionsare observed. Occasionally, small,superficial pustules or abscesses(Figure 7) are seen on the skin ofdead kits or littermates. Diagno‑sis usually depends on isolatingS. aureus from the heart blood.The organism generally entersthe young kit from ingested milkfrom mammary glands, or it mayenter the body through abrasionsor scratch wounds that becomecontaminated with S. aureus. Staphylococci might be sen‑sitive to several medications;however, some strains of theorganism are resistant to one ormore of these drugs. Laboratorytests may be necessary to deter‑mine which drugs should beused. Consult a veterinarian forcurrent recommendations.Mastitis Mastitis most commonlyis caused by Staphylococcusaureus; it is discussed under“Staphylococcosis,” page 12.Conjunctivitis (weepy eye) Conjunctivitis is a commonmalady of young rabbits raisedunder crowded conditions.Mature does and bucks occasion‑ally are affected. Red, swolleneyes with a copious exudate arecharacteristic of this disease. Inyoung rabbits, the eyelids oftenare stuck shut (Figure 8). It mayaffect only one eye or both. Thebacteria most often isolated areStaphylococcus aureus and Pasteu-rella multocida. Conjunctivitisis treated by opening the eye‑lids, if stuck shut, cleaning thesurrounding tissues, flushing theeye with sterile saline or boricacid solution, and applying anophthalmic ointment containingan antibiotic. Conjunctivitis sometimesbecomes a chronic problem inshow rabbits, where the lacrimalsecretions cause a loss of fur atthe medial canthus of the eye.This condition sometimes is alle‑viated by intravenous antibioticadministration or by repeatedlyflushing the lacrimal duct withan antibiotic solution. Thisprocedure is best done with therabbit under anesthesia and witha small-gauge cannula insertedinto the opening of the delicateand tortuous lacrimal duct foundon the lower eyelid near themedial canthus.Treponematosis(vent disease) Treponematosis, sometimescalled “vent disease,” spirochet‑osis, or rabbit syphilis, is causedby Treponema cuniculi. Othermembers of the genus includeT. pallidum, the cause of humansyphilis. Some of the early workon human syphilis was donewith rabbits. After finding thatrabbits had a natural spiro‑chete, T. cuniculi, the validityof this early work in rabbits wasquestionable. There is a great deal of confu‑sion concerning the incidence oftreponematosis in rabbits.Recent reports indicate it ismuch more common in com‑mercial rabbitries than previouslyFigure 8.—Conjunctivitis (weepy eye)caused by Staphylococcus infection.
14believed. In fact, serological testshave demonstrated antibodies toT. cuniculi in a high percentageof adult rabbits despite theabsence of observed lesions.Transmission of the organismoriginally was believed to be bysexual contact, and this methodstill is thought to be primary;however, vertical transmissionfrom mother to offspring hasbeen demonstrated. Verticaltransmission accounts forthe rabbits 6–8 weeks ofage that show evidence of treponematosis. Lesions of treponematosismay resemble those of injury,fungal infection, or ectoparasites.A correct diagnosis is importantbecause the disease is transmittedprimarily by breeding, and anisolated case can lead to an out‑break among the breeding stock.Exchange of infected bucks mayspread the infection amongcolonies. The first signs usually aresmall blisters around the externalsex organs. Lesions involving thenose, mouth, and ears also occurin both sexes. The lesions areirregular in shape, tan‑brown,and either edematous or dryand scaly. Sometimes weeping,coalescing vesicles are found.Facial and other lesions usu‑ally are secondary and the resultof reinfection by contact withgenital‑anal lesions when theanimal cleans itself. All lesionsshow many spirochetes by spe‑cial microscopic (dark‑field)examination. Spirochetes also are found inregional lymph nodes, andthey seem to survive in this tis‑sue much longer than on theskin surface. Old lesions healcompletely without scarring, butrecovered rabbits are susceptibleto later infection. The spread of spirochetosiscan be prevented by examiningthe genitals of both sexes beforemating and by eliminating rab‑bits with lesions. The organismis sensitive to arsenicals andpenicillin. Three subcutaneousinjections of benzathene peni‑cillin G-procaine penicillin G(42,000 IU/kilogram of bodyweight) are necessary to eradi‑cate treponematosis from a rab‑bit herd. Injections are given atweekly intervals, and all rabbitsmust be treated, regardless of thepresence or absence of lesions.Penicillin, however, may causefatal enterotoxemias in somerabbits.Hutch burn Hutch burn often is confusedwith rabbit syphilis. It is difficultto differentiate the two diseaseswithout the use of a dark‑fieldmicroscope. With this micro‑scope, the spirochetes of trepo‑nematosis are seen easily. Hutchburn affects the membranesof the anus and genital region.They become very red andchapped. The major cause iswet and dirty cage floors thatcome in contact with thesemembranes. The area soonbecomes secondarily infectedwith pathogenic bacteria andbecomes very sore. Antibioticsalves and ointments hasten heal‑ing, but cleaning and drying thefloors are essential to preventrecurrence.Pseudotuberculosis Pseudotuberculosis is anuncommon disease, but some‑times occurs in rabbitries withsubstandard sanitation. Thecausative agent is a bacterium,Yersinia pseudotuberculosis.Granulomatous nodules resem‑bling tuberculosis are observedat necropsy throughout theintestine and occasionally in theparenchyma of the liver, lungs,or spleen. The organism, whichseems to thrive in filthy condi‑tions, enters the host throughcontaminated food or water.The disease is a chronic, debili‑tating condition with signs ofpoor appetite, depression, slowlydeveloping emaciation, andeventual death. Treatment of this diseaseseldom is effective. Preventioncan be accomplished by goodsanitation procedures, includingdisinfecting cages, nest boxes,and ancillary equipment. Thisdisease has been diagnosed inhumans and other animals;therefore, affected rabbits shouldbe destroyed and not marketed.Tularemia Tularemia, sometimes calledrabbit fever or deer fly fever, is aninfectious disease of wild animalsand humans that is caused by
15Francisella tularensis. Tularemiacan be carried by many wildand domestic animals, certainbirds, deer flies, and ticks. It isan important malady of wildrabbits, but not of domesticranch‑raised rabbits. Infected wild rabbits movesluggishly and are visibly sick.Yellow or white spots on the liveror spleen are common lesions.Diagnosis is made by bacterialcultures of suspect lesions.Domestic rabbits are susceptibleto infection with this organismunder laboratory conditions, butthe disease has not been reportedto occur naturally in commercialrabbitries. Tularemia might betransmitted from rabbit tissuesto humans.Viral diseasesMyxomatosis The myxoma virus was iso‑lated first in South Americafrom diseased laboratory rabbits;the virus later was found to bea widespread natural infectionin wild cottontail rabbits. Inwild brush rabbits (Sylvilagusbachmani), it causes only mildtumors, which regress after sev‑eral weeks; the disease is fatalonly in the very young. In con‑trast, the disease can completelywipe out some susceptible popu‑lations of domestic rabbits. Confirmed cases of myxoma‑tosis follow the geographical dis‑tribution of the California brushrabbit, which is limited by thePacific Ocean, the ColumbiaRiver in Oregon, the Cascade‑Sierra Nevada Mountains, andthe tip of the peninsula of BajaCalifornia. Transmission of the diseaseby mosquitoes led to the name“mosquito disease.” Myxoma‑tosis also is referred to as “bighead disease” because of edemaaround the eyes, ears, lips,and nose in the early stages ofinfection. Clinical signs include lus‑terless eyes with a purulentdischarge and elevated bodytemperature. Edema of the earscauses them to become heavyand pendulous (Figure 9). As thedisease progresses, edema of thehead and anogenital region and anasal discharge occur; deathfollows in 10–12 days. In sur‑vivors, widespread subcutane‑ous gelatinous tumors developall over the body, including theeyelids. Occasionally, acute outbreaksof myxomatosis occur and rab‑bits die in 24–48 hours. Aboutthe only clinical signs observedare a slight redness in the con‑junctival membranes and anincreased body temperature(about 108°F). Rabbits dying from myxo‑matosis exhibit no characteristicgross visual changes by whichthe infection can be diagnoseddefinitely. Usually, there is con‑gestion and consolidation of thelungs, and the spleen is enlarged,dark red, and pulpy. The cut sur‑face of each edematous subcuta‑neous tissue is white, gelatinous,and glistening; when pressed,clear fluid exudes. Microscopic tissue examina‑tion or virus isolation is requiredfor a definite diagnosis of myxo‑matosis. Large eosinophiliccytoplasmic inclusion bodies inthe conjunctival membranes areobserved microscopically. Thisfinding, along with appropri‑ate clinical signs, is evidence ofmyxomatosis. The virus is spread by directcontact and by biting insectssuch as mosquitoes and fleas,which act as mechanical vectors.Control consists of prompt iden‑tification of the disease, destruc‑tion of infected animals, andreduction of mosquito popula‑tions by draining or sprayingbreeding areas. Screen enclosureof the entire rabbitry is an effec‑tive but costly solution. Antibi‑otics are not effective in treatingsick animals. An attenuatedvaccine is used for preventingmyxomatosis in Europe, but thevaccine is not approved for usein the United States. The onlyeffective measures available foruse in California and Oregon aretest and slaughter. Check rectalFigure 9.—This animal, affected withmyxomatosis, shows heavy, pendulousears and matted eyes.
16temperature of suspect rabbitsand immediately kill sick rabbitswith a temperature greater than104°F. Bury or burn the car‑casses. This method, along withimplementing a control programfor flying insects, has been suc‑cessful in stopping several majoroutbreaks in large rabbitries.Rabbit pox This rare disease can occurwith or without manifestationof clinical disease. In either case,the lesions include lymphadeni‑tis, papular nodules on themucous membranes, and orchi‑tis. Mortality is highest amongthe unweaned young and mayreach 75 percent. Rabbit poxvirus rarely is a cause of epizoot‑ics, but usually is very seriouswhen it does occur. Vaccinationwith vaccinia virus confersimmunity.Fibroma Rabbit fibroma virus wasisolated from nodules beneaththe skin of wild cottontail rab‑bits. These viral fibromas (firmgrowths) were transmitted todomestic rabbits. It once wasbelieved that fibroma virusinfected only wild cottontail rab‑bits; however, an outbreak hasbeen reported in a commercialrabbitry. In the cottontail rabbit,fibroma virus causes a benigntumor that regresses within a fewweeks. Young domestic rabbits,on the other hand, developsmall, subcutaneous nodules todiffuse indurations involvingmuscle and tendon. The exter‑nal genitalia become red andswollen. Death is frequent inunweaned young. The cut surfaces of the nod‑ules are pale and glistening andmay have radiating white streaks.In young animals, the tumorsare more widely spread over thebody and often coalesce. Theremay be involvement of the kid‑neys, liver, intestinal tract, bonemarrow, and mesentery. The role of mosquitoes andother insects as vectors of rabbitfibroma virus has been estab‑lished. Given the proper envi‑ronment (such as an epizootic inwild cottontail rabbits) and anadequate mosquito population,this viral disease could resultin significant economic loss ofyoung domestic rabbits.Herpes virus infection Virus III or Herpesvirus cunic-uli of rabbits exists as a latentinfection in some stock lines ofdomestic rabbits. The virus doesnot produce a natural disease,nor are other species of animalssusceptible. A virus with char‑acteristics of the herpes grouphas been recovered from rabbitswith respiratory signs. Its roleas a pathogen has not been elu‑cidated, but its association withrespiratory disease may beimportant. Another herpes virus that maybe responsible for producinglymphoid tumors in cottontailrabbits recently has been isolatedfrom these rabbits.Rabbit papilloma Rabbit papilloma virus hasbeen identified as the causativeagent of wartlike growth on theskin of cottontail rabbits(Figure 10). Domestic rabbitsand jackrabbits are susceptible toexperimental infection. The viruscan be recovered from lesions oncottontail rabbits, but not frompapillomas on domestic rabbits.Naturally occurring papilloma‑tosis has been found in domesticrabbits in southern California,but the virus produces no evi‑dence of a generalized illness. The most common sites forpapillomas are the ears and eye‑lids, and the growths vary in sizeand conformity. The growths arewell keratinized, and the uppersurfaces are irregular and oftensplit. The lower portions of thegrowth are pinkish and fleshy tothe touch. As the warts becomeolder, they increase in size,become more cornified, and arehard to the touch. At this stage,they are easily scratched off bythe rabbit or knocked off whenhandled. Papillomas removedin this way leave a free‑bleedingsurface, which heals withoutcomplications. Rabbit papilloma virus prob‑ably is spread by free‑flyinginsects such as mosquitoes; there
17is no virus multiplication ininsect tissue. Transmission of thevirus from lesions of cottontailrabbits to domestic rabbits ismost likely.Oral papilloma Wartlike growths in themouth, especially on the lowersurface of the tongue, arecaused by a virus (one of thepapovaviruses) different fromthe rabbit papilloma virus. Sev‑eral spontaneous outbreaks ofthis disease have occurred, all inNew York and Massachusetts.The growths on the tongueusually regress without specifictreatment.Viral enteric diseases During the past decade, sev‑eral viruses have been isolatedfrom rabbits with diarrhea.Rotovirus, coronavirus, andadenovirus all have been incrimi‑nated in enteritis outbreaks. Theclinical signs and pathology ofthe viral enteric diseases are verysimilar to those described underthe section on bacterial diseases.It is not clear whether virusesact as the primary agent (withpathogenic bacteria as secondaryinvaders) or whether natural out‑breaks of enteritis can be causedby these viral entities alone. Agreat deal of work currently isbeing done to answer the ques‑tions of viral pathogenicity andimmunology.Viral hemorrhagicdisease Viral hemorrhagic disease(VHD) first was reported inChina in 1984. Since then, it hasoccurred in many European rab‑bit-raising countries, in Mexico,and in the United States. Rab‑bits with the disease show inco‑ordination, convulsions, andevidence of severe pain. Thereusually is a bloody nasal dis‑charge. Mortality rate of affectedanimals is very high. Postmortem examinationreveals hemorrhages throughoutthe body organs such as thelungs, liver, heart, spleen, andmucous membranes. The liver isextremely swollen and brownishred. Although the disease is veryrare in the United States, ani‑mal health authorities keep avigilant eye on imported rabbitsand rabbit meat. The disease hasescaped from quarantine centersin Australia and New Zealandand is decimating wild Oryctol‑lagus rabbit populations in thosecountries.Figure 10.—Rabbit papilloma. Scaly growths on the ear were caused bypapilloma virus.
18Fungal diseases Two main groups of fungi,Trichophyton and Microsporum,are found on rabbits and pro‑duce disease of the skin andfur under certain conditions.Not only can rabbits serve asreservoirs for human infection,but humans can transmit theirfungus infection to rabbits.Because they produce a similardisease known as ringworm,the two organisms are discussedtogether in this section. Fungus infections causepatchy areas of hair loss andthickened skin covered withyellow, dry crusts (Figure 11).The hairs may be broken closeto the skin surface and becomematted. The name “ringworm” issuggested by the circular lesionthat often develops from theoutward growth of the fungi.Lesions usually are found onthe nose, ears, eyelids, and feet.Their size varies, and in severecases whole areas of the bodymay be involved. The infectionusually is most severe in nurs‑ing young; single small lesionsare more likely found in adults.Diagnosis of fungus infectiondepends on finding fungi inskin and hair scrapings and byculture. Examination underWood’s (ultraviolet) light mayindicate Microsporum but notTrichophyton. Infection of young rabbitsprobably occurs in the nest box.The nest‑box material becomescontaminated with fungusfrom the adult, and minor skinabrasions allow the fungusto become established on theyoung. When nursing, the youngare in direct contact with skinand fur around the doe’s teats,and the fungus is easily trans‑ferred to the mouth and noseregions of the infants. Thesesame fungal organisms are foundon dogs, cats, domestic livestock,and wild rodents around farmbuildings. Fungal infections must be dif‑ferentiated from other types ofskin problems, such as miteinfestations, hair pulling, fightwounds, molting, and vitamindeficiencies. If ringworm is sus‑pected after an evaluation of thelesions and clinical history, a skinscraping should be performed.The scraping should be takenfrom the periphery of thelesions, treated with 10 percentpotassium hydroxide, and exam‑ined under a light microscopewith reduced illumination. Fun‑gal forms are identified easily bytrained personnel. When small numbers of ani‑mals are involved, a topicalantifungal medication may beapplied directly to affected areas.In larger outbreaks, an oral orFigure 11.—Ringworm infection showing loss of fur and scaling of skin on theears (arrow).
19systemic medication is preferred.Griseofulvin, an antifungal drug,is the medication of choice. Eachanimal should receive 12 mil‑ligrams (mg) per pound ofbody weight per day for at least15 days. Dissolve the drug inwater and administer to the rab‑bit by gastric intubation. Duringtreatment, add a fungicidal dustsuch as sulfur to the nest‑boxmaterial. Griseofulvin can be added tothe feed at the rate of 370 mgper pound of feed and fed to allrabbits in the herd for a periodof 2 weeks. While this is anextremely effective and easy wayto treat ringworm, it presentsa problem: The drug has neverbeen cleared for use in rabbitfeed in the United States and,therefore, cannot be added to thefeed by a commercial feed com‑pany. This situation may beresolved in the near future.Parasitic diseases Rabbits are susceptible to anumber of parasites, but only afew are of economic importance.The problems caused by all ofthese parasites are greatly influ‑enced by methods of feeding,handling, and housing. If theseare satisfactory, and if recentlyacquired animals are quaran‑tined for a few days and checkedfor disease, most economicallyimportant parasitisms can beavoided.Prevention and control Prevention of parasite infec‑tion is far cheaper and preferableto treatment. The best preventivemeasures are sanitation, goodhousing, adequate food ration,and an understanding of poten‑tial parasite problems. Wheregood husbandry is the rule,rabbits rarely are infested withparasites in significant numbers.Modern pens are constructed sothat they can be kept clean andfree from the infective formsof parasites. Proper cleaning ofcages and use of good disinfec‑tants, together with a good diet,are the keys to parasite control.Figure 12.—Treating ear mites with a cotton swab soaked in medicated oil.
20External parasitesEar mites Psoroptes cuniculi, the com‑mon ear mite of rabbits, causesear mange or canker. This condi‑tion is a very common parasiticdisease in commercial rabbitries. The mites live in the ear canaland damage the skin lining thisarea. An exudate of brown, waxymaterial soon covers the innerear (Figure 12). This darkencrustation consists of cellulardebris, keratin, dried blood,and mites in varying stages ofdevelopment. The complete life cycle of themite takes less than 3 weeks, anda severely infested ear can con‑tain as many as 10,000 mites. Insevere cases, the entire innersurface of the pinna may beinvolved, as well as the side ofthe head, the neck, and eventhe chin and shoulders. Severelyaffected rabbits lose flesh, fail toreproduce, and succumb to sec‑ondary infections. Treatment of ear mite infesta‑tions requires a plan and perse‑verance. If ear mites are detectedin one rabbit, they likely are inothers in the herd also. To rid theherd of this bothersome para‑site, treat all rabbits in the herdregardless of whether ear mitesare detected. Treating just theone rabbit will result in continu‑ally treating one or two rabbits aweek. Most mineral‑oil‑based earmite medications containing aparasiticide are effective, as aretreatments using ivermectin.Place oil-based preparations (twoor three drops) in both ears of alladult and potential replacementrabbits in the herd. Massagingthe base of the ear after adminis‑tering the medication distributesthe drug throughout the sur‑face of the ear canal. If rabbitsare severely infected and havea large amount of debris in theear canal, soften the debris withmineral oil and remove it withcotton-tipped applicators andtweezers before drug application.Treat rabbits with noticeable earmite infestations every day forthree treatments, every otherday for three treatments, andthen weekly for three treatments.Treat rabbits without notice‑able ear mites monthly for threetreatments. Ivermectin is giventwo or three times at 2-weekintervals.Fur mites Cheyletiella parasitovorax andListrophus gibbus are two com‑mon mites inhabiting the skinof rabbits. In healthy, well‑fedrabbits these mites seldom causea problem and rarely are noticed.If a rabbit becomes sick or isunderfed, alopecia, sores, orscabs may develop in the neckor dorsal trunk areas. Intenseitching may occur, which causesconstant scratching with thehind legs and the consequentloss of hair and injury to theskin. Diagnosis of fur mites is bestaccomplished by scraping theskin of the affected area with ascalpel blade dipped in mineraloil. The resulting debris then isexamined microscopically forevidence of mites and eggs. Totreat fur mites in a few rabbits,apply a cat flea powder at weeklyintervals for several treatments.If a fur mite infestation becomesa herd problem, treat with injec‑tions of ivermectin or dip rabbits(wear gloves) in a 0.5 percentmalathion solution at 10‑dayintervals for two treatments.Cuterebrid flies Larvae of Cuterebra flies arecommon subcutaneous parasitesof wild rabbits but infrequentparasites of domestic rabbits.The adult fly appears whereverpopulations of wild rabbits exist.Rabbits are infected when the flydeposits eggs on the fur. Grubworms hatch from these eggsand burrow into the skin to formwarbles. The larvae grow underthe skin and may get as long asthree‑quarters of an inch(Figure 13). When full-grown,the grubs leave the skin, dropto the ground, and develop intoadult flies. The warbles causeFigure 13.—Cuterebra larva. Aneraser on a pencil is shown for sizecomparison.
21little trouble when they arefound in small numbers. Thelarvae can be removed by enlarg‑ing the opening in the skin anddrawing them out gently withtweezers. Paint the wound withan antiseptic.Fleas and ticks Rabbits are not commonlyinfested with fleas; however, therabbit flea, Spilopsyllus cuniculi,and the dog and cat fleas, Cteno-cephalides canis and C. felis, occa‑sionally have been reported onrabbits. There are four stages inthe life cycle of these fleas—egg,larva, pupa, and adult. The eggsare deposited on bedding and incracks of nest boxes and developinto larvae in a short time. Theselarvae then form pupae fromwhich adult fleas emerge. Control is aimed at killing theadults on the host and theimmature forms in the nest box.To destroy adult fleas, dust rab‑bits with a commercial prepara‑tion of pyrethrum or rotenone.Repeat several times during a2‑week period. Control imma‑ture forms by burning oldnest‑box litter and scrubbingnest boxes with hot water andhousehold bleach. More moderndrugs for preventing and treat‑ing ectoparasitism in dogs andcats may be used in rabbits also.Consult a veterinarian. The rabbit tick, Haemaphysa-lis leporispalustris, is a commonparasite of wild rabbits, butrarely is found on domestic rab‑bits because their housing is notcompatible with the life cycle ofthe tick; however, this tick is oneof the reservoirs of tularemia,a serious human disease. Takecare to ensure that wild rabbitsare not allowed access to areas inwhich domestic rabbits are beingraised.Internal parasitesCoccidiosis Coccidiosis is a prevalentparasitic disease of domestic rab‑bits. It is caused by a microscopicprotozoal parasite that invadesthe intestine or liver. In theselocations, the parasite multipliesextensively and then sheds eggsin the feces. At least four speciesor types of coccidia live in theintestine, and one species growsin the liver. Not all species of coccidia areequally harmful, and rabbitstolerate moderate numbers ofsome without displaying illness.The most dangerous of the intes‑tinal forms are Eimeria magna,E. media, E. perforans, andE. irresidua. These produce diar‑rhea, poor appetite, weight loss,and sometimes death. E. irre-sidua evokes the most severetissue damage. In some cases,patches of epithelium die andslough away from the intestinalwall. The diagnosis of coccidiosisdepends on the finding of theoocysts (eggs) in the feces orintestinal contents. However,Figure 14.—Life cycle of coccidia.
22experience is needed to judgewhether sufficient numbers ofparasites are present to accountfor the disease signs, becauseother disorders may producesimilar signs. Control of intestinal coccid‑iosis depends largely on manage‑ment practices that minimize thedanger of fecal contaminationof feed, water, and hutch floors.Wire‑bottom floors greatlyreduce the hazard presented bysolid floors or slots. However,brush wire floors daily with awire brush to ensure that fecalmaterial falls through the wires.This breaks the life cycle of theorganism. Design feeders so thatfecal contamination is held to aminimum. An automatic watersystem is recommended. Oocystspassed out in the feces requiremoisture and warmth to sporu‑late and become infective(Figure 14). Dry wire floors andautomatic water systems hin‑der sporulation of the parasite.Oocytes persist in the environ‑ment and are difficult to killwith most common sanitizingagents. Treatment has only a tempo‑rary effect during the early stagesof intestinal coccidiosis, but itmay be useful in controllingoutbreaks. When indicated, aration containing 0.025 percentsulfaquinoxaline may be fed for2 to 3 weeks to reduce the num‑bers of parasites to a level wherecontrol can be accomplished byproper management. Intestinalcoccidia develop a tolerance tothe drug if used continuously, sotreatment is not suggested unlessclinical disease appears. Meatrabbits so treated must be heldfor at least 10 days followingcessation of treatment to allowbreakdown of antimicrobial resi‑due in muscle tissue. Eimeria stiedae, the one spe‑cies that multiplies in the liver, isconsidered to be the most patho‑genic coccidium of rabbits. Likethe other forms, it enters theintestinal wall, but it migratesto the bile ducts, where it repro‑duces. Infections lasting morethan 16 days can be recognizedby white circular nodules on theliver (Figure 15). The parasitemultiplies in the epithelial cellsof the bile ducts, which becomethickened and tortuous and con‑tain a vast number of oocysts.In the early stages of infection,there are no unusual symp‑toms. Then appetite decreases,a potbelly develops, and deathsometimes follows. In moderateinfections, there is no mortality,but disfigurement of the livermakes it unmarketable; hencethis type of coccidiosis always isof economic significance. Liver coccidiosis is acquiredin the same manner as intes‑tinal coccidiosis. The controlmeasures also are similar; how‑ever, liver coccidiosis can becontrolled more easily by propermanagement. When the diseasedoes occur, feed containing0.025 percent sulfaquinoxaline isan effective treatment. It can befed at this level for 3 weeks; useit only until management con‑trol measures can be introduced.Encephalitozoonosis Encephalitozoon cuniculi (aprotozoan parasite) is the causeof a mild but long-standing dis‑ease in rabbits. The conditionwas first described as a chronicencephalitis, sometimes withclinical signs such as a spontane‑ous paralytic disease. A chronicnephritis caused by the parasitewas overlooked for many years,but current studies indicate thatmany apparently healthy ani‑mals have kidney lesions relatedto this infection. These lesionsvary from cortical scarringwith multiple small, indented,gray areas on the surface toFigure 15.—Livers of rabbits affected with hepatic coccidiosis.
23a granulomatous nephritis(Figure 16). The scars extendfrom the cortical surface to themedulla. Encephalitozoonosis is a con‑tagious, colony infection. Theorganisms are passed in the urineand transmitted when there isurinary contamination of feedor water. A diseased doe also cantransmit the disease to unbornrabbits in the uterus. The diseasecan be controlled by providinggood sanitation and preventingcontamination of food andwater by urine. No treatment isavailable. Diagnosis of encephalito-zoonosis in a rabbit herd isdifficult. It usually is done atnecropsy by observing histo‑pathologic lesions typical of thedisease. Recently, several diag‑nostic tests have been developedthat will help with the diagnosisin live rabbits. An Encephalito-zoon infection can be detected byan indirect fluorescent antibodytest, a skin test, or by a carbonimmunoassay utilizing Indiaink. These tests may be helpfulin antemortem diagnosis andalso in screening rabbits to pointout possible carriers or infectedanimals.Toxoplasmosis Toxoplasmosis is an uncom‑mon protozoal disease of rabbitscaused by Toxoplasma gondii.The disease has been reportedworldwide in both domesticand wild rabbits. The diseaseprobably is more common thanreported, as antibody tests onrabbit herds have shown thatas many as 50 percent of clini‑cally normal rabbits have beenexposed. There are two forms of thedisease. In the acute form, therabbit develops anorexia, fever,lethargy, and (in a few days) cen‑tral nervous symptoms rangingfrom ataxia or posterior paraly‑sis to generalized convulsions.Death usually occurs about aweek after symptoms are firstnoted. In the chronic form,the disease occurs over a muchlonger period of time. In fact, itmay be latent, with onset stimu‑lated by stress. With the chronicform, either no symptoms areobserved or there is a progressiveemaciation that might end inposterior paralysis and death. Transmission of the diseasemay occur in two ways. Cats canshed the parasite in their stooland thereby contaminate storedrabbit feed; then the contami‑nated feed is ingested by rabbits.The parasite also can be trans‑mitted through the placenta of apregnant doe to her offspring. At necropsy, the lesions of thisdisease vary. In the acute form,there is extensive necrosis of thelymph nodes, liver, spleen, andlungs. This generally is observedhistologically, but grossly theorgans may be swollen, andnecrotic small white foci may beobserved. The parasitic organ‑ism often is found with the aidof a microscope in these necroticfoci. In the chronic form, theremay be microscopic lesions butno apparent gross lesions, andorganisms often are confined tothe central nervous system. Diagnosis of toxoplasmosisgenerally is accomplished atnecropsy by observation of his‑tologic lesions and organisms.Various serological tests alsomight be useful. Treatment inmost cases is not practical, andthe emphasis should be on pre‑vention. Cats, the primarycarrier of this organism, shouldbe kept out of rabbitries or atleast away from feed storageareas. Take precautions to ensurethat feed and water are not con‑taminated with toxoplasmaoocysts.Roundworms Only one roundworm pres‑ents a problem in domesticrabbits. Several more have beenreported in wild rabbits, butthese rarely occur in domesticrabbits. The pinworm, Passalurusambiguus, is a very commonparasite of domestic rabbits, butit does not affect other animalsor people.Figure 16.—Halves of kidneys from tworabbits showing pitting of the surfacecaused by Encephalitozoon cuniculi(right).
24 These pinworms are glisten‑ing white, and 1⁄2 inch long. Theyoften are seen on the surface offreshly passed feces or throughthe wall of the cecum when rab‑bits are slaughtered. Ordinarily,pinworms do little harm. As themature worms become inactive,they are passed out of the cecumas fecal pellets are formed. Theseparasites are spread from ani‑mal to animal by ingesting feedand water contaminated by thedroppings of infected animals.Management methods used tocontrol coccidiosis are effectiveagainst pinworms. When treat‑ment is necessary, piperazinecitrate is effective when admin‑istered at 100 mg/100 milliliters(ml) drinking water for 1 day.Reinfection occurs readily.Tapeworms Tapeworms occur in rabbitsas adults in the intestine and aslarval forms in the liver andabdominal cavity. Theadult forms are very rare inhutch‑raised rabbits, but larvalforms occasionally are observed. The rabbit tapeworm Cit-totaenia variablis is uncommonin domestic rabbits. It is flat,ribbon‑shaped, and made upof numerous segments. It hasa head with four suckers withwhich the worm attaches to thelining of the intestine. Rabbitsharboring a few tapeworms showno signs of the disease. Whenmany tapeworms are present,diarrhea and emaciation mightoccur. Control is readilyaccomplished by goodsanitation. The larval forms of tapewormmost often found are those ofTaenia pisiformis. They are foundin the abdominal cavity and inthe liver. Rabbits acquire thesetapeworms by ingesting contam‑inated feed and water containingtapeworm segments and eggsfrom the feces of dogs. The young larvae then arereleased from the eggs, penetratethe digestive tract, and migrateto the liver. They migrate withinthe liver, leaving white streaksbehind, then leave the liver andenter the abdominal cavity. Theyform small, fluid‑filled cysts (cys‑ticerci), which may be attachedto the membranes holding theintestinal tract or may exist freein the abdominal cavity(Figure 17). Each cyst containsan embryonic tapeworm that,when consumed by a dog, willdevelop into a mature tapeworm. By excluding dogs from therabbitry, transmission of tape‑worm eggs can be prevented(Figure 18). Dogs kept onFigure 18.—Life cycle of the dog tapewarm.Figure 17.—Rabbit liver with severalcysticerci attached (arrow).
25premises where rabbits are raisedshould not be allowed to eatany part of a raw rabbit carcass.Treatment for larval stages in therabbit is not practical, so con‑trol must be accomplished bymanagement.NutritionaldiseasesPregnancy toxemia Also known as “ketosis,” thisdisease is a toxemia of pregnancythat is most common in firstlitter females. Signs of ketosis aredullness of the eyes, sluggishness,respiratory distress, prostration,and death after 1 to 4 days. Thedisease occurs in the last weekof pregnancy and is much moreprevalent in obese animals. Theprobable major cause is starva‑tion with subsequent metaboliceffects on the doe and young.For some reason, there is a loss ofappetite and failure to eat. Thismay be the result of minor diges‑tive upset (hairballs in the stom‑ach are common), an abruptreduction in exercise, or a rationcontaining too little digestiblecarbohydrate. When carbohy‑drate energy declines, body fat ismobilized for energy, and ketonebodies are produced and enterthe bloodstream. The liverbecomes fatty and appears brownand soft. Birth of the litter or abortionis apt to be curative if eitheroccurs shortly after the onsetof signs. Injections of fluidscontaining glucose may reversethe breakdown of body fatsand halt production of ketones.Junior does should not be too fatwhen bred for the first litter.Vitamin A deficiency Low‑grade vitamin A defi‑ciency adversely affects thereproductive performance offemales, often before other signsare noted. Premature degenera‑tion of the ovum and reducednumbers of fertilized ova result.Resorption of the fetus or abor‑tion during late gestation also isnoted. Rabbits born to females fed adiet deficient in vitamin A maybe hydrocephalic at birth.Hydrocephalus, or “water onthe brain,” is characterized bydistention of the portion of theskull that covers the brain. Casesmay not be apparent becausethe young die soon after birth orare born dead. Animals that liveshow signs of nervous systeminvolvement. Wryneck, loss ofequilibrium, and incoordinationpersist for several days or weeks.Impaired coordination may pre‑vent animals from eating, andeventually they die of starva‑tion. Enlargement of the headis caused by increased pressurewithin the brain. On cut section,the ventricles (cavities) of thebrain are greatly enlarged andfilled with a clear, colorless fluid. Hydrocephalus is causedby low maternal blood levelsof vitamin A throughout thegestation period. When maternalblood levels fall below 20 micro‑grams (ug) per 100 ml serum,hydrocephalus appears in a largepercentage of the young. Com‑mercial diets, in general, supplyadequate levels of vitamin A;however, the vitamin does dete‑riorate after prolonged storage ofalfalfa hay. It has been shown by workersat Oregon State University’s Rab‑bit Research Center thatexcess levels of vitamin A cancause the same signs and symp‑toms as deficiency of the vitamin.Low fertility, abortions, resorp‑tion, and hydrocephalus wereseen in does given excessive vita‑min A in the diet. Excess vitaminA may be a problem if a vitaminpremix is added to rabbit dietscontaining high levels of alfalfa.Vitamin E deficiency Infant mortality, character‑ized by death of entire littersat 3 to 10 days of age withoutclinical signs prior to death, hasbeen associated with vitamin Edeficiency. Affected infants donot reveal any gross lesions ofdiagnostic significance. Produc‑ing females become less fertileas the deficiency progresses.The problem can be treatedbecause adequate supplementa‑tion of vitamin E will stop infantmortality and correct infertility.Alfalfa hay is a suitable source ofvitamin E in commercial rations,and 8–9 mg/100 grams (g) feedis adequate.
26HereditarydiseasesGlaucoma Glaucoma (buphthalmia)occurs in both laboratory andcommercial rabbit colonies. Thiscondition is of interest to oph‑thalmologists because of its simi‑larity to congenital glaucoma inhumans, and rabbits may serveas a useful animal model. Glaucoma appears first as alight bluish cloudiness on thecornea. One or both eyes may beaffected. Progressive opacity fol‑lows, and protrusion of the eye‑ball becomes noticeable. Cornealopacity may lead to blindness. Glaucoma probably is theresult of an abnormal drainagemechanism and the inability tomaintain normal fluid relation‑ships in the eye. It is a semilethaldefect that is transmitted as arecessive trait.Malocclusion Malocclusion and tooth over‑growth, or “wolf teeth,” havelong been recognized as commonproblems in rabbit colonies. Thedental formula of the rabbit is:incisors 2/1, canines 0/0, premo‑lars 3/2, and molars 3/3. Con‑stant chewing and gnawing keepthe teeth ground down to properlength and size. When the lowerjaw is shorter or longer than theupper jaw or teeth are damaged,malocclusion of the incisorsmight result in overgrowth(Figure 19). The cheek teeth(premolars and molars) meet andgrind evenly in normal animals.These teeth continue to growand depend on constant grind‑ing against opposing teeth tomaintain their shape. If there isa malposition of the jaw, brokenteeth, or malformation, over‑growth will occur in the cheekteeth similar to that whichoccurs in the incisors. Signs of malocclusion aregradual loss of appetite andweight. Both sides of the mouthmay become stained with saliva.Animals become progressivelylistless, dehydrated, and unableto chew properly. Complicationsare abscessed teeth, growth ofteeth into the upper jaw, anddeath from starvation. Malocclusion of the incisorscan be corrected temporarilyby cutting back the teeth so theanimals can eat and attain goodcondition before slaughter. However, never use these ani‑mals as breeding stock becausemany types of malocclusion areinherited. Young rabbits occa‑sionally pull on cage wires orfeeders with their teeth and causemisalignment, which also resultsin malocclusion. This type ofmalocclusion is difficult to dif‑ferentiate from inherited maloc‑clusion. Therefore, the bestsolution is to regard all maloc‑clusion as inherited. The reces‑sive malocclusion genes can beeliminated from a breeding herdby selective breeding.Splay leg and ataxia Splay leg in rabbits is due toone or more recessive geneticfactors. The condition mightbe similar to the hip dysplasiafound in certain breeds of dogs. The disease is characterizedby an inability to put weight onone or both hind legs, and mighteven involve all four limbs. Thelimbs are twisted so the animalshave a double-jointed posture.Affected animals are not para‑lyzed. They eat normally, seemto be well, and move by wrig‑gling along on their belly andchest. The pathologic effects arelimited to the hip and shoulder. Ataxia (muscle incoordina‑tion) resembles splay leg in somerespects. It is, however, a lethalrecessive genetic factor. The dis‑ease usually appears when theanimal is 2 to 3 months of ageand runs its course in 30 days. Inataxia, the nervous system isinvolved, and at first the animalmight not be able to use its hindlegs effectively. Later the animalcannot move, and its body tem‑perature drops below normaluntil death ensues.Figure 19.—Malocclusion.
27MiscellaneousCannibalism Most cases of cannibalismare the result of a diet that isinadequate in either quality orquantity, injury or abnormalityin a baby rabbit, or disturbanceof the doe following kindling.Proper feeding and seclusionat kindling usually prevent thetendency. A valuable doe thatdestroys her first litter should begiven another chance. If she con‑tinues to kill young, she shouldbe culled from the breedingpopulation.Heat prostration Heat prostration results fromprolonged exposure to excessiveheat. Losses may be high infemales due to kindle or in babyrabbits if nest boxes are poorlyventilated. Just before dying, ani‑mals breathe rapidly and becomecomatose. Provide relief to adult animalssuffering from the heat by spray‑ing them with water or placing awet burlap feed sack on the cagefloor for them to rest on.Remove some bedding and furfrom nest boxes to improve cir‑culation of air around kits. In locations subject to hightemperatures, overhead watersprinklers help to reduce theair’s temperature by evaporation.Aluminum‑roofed sheds reflectthe heat, and burlap sacks soakedin water can be hung from theedges of the roofs to shade andcool the air. Draining water lines or crocksand refilling with cold water forimmediate consumption aid inreducing rabbits’ body tempera‑ture. It is also helpful to changebreeding schedules to reducethe number of late‑pregnancydoes in the hottest part of thesummer.Broken back This condition is character‑ized by sudden paralysis with noapparent cause. Paralysis extendsposterior from the middle ofthe back and may be completeor partial (paresis). The animalmoves with its front legs anddrags the hindquarters. The uri‑nary bladder may become greatlydistended. Paralyzed animalshave a displaced or slipped verte‑bra. Malposition of the vertebracompresses and damages the spi‑nal cord with resulting paralysis.Injury to the vertebra may becaused by improper handling,use of a tattoo box too short forthe animal, or injury. Many inju‑ries occur at night when predatoranimals invade the rabbitry. Inan effort to evade the predatorand protect the young, the adult“stamps” firmly with its hindfeet. As a result, a vertebrabecomes displaced, and the spi‑nal cord is damaged. Adult rabbits have beenobserved to cause a luxationof the vertebrae by suddenFigure 20.—Sore hocks.
28movements when startled bya person entering the rabbitry.This is especially true if back‑ground noise (such as a radio) isnot available and the person is astranger. If a rabbit is completelyparalyzed, it generally is killed.However, some success has beenobserved in does with paresis(some motor function or sensorycapability) by putting the rabbitin a small cage for 30 to 60 days.The smaller cage limits the rab‑bit’s activity and allows time forrepair of the injury.Sore hocks Sore hocks are inflamed barespots, devoid of fur, found onthe bottom surface of the hindlegs (Figure 20). In severelyaffected cases, secondary infec‑tions with Staphylococcus occur.Both front and hind feet mightbecome involved. As the hocksof the hind feet become painful,the animal throws more weightto the front feet, adding stress tothe front feet and causing themto become affected. Wet, dirtyhutch floors and the irritatingaction of urine salts are predis‑posing factors. The breed alsois a factor in the developmentof sore hocks; the disease is seenmore often in large breeds thanin smaller breeds. Rex rabbits areprone to the disease because ofthin foot pads. Treatment of sore hocks oftenis nonproductive. Even if treat‑ment is successful, the lesionalmost always returns, and theanimal seldom is useful as abreeder. The best method oftreatment is prevention. Preven‑tion is accomplished in threeways. First, cull all affectedbreeders from the breeding herdbecause of a genetic predilectionfor sore hocks (thickness of thefoot pad). Second, clean cagefloors daily and never allowmanure to hang on cage floors.Third, inspect cage floorsfrequently for rough spots orrusty areas.Tumors Spontaneous tumors in rabbitsrarely are reported because theanimals are slaughtered beforethey reach the age at whichtumors are most apt to occur.With the increasing use ofrabbits as laboratory animals,interest in these growths can beexpected. Tumors have beenobserved in the uterus, kidneys,blood, lymph nodes, bones,testicles, skin, and other organs.Adenocarcinomas of the uteri arenot uncommon in does over2 years of age. Usually they aremultiple and occur in both uteri.Most cases of lymphosarcoma(tumors of cells from lymphnodes) occur in mature females.Neoplastic cells are found innumerous body organs, but themost outstanding lesions arein the kidneys. Another tumororiginates from embryoniccells in the kidneys (embryonalnephroma) and is observed withsome frequency in domesticrabbits.Fur eating andhairballs Several rabbits in a hutchmay eat body fur, eyelashes, andwhiskers. Single rabbits eat furon their sides, back, and rump.The cause generally is a defi‑ciency of dietary fiber and gastricatony. Diets high in cereal grainsand low in alfalfa often have alow fiber content. Because therabbit’s digestive system isdesigned for handling largeamounts of fiber, a deficiency inthe diet causes the animal to seekanother source of fiber, and hairchewing begins. Increasing fiberin the diet almost always elimi‑nates the problem. Overcrowd‑ing in a cage also can cause hairloss, mainly from fighting. Rabbits also eat small amountsof hair by licking or groomingthemselves. The hair may accu‑mulate in the stomach and formhairballs. These usually cause nodisease, but they may obstructthe stomach. When obstructionoccurs, the rabbit quits eating,loses weight, and may die. If a hairball is suspected,parenteral fluids, gastric musclestimulation, massage of the(delicate) stomach, and, perhaps,administration of 10 ml of pine‑apple juice by stomach tube ormedicine dropper 3 days in arow might help. An enzyme inthe juice might help break upthe hairball and allow it to passthrough the digestive system.Surgery might be needed insome cases.
29Coprophagy Rabbits take soft fecal pelletsfrom the vent and swallow themintact. This is a natural physi‑ological process for rabbits andshould not be misinterpretedas a nutritional condition ordepraved appetite. Coprophagyis practiced at night by tame rab‑bits and during the day by wildrabbits in their burrows. Fermen‑tation of the feces in the largeintestine supplies an abundanceof certain B vitamins to the fecalpellets, probably improves thequality of the protein in the softpellets, and improves fiber break‑down by bacterial action. By per‑mitting a second passage of foodthrough the digestive tract, therabbit gains additional nutritivevalue from the food.Yellow fat Yellow body fat is an inher‑ited condition in rabbits. It isincluded here only to preventmisunderstanding or associationwith a disease condition (jaun‑dice). Yellow fat is a genetictrait determined by a recessivegene. Alfalfa and other greenfeeds contain xanthophyll, afat‑soluble compound that is yel‑low in color. Animals with theyellow fat gene lack an enzymethat reduces (changes) the xan‑thophyll pigment to a colorlessproduct. Therefore, the xantho‑phyll is deposited in the bodyfat, making it yellow. White fatin meat rabbits is preferred toyellow fat. Plant pigments alsoaffect urine colorWinter breedingdepression A very common occurrence inrabbitries in cold climates is adecrease in productivity duringthe winter. The syndrome usu‑ally has these common elements:small litters, abortions, weaklitters that can’t nurse, does thatdon’t have enough milk, anddoes that will not breed. All ofthese factors lead to a decreasednumber of fryers toward the endof the winter. Although manycauses for this syndrome havebeen postulated, the basic prob‑lem is inadequate nutrition. Breeding does (and sometimesbucks) require more energy incold weather to keep warm. Ifyou use a restricted feeding pro‑gram (rabbits are not fed all theywant), increase the amount offeed in cold weather. Otherwise,the doe will not have enoughfood calories to provide bodyheat and energy for the repro‑duction process. Reproductionwill be suspended until adequatenutrition is available, which usu‑ally occurs as warmer weatherarrives. The treatment for this syn‑drome is either to increasegradually the amount of feed(usually to about double) or toincrease the amount of energyin the diet by increasing theamount of carbohydrate or fat.How to pack andship specimensfor laboratorydiagnosis The best way to obtain anaccurate diagnosis is to take deadanimals or two or three sick ani‑mals showing typical signs to thenearest animal diagnostic labora‑tory and supply any additionalinformation the pathologist mayneed. If delivery in person is notconvenient, the dead animals canbe shipped.Shipping dead animals If you cannot take your rab‑bits to a diagnostic laboratorybecause of distance, the next bestthing is to send the dead rabbitsto the laboratory. Because it is against postal reg‑ulations to send frozen carcassesof diseased animals through themail, shipment must be made bybus or air express. United ParcelService will not accept carcasses.Label the outside of the box“Biological specimen,” “Rush,”and “Keep in a cool place.” If the carcass is to be shippeda short distance, chill (but neverfreeze) it thoroughly and placeit in the center of a box contain‑ing sawdust or shavings. Forlong-distance shipments, placedry ice around the carcass, thenpack it as indicated above. Neverput dry ice in an airtight jar orcan. If the gas cannot escape, itmay cause an explosion. Properly
30used, dry ice will prevent spoil‑age for 2 or 3 days. Many specimens decomposeafter arriving at the laboratorybecause no one is available totake care of them promptly.With this in mind, do not sendfresh specimens that will arriveon a weekend; most laboratoriesdo not operate on Saturday orSunday. Address the package tothe laboratory itself, not to anindividual employee. This willensure more immediate atten‑tion. Do not send carcasses thathave started to decompose. Itis better to kill an animal ortwo that show typical signs, orto ship them alive if there is achance they may reach their des‑tination before death.Accompanyinginformation Letters that do not containsufficient information are a prob‑lem to the pathologist. In somediseases, a complete history ismore useful than the carcass. Theaccompanying letter should con‑tain the following information:• Number of rabbits on theranch• Number of sick or deadanimals• Age and sex of affectedanimals• Description of the disease asyou observed it. For example,“Rabbits develop watery diar‑rhea, quit eating and drinking,and die in 1 or 2 days.”Use pesticides safely!When you use any pesticide, observe these rules:• Wear protective clothing and safety devices as recom‑mended on the label. Bathe or shower after each use.• Read the pesticide label—even if you’ve used the pesticidebefore. Follow closely the instructions on the label (and anyother directions you have).• Be cautious when you apply pesticides. Know your legalresponsibility as a pesticide applicator. You may be liable forinjury or damage resulting from pesticide use.• Dates of first losses and subse‑quent losses• Incidence of infection(whether it is in just onehouse or pen, or scatteredthroughout the rabbitry)• What treatment, if any, hasbeen given• Type and brand of feed andfeeding methods used for thepast 6 months• Type of housing (whether therabbits are kept on wire orsolid floors)• Any other informationthat might help explain theoutbreak It is best to telephone the lab‑oratory so the staff can be alertedto the arrival of the specimen. Ifthey need further information,they can ask at that time.