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Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys - IP372


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Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys - IP372

  1. 1. A project of the National Center for Appropriate Technology 1-800-346-9140 • www.attra.ncat.orgParasite Management for Natural andOrganic Poultry: Blackhead in TurkeysBy Terrell Spencer, Blackhead disease, also called Histomoniasis, is a serious disease capable of decimating turkey flocksNCAT Agriculture and negatively affecting other poultry. Caused by the protozoan Histomonas meleagridis, BlackheadSpecialist can also have a significant economic impact on chicken production. Recent research has revealed new© 2010 NCAT information about the bird-to-bird transmission of Blackhead through a previously unknown path- way—cloacal drinking. This publication addresses the new research as well as focusing on the history,Contents life cycle, diagnosis, prevention, and management of Blackhead disease, primarily in turkeys. The effectIntroduction ......................1 Histomoniasis has on other poultry species (chickens, gamebirds, and peafowl) is also discussed briefly.The Life Cycle andInfectious Pathwayof Blackhead......................2Poultry Species asBlackhead Reservoirs .....2Blackhead Transmissionthrough Cecal WormEggs and Soil.....................2Horizontal Spreadingof Blackhead throughTurkey Flocks.....................3Oral Ingestionand Contractionof Blackhead......................4Diagnosis andSymptoms ofInfected Turkeys ..............4Prevention andManagement ofBlackhead Disease ..........5Conclusion .........................8References .........................8 Photo by Jeannette Beranger, American Livestock Breeds Conservancy. demands of an expanding population, turkey Introduction production dropped from 11 million birds in 1890, just years before the first Blackhead out- History of Blackhead break, to an average of 3.7 million turkeys perThe National Sustainable in the United States year during the 1910–1920 decade. The devel- TAgriculture Information Service, he first reported case of Blackhead dis- opment of antihistomonal drugs in the 1960sATTRA (,was developed and is managed ease in the United States occurred in led to a dramatic decrease in Blackhead-relatedby the National Center forAppropriate Technology (NCAT). Rhode Island in 1893, possibly carried turkey deaths. Unfortunately for poultry pro-The project is funded through to the U.S. by pheasants imported the decade ducers, the drugs developed to treat Histomo-a cooperative agreement withthe United States Department before. Blackhead then spread throughout the niasis were eventually banned (McDougald,of Agriculture’s Rural Business-Cooperative Service. Visit the U.S., ravaging turkey flocks in New England 2005). As more farmers enter into free-rangeNCAT website ( and following production like a faithful shadow. and pastured-poultry systems, often combiningsarc_current.php) formore information on Outbreaks of Blackhead rapidly spread down multiple poultry species on the same land,our other sustainableagriculture and the Eastern Seaboard, into the Midwest and the Blackhead outbreaks may be of increasingenergy projects. far western United States. Despite the growing concern and economic impact.
  2. 2. The Life Cycle and Infectious Blackhead does not kill the infected bird, and the disease requires a secondary bacterial infection to Pathway of Blackhead be virulent and eventually fatal. Escherichia coli, Blackhead occurs when the causal agent, the Bacillus subtilis, and Clostridium sp. are some of protozoan Histomonas meleagridis, gains access the bacteria noted in the secondary infections to the ceca, or blind pouches of the intestines. that caused death (McDougald, 2005). Blackhead infects poultry using three separate pathways that will be examined in detail in this publication: Poultry Species as • Ingestion of soil or earthworms Blackhead Reservoirs containing eggs of the cecal worm Among poultry species, there are varying Heterakis gallinarum, infected with degrees of susceptibility to Blackhead. SomeRelated ATTRA birds, such as pheasants, ducks, and geese, arepublications H. meleagridis nearly immune to the effects of Blackhead.Parasite Management • Uptake of H. meleagridis directly into Chickens are somewhat resistant to the disease,for Natural and Organic the lower digestive tract through the while turkeys and peafowl are extremely vulner-Poultry: Coccidiosis process of “cloacal drinking” able and have high mortality rates when infected • Oral ingestion of live H. meleagridis with H. meleagridis. Experiments have shown protozoa when stomach is not acidic that infected pheasants and chickens are capable enough to kill the pathogen of transmitting Blackhead to young turkeys (Lund and Chute, 1972). Once access into the digestive tract has been achieved, H. meleagridis multiplies in the ceca Traditional wisdom dictating that chickens and and attacks the tissues of the cecal walls. As the turkeys not be raised together is most likely disease progresses, a cheese-like, foul-smelling, based on experience with Histomoniasis. Chick- yellow substance fi lls the ceca. Th is substance ens are excellent hosts for the cecal worm that can vary in form from a hardened plug to more H. meleagridis uses as a vector. It is not unrea- liquid in nature, and is composed of dead cecal sonable to assume that the majority of Black- cells and blood. In highly susceptible birds such head outbreaks, especially among small, diver- as turkeys, the Blackhead protozoa then enter sified farmers, can be traced back to chickens. the bloodstream through the damaged ceca and are deposited into the liver, where they do even Among chickens, laying hens and breeding more damage, creating signature “bulls-eye” roosters have the potential to shed many more zones of necrosis (dead tissue). Occasionally, cecal worm eggs than broilers due to age dif- H. meleagridis also enters into other organs ferences in production—a broiler is usually such as the kidneys, lungs, heart, and brain. slaughtered at six to 12 weeks (six to eight weeks for Cornish cross; 12+ weeks for slower-grow- ing breeds), while a hen may be kept for two orFigure 1. Turkey Digestive Tract. By Terrell Spencer, NCAT. more years. The cecal worm in question, H. gal- linarum, takes approximately a month to mature and begin shedding eggs. This time frame, cou- pled with the two to four weeks chicks spend in the brooder, allows little to no time for a broiler to contaminate the soil with cecal worm eggs. On the other hand, a hen in production for sev- eral years can seed tremendous amounts of cecal worm eggs into the soil during her lifetime. Blackhead Transmission through Cecal Worm Eggs and Soil The indirect ingestion of Blackhead protozoa through consumption of earthworms and cecal worm eggs is the most commonly known meansPage 2 ATTRA Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys
  3. 3. Figure 2. Blackhead life cycle by By Terrell Spencer, NCAT.of contracting Histomoniasis. When exposed Horizontal Spreadingto the elements, the Blackhead pathogen isshort-lived, being highly susceptible to envi- of Blackhead throughronmental stresses—sunlight, wind, and tem- Turkey Flocksperature extremes. H. meleagridis has over- The contraction of Blackhead disease bycome this limitation through infecting cecal turkeys has traditionally been attributed solelyworm eggs, as these eggs are extremely hardy. to the vectoring of the disease through cecalThe eggs can remain viable up to three years worm eggs and earthworms. However, recentin the soil; in addition, cecal worms are very research has shown that turkeys can infect othercommon in many poultry species, especially members of the flock directly through a processchickens. Contaminated cecal worm eggs are known as cloacal drinking (Hu et al., 2004,consumed when birds ingest soil either inten- McDougald and Fuller, 2005).tionally or during foraging. Earthworms alsoact as an intermediate vehicle for spreading Cloacal drinking is the reflexive intake of fluidsthe disease, as the earthworms consume soil through the cloaca in order to inoculate thecontaining the infected cecal worm eggs. The young bird’s immune system with the micro-earthworms, in turn, are readily consumed by bial flora of the surrounding environment.all types of ATTRA Page 3
  4. 4. Unfortunately for both the turkey and the ically, the proventriculus—due to the stomach farmer, the turkey immune system has little to acids produced. Therefore, Blackhead is typi- no defense against Blackhead, and the Black- cally not transmitted orally (Hu et al., 2004). head protozoans that enter through the cloaca When a turkey feeds, acid is produced to aid multiply unrestricted. Uptake of H. meleagridis in digestion, and this acidification destroys through the cloaca occurs when a turkey’s clo- H. meleagridis. After six hours of not feeding, aca comes into contact with contaminated fecal however, the lack of stomach acid allows the matter, most likely while resting. The patho- turkey’s gastrointestinal tract to go from being genic protozoa are then drawn into the digestive acidic to neutral in pH, and this change can tract through the cloacal drinking process and migrate to the ceca, where infection occurs. allow H. meleagridis to survive oral ingestion (McDougald, 2010). Historically, contraction of Blackhead through cecal worm eggs has explained the begin- ning of outbreaks in poultry f locks, but Diagnosis and Symptoms failed to account for the rapidity with which of Infected Turkeys Blackhead spreads throughout the flock. The lack of an explanation for the continued trans- Physical Symptoms of Blackhead mission of Histomoniasis through a f lock, • Mustardy, yellowish colored stool— despite the exclusion of earthworms and soil varies from a watery, foamy diarrhea containing cecal worm eggs, has been a source to a dry, solid black stool with waxy of frustration and setback for farmers. Now, yellowish streaks thanks to recent research findings, this gap in • Bulls-eye-shaped necrotic pitting the basic understanding of the Blackhead life- on liver cycle has been closed. • Ceca filled with yellow, cheesy substance Oral Ingestion and Behavioral Signs of Blackhead Contraction of Blackhead • Lethargy When the turkey is given a constant supply of • Drooping wings food, experiments have suggested that H. melea- gridis ingested orally is not capable of surviving • Dry, ruffled feathers the passage through the stomach—more specif- • Suppressed appetite, increased thirst Regular (on left) and Blackhead-infected (right)An ill turkey showing classic signs of sickness: lethargy (as seen by the closed eyes), turkey droppings. The tell-tale sulfur colored droppingslack of inquisitiveness, retracted neck, and drooping wings. Photo by indicative of a Blackhead infection are clear.Terrell Spencer, NCAT. Photo by Terrell Spencer, NCAT.Page 4 ATTRA Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys
  5. 5. On farm dissection showing characteristic liver necrosis due to Enlarged cecum filled with yellowish necrotic tissue in a BlackheadBlackhead. Photo by Terrell Spencer, NCAT. infected turkey. Photo by Terrell Spencer, NCAT. • Decreased/lack of f light distance in chickens often are undiagnosed, though (distance the turkey keeps between in chickens the impact of Blackhead has itself and humans) been described as being at least as severe as • Decreased/lack of inquisitiveness coccidiosis, and in some broiler breeder flocks, mortality may reach as high as 10% (McDou-Blackhead infections vary in the time required gald, 2005). Bobwhite quail farmers have alsoto manifest signs, depending on the path- occasionally experienced outbreaks of Black-way and initial amount of infection. Signs head disease, especially when these growersof infection begin to appear seven to 14 days utilize old chicken houses.after exposure. In turkeys, the yellow-col-ored fecal matter is the definitive symptom ofBlackhead disease. From personal experience, Prevention and Managementwhen behavioral symptoms become apparent, of Blackhead Diseasemortality usually occurs in one to three days. Prevention is the key to successful BlackheadPositive diagnosis of dead birds can be easily management. Due to the previously mentionedobtained through a post-mortem dissection banning of the antihistomonal medicines used(necropsy) by the farmer. The abdominal cavity to treat outbreaks, there are no established treat-can be opened and the cecum examined. The ments for turkeys once they are infected andchest/breast can then be split down the middle symptomatic. It is imperative that any trulyusing heavy duty shears or tin snips to reveal sustainable turkey operation have a Blackheadthe liver. Once the ceca and liver are exposed, prevention plan.the organs can be inspected for necrosis asdescribed above. Preventative andDespite the descriptive name of the disease,Blackhead rarely, if ever, causes the head of Post-Infection Measuresthe infected bird to darken or turn black, so The most economical and sustainable method ofthe common name is somewhat of a misnomer Blackhead management is complete avoidance(Davidson and Doster, 2010). of the disease through preventive treatments.Turkeys demonstrate the most severe symp- • Separation of poultry flocks by speciestoms of any poultry from H. meleagridis infec- and age – separation of susceptibletion and, consequently, the highest mortal- (turkeys and peafowl) and resistantity rates. Indeed, expectations of 80-100% (chickens, pheasants, quail, etc.) poultrymortality are plausible in turkey Blackhead species has been the principal means ofoutbreaks. Chickens are usually able to stop Histomoniasis prevention since thethe disease before destruction of the ceca and cecal worm role in disease transmissiondegradation of the liver take place. Infections was identified in the 1930s. ATTRA Page 5
  6. 6. should also include ground that has been Whites, heritage turkeys can be selected used for different poultry species. Land for resistance to Blackhead. If a Black- that has been used to house/pasture head outbreak occurs in a heritage chickens or gamebirds should not be flock, the surviving individuals may used for turkeys or peafowl production. have some trait, either genetic or behav- • Fallowing of contaminated ground or ioral, that increases their chance of sur- houses – Cecal worm eggs are viable up viving or avoiding a Blackhead infec- to three years in the soil and litter, and tion. These birds could be saved and research has shown that H. meleagridis bred to obtain next season’s poults, and harbored inside of the eggs remains at least some resistance to Blackhead infectious even after 150 weeks. There- could be bred into a producer’s flock. fore, three years should be the mini- • Preventative feed additives: mum time considered for fallowing. – Histostat™ (active ingredient is Nitar- • Selecting for resistance – while this strategy sone) is an effective preventative feed is not plausible for Broadbreasted additive and can be premixed into feed. It is a non-organic additive that contains arsenic and is the only drug Breeding Resistance approved for the prevention of Black- into the Flock head. At the time of this writing, Blue Nature’s Harmony Farm Seal Feeds™, located in the Northeastern Located in Elberton, Georgia, and Mid-Atlantic regions of the United Nature’s Harmony Farm is a 126- States, sells a pre-mixed medicated acre diversified meat and dairy turkey feed containing Histostat. farm built by Tim and Liz Young. Raising pasture-based pork, poul- Other than within the Blue Seal prod- try, cattle, sheep, and rabbit, as uct, the use of Histostat is difficult at well as running a grass-fed dairy, best for a small producer. The drug is the Youngs have taken a holistic only sold in 55-pound bags – enough approach towards the manage- Histostat to mix more than 65 tons of ment of their farm. Tim and Liz again.’ We said no, we’re going to feed. Additionally, the drug can only examine all of their endeavors build resistance to Blackhead, and be purchased by registered feed mills, with an eye towards long-term all the other diseases. We raise tur- and Histostat must be mixed into the biological sustainability. One criti- keys with our chickens, we don’t ration as the feed is milled. Finally, at cal objective of Nature’s Harmony worry about any of these things, approximately $15/pound, Histostat Farm’s holistic planning is breeding and we just let nature sort it out.” is a costly drug to buy in bulk. Histo- disease resistance into their live- stock, including Blackhead resis- Liz adds, “We find the strongest stat cannot be fed to actively produc- tance in turkeys. birds, those are the ones we breed ing layers and has a short withdrawal and their offspring have proven to period (5 days) to allow the arsenic “Now that we’re breeding our own be so much hardier than all the ingested by the bird to be flushed animals on the farm”, says Tim, other animals on the farm. It will from the system. In addition, Histostat “we worry a lot less about disease take a number of years to get where is toxic to dogs, ruminants, and water- mortality problems. We had such we want to be, but the results so far huge issues with pastured poul- fowl. The toxicity to other species is an give us a lot of hope.” try two years ago with Blackhead, additional burden to mills that must sinusitis, mycoplasm, etc., which “This was a huge, calculated risk thoroughly clean their feed machinery we either don’t see any more or we took as new farmers a couple of before mixing non-poultry feeds. see drastically less of. Our birds years ago,” Tim acknowledges, “but look so healthy now, but just a we were so convicted in our values – Natustat™ is a plant-based additive few years ago, we had depressing that we felt it was the right thing to manufactured by Alltech, Inc. that, mortality rates among birds that do, even though it was counter to just like Histostat, is mixed into the were shipped in from commer- all the advice. We’re really happy ration when the feed is milled. Natu- cial hatcheries. We’d have experts with the decisions we made back stat promotes poultry well-being come out, and they’d say ‘Just burn then, and with the health of the and discourages Blackhead by act- your entire flock and start all over birds we have today.” ing as an immune system booster that stimulates good health. ThePage 6 ATTRA Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys
  7. 7. company’s research trials have shown • Good biosecurity techniques – infected that it is comparable to Histostat in cecal worm eggs can be transported the prevention of Blackhead when on the bottom of boots/equipment birds are exposed to infected litter, into brooders, clean pastures, land, but it is not effective in preventing and poultry houses. On small farms, Blackhead when poultry are exposed where multiple poultry species are often to the parasite directly (as through kept, pay particular care when incor- cloacal drinking). porating new stock from off the farm into the existing operation. When pos- Natustat is available to small growers sible, chores and farm activity should directly in 55-pound bags. During the be planned around dealing with sus- summer of 2010, the price per bag was $175, enough to treat 25 tons of feed. ceptible poultry first and dealing with Natustat doesn’t have the legal purchas- resistant species later when Blackhead is ing restrictions that make Histostat so suspected or a concern. The American difficult for small producers to access. Livestock Breed Conservancy (ALBC) There is no withdrawal time, and there has excellent resources for addressing a is no secondary toxicity threat to other farm’s biosecurity needs. The resources animal species. can be viewed on their website at Feed additives are effective only if biosecurity.html. administered before a Blackhead infec- • Encouragement of roosting behavior – tion occurs. Once signs of infection are getting poultry off of the ground and present (yellow fecal matter, behavioral onto roosts reduces the chance of cloa- signs), preventative drugs are no longer cal contact with infected fecal matter. effective. There are no legal drugs or Turkeys and other poultry will huddle substances to treat Histomoniasis once together and sleep on the ground in the infection has occurred. absence of a suitable roost. The direct – Dimetridazole was a low-cost, highly contact from huddling greatly increases effective drug that was once used to the chance of Blackhead transmission cure infected turkey flocks and regen- as the birds defecate through the night. erate liver damage. The drug was Heritage breeds of turkeys will roost banned in 1988 in the US and the instinctively. Broadbreasted Whites late 1990s in Europe and Bronzes have difficulty flying onto – Capsicum from hot peppers (i.e., Cay- roosts due to their size, but can be enne) has anecdotal success as a natural coaxed into roosting by providing a lad- treatment for Blackhead disease. How- der or some type of plane. ever, the effectiveness of treating Black- head with Capsicum has not been veri- Management During Infections fied through documented research. • Frequent movement to fresh ground – once a flock has been infected with • Promotion of good health and robust Blackhead, frequently moving the flock immune systems – generally, a stressed to fresh pasture minimizes the amount animal is more susceptible to any dis- of manure and exposure time that the ease, so reducing the stresses (by pro- birds are subject to the pathogens shed viding adequate shelter, balanced feed, proper stocking densities, clean water in the infective manure. access) in turkeys and other poultry can • Isolation of sick birds – isolation of help develop robust immune systems less sick birds removes the source of direct susceptible to Blackhead. As mentioned transmission from the flock. Identifica- before, running out of feed can allow tion of sick birds before behavioral signs establishment of H. meleagridis through develop can occur by spotting the birds oral ingestion, so care must be taken to that expel the yellow manure characteristic assure that feeders are never empty. to the ATTRA Page 7
  8. 8. • Reduction in stocking rate – reducing the • Preventative feed additives – once Black- amount of birds in a given unit of area head has appeared in the flock, it is of (acre, paddock, etc.) has an effect similar critical importance to prevent the rest to moving the turkeys to fresh ground. of the flock from becoming infected. Feed preventatives can be a powerful • Encourage natural sterilization – ultra- tool against contraction or the spread of violet light from sunshine, the drying Blackhead in poultry flocks. action of wind, the heat of summer, and the chill of winter are all detri- mental to the survival of H. meleagri- Conclusion dis. Any natural weathering process Blackhead is a serious disease in poultry that that breaks down poultry manure— has affected poultry farmers in the United States and therefore the hospitable niche of for well over a century. Turkeys and peafowl are the Blackhead pathogen—should be highly susceptible to death from the disease. encouraged. H. meleagridis requires Chickens are excellent carriers of Blackhead, and moisture to survive and spread, and care must be taken to keep chickens and turkeys moving the flock to dry ground makes separate. There is no treatment for Blackhead, the spread of Blackhead more difficult. and so the best strategy is prevention. Heterakis gallinarum, Histomonas meleagridis, andReferences Parahistomonas wenrichi. Journal of Parasitology.Davidson, W.R. and G.L. Doster. 2010 (viewed). Blackhead Volume 58, p. 940-945.Does Not Cause Blackhead. National Wild Turkey Federation. McDougald, L.R. 2005. Blackhead Disease (Histomoniasis)Bulletin 25. in Poultry: A Critical Review. Avian Diseases. Vol. 49, p.Hu, J., L. Fuller and L.R. McDougald. 2004. Infection of 462–476.Turkeys with Histomonas meleagridis by the Cloacal Drop McDougald, L.R. and L. Fuller. 2005. Blackhead DiseaseMethod. Avian Diseases. Vol. 48, p. 746-750. in Turkeys: Direct Transmission of Histomonas meleagridisLund, E.E. and A.M. Chute. 1972. Reciprocal Responses from Bird to Bird in a Laboratory Model. Avian Diseases.of Eight Species of Galliform Birds and Three Parasites: Vol. 49, p. 328–331. Parasite Management for Natural and Organic Poultry: Blackhead in Turkeys By Terrell Spencer NCAT Agriculture Specialist © 2010 NCAT Tracy Mumma, Editor Amy Smith, Production This publication is available on the Web at: or IP372 Slot 370 Version 102510Page 8 ATTRA