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Abortion in animals

This document discusses causes of abortion in large animals. It describes infectious causes such as bacterial (e.g. Brucella abortus, Campylobacter fetus, Listeria monocytogenes), fungal (e.g. Aspergillus sp.), and protozoal (e.g. Neospora caninum, Tritrichomonas foetus) agents. It also discusses non-infectious causes including genetic factors, nutritional deficiencies, heat stress, and various toxins. The document provides details on abortion rates, timing, lesion presentation, and samples needed for diagnosis for many of the common infectious causes. It emphasizes the importance of rapid and proper sample collection and handling for determining the etiology of abortion

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Abortion in Large Animals Dr. Karima Al salihi
Definition Abortion is the termination of pregnancy after organogenesis is complete but before the expelled fetus can survive. If pregnancy ends before organogenesis, it is called early embryonic death. A dead, full-term fetus is a stillbirth (its lungs are not inflated). Many etiologies of abortion also cause stillbirths, mummification, and weak or deformed neonates.
The etiologic diagnosis of abortion in livestock is a difficult and often frustrating task. • Numerous factors complicate diagnosis. • Often, abortion follows initial infection by weeks or months, so the causative agent is no longer apparent when abortion occurs. • Expulsion may follow fetal death by hours or days, with lesions obscured by autolysis. • Fetal membranes and the aborted fetus are usually contaminated by environmental agents before examination. • Many sporadic abortions are likely the result of noninfectious (ie, toxic or genetic) causes, about which much less is known than infectious causes; many diagnostic laboratories are not equipped or staffed to deal with these causes of abortion.
Abortion's samples  • Another problem in determining the cause of abortions is improper or inadequate specimen selection and handling. • The best specimen is the complete feto-placental unit in fresh condition, along with maternal serum. • The placenta and fetus should be cleaned with water or saline, packed in clean plastic bags, chilled (but not frozen), and rapidly transported to the diagnostic laboratory. • In most cases, autolysis proceeds at a much slower rate in fetuses than in carcasses of animals born alive. • If chilled as soon as possible, most fetuses will be suitable for examination, even if they do not reach the laboratory for 1–2 days. • Fetal pigs, sheep, and goats are usually small enough to transport or ship whole with the placenta. • If there are multiple fetuses, three to five should be submitted with their placentas. • It is best to submit calves and foals whole, but in many cases it is more convenient to perform a necropsy and collect samples for submission.
• The specimens routinely used for testing includes stomach or abomasal contents; heart blood or fluid from a body cavity; unfixed lung, liver, kidney, and spleen (some laboratories also request tissues such as thyroid glands, thymus, heart, brain, abomasum, and stomach); placenta (if available); and dam’s serum. • These should be submitted in sterile containers to allow for microbiologic cultures. • Because they are always contaminated, placentas should not be mixed with other tissues. • Representative samples of the following should also be submitted in 10% buffered formalin for histopathologic examination: lung, liver, heart, kidney, spleen, brain, skeletal muscle, thyroid, adrenal glands, intestines, and placenta • In a large majority of cases, gross lesions other than signs of autolysis (increased pleural and peritoneal fluid and blood-tinged subcutaneous edema) are not present. • However, if lesions are found, fresh and formalin-fixed samples of affected tissues should be included.
• Most agents, especially bacteria and fungi, infect the placenta and thus gain entry into the amniotic fluid, which is swallowed by the fetus. • Stomach contents can be obtained aseptically, making it the best specimen for detection of fungi and most bacteria. • Isolation from the stomach contents is much easier than from the placenta, which is always heavily contaminated. • Lungs, liver, spleen, and kidneys are also good for culture. • Several agents (eg, fungi, Chlamydia, Coxiella) primarily affect the placenta; failure to include placenta decreases the probability they will be identified. • Fetuses sometimes produce antibodies to certain agents (eg, bovine viral diarrhea virus, Neospora spp, Leptospira spp), and fetal serum or fluid from a body cavity can be tested for antibodies. • The presence of precolostral antibodies is evidence of in utero exposure.
•A single antibody titer in the dam rarely provides evidence of abortion caused by a particular agent unless background herd titer levels are known. •High maternal titers may as likely be the reason an animal did not abort due to that agent, but absence of a titer can be used to exclude an agent. •Antibody titers to agents with control programs (eg, Brucella abortus, pseudorabies virus) are always significant, even if the abortion was caused by something else. •Demonstration of a 4-fold increase in antibody titer is required to prove active infection by a specific agent. • Often, abortion occurs weeks or months after initial infection of the dam, and her titer is stable or declining at the time of abortion. •Paired serum samples obtained 2 weeks apart from 10% of the herd or a minimum of 10 animals often demonstrate seroconversion and provide evidence of active infection in the herd.
Causes of abortion Noninfectious Causes Infectious causes
Non infectious causes • The actual incidence of abortions in cows due to genetic factors is unknown. Some genetically caused abortions may not have phenotypically recognizable lesions. Most lethal genes cause early abortion or early embryonic death. • Vitamins A and E, selenium, and iron have been implicated in bovine abortions, but documentation based on experiments is available only for vitamin A. • Heat stress causes fetal hypotension, hypoxia, and acidosis. High maternal temperature due to pyrexia may be more important than environmentally induced heat stress. • Although severe trauma may rarely result in abortion (the bovine fetus is well protected by the amniotic fluid), farmers undoubtedly blame too many abortions on the cow “getting bumped.”
•A number of toxins can cause abortion in cows. Ponderosa pine needles can cause abortion if ingested in the last trimester; the cows may become moribund after delivery and hemorrhage excessively. •Broomweed (Guttierrezia microcephala) ingestion can also cause abortion, as can coumarins from rat poison, many grasses, or moldy sweet clover. •Sodium iodide, IV, has been contraindicated in pregnant cows, but no abortions or adverse effects occurred in pregnant cows treated with a single high dose in some studies. • Mycotoxins, especially those with estrogenic activity, have been implicated in bovine abortions. •Nitrates or nitrites have also been incriminated, but experimental evidence is controversial.
Infectious cause 1. Bacterial causes Infectious factor
 Common names Abortion rate Abortion timing Recurrence of abortion Foetal lesions Samples Brucella abortus Brucellosis Bang’s disease Zoonosis Up to 80% of unvaccinated animals infected in 1st or 2nd    trimester 6-9 months Abortion or stillbirth 2 wk to 5 mo after infection Majority abort only once Placenta: retained, cotyledons necrotic, red-yellow,; area between thickened Calf: normal or autolytic with bronchopneumonia placenta, foetus, or uterine discharge Diagnosis: maternal serology, IFAT for Abs in placenta, bacteria isolation Campylobacter fetus venerealis Vibriosis >10% 5-8 months Uncommon, convalescent cows resistant to infection Placenta: mild placentitis, hemorrhagic cotyledons and an edematous intercotyledonary area. Foetus: fresh or autolysed; mild fibrinous pleuritis, peritonitis, bronchopneumonia. Placenta, foetal abomasal contents, vaginal flushing Diagnosis: microscopic detection, isolation C fetus fetus C jejuni Sporadic 4-9 months Uncommon, convalescent cows resistant to infection See above See above
Leptospira interrogans, serovarsgrippotyphos a, pomona, hardjo, ca nicola, icterohaemorr hagiae Zoonosis 5-40% Last trimester Abortion 2-5 weeks after infection Immunity to the serotype causing abortion but sensitive to other types Placenta: diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areasFoetus: autolysed Placenta, foetus Diagnosis: IFAT foe Abs or PCR testing forLeptospira Arcanobacterium (Actinomyces) pyogenes Sporadic Any stage Not known Placenta: endometritis and diffuse placentitis, reddish brown to brown colour. Foetus: autolysed, fibrinous pericarditis, pleuritis, or peritonitis Placenta, foetus Identification in bacterial culture from placenta or abomasal contents Listeria monocytogenes Zoonosis Usually sporadic but can reach 50% Last trimester May recur Dam: fever, inappetance Placenta: retained Foetus: autolysed Fibrinous polyserositis and white necrotic foci in the liver and/or cotyledons Placenta, foetus Identification in bacterial culture from placenta or abomasal contents
Aspergillus sp (60-80% Mucor sp, Absidia , orRhizopus sp Usually sporadic but can reach 5-10% 4 months to term most common in winter May recur Placenta: severe, necrotising placentitis Cotyledons enlarged, necrotic, intercotyledona ry area is thickened and leathery. Foetus: autolysed~30% have gray ringworm-like skin lesions principally involving the head and shoulders Foetus, placenta Diagnosis: isolation from the stomach contents, placenta, and skin lesions. Fungal causes
Protozoan Tritrichomonas (Trichomonas) foetus Trichomoniasis Sporadic first half of gestation Animal gains immunity but probably not life- long Placenta: retained, mild placentitis with hemorrhagic cotyledons and thickened intercotyledonary areas covered with flocculent exudates Foetus: no specific lesions Placenta, foetus, vaginal/uterine discharge Diagnosis: detection in abomasal contents, placental fluids, and uterine discharges Neospora caninum Neosporosis High in first gestation and when infection enters the naïve herd Up to 30% first outbreak Enzootic: 5-10% Any stage, but most often 5-6 months Decreases with parity but always possible Placenta, foetus: no specific gross lesions, autolysed Microscopic: focal encephalitis with necrosis and nonsuppurative inflammation, hepatitis in Placenta, foetus (brain, heart, liver, body fluids), serum samples from the dam Diagnosis: detection of antigen in brain histology samples Immunochemistry in tissue samples Abs - PCR, ELISA
Viral causes ovine Viral Diarrhoea Virus BVD-MD Usually low Complex pathology Abortion usually up to 4 months Uncommon, immunity develops Placenta: retained, no specific lesions Foetus: no specific lesions, autolysed, mummified Placenta, foetus (preferred - spleen), dam and herdmates serum Diagnosis: isolation, immunologic staining, PCR, or detection of precolostral antibodies in aborted calves Bovine Herpesvirus type I (BHV I) Infectious Bovine rhinotracheitis virus (IBRV) IBR IBR-IPV 5-60% in non vaccinated herds Possibly any stage but most common from 4 months to term Uncommon, immunity develops In the majority of cases there are no gross lesions in the placenta or foetus Placenta: necrotizing vasculitis Foetus: autolysed, foci of necrosis in the liver Placenta, foetus, serum samples from the dam Diagnosis: Immunochemistry in samples from kidney and adrenal glands, blood serology, PCR Blue tongue virus Blue tongue Usually low Variable Unlikely No specific Foetus: autolysed Placenta, foetus, serum samples from the dam Diagnosis: virus isolation Epizootic Bovine Abortion Foothill Abortion etiologic agent has not been definitively determined, vector – tickOrnithodoros coriaceus Can reach 75% Limited mainly to California in the US Usually in the last trimester Unlikely Placenta: No specific Foetus: hepatomegaly, splenomegaly, and generalized lymphomegaly. Microscopically - marked lymphoid hyperplasia in the spleen and lymph nodes and granulomatous inflammation in most organs. Anamnesis Diagnosis: elevated foetal Ig-G
Factors not typical for cattle or rarely occurring Chlamydophila abortus (Chlamydia psittaciserotype 1) enzootic abortion of ewes Zoonosis Sporadic Near the end of the last trimester Unlikely Placenta: placentitis, thickening and yellow- brown exudate adhered to the cotyledons and intercotyledonary areas. Foetus: fresh, minimal autolysis, pneumonia,  hepatitis Placenta, foetus Diagnosis: identification in stained smears of the placenta or by ELISA, fluorescent antibody staining, PCR, or isolation in embryonated chicken eggs or cell culture. Ureaplasma diversum Usually sporadic, but outbreaks possible Third trimester Possible Placenta: retained, intercotyledonary areas thickened, nonsuppurative placentitis Foetus: no gross lesions, pneumonia Placenta, foetus Diagnosis: isolation from the placenta, lungs, and/or abomasal contents Salmonella spp Usually sporadic but can take form of an abortion storm Any stage Possible Cows: clinically ill Placenta and foetus: autolysed and emphysematous. Placenta, foetus Diagnosis: isolation from the abomasal contents other tissues. Other infectious factors that potentially can cause abortion in cattle: Parainfluenza 3 Virus (PI3V), Mycoplasma spp ,  Histophilus somni (Haemophilus somnus), Staphylococcus spp, Streptococcus spp, Pasteurella spp, E.coli,
Infectious cause 1. Neosporosis: • Neospora caninum is found worldwide and is the most common cause of abortion in dairy and beef cattle . • Dogs and coyotes are definitive hosts for N caninum and can be the source of infection. Abortion can occur any time after 3 mo of gestation but is most common between 4 and 6 mo of gestation.  • Neospora can be associated with sporadic abortions or abortion storms, and repeat abortions in cows have been reported. Most infections result in an asymptomatic congenitally infected calf. • Some infected calves are born with paralysis or proprioceptive deficits. Cows are not clinically ill, and placental retention is not common. • The fetus is usually autolyzed or, in a few cases, mummified and rarely has gross lesions. Microscopically, nonsuppurative inflammation is common in the brain, heart, and skeletal muscles. • Organisms can be identified in these tissues and the kidneys by immunohistochemical staining and PCR. • Many late gestation fetuses have precolostral antibodies. • They remain infected for years and possibly for life. • Vertical transmission is common. • During pregnancy, Neospora organisms can become activated and infect the fetus. This is thought to be the most common source of infection. There is no treatment. Strict hygiene to prevent fecal contamination of feed by dogs or coyotes may aid in prevention. A  commercial vaccine is available.
Bovine Viral Diarrhea (BVD): • In several surveys, BVD was the most commonly diagnosed virus in bovine abortion cases. • The pathology of BVD in the developing fetus is complex. Infection before insemination or during the first 40 days of pregnancy results in infertility or embryonic death. • Infection between 40 and 125 days of pregnancy results in birth of persistently infected calves if the fetus survives. • Fetal infection during the period of organogenesis (100– 150 days) may result in congenital malformations of the CNS (cerebellar hypoplasia, hydrancephaly, hydrocephalus, microencephaly, and spinal cord hypoplasia). • Congenital ocular defects have also been seen (cataracts, optic neuritis, retinal degeneration, microphthalmia).
•After 125 days of gestation, BVD may cause abortion, or the fetal immune response may clear the virus. •Diagnosis is by identification of BVD virus by isolation, immunologic staining, PCR, or detection of precolostral antibodies in aborted calves. •The virus is present in a wide variety of tissues, but the spleen is the tissue of choice. Rising antibody titers to BVD in aborting animals or herdmates is diagnostic of recent infection. •BVD virus is immunosuppressive and is found in many fetuses infected by other agents (eg, bacteria, N caninum). •Outbreaks of abortions by organisms that normally cause sporadic abortion should raise suspicion of possible concurrent BVD virus infection. Prevention should focus on removal of persistently infected cattle and herd vaccination.
Infectious Bovine Rhinotracheitis (IBR, Bovine Herpesvirus 1): • Infectious bovine rhinotracheitis (IBR) is a major cause of viral abortion in the world, with abortion rates of 5%–60% in nonvaccinated herds. • The virus is widespread, causes latent infections, and can recrudesce; therefore, any cow with a positive IBR titer is a possible carrier. • The virus is carried to the placenta in WBCs; over the next 2 wk to 4 mo, it causes a placentitis, then infects the fetus and kills it in 24 hr. Abortion can occur any time but usually is from 4 mo to term. • Autolysis is consistently present. Occasionally, there are small foci of necrosis in the liver, but in a large majority of cases there are no gross lesions in the placenta or fetus. • Microscopically, small foci of necrosis with minimal inflammation are consistently present in the liver. • Necrotizing vasculitis is common in the placenta. Diagnosis can be made by immunologic staining of the kidney, lung, liver, placenta, and adrenal glands. IBR virus can be isolated from ~50% of infected fetuses (most successfully from the placenta). • In most cases, maternal titers have peaked by the time of abortion. In abortion storms, rising titers can often be demonstrated in herdmates. Control is by herd vaccination; intranasal, modified-live virus, and killed vaccines are available.
Leptospirosis • The pathogenic leptospires were formerly classified as serovars of Leptospira interrogans, but they have been reclassified into 7 species with >200 recognized serovars. Leptospira serovars Grippotyphosa, Pomona, Canicola, and Icterohaemorrhagiae usually cause abortions in the last trimester, 2–6 wk after maternal infection. • Serovar Hardjo is host adapted to cattle and can establish lifelong infections in the kidneys and reproductive tracts. • In addition to third trimester abortions, serovar Hardjo reduces conception rates in carrier cows and cows bred to carrier bulls. • Although dams may show clinical signs of leptospirosis, most abortions are in otherwise healthy cattle. • Abortion rates vary from 5%–40% or more. The leptospires cause a diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areas. • The fetus usually dies 1–2 days before expulsion and therefore is autolyzed. Occasionally, calves are born alive but weak. Fetuses infected with serovar Pomona may show icterus. • There are no specific lesions, but placenta and fetus should be submitted to the laboratory for fluorescent antibody staining or PCR testing for Leptospira. Although maternal titers are probably waning by the time of abortion, an initial titer of >1:800 may be suspicious. • Approximately one-third of cows aborting because of serovar Hardjo have titers of <1:100 at the time of abortion. • Cows infected with serovar Hardjo can shed the organism in urine throughout life. For other serovars, the dam’s urine can be cultured or examined for leptospires within 2 wk of abortion.
• For control, sources of infection (such as feed or water contaminated by dogs, rats, or wildlife) should be identified and eliminated. • Vaccination with a five-way bacterin every 6 mo provides good protection against serovars Grippotyphosa, Pomona, Canicola, and Icterohaemorrhagiae but does not protect against infection and renal shedding by serovar Hardjo. • New monovalent serovar Hardjo vaccines that prevent infection, but do not cure existing infections, are available. • The following treatments have been found to eliminate the renal carrier state: a single injection of oxytetracycline (20 mg/kg, IM), a single injection of tilmicosin (10 mg/kg, SC), ceftiofur (5 mg/kg/day, IM, for 5 days or 20 mg/kg/day, IM, for 3 days), or amoxicillin (15 mg/kg, IM, two injections 48 hr apart). • Leptospirosis is zoonotic, and urine and milk of dams may be infective for up to 3 mo, except for Hardjo, in which case cows can be infective for life if not treated.
Brucellosis: • Brucellosis (Bang’s disease) is a threat in most countries where cattle are raised. In the USA, active control programs, including test, slaughter, and heifer vaccination, have greatly decreased its incidence. • Brucellosis causes abortions in the second half of gestation (usually ~7 mo), and ~80% of unvaccinated cows in later gestation will abort if exposed to Brucella abortus. • The organisms enter via mucous membranes and invade the udder, lymph nodes, and uterus, causing a placentitis, which may be acute or chronic. • Abortion or stillbirth occurs 2 wk to 5 mo after initial infection. Affected cotyledons may be normal to necrotic, and red or yellow. The intercotyledonary area is focally thickened with a wet, leathery appearance. • The fetus may be normal or autolytic with bronchopneumonia. Diagnosis can be made by maternal serology combined with fluorescent antibody staining of placenta and fetus or isolation of B abortus from placenta, fetus (abomasal contents and lung), or uterine discharge. Prevention is by calfhood vaccination of heifers. • Brucellosis is a serious zoonosis and a reportable disease, and the appropriate authorities should be contacted.
Mycotic Abortion: • Fungal placentitis due to Aspergillus sp (septated fungi, 60%–80% of cases), or to Mucor sp, Absidia, Rhizopus sp, and a few other nonseptated fungi, is an important cause of bovine sporadic abortion. • Abortions occur from 4 mo to term and are most common in winter. It is believed the fungi gain entry through the oral or respiratory tracts and travel hematogenously to the placenta. • Placentitis is severe and necrotizing. Cotyledons are enlarged and necrotic with turned-in margins. The intercotyledonary area is thickened and leathery. • Adventitious placentation is common. The fetus seldom is autolyzed, although it may be dehydrated; ~30% have gray ringworm-like skin lesions principally involving the head and shoulders. • The diagnosis is based on the presence of fungal hyphae associated with necrotizing placentitis, dermatitis, or pneumonia. • Fungi can also be isolated from the stomach contents, placenta, and skin lesions. Isolation must be correlated with microscopic and gross lesions to exclude contamination after abortion. • For control, moldy feed should be avoided.
Trichomoniasis: • Tritrichomonas foetus infection causes a venereal disease that usually results in infertility but occasionally causes abortion in the first half of gestation. • Placentitis is relatively mild, with hemorrhagic cotyledons and thickened intercotyledonary areas covered with flocculent exudate. The placenta is often retained, and there may be pyometra. • The fetus has no specific lesions, although T foetus can be found in abomasal contents, placental fluids, and uterine discharges. Infected cows typically clear the organism within 20 wk, but bulls, especially those infected after 3 yr of age, can become lifelong carriers. • There is no legal, effective treatment for individual animals. Herd treatment is based on identifying and segregating pregnant females from “at-risk" females for ≥5 mo and by identifying and culling all infected bulls. • Prevention is by artificial insemination or natural insemination using noninfected bulls. A killed, whole-cell vaccine is available for use in cows.
Campylobacteriosis: • Campylobacter fetus venerealis causes venereal disease that usually results in infertility or early embryonic death but occasionally causes abortion between 4 and 8 mo of gestation. C fetus fetus and C jejuni are transmitted by ingestion and subsequent hematogenous spread to the placenta. • Both cause sporadic abortions, usually in the last half of gestation. The fetus can be fresh with partially expanded lungs or severely autolyzed. • Mild fibrinous pleuritis and peritonitis may be noted, as well as bronchopneumonia. Placentitis is mild with hemorrhagic cotyledons and an edematous intercotyledonary area.  • Campylobacter spp can be identified by darkfield examination of abomasal contents or culture of placenta or abomasal contents. Isolation and identification of the species involved is important if vaccination is to be instituted. • Venereal campylobacteriosis can be controlled by artificial insemination and vaccination.  • Campylobacter spp are zoonotic, and C jejuni is an important cause of enteritis in people.
Listeriosis: • Listeria monocytogenes can cause placentitis and fetal septicemia. Abortions are usually sporadic but may affect 10%–20% of a herd. • Abortion is at any stage of gestation, and the dam may have fever and anorexia before the abortion; retained placenta is common. • The fetus is retained for 2–3 days after death, so autolysis may be extensive. Fibrinous polyserositis and white necrotic foci in the liver and/or cotyledons are common. • Diagnosis is by culture of Listeria from fetus or placenta. There is no available bacterin. • Listeriosis is a reportable disease in many areas and is a serious zoonosis, with spread possible through improperly pasteurized milk.
Chlamydiosis: • Chlamydia abortus, the cause of enzootic abortion of ewes, causes sporadic abortion in cattle. • Most abortions occur near the end of the last trimester, but they can occur earlier. Placental lesions consist of thickening and yellow-brown exudate adhered to the cotyledons and intercotyledonary areas. • Histologically, placentitis is consistently present, and pneumonia and hepatitis can be found in some cases. C abortus can be identified by examination of stained smears of the placenta or by ELISA, fluorescent antibody staining, PCR, or isolation in embryonated chicken eggs or cell culture. • Organisms can often be identified in the lungs and liver but not as consistently as in the placenta. • There are no vaccines for cattle, although they are produced for sheep. • The bacterium is zoonotic, occasionally producing life-threatening disease and abortion in pregnant women.
Ureaplasma diversum Infection: • Ureaplasma diversum is a common inhabitant of the vagina and prepuce of cattle that also causes abortions. Abortions are usually single, but severe outbreaks occur on occasion. • The infection may also result in stillbirths and birth of weak calves. Most fetuses are aborted in the third trimester and are well preserved. The cows are not sick, but retained placentas are common. • Placentitis and a necrotic amniotic membrane are common features. The intercotyledonary areas are usually thickened and sometimes contain areas of fibrin deposition and hemorrhage. • There are no gross lesions in the fetus. Microscopically, there is nonsuppurative placentitis and pneumonia characterized by accumulations of lymphocytes around bronchi and by diffuse alveolitis. • Diagnosis is by isolation of U diversum from the placenta, lungs, and/or abomasal contents.
Blue tongue: • Bluetongue is caused by an Orbivirus with 24 serotypes and is transmitted by biting midges of the genus Culicoides. • Historically, blue tongue occurred from approximately latitude 35°S to 40°N, except in the western USA, where it occurs to 45°N. • After introduction of an attenuated, live virus serotype 10 vaccine in the 1950s, abortion, mummification, stillbirth, and the birth of live offspring with CNS malformations occurred in cattle and sheep. Since then, multiple blue tongue serotypes have been identified as causes of similar reproductive losses in cattle and sheep. • Attenuation of blue tongue virus can increase its ability to cross the placenta. • There is evidence that before 2007, reproductive losses were caused by attenuated blue tongue vaccine viruses, either by vaccination of pregnant animals or by spread of vaccine virus in nature by Culicoides spp. • In 2006, serotype 8 blue tongue virus appeared, spread, and became endemic across northwestern Europe (north of 50°N), where blue tongue was previously unknown. • Beginning in 2007, abortions and birth of “dummy” calves with brain malformations occurred in blue tongue-infected herds; affected calves were documented to have been infected in utero. Since then, many such cases have been reported. • Diagnosis is by identification of precolostral antibodies to blue tongue or identification of the virus by PCR. • Brain, spleen, and whole blood are the preferred samples from fetuses and neonates for PCR. Control of blue tongue is by vaccination and management procedures to reduce exposure to biting midges. • Modified-live and inactivated vaccines are available, but their availability and use varies between countries
Other Causes of Abortion: • Akabane virus (where present) causes abortion and fetal anomalies. • Parainfluenza-3 virus causes abortion in experimentally inoculated seronegative cattle, but is seldom, if ever, diagnosed in field cases of abortion. • Occasionally, Salmonella spp cause abortion storms. The cows are usually sick, and the fetuses and placentas are autolyzed and emphysematous. Salmonellae can be isolated from the abomasal contents and fetal tissues and from uterine fluids and the dams’ feces.  • Mycoplasma spp, Histophilus somni, and a wide variety of other bacteria can also cause sporadic abortions in cattle. • Schmallenberg virus, discovered in Europe in 2011, belongs to the Simbu serogroup and has been associated with infertility, abortion, and fetal malformation in several ruminant species.

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Abortion in animals

  • 1.
  • 2.
    Definition Abortion is thetermination of pregnancy after organogenesis is complete but before the expelled fetus can survive. If pregnancy ends before organogenesis, it is called early embryonic death. A dead, full-term fetus is a stillbirth (its lungs are not inflated). Many etiologies of abortion also cause stillbirths, mummification, and weak or deformed neonates.
  • 3.
    The etiologic diagnosisof abortion in livestock is a difficult and often frustrating task. • Numerous factors complicate diagnosis. • Often, abortion follows initial infection by weeks or months, so the causative agent is no longer apparent when abortion occurs. • Expulsion may follow fetal death by hours or days, with lesions obscured by autolysis. • Fetal membranes and the aborted fetus are usually contaminated by environmental agents before examination. • Many sporadic abortions are likely the result of noninfectious (ie, toxic or genetic) causes, about which much less is known than infectious causes; many diagnostic laboratories are not equipped or staffed to deal with these causes of abortion.
  • 4.
    Abortion's samples  • Anotherproblem in determining the cause of abortions is improper or inadequate specimen selection and handling. • The best specimen is the complete feto-placental unit in fresh condition, along with maternal serum. • The placenta and fetus should be cleaned with water or saline, packed in clean plastic bags, chilled (but not frozen), and rapidly transported to the diagnostic laboratory. • In most cases, autolysis proceeds at a much slower rate in fetuses than in carcasses of animals born alive. • If chilled as soon as possible, most fetuses will be suitable for examination, even if they do not reach the laboratory for 1–2 days. • Fetal pigs, sheep, and goats are usually small enough to transport or ship whole with the placenta. • If there are multiple fetuses, three to five should be submitted with their placentas. • It is best to submit calves and foals whole, but in many cases it is more convenient to perform a necropsy and collect samples for submission.
  • 5.
    • The specimensroutinely used for testing includes stomach or abomasal contents; heart blood or fluid from a body cavity; unfixed lung, liver, kidney, and spleen (some laboratories also request tissues such as thyroid glands, thymus, heart, brain, abomasum, and stomach); placenta (if available); and dam’s serum. • These should be submitted in sterile containers to allow for microbiologic cultures. • Because they are always contaminated, placentas should not be mixed with other tissues. • Representative samples of the following should also be submitted in 10% buffered formalin for histopathologic examination: lung, liver, heart, kidney, spleen, brain, skeletal muscle, thyroid, adrenal glands, intestines, and placenta • In a large majority of cases, gross lesions other than signs of autolysis (increased pleural and peritoneal fluid and blood-tinged subcutaneous edema) are not present. • However, if lesions are found, fresh and formalin-fixed samples of affected tissues should be included.
  • 6.
    • Most agents,especially bacteria and fungi, infect the placenta and thus gain entry into the amniotic fluid, which is swallowed by the fetus. • Stomach contents can be obtained aseptically, making it the best specimen for detection of fungi and most bacteria. • Isolation from the stomach contents is much easier than from the placenta, which is always heavily contaminated. • Lungs, liver, spleen, and kidneys are also good for culture. • Several agents (eg, fungi, Chlamydia, Coxiella) primarily affect the placenta; failure to include placenta decreases the probability they will be identified. • Fetuses sometimes produce antibodies to certain agents (eg, bovine viral diarrhea virus, Neospora spp, Leptospira spp), and fetal serum or fluid from a body cavity can be tested for antibodies. • The presence of precolostral antibodies is evidence of in utero exposure.
  • 7.
    •A single antibodytiter in the dam rarely provides evidence of abortion caused by a particular agent unless background herd titer levels are known. •High maternal titers may as likely be the reason an animal did not abort due to that agent, but absence of a titer can be used to exclude an agent. •Antibody titers to agents with control programs (eg, Brucella abortus, pseudorabies virus) are always significant, even if the abortion was caused by something else. •Demonstration of a 4-fold increase in antibody titer is required to prove active infection by a specific agent. • Often, abortion occurs weeks or months after initial infection of the dam, and her titer is stable or declining at the time of abortion. •Paired serum samples obtained 2 weeks apart from 10% of the herd or a minimum of 10 animals often demonstrate seroconversion and provide evidence of active infection in the herd.
  • 8.
    Causes of abortion NoninfectiousCauses Infectious causes
  • 9.
    Non infectious causes •The actual incidence of abortions in cows due to genetic factors is unknown. Some genetically caused abortions may not have phenotypically recognizable lesions. Most lethal genes cause early abortion or early embryonic death. • Vitamins A and E, selenium, and iron have been implicated in bovine abortions, but documentation based on experiments is available only for vitamin A. • Heat stress causes fetal hypotension, hypoxia, and acidosis. High maternal temperature due to pyrexia may be more important than environmentally induced heat stress. • Although severe trauma may rarely result in abortion (the bovine fetus is well protected by the amniotic fluid), farmers undoubtedly blame too many abortions on the cow “getting bumped.”
  • 10.
    •A number oftoxins can cause abortion in cows. Ponderosa pine needles can cause abortion if ingested in the last trimester; the cows may become moribund after delivery and hemorrhage excessively. •Broomweed (Guttierrezia microcephala) ingestion can also cause abortion, as can coumarins from rat poison, many grasses, or moldy sweet clover. •Sodium iodide, IV, has been contraindicated in pregnant cows, but no abortions or adverse effects occurred in pregnant cows treated with a single high dose in some studies. • Mycotoxins, especially those with estrogenic activity, have been implicated in bovine abortions. •Nitrates or nitrites have also been incriminated, but experimental evidence is controversial.
  • 11.
    Infectious cause 1. Bacterialcauses Infectious factor
 Common names Abortion rate Abortion timing Recurrence of abortion Foetal lesions Samples Brucella abortus Brucellosis Bang’s disease Zoonosis Up to 80% of unvaccinated animals infected in 1st or 2nd    trimester 6-9 months Abortion or stillbirth 2 wk to 5 mo after infection Majority abort only once Placenta: retained, cotyledons necrotic, red-yellow,; area between thickened Calf: normal or autolytic with bronchopneumonia placenta, foetus, or uterine discharge Diagnosis: maternal serology, IFAT for Abs in placenta, bacteria isolation Campylobacter fetus venerealis Vibriosis >10% 5-8 months Uncommon, convalescent cows resistant to infection Placenta: mild placentitis, hemorrhagic cotyledons and an edematous intercotyledonary area. Foetus: fresh or autolysed; mild fibrinous pleuritis, peritonitis, bronchopneumonia. Placenta, foetal abomasal contents, vaginal flushing Diagnosis: microscopic detection, isolation C fetus fetus C jejuni Sporadic 4-9 months Uncommon, convalescent cows resistant to infection See above See above
  • 12.
    Leptospira interrogans, serovarsgrippotyphos a, pomona, hardjo, ca nicola, icterohaemorr hagiae Zoonosis 5-40% Last trimester Abortion 2-5weeks after infection Immunity to the serotype causing abortion but sensitive to other types Placenta: diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areasFoetus: autolysed Placenta, foetus Diagnosis: IFAT foe Abs or PCR testing forLeptospira Arcanobacterium (Actinomyces) pyogenes Sporadic Any stage Not known Placenta: endometritis and diffuse placentitis, reddish brown to brown colour. Foetus: autolysed, fibrinous pericarditis, pleuritis, or peritonitis Placenta, foetus Identification in bacterial culture from placenta or abomasal contents Listeria monocytogenes Zoonosis Usually sporadic but can reach 50% Last trimester May recur Dam: fever, inappetance Placenta: retained Foetus: autolysed Fibrinous polyserositis and white necrotic foci in the liver and/or cotyledons Placenta, foetus Identification in bacterial culture from placenta or abomasal contents
  • 13.
    Aspergillus sp (60-80% Mucor sp, Absidia , orRhizopus sp Usually sporadic but can reach 5-10% 4months to term most common in winter May recur Placenta: severe, necrotising placentitis Cotyledons enlarged, necrotic, intercotyledona ry area is thickened and leathery. Foetus: autolysed~30% have gray ringworm-like skin lesions principally involving the head and shoulders Foetus, placenta Diagnosis: isolation from the stomach contents, placenta, and skin lesions. Fungal causes
  • 14.
    Protozoan Tritrichomonas (Trichomonas) foetus Trichomoniasis Sporadic first half of gestation Animalgains immunity but probably not life- long Placenta: retained, mild placentitis with hemorrhagic cotyledons and thickened intercotyledonary areas covered with flocculent exudates Foetus: no specific lesions Placenta, foetus, vaginal/uterine discharge Diagnosis: detection in abomasal contents, placental fluids, and uterine discharges Neospora caninum Neosporosis High in first gestation and when infection enters the naïve herd Up to 30% first outbreak Enzootic: 5-10% Any stage, but most often 5-6 months Decreases with parity but always possible Placenta, foetus: no specific gross lesions, autolysed Microscopic: focal encephalitis with necrosis and nonsuppurative inflammation, hepatitis in Placenta, foetus (brain, heart, liver, body fluids), serum samples from the dam Diagnosis: detection of antigen in brain histology samples Immunochemistry in tissue samples Abs - PCR, ELISA
  • 15.
    Viral causes ovine ViralDiarrhoea Virus BVD-MD Usually low Complex pathology Abortion usually up to 4 months Uncommon, immunity develops Placenta: retained, no specific lesions Foetus: no specific lesions, autolysed, mummified Placenta, foetus (preferred - spleen), dam and herdmates serum Diagnosis: isolation, immunologic staining, PCR, or detection of precolostral antibodies in aborted calves Bovine Herpesvirus type I (BHV I) Infectious Bovine rhinotracheitis virus (IBRV) IBR IBR-IPV 5-60% in non vaccinated herds Possibly any stage but most common from 4 months to term Uncommon, immunity develops In the majority of cases there are no gross lesions in the placenta or foetus Placenta: necrotizing vasculitis Foetus: autolysed, foci of necrosis in the liver Placenta, foetus, serum samples from the dam Diagnosis: Immunochemistry in samples from kidney and adrenal glands, blood serology, PCR Blue tongue virus Blue tongue Usually low Variable Unlikely No specific Foetus: autolysed Placenta, foetus, serum samples from the dam Diagnosis: virus isolation Epizootic Bovine Abortion Foothill Abortion etiologic agent has not been definitively determined, vector – tickOrnithodoros coriaceus Can reach 75% Limited mainly to California in the US Usually in the last trimester Unlikely Placenta: No specific Foetus: hepatomegaly, splenomegaly, and generalized lymphomegaly. Microscopically - marked lymphoid hyperplasia in the spleen and lymph nodes and granulomatous inflammation in most organs. Anamnesis Diagnosis: elevated foetal Ig-G
  • 16.
    Factors not typicalfor cattle or rarely occurring Chlamydophila abortus (Chlamydia psittaciserotype 1) enzootic abortion of ewes Zoonosis Sporadic Near the end of the last trimester Unlikely Placenta: placentitis, thickening and yellow- brown exudate adhered to the cotyledons and intercotyledonary areas. Foetus: fresh, minimal autolysis, pneumonia,  hepatitis Placenta, foetus Diagnosis: identification in stained smears of the placenta or by ELISA, fluorescent antibody staining, PCR, or isolation in embryonated chicken eggs or cell culture. Ureaplasma diversum Usually sporadic, but outbreaks possible Third trimester Possible Placenta: retained, intercotyledonary areas thickened, nonsuppurative placentitis Foetus: no gross lesions, pneumonia Placenta, foetus Diagnosis: isolation from the placenta, lungs, and/or abomasal contents Salmonella spp Usually sporadic but can take form of an abortion storm Any stage Possible Cows: clinically ill Placenta and foetus: autolysed and emphysematous. Placenta, foetus Diagnosis: isolation from the abomasal contents other tissues. Other infectious factors that potentially can cause abortion in cattle: Parainfluenza 3 Virus (PI3V), Mycoplasma spp ,  Histophilus somni (Haemophilus somnus), Staphylococcus spp, Streptococcus spp, Pasteurella spp, E.coli,
  • 17.
    Infectious cause 1. Neosporosis: •Neospora caninum is found worldwide and is the most common cause of abortion in dairy and beef cattle . • Dogs and coyotes are definitive hosts for N caninum and can be the source of infection. Abortion can occur any time after 3 mo of gestation but is most common between 4 and 6 mo of gestation.  • Neospora can be associated with sporadic abortions or abortion storms, and repeat abortions in cows have been reported. Most infections result in an asymptomatic congenitally infected calf. • Some infected calves are born with paralysis or proprioceptive deficits. Cows are not clinically ill, and placental retention is not common. • The fetus is usually autolyzed or, in a few cases, mummified and rarely has gross lesions. Microscopically, nonsuppurative inflammation is common in the brain, heart, and skeletal muscles. • Organisms can be identified in these tissues and the kidneys by immunohistochemical staining and PCR. • Many late gestation fetuses have precolostral antibodies. • They remain infected for years and possibly for life. • Vertical transmission is common. • During pregnancy, Neospora organisms can become activated and infect the fetus. This is thought to be the most common source of infection. There is no treatment. Strict hygiene to prevent fecal contamination of feed by dogs or coyotes may aid in prevention. A  commercial vaccine is available.
  • 18.
    Bovine Viral Diarrhea(BVD): • In several surveys, BVD was the most commonly diagnosed virus in bovine abortion cases. • The pathology of BVD in the developing fetus is complex. Infection before insemination or during the first 40 days of pregnancy results in infertility or embryonic death. • Infection between 40 and 125 days of pregnancy results in birth of persistently infected calves if the fetus survives. • Fetal infection during the period of organogenesis (100– 150 days) may result in congenital malformations of the CNS (cerebellar hypoplasia, hydrancephaly, hydrocephalus, microencephaly, and spinal cord hypoplasia). • Congenital ocular defects have also been seen (cataracts, optic neuritis, retinal degeneration, microphthalmia).
  • 19.
    •After 125 daysof gestation, BVD may cause abortion, or the fetal immune response may clear the virus. •Diagnosis is by identification of BVD virus by isolation, immunologic staining, PCR, or detection of precolostral antibodies in aborted calves. •The virus is present in a wide variety of tissues, but the spleen is the tissue of choice. Rising antibody titers to BVD in aborting animals or herdmates is diagnostic of recent infection. •BVD virus is immunosuppressive and is found in many fetuses infected by other agents (eg, bacteria, N caninum). •Outbreaks of abortions by organisms that normally cause sporadic abortion should raise suspicion of possible concurrent BVD virus infection. Prevention should focus on removal of persistently infected cattle and herd vaccination.
  • 20.
    Infectious Bovine Rhinotracheitis(IBR, Bovine Herpesvirus 1): • Infectious bovine rhinotracheitis (IBR) is a major cause of viral abortion in the world, with abortion rates of 5%–60% in nonvaccinated herds. • The virus is widespread, causes latent infections, and can recrudesce; therefore, any cow with a positive IBR titer is a possible carrier. • The virus is carried to the placenta in WBCs; over the next 2 wk to 4 mo, it causes a placentitis, then infects the fetus and kills it in 24 hr. Abortion can occur any time but usually is from 4 mo to term. • Autolysis is consistently present. Occasionally, there are small foci of necrosis in the liver, but in a large majority of cases there are no gross lesions in the placenta or fetus. • Microscopically, small foci of necrosis with minimal inflammation are consistently present in the liver. • Necrotizing vasculitis is common in the placenta. Diagnosis can be made by immunologic staining of the kidney, lung, liver, placenta, and adrenal glands. IBR virus can be isolated from ~50% of infected fetuses (most successfully from the placenta). • In most cases, maternal titers have peaked by the time of abortion. In abortion storms, rising titers can often be demonstrated in herdmates. Control is by herd vaccination; intranasal, modified-live virus, and killed vaccines are available.
  • 21.
    Leptospirosis • The pathogenicleptospires were formerly classified as serovars of Leptospira interrogans, but they have been reclassified into 7 species with >200 recognized serovars. Leptospira serovars Grippotyphosa, Pomona, Canicola, and Icterohaemorrhagiae usually cause abortions in the last trimester, 2–6 wk after maternal infection. • Serovar Hardjo is host adapted to cattle and can establish lifelong infections in the kidneys and reproductive tracts. • In addition to third trimester abortions, serovar Hardjo reduces conception rates in carrier cows and cows bred to carrier bulls. • Although dams may show clinical signs of leptospirosis, most abortions are in otherwise healthy cattle. • Abortion rates vary from 5%–40% or more. The leptospires cause a diffuse placentitis with avascular, light tan cotyledons and edematous, yellowish intercotyledonary areas. • The fetus usually dies 1–2 days before expulsion and therefore is autolyzed. Occasionally, calves are born alive but weak. Fetuses infected with serovar Pomona may show icterus. • There are no specific lesions, but placenta and fetus should be submitted to the laboratory for fluorescent antibody staining or PCR testing for Leptospira. Although maternal titers are probably waning by the time of abortion, an initial titer of >1:800 may be suspicious. • Approximately one-third of cows aborting because of serovar Hardjo have titers of <1:100 at the time of abortion. • Cows infected with serovar Hardjo can shed the organism in urine throughout life. For other serovars, the dam’s urine can be cultured or examined for leptospires within 2 wk of abortion.
  • 22.
    • For control,sources of infection (such as feed or water contaminated by dogs, rats, or wildlife) should be identified and eliminated. • Vaccination with a five-way bacterin every 6 mo provides good protection against serovars Grippotyphosa, Pomona, Canicola, and Icterohaemorrhagiae but does not protect against infection and renal shedding by serovar Hardjo. • New monovalent serovar Hardjo vaccines that prevent infection, but do not cure existing infections, are available. • The following treatments have been found to eliminate the renal carrier state: a single injection of oxytetracycline (20 mg/kg, IM), a single injection of tilmicosin (10 mg/kg, SC), ceftiofur (5 mg/kg/day, IM, for 5 days or 20 mg/kg/day, IM, for 3 days), or amoxicillin (15 mg/kg, IM, two injections 48 hr apart). • Leptospirosis is zoonotic, and urine and milk of dams may be infective for up to 3 mo, except for Hardjo, in which case cows can be infective for life if not treated.
  • 23.
    Brucellosis: • Brucellosis (Bang’sdisease) is a threat in most countries where cattle are raised. In the USA, active control programs, including test, slaughter, and heifer vaccination, have greatly decreased its incidence. • Brucellosis causes abortions in the second half of gestation (usually ~7 mo), and ~80% of unvaccinated cows in later gestation will abort if exposed to Brucella abortus. • The organisms enter via mucous membranes and invade the udder, lymph nodes, and uterus, causing a placentitis, which may be acute or chronic. • Abortion or stillbirth occurs 2 wk to 5 mo after initial infection. Affected cotyledons may be normal to necrotic, and red or yellow. The intercotyledonary area is focally thickened with a wet, leathery appearance. • The fetus may be normal or autolytic with bronchopneumonia. Diagnosis can be made by maternal serology combined with fluorescent antibody staining of placenta and fetus or isolation of B abortus from placenta, fetus (abomasal contents and lung), or uterine discharge. Prevention is by calfhood vaccination of heifers. • Brucellosis is a serious zoonosis and a reportable disease, and the appropriate authorities should be contacted.
  • 24.
    Mycotic Abortion: • Fungalplacentitis due to Aspergillus sp (septated fungi, 60%–80% of cases), or to Mucor sp, Absidia, Rhizopus sp, and a few other nonseptated fungi, is an important cause of bovine sporadic abortion. • Abortions occur from 4 mo to term and are most common in winter. It is believed the fungi gain entry through the oral or respiratory tracts and travel hematogenously to the placenta. • Placentitis is severe and necrotizing. Cotyledons are enlarged and necrotic with turned-in margins. The intercotyledonary area is thickened and leathery. • Adventitious placentation is common. The fetus seldom is autolyzed, although it may be dehydrated; ~30% have gray ringworm-like skin lesions principally involving the head and shoulders. • The diagnosis is based on the presence of fungal hyphae associated with necrotizing placentitis, dermatitis, or pneumonia. • Fungi can also be isolated from the stomach contents, placenta, and skin lesions. Isolation must be correlated with microscopic and gross lesions to exclude contamination after abortion. • For control, moldy feed should be avoided.
  • 25.
    Trichomoniasis: • Tritrichomonas foetus infectioncauses a venereal disease that usually results in infertility but occasionally causes abortion in the first half of gestation. • Placentitis is relatively mild, with hemorrhagic cotyledons and thickened intercotyledonary areas covered with flocculent exudate. The placenta is often retained, and there may be pyometra. • The fetus has no specific lesions, although T foetus can be found in abomasal contents, placental fluids, and uterine discharges. Infected cows typically clear the organism within 20 wk, but bulls, especially those infected after 3 yr of age, can become lifelong carriers. • There is no legal, effective treatment for individual animals. Herd treatment is based on identifying and segregating pregnant females from “at-risk" females for ≥5 mo and by identifying and culling all infected bulls. • Prevention is by artificial insemination or natural insemination using noninfected bulls. A killed, whole-cell vaccine is available for use in cows.
  • 26.
    Campylobacteriosis: • Campylobacter fetusvenerealis causes venereal disease that usually results in infertility or early embryonic death but occasionally causes abortion between 4 and 8 mo of gestation. C fetus fetus and C jejuni are transmitted by ingestion and subsequent hematogenous spread to the placenta. • Both cause sporadic abortions, usually in the last half of gestation. The fetus can be fresh with partially expanded lungs or severely autolyzed. • Mild fibrinous pleuritis and peritonitis may be noted, as well as bronchopneumonia. Placentitis is mild with hemorrhagic cotyledons and an edematous intercotyledonary area.  • Campylobacter spp can be identified by darkfield examination of abomasal contents or culture of placenta or abomasal contents. Isolation and identification of the species involved is important if vaccination is to be instituted. • Venereal campylobacteriosis can be controlled by artificial insemination and vaccination.  • Campylobacter spp are zoonotic, and C jejuni is an important cause of enteritis in people.
  • 27.
    Listeriosis: • Listeria monocytogenes cancause placentitis and fetal septicemia. Abortions are usually sporadic but may affect 10%–20% of a herd. • Abortion is at any stage of gestation, and the dam may have fever and anorexia before the abortion; retained placenta is common. • The fetus is retained for 2–3 days after death, so autolysis may be extensive. Fibrinous polyserositis and white necrotic foci in the liver and/or cotyledons are common. • Diagnosis is by culture of Listeria from fetus or placenta. There is no available bacterin. • Listeriosis is a reportable disease in many areas and is a serious zoonosis, with spread possible through improperly pasteurized milk.
  • 28.
    Chlamydiosis: • Chlamydia abortus,the cause of enzootic abortion of ewes, causes sporadic abortion in cattle. • Most abortions occur near the end of the last trimester, but they can occur earlier. Placental lesions consist of thickening and yellow-brown exudate adhered to the cotyledons and intercotyledonary areas. • Histologically, placentitis is consistently present, and pneumonia and hepatitis can be found in some cases. C abortus can be identified by examination of stained smears of the placenta or by ELISA, fluorescent antibody staining, PCR, or isolation in embryonated chicken eggs or cell culture. • Organisms can often be identified in the lungs and liver but not as consistently as in the placenta. • There are no vaccines for cattle, although they are produced for sheep. • The bacterium is zoonotic, occasionally producing life-threatening disease and abortion in pregnant women.
  • 29.
    Ureaplasma diversum Infection: • Ureaplasmadiversum is a common inhabitant of the vagina and prepuce of cattle that also causes abortions. Abortions are usually single, but severe outbreaks occur on occasion. • The infection may also result in stillbirths and birth of weak calves. Most fetuses are aborted in the third trimester and are well preserved. The cows are not sick, but retained placentas are common. • Placentitis and a necrotic amniotic membrane are common features. The intercotyledonary areas are usually thickened and sometimes contain areas of fibrin deposition and hemorrhage. • There are no gross lesions in the fetus. Microscopically, there is nonsuppurative placentitis and pneumonia characterized by accumulations of lymphocytes around bronchi and by diffuse alveolitis. • Diagnosis is by isolation of U diversum from the placenta, lungs, and/or abomasal contents.
  • 30.
    Blue tongue: • Bluetongueis caused by an Orbivirus with 24 serotypes and is transmitted by biting midges of the genus Culicoides. • Historically, blue tongue occurred from approximately latitude 35°S to 40°N, except in the western USA, where it occurs to 45°N. • After introduction of an attenuated, live virus serotype 10 vaccine in the 1950s, abortion, mummification, stillbirth, and the birth of live offspring with CNS malformations occurred in cattle and sheep. Since then, multiple blue tongue serotypes have been identified as causes of similar reproductive losses in cattle and sheep. • Attenuation of blue tongue virus can increase its ability to cross the placenta. • There is evidence that before 2007, reproductive losses were caused by attenuated blue tongue vaccine viruses, either by vaccination of pregnant animals or by spread of vaccine virus in nature by Culicoides spp. • In 2006, serotype 8 blue tongue virus appeared, spread, and became endemic across northwestern Europe (north of 50°N), where blue tongue was previously unknown. • Beginning in 2007, abortions and birth of “dummy” calves with brain malformations occurred in blue tongue-infected herds; affected calves were documented to have been infected in utero. Since then, many such cases have been reported. • Diagnosis is by identification of precolostral antibodies to blue tongue or identification of the virus by PCR. • Brain, spleen, and whole blood are the preferred samples from fetuses and neonates for PCR. Control of blue tongue is by vaccination and management procedures to reduce exposure to biting midges. • Modified-live and inactivated vaccines are available, but their availability and use varies between countries
  • 31.
    Other Causes ofAbortion: • Akabane virus (where present) causes abortion and fetal anomalies. • Parainfluenza-3 virus causes abortion in experimentally inoculated seronegative cattle, but is seldom, if ever, diagnosed in field cases of abortion. • Occasionally, Salmonella spp cause abortion storms. The cows are usually sick, and the fetuses and placentas are autolyzed and emphysematous. Salmonellae can be isolated from the abomasal contents and fetal tissues and from uterine fluids and the dams’ feces.  • Mycoplasma spp, Histophilus somni, and a wide variety of other bacteria can also cause sporadic abortions in cattle. • Schmallenberg virus, discovered in Europe in 2011, belongs to the Simbu serogroup and has been associated with infertility, abortion, and fetal malformation in several ruminant species.