Failure of Pregnancy in Cattle

Rob Foster

University of Guelph


Table of Contents

General considerations

Nonlesion lesions

Embryonic mortality







In beef cattle, About 80% of cows are found to be pregnant, about 10% of pregnancies fail and the weaning rate is about 68%.


Adventitial placentation

Amorphous globosus

Occasionally, a blob of tissue is found in the placenta of a calf. This blob often has haired skin on the outside and fat and myxomatous tissue internally. Most of the ones I have seen are about 20-30 cm diameter. They have a thin vascular cord attached. I have always considered them a malformed twin.

Weber et al (2017) described an unusual example. The live calf was a male and the amorphous globosus was female. It was dizygotic and had rudimentatry organs and an external vulva.

Weber J, Rudolph N, Freick M. Facets of Clinical Appearance and Aetiology in an Unusual Bovine Amorphus Globosus. Anat Histol Embryol 2017; 46: 502-506.



In dairy cows, embryonic death is death of the conceptus at the embryonic stage, the period of 'differentiation', which is up to about 42 days of gestation.

Embryonic death is divided into 2 parts - early and late. Early embryonic mortality is from conception to the time when pregnancy is recognised - when serum pregnancy-specific protein B is found. Early embryonic death is thus loss of the embryo from fertilisation to about day 15-17. Late embryonic loss is from then until about day 42 of gestation.

General guidelines of pregnancy loss are based on some assumptions. About 85-95% of cows become pregnancy. About 30-40% fail in the early embryonic period and 5-10% are lost in the late embryonic phase.

The expected loss from day 29 to day 42 is about 7% (Gabor et al 2016). From days 29 to 45 the expected loss is about 8 to 11%. Pregnancy testing by per rectal palpation does not appear to influence embryonic or fetal death.

Ultrasound evaluation allows for identification of pregnancy from about day 29-35 on. Bovine Pregnancy Specific Protein B (bPSPB) is secreted by trophoblasts and is found in bovine maternal serum at about day 22, but is better from about day 29.

Infectious causes of embryonic loss

Little is known of the cause of this early loss. An interaction of embryonic and maternal factors including immunology and hormones may be involved.

Garcia-Ispierto and Lopez-Gatius (2016) found that seroconversion to Mycobacterium avium paratuberculosis was correlated to a 30% loss of pregnancy in the early embryonic/fetal period.

Bovine viral diarrhoea virus is responsible for early embryonic mortality and it appears to alter INF tau and prostaglandin production that is critical for maternal recognition of pregnancy (Cheng et al 2016).

Noninfectious causes of embryonic loss

Low progesterone

Gabor et al (2016) examined a large number of dairy cows and found that cows with a low concentration of progesterone were more likely to fail their pregnancy. Cows with low PSPB and progesterone has the highest pregnancy loss.


Cows in late parity are more likely to suffer embryonic loss (Gabor et al 2016))

Hot weather

Cows at hot times of the year are more likely to suffer embryonic loss (Gabor et al 2016)

High milk production

Cows with high milk production. are more likely to suffer embryonic loss (Gabor et al 2016)

Inbreeding and genetics

Jersey cattle with an autosomal recessive genetic defect called JH1 are likely to loose their pregnancy in the embryonic period. The affected gene is called the CWC15 gene. This defect is thought to result from inbreeding - something that is recognised in the Jersey breed. This gene is a lethal defect as there are no living homozygotes

Cheng Z, Abudureyimu A, Oguejiofor CF, Ellis R, Barry1 AT, Chen X, Anstaett OL, Brownlie J, Wathes DC. BVDV alters uterine prostaglandin production during pregnancy recognition in cows. Reproduction 2016; 151: 605-614

Fordyce G, Holroyd RG, Taylor J, Kirkland PD. (2013) Neospora caninum and reproductive wastage in extensively managed Queensland beef herds. Aust Vet J. 2013; 91: 385-390.

Gábor G, Kastelic JP, Abonyi-Tóth Z, Gábor P, Endrődi T, Balogh OG. Pregnancy Loss in Dairy Cattle: Relationship of Ultrasound, Blood Pregnancy-Specific Protein B, Progesterone and Production Variables. Reprod Domest Anim 2016; 51: 467-473

Garcia-Ispierto I, López-Gatius F. Early Foetal Loss Correlates Positively with Seroconversion against Mycobacterium avium paratuberculosis in High-Producing Dairy Cows. Reprod Domest Anim 2016; 51: 227-231

Romano JE, Fahning ML, (2013) Effects of early pregnancy diagnosis by per rectal palpation of the amniotic sac on pregnancy loss in dairy cattle. J Am Vet Med Assoc 2013; 243: 1462-1467

Zhang Y, Guo G, Huang H, Lu L, Wang L, Fang L, Liu L, Wang Y, Zhang S. Screening for JH1 genetic defect carriers in Jersey cattle by a polymerase chain reaction and restriction fragment length polymorphism assay. J Vet Diagn Invest. 2015; 27: 596-599


Abortion is generally defined as a loss of a fetus – during the fetal period of development. This is from about day 42 to just before parturition.


Mortality appears to be greater during the early phase of fetal development. From day 46 to 60, fetal loss is between one and 4% and from days 61 to 90, it is about 1%.Walder et al (2010) reported on abortions, stillbirths and calf mortalities of beef cattle in western Canada. They found that, based on a survey of 203 herds with a total of 29,713 pregnanct cows, the loss was 1.6%

Romano JE, Fahning ML, (2013) Effects of early pregnancy diagnosis by per rectal palpation of the amniotic sac on pregnancy loss in dairy cattle. J Am Vet Med Assoc 2013; 243: 1462-1467


Walder et al (2010) reported on abortions, stillbirths and calf mortalities of beef cattle in western Canada. Of 183 fetuses examined (abortion), 36% had no diagnosis, 10% had maternal death, 10% had thryoid gland lesions, 6% had a developmental anomaly, 6% had placentitis, 2% had heart failure. BVD and IBR accounted for 2%

Borel et al (2014) provide a review of major causes of abortion in ruminants in Europe. These include viral, bacterial and fungal causes listed below.

Jonker and Michel (2021) reviewed bacterial and fungal causes of abortion in South Africa over a ten-year period. They had 288 cases. 58 had fetus and placenta, 224 were fetus only and six were placenta only. Diagnosis was made in 101 cases with an overall diagnostic rate of 35.1%. Bacteria and fungi represented 63 cases (21.9%). Brucella was detected in 21 cases (7.3%). The next common bacterium was Trueperella pyrogen ease and 1.7%. There were a large number of individual isolated microorganisms


Borel N, Frey CF, Gottstein B, Hilbe M, Pospischil A, Franzoso FD, Waldvogel A. (2014) Laboratory diagnosis of ruminant abortion in Europe. Vet J 2014; 200: 218-229.

Jonker A, Michel AL. Retrospective study of bacterial and fungal causes of abortion in domestic ruminants in northern regions of South Africa (2006-2016). Aust Vet J. 2021; 99: 66-71.

NonInfectious causes

For general discussion on the non-infectious causes of abortion, please see the section on general failure of pregnancy.

From a bovine specific point of view, non-infectious causes of failure of pregnancy include the following.

Inherited diseases

There are many inherited diseases that result in failure of pregnancy. The Online Mendelian Inheritance of Animals provides a database of inherited diseases, and there are more than 50 reported instances of increased pregnancy loss that are inherited.

Some of the genetic mutations considered important in failure of pregnancy include:



Adams HA, Sonstegard TS, VanRaden PM, Null DJ, Van Tassell CP, Larkin DM, Lewin HA. Identification of a nonsense mutation in APAF1 that is likely causal for a decrease in reproductive efficiency in Holstein dairy cattle. J Dairy Sci 2016; 99: 6693-6701.

Anomalies and malformations

Macroscopically visible



Testoni et al (2006) reported on 2 calves of the Chianina breed with ichthyosis.

O'Rourke et al (2017) reported on a polled Hereford and a Shorthorn fetus with ichthyosis. They did not have the ABCA12 gene mutation seen in Chianina. The keratin was epidermal and infundibular and orthokeratotic and very thick.

O'Rourke BA, Kelly J, Spiers ZB, Shearer PL, Porter NS, Parma P, Longeri M. Ichthyosis fetalis in Polled Hereford and Shorthorn calves. J Vet Diagn Invest 2017; 29: 874-876.

Testoni S, Zappulli V, Gentile A. Ichthyosis in two Chianina calves. Dtsch Tierarztl Wochenschr. 2006; 113: 351-354.

Microscopic only




Trace mineral deficiency or excess

There is evidence that trace mineral deficiency being responsible for failure of pregnancy. Graham et al (1994) considered differences between measurable minerals of mothers and fetuses was the result of abortion and not the cause.

Waldner and Blakley (2014) provided information on micronutrients in abortion, stillbirth, neonatal and postnatal loss. They highlighed the difficulty in determining normal values, considering there could be significant subclinical effects.

Graham TW, Thurmond MC, Mohr FC, Holmberg CA, Anderson ML, Keen CL. (1994) Relationships between maternal and fetal liver copper, iron, manganese, and zinc concentrations and fetal development in California Holstein dairy cows. J Vet Diagn Invest 1994; 6: 77-87.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest. 2014; 26: 376-389.


Waldner and Blakley (2014) found that 15% of aborted beef calves had deficiency in liver concentrations.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest 2014; 26: 376-389.


Waldner and Blakley (2014) found that 10% of calves had hemosiderosis and liver iron higher than 1,800 ppm

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest. 2014; 26: 376-389.


Little is know of magnesium toxicosis or deficiency in calves.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest. 2014; 26: 376-389.


Manganese deficiency of pregnant cattle can result in weak calves, and chondrodysplasia with spinal anomalies and arthrogryposis.

Mn increases in concentration after birth.

Dittmer KE, Thompson KG. Approach to Investigating Congenital Skeletal Abnormalities in Livestock. Vet Pathol 2015; 52: 851-861.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest 2014; 26: 376-389.



Deficiency of selenium can result in congenital white muscle disease with cardiac and skeletal myonecrosis. This can lead to failure of pregnancy. Selenium supplementation results in a return to normal birth rates.

Waldner and Blakley (2014) found that 30% of beef calves had deficiency in liver concentrations after 3 days of age.

Giadinis ND, Loukopoulos P, Petridou EJ, Panousis N, Konstantoudaki1 K, Filioussis G. Tsousis G, Brozos C, Koutsoumpas AT, Chaintoutis SC, Karatzias H. Abortions in Three Beef Cattle Herds Attributed to Selenium Deficiency. Pakistan Vet J 2016; 36: 145-148.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest 2014; 26: 376-389.

Vitamin A

Calves are born with little vitamin A and acquire it in colostrum and milk.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves. J Vet Diagn Invest 2014; 26: 376-389.

Vitamin E


Waldner and Blakley (2014) found that 10% of fetuses, stillborn and neonatal deaths of beef calves had deficiency in liver concentrations

Dittmer KE, Thompson KG. Approach to Investigating Congenital Skeletal Abnormalities in Livestock. Vet Pathol. 2015; 52: 851-861.

Waldner CL, Blakley B. Evaluating micronutrient concentrations in liver samples from abortions, stillbirths, and neonatal and postnatal losses in beef calves.J Vet Diagn Invest 2014; 26: 376-389.


Congenital neoplasia is really rare. The following have been reported

Yolk sac tumor

Yolk sac tumors are reported in the testes and throughout the abdomen in calves. They are discussed in neoplasia of the testes of bulls.


Pine needle abortion

Consumption of pine needles from some cypress (Cupressus sp), juniper (Juniperus sp), pine (Pinus sp) and spruce (Picea sp) trees can result in failure of pregnancy. Some of the first reports were from British Columbia, Canada. The abortion disease was characterised by feeding ponderosa pine (Pinus ponderosa) needles to cattle. It became commonly known as ponderosa pine abortion. Cattle consume pine needles/foliage when they have no or limited access to any other food because of inclement weather, snow coverage or other limiting conditions.

The toxic agent is considered to be isocupressic acid (ICA), a diterpene labdane acid. Once ICA or its metabolites are absorbed and metabolised in the liver, agathic acid, dihydroagathic acid and tetrahydroagathic acid is found in the blood stream of cows. ICA and metabolites cause ischemia by construction of caruncular vessels leading to fetal hypoxia, death and then abortion.

Pine needle abortion is diagnoses when there is an appropriate history, by measuring agathic acid in the serum of affected cows, and by measuring the metabolite tetrahydroagathic acid in fetal (thoracic) fluid and abomasal fluid of aborted fetuses by gas chromatography - mas spectrometry. There are no specific lesions in aborted fetuses.


Snider DB, Gardner DR, Janke BH, Ensley SM. Pine needle abortion biomarker detected in bovine fetal fluids. J Vet Diagn Invest 2015; 27: 74-79.

Induced mannosidosis

There are several plants including Astragalus, Oxytropis, and Ipomea carnea that induce mannosidosis. Sida carpinifolia, a subshrub in Brazil also contains the indolizidine alkaloid, swainsonine which is an alpha mannosidase inhibitor. This induces mannosidosis and transplacental toxocosis of the fetus. Cows affected by this develop hydrallantois.

Cistus salviifolius toxicosis

Abortion is reported in cows that ingest Cistus salviifolius. This plant usually causes erosion of the bladder and intestines because of the tannins and phenolic compounds.


Mignacca SA, Mucciarelli M, Colombino E, Biasibetti E, Muscia S, Amato B, Presti VDML, Vazzana I, Galbo A, Capucchio MT. Cistus salviifolius Toxicity in Cattle. Vet Pathol. 2020; 57: 115-121.



Many twin pregnancies go to term. Garcia-Ispierto and López-Gatius (2019) reported on 1194 twin pregnancies in 2 herds in Spain. 512 were bilateral and 672 were inilateral. 278 (23.3%) aborted before day 280 of gestation. Most of these were unilateral pregnancies.


Garcia-Ispierto I, López-Gatius F. Abortion in dairy cattle with advanced twin pregnancies: Incidence and timing. Reprod Dom Anim 2019; 54: 50-53

Infectious Causes



Bacteria induce lesions in the placenta, fetus or both.

Placental lesions

Fetal lesions


Fetal pneumonia occurs when amniotic fluid is aspirated because of fetal distress. The distribution in the lung is diffuse - all parts of the lung are affected.

Lopez A, Pérez A, Angulo G. Distribution of lesions in the lungs of aborted bovine fetuses. Can Vet J 1989; 30: 519-521

Protoebacteria: Anaplasma

Anaplasma phagocytophilum is implicated in failure of pregnancy, particularly late term abortion. A particular genotype (triple-repeat APV-A VNTR allele ) is a potential abortogenic agent. It is unknown if this is a primary agent, or one that alters immunocompetence to other agents.

Dugat T, Haciane D, Durand B, Lagrée A -C, Haddad N, Boulouis H -J. Identification of a Potential Marker of Anaplasma Phagocytophilum Associated with Cattle Abortion. Transboundry and Emerging Diseases 2017; 64: e1-e4

Bacillus licheniformis

Brucellosis (epizootic bovine abortion)

Brucella abortus is a classical bacterial cause of failure of pregnancy in cattle. It was originally called epizootic bovine abortion, although that term is used for Foothills Abortion of California (see below)

Brucella abortus is eradicated from many juristictions but remains an important agent in some countries and locales.

Endemic regions may vaccinate calves using Brucella abortus strain RB51. If pregnant animals are vaccinated, they may develop placentitis and pneumonia, just as with the virulent bacterium.

Mahajan et al (2017) reported on natural cases of B abortus abortion. Immunohistochemistry results were reported and there were 5 positive out of 27 positive. Histological findings were of a necrotic placentitis. Organisms were in trophoblasts and there were neutrophils and lymphoid cells in the tissues.Neutrophils and lymphoid cells were in the bronchi and interstitium of the lung. The kidney had mononuclear cells in the interstitium. Similar cells were in the corneal stroma.

B melitensis and B suis are also capable of causing FOP in cattle


Fluegel Dougherty AM, Cornish TE, O'Toole D, Boerger-Fields AM, Henderson OL, Mills KW. Abortion and premature birth in cattle following vaccination with Brucella abortus strain RB51. J Vet Diagn Invest 2013; 25: 630-635.

Mahajan V, Banga HS, Filia G, Gupta MP, Gupta K. Comparison of diagnostic tests for the detection of bovine brucellosis in the natural cases of abortion. Iran J Vet Res. 2017;18: 183-189.



Organisms of the Order Chlamydiales include Chlamydiaceae, Simkaniaceae, Waddliaceae, and Parachlamydiaceae. The first 3 Families have gram-negative extracellular infectious bodies (EBs). Chlamydia is the most common genus.


Chlamydia abortus

Chlamydia abortus can be identified in the placentas of bovine abortion by PCR. In a swiss study, Chlamydia abortus was identifed in 24 of 292 cases of abortion and there were histological lesions of placentitis and placental necrosis (Vidal et al 2017). Other Chlamydiales were found in rare cases.

Kreizinger et al (2015) reported finding 2 cases of 85 cases of placentitis in bovine abortion in Hungary.

Kreizinger Z, Szeredi L, Bacsadi Á, Nemes C, Sugár L, Varga T, Sulyok KM, Szigeti A, Ács K, Tóbiás E, Borel N, Gyuranecz M. Occurrence of Coxiella burnetii and Chlamydiales species in abortions of domestic ruminants and in wild ruminants in Hungary, Central Europe. J Vet Diagn Invest. 2015; 27: 206-210.

Borel N, Polkinghorne A, Pospischil A. A Review on Chlamydial Diseases in Animals: Still a Challenge for Pathologists? Vet Pathol 2018; 55: 374-390.

Vidal S, Kegler K, Greub G, Aeby S, Borel N, Dagleish MP, Posthaus H, Perreten V, Rodriguez-Campos S. Neglected zoonotic agents in cattle abortion: tackling the difficult to grow bacteria. BMC Vet Res 2017; 13: 373.

Chlamydia pecorum

Chlamydia pecorum is reported to cause late term abortion. Serum samples of dairy cattle tested for Chlamydia indicate widespread subclinical infection.

Struthers et al (2021) reported on a dairy herd of 2000 cows that had 33 aborted fetuses evaluated (1.65%). All had autolysis with bloody fluid in cavities. 18 had meningoencephalitis of all parts of the brain. 11 of 11 tested fetuses were PCR positive for Chlamydia. 14 of 18 had PCR or IHC positivity for Chlamydia. C pecorum is the identified organism. 54 cows. 5 of 8 cows had brain lesions and Chlamydia was identified in 2. 4 neonates had brain lesions and 1 had Chlamydia identified.

Struthers JD, Lim A, Ferguson S, Lee JK, Chako C, Okwumabua O, Cuneo M, Valle AM, Brower A. Meningoencephalitis, Vasculitis, and Abortions Caused by Chlamydia pecorum in a Herd of Cattle. Vet Pathol. 2021; 58: 549-557.




Kreizinger et al (2015) reported finding 1 case of 85 cases of placentitis in bovine abortion in Hungary.

Kreizinger Z, Szeredi L, Bacsadi Á, Nemes C, Sugár L, Varga T, Sulyok KM, Szigeti A, Ács K, Tóbiás E, Borel N, Gyuranecz M. Occurrence of Coxiella burnetii and Chlamydiales species in abortions of domestic ruminants and in wild ruminants in Hungary, Central Europe. J Vet Diagn Invest 2015; 27: 206-210.



Waddlia chondrophila

Kreizinger et al (2015) reported finding 4 cases of 85 cases of placentitis in bovine abortion in Hungary.

Kreizinger Z, Szeredi L, Bacsadi Á, Nemes C, Sugár L, Varga T, Sulyok KM, Szigeti A, Ács K, Tóbiás E, Borel N, Gyuranecz M. Occurrence of Coxiella burnetii and Chlamydiales species in abortions of domestic ruminants and in wild ruminants in Hungary, Central Europe. J Vet Diagn Invest 2015; 27: 206-210.


Clostridium chauvoei

Abreu et al (2017) reported a single case of a 25 month old cow that died of blackleg, having myocardial and multiple muscle lesions. The unborn calf had lesions of systemic infection with Clostridium chauvoei.

Abreu CC, Edwards EE, Edwards JF, Gibbons PM, Leal de Araújo J, Rech RR, Uzal FA. Blackleg in cattle: A case report of fetal infection and a literature review. J Vet Diagn Invest 2017; 29: 612-621


Coxiella burnetii

Coxiella burnetii (Phylum Proteobacteria, Class Gammaproteobacteria, Order Legionellales, Family Coxiellaceae, Genus Coxiella) is a gram negative intracellular bacterium.

The agent of IQ fever is a cause of abortion, stillbirth and perinatal mortality. The placental lesions are subtle with intercotyledonary translucency. The number of organisms on histology is really impressive. There is a relatively mild placentitis.


Macías-Rioseco M, Riet-Correa F, Miller MM, Sondgeroth K, Fraga M, Silveira C, Uzal FA, Giannitti F. Bovine abortion caused by Coxiella burnetii: report of a cluster of cases in Uruguay and review of the literature. J Vet Diagn Invest. 2019;31(4):634-639.


Family Leptospiraceae, Genus Leptospira are the causes of leptospirosis.

The major cause of leptospiral disease in cattle is either Leptospira borgpetersenii serovar Hardjo subtype Hardjobovis (North America, New Zealand) and Leptospira interrogans serovar Hardjo type Hardjoprajitno. Leptospira interrogans serovars Pomona and Grippotyphosa are also implicated occasionally but are usually seen in pigs.

"infertility", abortions and stillbirths are all attributed to leptospirosis in cattle. Abortions occur many weeks after initial infection and rather than producing an abortion storm, sporadic abortion is the more common. Bacteria can be isolated from multiple locations in the reproductive tract and infection may persist for greater than 12 months.

The lesions include placental edema macroscopically and microscopic placentitis, meningitis, hepatic necrosis and renal tubular necrosis and nephritis.



Listeria monocytogenes

Listeria monocytogenes (Class Bacilli, Order Bacillales, Family Listeriaceae, Genus Listeria) is a gram positive bacterium.


Causes a necrotic colitis in near term fetuses




Pajaroellobacter abortibovis (Epizootic bovine abortion; foothills abortion) (Pa-ha-hel-lo)

Order Myxococcales; Class Deltaproteobacteria; Family

Epizootic bovine abortion of the dry foothill and mountainous regions of California, Nevada and Oregon is not the original epizootic bovine abortion - that is brucellosis. It is an abortion disease with a distinctive gross and histological appearance that is recognised in areas within the geographical boundaries of the Pajahuello tick Ornithodoros coriaceus. Abortion is typically in the last third of pregnancy. Calves have ascites and large lymph nodes and thymus, and large spleens and livers.

Histologically there may be multiple foci of necrosis in the spleen and thymus. Many macrophages/histiocytes are found in the sinuses of lymph nodes especially the superficual cervical node. Histiocytes/macrophages are prominent in the connective tissue of the thymus and portal tracts of the liver and around the central veins. Lymphoid hyperplasia is prominent in the lymph node and lymphoblasts are within the sinuses of the spleen.

The organism is visualised in tissue using a silver stain and immunohistochemistry. It can be seen with certain modified Gram stains such as MacDonald's and Sandiford's - they are gram-negative.


Brooks RS, Blanchard MT, Clothier KA, Fish S, Anderson ML, Stott JL. Characterization of Pajaroellobacter abortibovis, the etiologic agent of epizootic bovine abortion. Vet Microbiol. 2016; 192: 73-80.

Kennedy PC, Casaro AP, Kimsey PB, Bon Durant RH, Bushnell RB, Mitchell GM. Epizootic bovine abortion: histogenesis of the fetal lesions. Am J Vet Res 1983; 44: 1040-1048.

Anderson ML, Kennedy PC, Blanchard MT, Barbano L, Chiu P, Walker RL, Manzer M, Hall MR, King DP, Stott JL. Histochemical and immunohistochemical evidence of a bacterium associated with lesions of epizootic bovine abortion. J Vet Diagn Invest 2006; 18: 76-80.

Anderson ML, Kennedy PC, Blanchard MT, Barbano L, Chiu P, Walker RL, Manzer M, Hall MR, King DP, Stott JL. Histochemical and immunohistochemical evidence of a bacterium associated with lesions of epizootic bovine abortion. Amer J Vet Res 1987; 48: 627-633



Staphylococcus spp

Staphylococcus lugdunensis:

Ardigò et al (2014) reported on finding S. lugdunensis in pure culture in the pooled tissues of an aborted fetus. No histology was reported.

Ardigò P, D'Incau M, Pongolini S. Abortion in cattle due to infection with Staphylococcus lugdunensis.J Vet Diagn Invest. 2014; 26: 818-820.

Trueperella pyogenes

Ureaplasma diversum

The Ureaplasma situation is muddied by a lack of information. U. diversum comes in types that vary in pathogenicity. Overall it is what I would call a low pathogenic organism. It infects the embryo early on, likely at fertilisation. Higher pathogenic types will kill the embryo early (return to service) and lower pathogenic types just kinda sit there for weeks or months.

Amnionitis is a classic lesion of ureaplasmosis. The amnionitis it causes is often not detected as it can be mild, so finding the organism in stomach contents to me is significant as it indicates infection. Whether it is the cause of loss, whether it allows other organisms to be more significant – that is the unanswered question. The people who worked on Ureaplasma years ago thought it was important.


Yersinia pseudotuberculosis

Protists (Protozoa)

Neospora caninum

Neospora caninum is a recognised cause of failure of pregnancy in dairy cattle. The evidence for its effect in creating reproductive wastage in beef cattle is more tenuous.

Infection is widespread in the prevalence in any particular herd can vary from zero through to almost 100%.
Dogs are definitive hosts with cattle being intermediate host's. Cattle are infected by horizontal and vertical transmission. Horizontal transmission can result in an epidemic but vertical transmission produces a more endemic loss in dairy cattle.

Infection early in gestation results in FOP with fetal death. Later, congenitally infected fetuses are born. Cantona et al (2014) identified differences in cytokine expression of cattle in early gestation that supports the belief that an altered TH1 response with prominent IL-12, IFN-gamma and TNF alpha cells seen in those dams with dead fetuses.



Cantóna GJ, Katzer F, Maleya SW, Bartleya PM, Benavides-Silvána J, Palarea-Albaladejo J, Panga Y, Smith SH, Rocchi M, Buxtona D, Innes EA, Chianini F (2014) Cytokine expression in the placenta of pregnant cattle after inoculation with Neospora caninum. Vet Immunol Immunopathol 2014; 161: 77–89.

Fordyce G1, Holroyd RG, Taylor J, Kirkland PD. (2013) Neospora caninum and reproductive wastage in extensively managed Queensland beef herds. Aust Vet J 2013; 91: 385-390.

Tritrichomonas foetus

Tritrichomonas foetus is known as a cause of infertility and early return to service (early embryonic mortality). Initial infection often causes vaginitis, cervicitis and endometritis.

Rhyan et al (1988) provides details on the lesions of Tritrichomonas foetus in the placenta and fetus after abortion. The gross lesions include fetuses that vary from two months through to term. The degree of autolysis is highly variable from mild to marked. There were no grossly observable lesions in eight of the 12 cases. There were, however, consistent histological lesions in the placenta and lungs of those where the various organs were available. Lesions of placentitis with large numbers of intralesional organisms (up to 10 µm long and 7 µm wide that are crescent -shaped, oval or pear shaped). The flagellae and undulating membranes were not visible on H and E but could be seen with Giemsa and a silver stain (not GMS). The lesions of placentitis with those of mild diffuse inflammatory cells that were mononuclear mostly and us lymphocytes and macrophages. The trichomonads were in large numbers throughout the chorion. The lung lesions were bronchopneumonia in six of 11 examined lungs. The alveolar sacs or bronchiolar ducts contain neutrophils and macrophages there were occasional multinucleated foreign body type giant cells in the airways. The trichomonads were in the airways and some were phagocytic lysed. Trichomonads were also within the crypts or glands of the abomasum and intestine.

Rhyan JC, Stackhouse LL, Quinn WJ. (1988) Fetal and placental lesions in bovine abortion due to Tritrichomonas foetus. Vet Pathol 1988; 25: 350-355.

Theileria orientalis

Theileria species are Phylum Apicomplexa; Order Piroplasmida;1 Family Theileriidae. The species that infect cattle are Theileria annulatam, T orientalis and T parva (East Coast Fever). They are tick borne organisms - Rhipicephalus (Boophilus) and Haemophysalus spp are involved). Merogony is in lymphoctyes and histiocytes especially. Merozoites invade erythrocytes to form the elongated bacillary or bayonet forms in red cells. T annulatam and parva cause proliferation/transformation of lymphocytes and monocyte/macrophage lineages. T orientalis doesnt transform cells, but proliferates in red cells causing anemia.

Deaths are usually only in a low percentage of affected animals and jaundice and anemia are the main clinical findings.

Abortion is presumably maternal in origin.

Forshaw D, Alex SM, Palmer DG, Cotter J, Roberts WD, Jenkins C, Hair S. Theileria orientalis Ikeda genotype infection associated with anaemia, abortion and death in beef cattle in Western Australia. Aust Vet J 2020; 98: 250-


Bovid alphaherpesvirus 1

BoHV 1 is in the Order Herpesvirales, Family Herpesviridae, Subfamily Alphaherpesvirinae, Genus Varicellovirus.

BoHV-1 is recognised as a cause of infertility, return to service/early embryonic mortality, abortion, stillbirth, perinatal mortality and weak neonatal calves

The main manifestations of BoHV-1 is infectious bovine rhinotracheitis (IBRV) and infectious pustular vulvovaginitis (IPVV). Both viruses also produce embryonic death, abortion, stillbirth and the birth of weak calves. IPVV is a less virulent virus and primarily affects the vulva and the penis and prepuce of the bull.

Drs Kennedy and Richards were the first to establish that BoHV-1, either field or vaccine strains, was a cause of abortion in cattle. They described the classical lesions of multifocal necrosis of liver, lung, spleen, thymus, adrenal cortex, skin, heart, placenta and endometrium. Inclusion bodies were not seen.The adrenal gland is a high yield organ for virus.

The placenta usually has no recognisable histological lesions but virus may be found in the endothelium of placental vessels. It is also identified by immunohistochemistry in the endothelium of vessels in multiple organs. The multifocal distribution of lesions in the liver suggests hematogenous spread from the placenta. Liver lesions occur in 8 of 10 cases (Crook et al 2012). This theory then suggests that further dissemination to the brain, lungs and other organs follows.

Miller et al later showed that BoHV-1 produces oophoritis and necrosis of the corpus luteum.

Crook et al (2012) found that the prevalence of BoHV-1 abortion was 2.5% in British cattle. Their work provides additional support for placental infection, spread to the liver and then dissemination throughout the body with endothelium being important in pathogenesis.

Gould et al (2013) found the prevalence in the USA to be 3.8% over a 10 year period. Vaccination reduced the prevalence of disease.

Crook T, Benavides J, Russell G, Gilray J, Maley M, Willoughby K. Bovine herpesvirus 1 abortion: current prevalence in the United Kingdom and evidence of hematogenous spread within the fetus in natural cases. J Vet Diagn Invest. 2012; 24: 662-670.

Gould S, Cooper VL, Reichardt N, O'Connor AM. An evaluation of the prevalence of Bovine herpesvirus 1 abortions based on diagnostic submissions to five U.S.-based veterinary diagnostic laboratories. J Vet Diagn Invest 2013; 25: 243-247

Mahajan et al (2013) reported on the diagnostic methods to diagnose abortion from BHV-1. Abortion occurred between 4 and 8 months. Twenty one fetuses and 14 cotyledons were examined. Specific macroscopic lesions were seen as focal necrosis in the liver, hemorrhage in the cerebrum and placental edema in some. One fetus was mummified. Diagnosis appeared to be made based on serology, although very difficult to parse out the various tissue and test correlations. Histological lesions were seen in 5 of 21 fetuses and 3 of 14 cotyledons. Immunohistochemistry was positive in 4 fetuses and 2 cotyledons.


Kennedy PC, Richards WPC. (1964). The Pathology of Abortion Caused by the Virus of Infectious Bovine Rhinotracheitis. Pathol vet 1964; 1: 7-17


O'Toole D, Chase CC, Miller MM, Campen HV. Kennedy, the early sixties, and visitation by the angel of death. Vet Pathol. 2014 Nov;51(6):1051-62.

Bovid alphaherpesvirus 4

BoHV 4 is in the Order Herpesvirales, Family Herpesviridae, Subfamily Gammaherpesvirinae, Genus Rhadinovirus. It is a cytomegalovirus, And is responsible for a number of disease conditions including, in South Africa, a disease called epivag.

BoHV 4 infects cattle or is reactivated at parturition. Its involvement in failure of pregnancy is controversial and could be coincident with abortion.

Delooz et al (2017) provided evidence based on rising titres in the dams and infection of 3 fetuses out of 368 that BoHV-4 may be involved in some bovine abortions.

Delooz L, Czaplicki G, Houtain JY, Dal Pozzo F, Saegerman C. Laboratory Findings Suggesting an Association Between BoHV-4 and Bovine Abortions in Southern Belgium. Transbound Emerg Dis. 2017; 64: 1100-1109

Pestivirus A, B (Bovine viral diarrhea virus [BVDV])

BVDV is in the family Flaviviridae, Genus Pestivirus. There are types - Pestivirus A (BVDV-1) and Pestivirus B (BVDV-2). These are also divided into noncytopathic (ncp) and cytopathic (cp) based on their propensity to induce cytopathic effect in cell culture. cpBVDV mutates from ncpBVDV. Abortions tend to be from cpBVDV, but can be from ncpBVDV.

Infertility, early embryonic mortality, abortion, and stillbirth have all been attributed to infection with BVDV. Cows infected with BVDV may abort 10 to 90 days later – this could be from ovarian dysfunction, uterine inflammation or direct effect on the fetus. The effects on the fetus are variable. Noncytopathic BVDV infection in the first 125 days of gestation is believed to result in immunotolerance and the animal become persistently infected. Cytopathic BVDV between days 100 and 150 can result in congenital anomalies involving the central nervous system. A fetus infected after 120 days can become immune and have no untoward effects.

BVDV is known to produce osteopetrosis and growth arrest lines (unmodelled metaphyseal trabeculae). Persisently infected fetuses have cyclicly reduced numbers of osteoclasts that results in unmodeled metaphyseal trabeculae (Webb et al 2012).

BVDV nucleic acid is very stable when stored under a variety of conditions. Ridpath et al (2014) determined that fetal tissues subjected to freezing and storage at -80, storage at 4 degrees, room temperature and 37 degrees had little effect on the ability to recover nucleic acid. Brain then skin and muscle were the better samples.



Fulton RW, Confer AW, Sorensen NJ, Ridpath JF, Burge LJ. Bovine viral diarrhea virus 1b fetal infection with extensive hemorrhage. J Vet Diagn Invest. 2017; 29: 880-884.

Lanyon SR, Hill FI, Reichel MP, Brownlie J. (2014) Bovine viral diarrhoea: pathogenesis and diagnosis. Vet J 2014; 199: 201-209.

Ridpath JF, Neill JD, Chiang YW, Waldbillig J. Stability of Bovine viral diarrhea virus 1 nucleic acid in fetal bovine samples stored under different conditions. J Vet Diagn Invest. 2014; 26: 6-9.

Webb BT, Norrdin RW, Smirnova NP, Van Campen H, Weiner CM, Antoniazzi AQ, Bielefeldt-Ohmann H, Hansen TR. (2012) Bovine Viral Diarrhea Virus Cyclically Impairs Long Bone Trabecular Modeling in Experimental Persistently Infected Fetuses. Vet Pathol 2012; 49: 930-940

Pestivirus H (HoBi virus)

The genus Pestivirus is within the Family Flaviviridae. The most well recognised is Pestivirus A and Pestivirus B. Pestivirus H virus (aka HoBi like virus, BVDV-3, atypical Pestivirus) is another member that is similar to Pestivirus A and Pestivirus B. Pestivirus H is similar in pathogenesis to Pestivirus A and B, with respiratory, enteric and reproductive disease manifestations.

Bauermann FV, Falkenberg SM, Ridpath JF. HoBi-Like Virus RNA Detected in Foetuses Following Challenge of Pregnant Cows that had Previously Given Birth to Calves Persistently Infected with Bovine Viral Diarrhoea Virus. Transboundary and Emerging Disease 2017: 64: 1624–1632

Pestivirus D (Border Disease Virus)

Pestivirus D (Border disease virus) of sheep will cross infect cattle and persistent infection of calves can occur. The effects on the calves are similar to those of BVDV including the presence of growth retardation lattices. Cattle in contact with persistently BDV-infected calves can become infected.

Fernandez et al (2018) examined the placentas of 6 pregnant heifers that were in contact with a persistently infected calf. Three of the placentas had BDV immunoreactivity with immunohistochemistry. They had cotyledonary fibrosis, necrosis and placentitis with macrophages and lymphocytes. In the fetuses, staining was prominent in the thyroid gland, rumen epithelium - basal layers.

Frei S, Braun U, Dennler M, Hilbe M, Stalder HP, Schweizer M, Nuss K. (2014) Border disease in persistently infected calves: radiological and pathological findings. Vet Rec. 2014; 174: 170.

Fernández M, Braun U, Frei S, Schweizer M, Hilbe M. Border Disease Virus Infection of Bovine Placentas. Vet Pathol 2018; 55: 425-433.

Bunyaviruses, Akabane orthobunyavirus (AKAV), Schmallenberg orthobunyavirus (SBV), Aino orthobunyavirus (AINOV)

Aino orthobunyavirus, Akabane orthobunyavirus, Peaton orthobunyavirus and Schmallenburg orthobunyavirus are of the Order Bunyavirales , Family Peribunyaviridae, Genus Orthobunyavirus.

Viruses of the Bunyaviridae are spread by the biting Culicoides insects. The lesions in cattle are similar to those in sheep (see Failure of Pregnancy in sheep).
The macroscopic lesions in 16 aborted foetuses included 12 cases of arthrogryposis, 10 with curvature of the spine, ate with cranial malformations and three with brachygnathia inferior. One animal had a ventricular septal defect and pulmonary hypoplasia. Six cases had cerebellar hypoplasia, three of hydrocephalus, two of hydranencephaly, three with brainstem hypoplasia and 2 with micromelia.

Histologically, one of 13 brain's had mild perivascular cuffs of lymphocytes and macrophages, and neuronal necrosis and criminal lysis were mainly in the brainstem. There was also mild astrogliosis and microgliosis, and the myelination. Cerebellar hypoplasia cases had a reduction in the Purkinje owns and thickness of the molecular layer. There was skeletal muscle myofibre will hypoplasia in one of eight cases.

Peperkamp et al (2015) provided details of the congenital abnormalities found in Schmallenburg orthobunyavirus infection of lambs and calves. There is porencephaly, hydranencephaly, cerebellar hypoplasia (called dysplasia) and dysplasia of the brainstem and spinal cord, a flattened skull, brachygnathia inferior, arthrogryposis, and vertebral column malformations. They suggest that loss of ventral horn neurones of the spinal grey matter and micromyelia is unique to SBV. Many have poliomyeloencephalitis.

Matsumori et al (2018) described the congential abnormalities in calves in Japan attributed to Peaton orthobunyavirus (PEAV).


Herder V, Wohlsein P, Peters M, Hansmann F, Baumgärtner W. (2012) Salient lesions in domestic ruminants infected with the emerging so-called Schmallenberg virus in Germany. Vet Pathol 2012; 49: 588-591.

Matsumori Y, Aizawa M, Sakai Y, Inoue D, Kodani M, Tsuha O, Beppu A, Hirashima Y, Kono R, Ohtani A, Yanase T, Shirafuji H, Kato T, Tanaka S, Yamakawa M. Congenital abnormalities in calves associated with Peaton virus infection in Japan. J Vet Diagn Invest 2018; 30: 855-861.


Peperkamp NH, Luttikholt SJ, Dijkman R, Vos JH, Junker K, Greijdanus S, Roumen MP, van Garderen E, Meertens N, van Maanen C, Lievaart K, van Wuyckhuise L, Wouda W. Ovine and Bovine Congenital Abnormalities Associated With Intrauterine Infection With Schmallenberg Virus.Vet Pathol 2015; 52(6):1057-1066.

Bluetongue virus (BTV)

The bluetongue viruses are of the Order Unassigned, Family Reoviridae, Subfamily Sedoreovirinae, Genus Orbivirus

There are many viruses of the Bluetongue group. Like the Orthobunyaviruses, they are spread by insects of the Culicoides genus and they cause a similar disease to that of the Orthobunyavirus genus. Early embryonic mortality and hydranencephaly is a common manifestation of infection of pregnant cows.

Epizootic hemorrhagic disease virus (EHDV), Ibaraki virus (IBAV), Chuzan virus (CHUV)

EHDV, IBAV and CHUV are of the Order Unassigned, Family Reoviridae, Subfamily Sedoreovirinae, Genus Orbivirus, just like bluetongue virus.

IBAVI is found in Japan and produces an oral and oesophageal disease just like bluetongue in sheep. EHDV and IBAV both can cause abortion and stillbirths in cattle. This is not a common manifestation, however.

CHUV is found in Japan where it produces microcephaly, hydranencephaly and cerebellar hypoplasia in newborn calves.

Rift Valley Fever phlebovirus (RVFV)

Rift Valley Fever phlebovirus is of the Order Unassigned, Family Bunyaviridae, Genus Phlebovirus. It is found in Africa in at least 18 countries, plus Saudi Arabia.

It produces fatal hepatic necrosis that is multifocal to confluent and acidophilic intranuclear inclusion bodies



Ungulate bocaparvovirus 1 (Bovine Parvovirus)

Ungulate bocaparvovirus 1 is of the Order Unassigned, Family Parvoviridae, Subfamily Parvovirinae, Genus Bocaparvovirus.

BPV is believed to cause abortion, stillbirth and weak born calves in naive pregnant cows. Cerebellar hypoplasia is reported. It is not routinely sought as a cause of FOP. Histologically there are intranuclear inclusion bodies in cells near foci of necrosis in the intestinal crypts, cerebellum, hepatocytes and adrenal cortex.


Geotrichium candidum

Although this fungus is ubiquitous in soil, organic matter and silage, it is rarely associated with pregnancy failure.

Antoniassi et al (2013) reported on an aborted fetus that had dermatitis and pneumonia from which this fungus was identifed and cultured.

Antoniassi NA, Juffo GD, Santos AS, Pescador CA, Ferreiro L, Driemeier D. Geotrichum candidum as a possible cause of bovine abortion. J Vet Diagn Invest. 2013; 25: 795-797.

Coxiella burnetii

Q fever is the common name for the disease caused by Coxiella burnetii. This pathogen is well known in small ruminants, and serology suggests infection in cattle is widespread. Garcia-Ispierto et al (2014) published a review of the effects of Coxiella burnetii in cattle.

PCR testing of placentas identifies the presence of organisms, but placentitis and fetal death directly attributed to this organism is surprisingly uncommon.

Garcia-Ispierto I, Tutusaus J, Lopez-Gatius F (2014) Does Coxiella burnetii Affect Reproduction in Cattle? A Clinical Update. Reprod Dom Anim 2014; 49: 529–535


Mycoplasma bovis

Mycoplasma bovis is implicated in causing failure of pregnancy.

It was isolated from the abomasum of an aborted calf by Byrne et al (1999). It was a field postmortem with collection of abomasal contents.

Byrne WJ, Brennan P, McCormack R, Ball HJ. Isolation of Mycoplasma bovis from the abomasal contents of an aborted bovine fetus. Vet Rec 1999 144: 211-212


Mortality rates

Walder et al (2010) reported on abortions, stillbirths and calf mortalities of beef cattle in western Canada. They found that, based on a survey of 203 herds with a total of 29,970 pregnant cows, the loss was 2.6%

In Japanese Black cattle, Uematsu et al (2013) reported that the stillbirth rate was 2.46% (1013 stillbirths). The rate was higher in winter (3.18%). Multiparous animals had a lower rate, and the longer the gestation length, the higher the rate also.

Calves derived from cloning are more likely to suffer stillbirth and perinatal mortality. Congenital defects including limb deformities are common. Of 31 calves in the study by Brisville et al (2013) 4 were stillborn and 5 had congenital defects. 14 took a long time to stand.

Causes of Stillbirth

Walder et al (2010) found that of 560 stillborn calves, 40% were because of dystocia, 22% were undetermined, 8% had thyroid lesions, 7% had myocarditis or myopathy, 4% had developmental anomalies, 4% had myonecrosis, 2% heart failure, 2% pneumonia, 1% placentitis, 1% trauma, and 1% were premature.

Mee et al (2008) reports that approximately 90% of calves are alive at the start of the birth process. Those that were not subject to dystocia must have failed in the transition from intrauterine to terrestrial environments.


Dystocia is a very important cause of stillbirth, and probably underestimated as the lesions are subtle or not identified. Walder et al (2010) found 40% of stillbirths were attributed to dystocia. Dystocia was a cause of perinatal mortality in 10% of those cases.

Dystocia is more common in first-calf heifers yet their calves are usually smaller.

Barrier et al (2013) studied dystocia and found that those calves with assisted delivery had greater haemorrhage and had large bruises. There was no difference in body weight, crown rump length or other confirmational parameters.


Barrier AC, Mason C, Dwyer CM, Haskell MJ, Macrae AI.(2013) Stillbirth in dairy calves is influenced independently by dystocia and body shape. Vet J 2013; 197: 220-223.

Brisville AC, Fecteau G, Boysen S, Desrochers A, Dorval P, Buczinski S, Lefebvre R, Helie P, Blondin P, Smith LC (2013). Neonatal Morbidity and Mortality of 31 Calves Derived from Somatic Cloning. J Vet Intern Med 2013; 27: 1218–1227

Uematsu M, Sasaki Y, Kitahara G, Sameshima H, Osawa T, (2013) Risk factors for stillbirth and dystocia in Japanese Black cattle. The Vet J 2013; 198: 212-216

Waldner CL, Kennedy RI, Rosengren LB, Pollock CM, Edward (Ted) G. Clark EG (2010) Gross postmortem and histologic examination findings from abortion losses and calf mortalities in western Canadian beef herds. Can Vet J 2010 ;51:1227–1238