- 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 after abortion. A significant proportion of cows develop pyometra.
- Neospora caninum is found worldwide and is the most common cause of abortion in dairy and beef cattle in many parts of the USA.
- Trueperella pyogenes causes sporadic abortion at any stage of pregnancy. Rarely, the incidence in a herd may reach epizootic levels. The bacterium is present in the nasopharynx of many healthy cows and in abscesses.
- 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.
- Bluetongue as a Cause of Abortion in Cattle. is caused by an Orbivirus with 24 serotypes and is transmitted by biting midges of the genus Culicoides.
- Infectious bovine rhinotracheitis (IBR) is a major cause of viral abortion worldwide, with abortion rates of 5%–60% in nonvaccinated herds.
- Chlamydophila 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.
- The pathogenic leptospires were formerly classified as serovars of Leptospira interrogans,.
- 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.
- Epizootic Bovine Abortion (Foothill Abortion) in Cattle
- In several surveys, bovine viral diarrhea (BVD) was the most commonly diagnosed virus in bovine abortion cases.
- 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 months), and ~80% of unvaccinated cows in later gestation will abort if exposed to Brucella abortus.
- Campylobacter fetus venerealis causes venereal disease that usually results in infertility or early embryonic death but occasionally causes abortion between 4 and 8 months 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.