pyogenes
This bacterium is rarely isolated and is found in late-term abortions. There is no vaccine available.
Bacillus licheniformis
This is a rare cause of abortion and is associated with the feeding of poor-quality forage. The cow is not ill but the bacterium is isolated from the fetus or the placenta. There is no vaccine available.
Bovine herpesvirus 1 (BHV 1)
This virus will cause abortion after 150 days post service. There is venereal spread of a strain of virus which appears to be different from the virus that causes respiratory signs. Animals which have aborted are then immune. There is a vaccine, which is not licensed in the UK, which should be given to heifers before service when at risk from the disease.
Bovine viral diarrhoea virus (BVDV)
BVDV may cause infertility problems related to early embryonic death, but abortion is rare. The virus will cause diarrhoea in adult cows and mucosal disease in calves infected in utero (these calves are PI). Infected cows will test serologically positive but virus negative, unlike the PI calves. There are very effective vaccines available.
Brucellosis
This is caused by the bacterium Brucella abortus. The disease has largely been eradicated in the EU and totally eradicated in the UK, where it is notifiable. It is highly contagious via the products of abortion and is a zoonosis. It will cause late abortion storms in naive cattle. There are two vaccines available, one of which does not interfere with the serology used for eradication programmes. Diagnosis is by bacteriological examination of the fetus, the placenta and milk, or by the detection of antibodies in blood or milk.
Campylobacter fetus subsp. veneralis
This is an obligate bacterial parasite of the reproductive tract and cannot survive outside the host for any appreciable time. Normally it causes early embryonic death. This can be reduced by blanket injections to the cows of streptomycin. Bulls can be cleaned by prepu-tial washing with an oily preparation of streptomycin for 3 days.
Chlamydophila abortus
This bacterium is a common cause of abortion in sheep, but is extremely rare in cattle. However, it is important as it is a zoonosis.
Coxiella burnetii
This bacterium causes Q fever which does occur sporadically in cattle causing late abortions and stillbirths. It is found worldwide (except in New Zealand). Diagnosis is best by histopathology and staining with a modified ZN stain. The organism is spread in milk, placenta, urine and faeces, and is zoonotic. At the time of writing there is no cattle vaccine but there is a vaccine for goats.
Leptospira icterohaemorrhagiae
This organism is very rare but is associated with a serious systemic illness in cattle, which will show clinical jaundice. In some instances, the pyrexia from the systemic disease will cause an abortion. In other instances, the organism will be isolated from the abortion products.
Leptospira serovar Hardjo (L. borgpetersenii serovar Hardjo and L. interrogans serovar Hardjo)
These bacteria will cause abortion but more commonly cause infertility. They are associated with transitory illness in cows which show a ‘milk drop’ syndrome. The condition is readily diagnosed on serology. It can be spread from infected urine and infected ditches, and also from infected sheep which are symptom-less carriers. It is a zoonosis. There are good vaccines available.
Leptospira serovar Pomona
This organism is not a primary cattle pathogen and is found in many mammalian species. It has been isolated in rare instances from aborted cattle fetuses.
Listeria monocytogenes
This bacterium causes primarily a neurological pyrexic, zoonotic disease. Abortions are normally sporadic but can affect up to 20% of the herd at any stage of gestation. Death of the fetus occurs 2 days before the abortion so the fetus is normally decomposed. The disease is normally associated with the feeding of silage. Treatment with antibiotics is helpful. There is no vaccine available.
Mycotic abortion
Aspergillus fumigatus is the main causal organism of mycotic abortion. Infection comes from eating mouldy bedding or feeding stuffs. The organism spreads in the bloodstream to the placenta, and causes late abortions. Diagnosis is by demonstration of the fungus in the placenta, which has ‘ring-worm’-like lesions.
Neospora caninum
This protozoan was first seen in dogs and spreads from them by the faecal-oral transfer to cattle. It has only recently been associated with bovine abortion. The organism is common in the UK but it may not be as common as serology might suggest. The definitive diagnosis is from immunohistochemistry of fetal brain tissue. This will differentiate N. caninum from Toxoplasma gondii. The main method of spread is vertical transmission from infected dams to congenitally infected calves. There is no vaccine available.
Parachlamydia acanthamoeba
This bacterium was first found in Switzerland causing suppurative and necrotizing placentitis. It is now found in southern Scotland. It can be diagnosed on PCR. It may have zoonotic implications.
Rift Valley fever
This viral disease caused by a bunyavirus is found in Africa and the Middle East. The main method of spread is by Aedes mosquitoes. The abortion rate can be 100%, with 10% of adult cattle dying, and showing icterus and pyrexia. Diagnosis can be confirmed with serum and heparanized blood that show high titres and by virus isolation. There is no treatment but there is a vaccine available.
Salmonellosis
This is a rare cause of abortion and might just be the raised temperature from a systemic infection, but in some instances S. dublin or S. typhimurium are isolated from the fetus or the placenta. The spread is via the contaminated environment. There is a vaccine against S. dublin available.
Schmallenburg virus (SBV)
The Orthobunyavirus that causes this disease of cattle is named after the town of Schmallenburg in North West Germany where it was first discovered in August 2011. By the time of writing, it had spread to most of Western Europe. SBV is spread by Culicoides obsoletus and C. dewulfi and is reportable but not notifiable in the UK. Clinical signs seen in cattle include fever, reduced milk yields, inappetence, weight loss and diarrhoea. These signs are transitory, but the most important result
