We recently investigated a number of abortions in this practice; they were caused by neospora caninum.

Neospora is a parasite that causes disease in cattle and dogs. The dog is the definitive host and cattle are the intermediate host. Infected dogs shed parasite eggs in their faeces which contaminate the environment.

These are ingested by cattle via contaminated feed or water. They then spread rapidly via the bloodstream, invading body cells and becoming cysts. These cysts lodge in tissues such as the afterbirth and as such cause abortion. They also lodge in the brain of the foetus and their presence in the brain on laboratory examination is a help in diagnosis.

Abortion can take place from onwards of three months of pregnancy and might even be confused with infertility if the cow comes back in heat at three months, though generally abortion occurs between the fifth and seventh month.

Dogs become infected by eating afterbirths or aborted foetuses. After a short time they start passing neospora eggs, which if picked up by pregnant cows cause abortions.

Calves born full-time to infected cows very often are infected, and this infection is activated when heifer calves eventually become pregnant, thus perpetuating the condition. This is called “vertical transmission”.

Introducing neospora

Neospora can be introduced to a farm by buying in infected animals or by infected dogs having access to animal feed (including grass).

Neospora will not necessarily cause abortion in all infected animals, but when infection strikes a naive herd then one is likely to see up to 10% abortion.

Diagnosis is by blood testing and testing of aborted foetuses. When submitting material to the laboratory it is important to submit afterbirths and foetuses as well as blood from the dam.

In uninfected herds, keeping a closed-herd policy will eliminate one of the transmission routes; if one must buy in stock then blood-testing them is important.

Presently there is no vaccine available for this disease, so in infected herds one should dispose of all afterbirths, prevent dogs from having access to cattle areas especially calving areas, breed heifers from blood test negative dams, and if possible cull blood test positive cows.