Neosporosis - Cattle

Description

Caused by the protozoan parasite Neospora caninum and is the commonest cause of abortion in dairy cattle. Neospora caninum is similar to Toxoplasma gondii and although the complete life cycle of the protozoa is unknown, the dog has been found to be the definitive host.

Stillborn calves can be born from infected dams and congenitally infected calves may be born with encephalomyelitis. Abortion usually occurs between 5-7 months of gestation but can occur as early as 3 months. Most cases of infection occur via vertical transmission however animals can become infected from their mothers milk, by eating food and water contaminated with dog feces containing neospora caninum oocysts, or from cow to cow.

Signalment

Neospora has been documented to infect cattle, sheep, goats and the dog.

Diagnosis

The histological appearance of lesions on an aborted fetus can be enough to confirm a diagnosis, tissue cysts may also be evident and can be identified. Additionally An indirect fluorescent antibody test can be used to detect antibodies from samples and an ELISA is available which will also detect antibodies. A PCR method to identify antigen is currently under development

Clinical Signs

Often infected cattle present with no clinical signs other than abortion.

Calves can be born with encephalomyelitis causing various neurological signs such as paresis.

Repeat abortions are often reported in affected animals due to a persistent infection.

Pathology

Non-suppurative encephalitis is most commonly seen in aborted faeces. non suppurative myocarditis myositis widespread non suppurative infiltrates in other organs

Treatment

Dogs should not be allowed access to calving cows, placental membranes and aborted or dead calves

Dogs should also be stopped from defecating in cattle feeding areas.

Seropositive cattle should be identified and culled and none of their progeny should be bred from.

Select seronegative cattle for breeding

Vaccinate is possible but only in the USA. It is a killed protozoal vaccine for healthy, pregnant cows and is given in the first 3 weeks of pregnancy and then every 3-4 weeks during gestation. Revaccination with 2 doses should be undertaken during each subsequent pregnancy.