What to look for

  • Abortions – multiple or single animals affected
  • Cows are usually in mid-pregnancy
  • The dead calf may be retained in the cow and become mummified
  • Calves might be born alive but weak

Cause - a protozoan organism (Neosporum caninum)

Domestic dogs (and possibly foxes) are the natural hosts, and can be persistently infected without any signs of illness. The parasite is deposited into the environment in dog faeces where it may be picked up by cows. It then spreads through the body tissues including the foetus. The organism may also spread from cow to cow, possibly by contact with newborn calves or afterbirth. A proportion of calves that are infected before birth are born healthy, but remain infected with Neospora organisms, and are likely to infect their own calves when they become pregnant.

Animals likely to be affected

Pregnant cows.

Other diseases with similar signs

Other causes of abortion.

Confirming the diagnosis

Characteristic microscopic changes in the aborted calf. Blood samples from cows that have aborted and from other animals in the herd may also help determine the cause of the abortion. Many infected animals are healthy and show no signs of infection.

Risks to people

Neosporum caninum does not infect people but other agents that cause abortions in cattle such as ListeriaLeptospirosis and Salmonella can cause serious diseases in people. Treat all aborted calves and the associated afterbirth as infectious and take care with personal hygiene to minimise exposure.

Risk factors

  •  Dogs have access to areas where cows are feeding
  • Persistently infected cows


Use a blood test to identify cows that are infected and either cull them or only use cows that are blood test negative for breeding future replacements. Embryo transfer may also be used to breed uninfected calves from infected mothers if the infected cow has a high genetic value.

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