What is Neospora?
Neospora caninum is a parasite that infects cattle and can cause abortion. Cattle can become infected in two ways: ·
- By eating Neospora oocysts (eggs) from the environment along with food or water.
- As an unborn calf when Neospora crosses the placenta from an infected cow.
Infection can arrive on farm by several routes:
- Via purchase of an infected cow.
- Via recently infected dogs.
- In feed or water contaminated by dog faeces.
Dogs are a vital part of the Neospora story. They become infected by eating Neospora infected placentae, foetuses, calves or wildlife. The parasite multiplies in their intestine and oocysts are passed in faeces for 2 to 3 weeks. After this the dog is immune and no longer a risk. As oocysts are only shed when the dog is infected for the first time this is most likely to occur in pups or young dogs. The oocysts are thought to survive in the environment for many months. After being eaten by a cow the oocysts multiply and then become dormant within tissue cysts. This has no ill effects on the cow which continues to appear healthy. The danger comes during pregnancy when the parasite re-activates and travels to the placenta and unborn calf. What happens next can include:
- Abortion - abortion storms can occur when infection is introduced to a herd for the first time.
- The birth of a healthy, but infected, calf which may go on to abort during its first pregnancy.
- The birth of a calf showing signs of nervous disease. This is uncommon.
Infected cows remain infected for life and maintain Neospora in the herd by giving birth to infected heifer replacements. There is no evidence of direct cow to cow spread.
- Not all infected cows will abort but they are three to seven times more likely to abort than uninfected cattle.
- Abortions are most common in heifers and in recently infected cows.
- It is estimated that, if retained in the herd, around 5% of infected cows will abort again.
- The best way to screen cows for Neospora is by testing a blood sample collected either after abortion or in late pregnancy. · To confirm that an abortion has been caused by Neospora, the full foetus and placenta need examined at a Disease Surveillance Centre.