It is now the most common cause of abortion in dairy herds in GB and the number of infected beef herds appears to be increasing. Infection is caused by a parasite, similar to Toxoplasma in sheep. There are two main routes of infection: vertical (from the dam to its calf in the womb) and horizontal. The infectious agent is shed in the faeces of dogs that have become infected after scavenging on infected abortion material or stillborn calves. If their faeces contaminate feed supplies it can result in cattle becoming infected which can range from a few animals to a large number e.g. if faeces have been dispersed through a batch of feed in a feed wagon.
The infection is transmitted very efficiently in the womb from an infected cow or heifer to its offspring resulting in about 85-90% of calves being born infected if the dam is infected. Infection is lifelong and infected animals are at a much higher risk of aborting than uninfected animals. The risk of abortion is highest during the first pregnancy after infection but subsequent pregnancies are also at a significant risk. Therefore, if possible, it is advisable not to keep female offspring from infected cows as breeding replacements. If infected females are identified in a dairy herd they can be bred to beef sires and the offspring can be finished for beef. It has also been shown that cross-breeding of infected dairy females can reduce the risk of abortion.
The greatest costs of the infection are from abortions and the loss of future genetic material as there are fewer uninfected female replacements to select from in infected herds.
To reduce the risk of dogs from becoming infected then all aborted foetuses, placentas, stillborn and dead calves should be stored in a way that prevents scavenging. Where possible, dogs should not be allowed access to cattle feed to prevent them from defecating in it.
Herds can be tested for Neospora and categorised as one of five risk levels.
Risk Level 1: Herds that have had three or more clear consecutive annual herd tests
Risk Level 2: Herds that have had one or two clear consecutive annual herd tests
Risk Level 3: Herds where less than 5% of the eligible animals were positive
Risk Level 4: Herds where more than 5% of the eligible animals were positive
Risk Level 5: Herds that are not complying with the CHeCS rules for the Neospora programme