Why be interested in Neospora caninum on farm?

The most common cause of abortion in submissions to Animal and Plant Health Agency (APHA) laboratories is Neospora caninum, according to the Veterinary Investigation Diagnosis Report (APHA, 2021). Identification of an aborting cow and loss of a fetus is the most obvious sign, with the impact of the loss to the herd evident. If this is part of an outbreak or ‘abortion storm’ then the production losses will be even more significant, but this only makes up a proportion of the impact of N. caninum. Not all N. caninum infections will lead to an abortion; cows can exist as carriers of this protozoan parasite with no outward signs, which makes monitoring and surveillance even more important to identify the impact of this disease.

Neospora infection in cattle can occur through vertical transmission (cow to calf) or horizontal transmission (Figure 1). Spread from cow to cow is not possible and this protozoan parasite requires a definitive host to complete the lifecycle. Dogs are a known definitive host. The protozoa has been detected in other wild carnivores, but there is no evidence that they shed oocysts and are unlikely to be the source of on-farm spread in the same way that dogs can be (Stuart et al, 2013). Oocysts have been found present in other mammalian species but there is no known zoonotic risk.