Neospora is now the most commonly diagnosed cause of abortion in cattle in New Zealand and some known facts about this problem are listed here: – The dog has been confirmed experimentally as a definitive host, spreading the infection through faeces. – Vertical transmission from cow to calf is proven which means that infected dams can produce infected calves if they dont abort. – In non-pregnant infected cattle, the infection is latent and is reactivated during pregnancy. The trigger for this reactivation is unknown. – Horizontal transmission from cow to cow is suspected but not yet proven. – Abortions can occur from conception to full term but are most frequently diagnosed during the fifth month of gestation and in cows four years old or younger. – Abortion storms due to Neospora are most common in April and May. Sporadic abortions can continue after this. It appears that these abortion storms are the result of point exposure to Neospora cysts 60 – 100 days prior to the abortions occurring. BVD virus infection might well be a trigger – Sporadic abortions occur in many herds at a low level. These cows are infected vertically and infection reactivated during pregnancy. In this situation there is no spread from cow to cow via infected placental or foetal material. – As less than 5-10% of cattle aborting from Neospora will re-abort, culling for this reason is not warranted. Even if these cows were culled there would remain a number of non-aborting latently infected cattle in the herd. The only control measure known at present, is to reduce the chance of dogs infecting cattle by preventing dogs having access to aborted material and raw beef and keeping dogs restrained when not working to limit faecal contamination of pastures.