Evidence of post-natal transmission of Neospora caninum in Dutch dairy herds

Eighteen dairy herds with neosporosis-associated abortions were analysed fo r antibodies against Neospora caninum. Blood samples of all cows, heifers a nd calves were collected on the same day for each farm. A total of 2430 hea ds of cattle were examined. For each herd, the seropositive and seronegativ e animals were plotted against month of birth. Analysis of seroprevalence i n relation to age showed an equal distribution of seropositives in all age- groups in 10 herds. In contrast, in eight herds an age-group could be ident ified which had a significantly higher seroprevalence than the other animal s in the herd. Most seropositive animals in the high seroprevalence age-gro ups had either seronegative dams or seronegative offspring, whereas there w as a strong relationship between the serostatus of dams and offspring in th e other animals in the herd. Aborting animals were mainly part of the high seroprevalence age-group. These findings strongly indicate a post-natal inf ection of the animals in the high seroprevalence age-groups, probably due t o a point source exposure to N. caninum. (C) 2001 Australian Society for Pa rasitology Inc. Published by Elsevier Science Ltd. All rights reserved.