Neospora species infection in a herd of dairy cattle.

Objective: To investigate the route of transmission of Neospora sp in a herd of dairy cattle in which sporadic abortions had been observed since the establishment of the farm in 1980.
Design: Serum samples were screened for antibodies to Neospora sp, and records from an artificial insemination program were analyzed.
Animals: 58 female cattle.
Procedure: An ELISA was used to screen serum samples of antibodies to Neospora sp. Fertility, calf mortality, and relationships between specific cattle were investigated. Statistical analysis was performed on the fertility data.
Results: Antibodies were detected in 17 of 58 (29%) tested cattle. All seropositive cattle were descendants of 2 cows purchased in 1980. Cattle that were descendants of those 2 cows were compared with their herdmates, but significant differences were not detected in the number of inseminations per confirmed pregnancy or in the number of cattle that required more than 1 insemination/ pregnancy. Since 1980, there were 323 confirmed pregnancies in the herd, and calf mortality (prenatal and perinatal mortality) was 24 of 323 (7%).
Clinical Implications: Congenital transmission of Neospora organisms together with the apparent lack of horizontal transmission observed in the herd reported here indicated that Neospora sp has the ability to be transmitted from dam to offspring for several generations. This mode of transmission would explain the maintenance of infection in a population of cattle despite the lack of a definitive host for the parasite.