EVIDENCE OF VERTICAL TRANSMISSION OF NEOSPORA SP INFECTION IN DAIRY-CATTLE

Objective-To determine whether heifers with naturally acquired congeni tal exposure to Neospora sp would transmit the infection to their offs pring during gestation. Design-Prospective cohort study. Animals-Neona tal heifers on a dairy with a history of Neospora sp infections were s elected for the study on the basis of their serum titers to Neospora s p, as determined by the use of indirect fluorescent antibody testing. Seropositive heifers (n = 25) had titers greater than or equal to 1:5, 120 and seronegative heifers (25) had titers less than or equal to 1:8 0. All heifers were raised and bred on the dairy, and samples were obt ained from heifers and their calves at the time of calving. Procedure- Blood samples were tested for Neospora sp antibodies. Histologic evalu ations, Neospora sp immunohistochemical examinations, and protozoal cu lturing were performed on samples obtained from selected offspring (se cond-generation calves). Results-Seropositive heifers gave birth to ca lves with titers greater than or equal to 1:1,280 to Neospoia sp. All offspring from seropositive heifers that were necropsied had evidence of Neospora sp infection. All seronegative heifers and their offspring had titers < 1:80 to Neospora sp. Clinical Implications-Congenitally acquired Neospora sp infection can persist in clinically normal heifer s and be transmitted transplacentally to their offspring. Vertical tra nsmission can be a way by which neosporosis is maintained in herds.