Evidence of point-source exposure to Neospora caninum and protective immunity in a herd of beef cows

Abstract
Objective—To determine whether cows with evidence of previous infection withNeospora caninumwere less likely to abort or give birth prematurely during an outbreak of neosporosis, compared with herdmates with evidence of primary infection.Design—Cohort study.Animals—208 pregnant beef cows.Procedure—Aborted fetuses and calves born prematurely were examined during an outbreak of neosporosis in a herd of beef cows. Sera were collected from all cows during the outbreak and again 71 days later. Cows were classified into groups on the basis of normal and abnormal reproductive outcomes. Sera were examined, using an avidity ELISA procedure forN caninum, and results were compared between groups and among time points.Results—Antibody concentrations decreased significantly and IgG avidity values increased significantly over time. During the outbreak, cows with normal reproductive outcomes were significantly more likely to have high IgG avidity values than cows with abnormal reproductive outcomes.Conclusions and Clinical Relevance—The herd had numerous abortions and premature births with evidence of recent point-source exposure toN caninum. Therefore, to reduce risk of transmission ofN caninumto cattle, attempts should be made to prevent canine feces from contaminating feed, especially feedstuffs used to prepare mixed rations for cattle. Cows with evidence of previous exposure toN caninumwere less likely to abort or give birth prematurely during the outbreak than cows with primary infections withN caninum; this finding suggests development of protective immunity in previously infected cows. (J Am Vet Med Assoc2000;217:881–887)

This publication has 34 references indexed in Scilit: