Daily feeding of diclazuril top dress pellets in foals reduces seroconversion to Sarcocystis neurona.

Thirty-three foals from a farm with a high exposure rate to Sarcocystis neurona were assigned to either an untreated or a diclazuril-treated group. Treated foals received daily 0.5 mg/kg of diclazuril pellets from 1 to 12 months of age. Monthly blood was tested for IgG against S. neurona using the indirect fluorescent antibody test. Following ingestion of colostral antibodies to S. neurona, there was a steady and continuous decline in seroprevalence to S. neurona until foals from both groups reached weaning age. Thereafter, the untreated foal group showed a significant increase in monthly seroprevalence compared to the diclazuril-treated foal group. The difference in temporal seroprevalence could be explained by the successful reduction of S. neurona infection in foals receiving a daily low-dose diclazuril.