CONGENITAL-DEFECTS IN NEWBORN FOALS OF MARES TREATED FOR EQUINE PROTOZOAL MYELOENCEPHALITIS DURING PREGNANCY

Three weak, recumbent neonatal foals with skin lesions, including a th in wooly coat, were born to mares being treated for equine protozoal m yeloencephalitis. Mares received sulfadiazine or sulfamethoxazole-trim ethoprim, pyrimethamine, folic acid, and vitamin E orally. Foals were anemic, leukopenic, azotemic, hyponatremic, and hyperkalemic. Serum fo late concentrations in the 3 foals and 2 mares were lower than those r eported in the literature for clinically normal broodmares. Treatment was unsuccessful. For each foal, necropsy revealed lobulated kidneys w ith thin cortices and a pale medulla, and the spleen and thymus were s mall. Histologic examination revealed marked epidermal necrosis withou t inflammatory cells, thin renal cortices, renal tubular nephrosis, ly mphoid aplasia, and bone marrow aplasia and hypoplasia. These observat ions indicate that oral administration of sulfonamides, 2,-4-diaminopy rimidines (pyrimethamine with or without trimethoprim), and folic acid to mares during pregnancy is related to congenital defects in newborn foals.