Diclazuril preventive therapy of gamma interferon knockout mice fed Sarcocystis neurona sporocysts

Gamma interferon knockout (KO) mice (n = 74) were fed a lethal dose of simi lar to 1000 sporocysts of the SN15-OP isolate of Sarcocstis neurona. Groups of mice were given pelleted rodent feed containing 50 ppm of diclazuril at different times before and after feeding sporocysts. All mice were examine d at necropsy and their tissues were examined immunohistochemically for S. neurona infection. Twenty mice were fed sporocysts and given diclazuril sta rting 5 days before feeding sporocysts and continuing 30-39 days post-infec tion (p.i.). One mouse died of causes unrelated to S, neurona with no demon strable parasites; the remaining 19 mice remained clinically normal and S. neurona organisms were not found in their tissues. Sarcocystis neurona orga nisms were not demonstrable by bioassay of the brains of these 19 mice in u ninfected KO mice, Sarcocystsis neurona organisms were not found in tissues of five mice treated with diclazuril, starting 7 days after feeding sporoc ysts and continuing up to 39 days p.i. Therapy was less efficient when dicl azuril was given 10 days p.i. Sarcocystis neurona organisms were found in t wo of :19 mice treated with diclazuril starting 10 days after feeding sporo cysts, in two of five mice starting therapy 12 days p.i., and in 10 of 10 m ice when treatment was delayed until 15 days p.i. All 15 mice fed S. neuron a, but not given diclazuril, developed neural sarcocystosis and were euthan ized 22-30 days after feeding sporocysts. Six mice not fed S. neurona. but given diclazuril for 44 days, remained clinically normal. Results indicate that diclazuril can kill the early stages of S. neurona. Published by Elsev ier Science B.V.