The effect of 5-fluorouracil and 5-fluorocytosine on the development of the filarial nematodes Brugia pahangi and Dirofilaria immitis.

5-fluorouracil and 5-fluorodeoxyuridine at 30 mg/kg body weight daily for four days inhibit microfilarial production in Brugia pahangi in the jird. Disruption of intrauterine embryogenesis was observed in treated female worms but the compounds were not macrofilaricidal or microfilaricidal under the conditions employed. 5-fluorocytosine possessed no filaricidal or embryostatic activity. The inhibition of microfilaria production by 5-fluorouracil was temporary and larval production was resumed within nine weeks. The compound also inhibited the development of B. pahangi and Dirofilaria immitis larvae in the mosquito Aedes aegypti, when administered to cages of mosquitoes as a 0.01 or 0.001% solution in a 10% aqueous sucrose solution on cotton wool wicks. The development of infective larvae of B. pahangi in the jird was inhibited by 5-fluorouracil.