Chemotherapy of filariasis in squirrel monkeys (Saimiri sciureus)

The effect of some known antifilarial drugs on naturally-occurring filariae in squirrel monkeys, Saimiri sciureus, was evaluated. Four drugs, dithiazanine iodide, naphuride sodium, thiacetarsamide sodium, and diethylcarbamazine were tested against Dipetalonema gracile and Tetrapetalonema marmosetae. Dipetalonema caudispina was included in some of the studies using diethylcarbamazine. These are the three most commonly encountered filarial species in squirrel monkeys. Dithiazanine iodide proved to be unsuitable for use because of lack of acceptance by the monkeys. Naphuride sodium (10 mg/kg/week for 5 weeks) did not exert filaricidal activity against the species tested during a 7-month evaluation period. Thiacetarsamide sodium (0.22 ml/kg twice daily for 2 days) had lethal effects on the adult parasites, but not the microfilariae, of all species tested. Diethylcarbamazine (50 mg/kg/day for 10 days) was found to be effective against both microfilaria and adults of all filarial species tested. Monkeys given this regimen were microfilaria-negative for 12-24 weeks following treatment.