Effects of repeated anthelmintic treatment on Enterobius vermicularis infection in chimpanzees

Effects of repeated treatment with pyrantel pamoate on Enterobius vermicularis infection in chimpanzees were assessed by observing worms discharged in the feces after administration of anthelmintic treatment. Three of 9 chimpanzees reared in a zoological garden in Japan were subjected to fecal worm count and morphometric observation, and all were given oral pyrantel pamoate 6 times at 10-day intervals simultaneously. Following the first and second treatments, more than 30,000 pinworms were discharged from 1 chimpanzee. The number of discharged worms abruptly decreased after the third treatment, and only a few worms were recovered after the fifth treatment, indicating that repeated treatment at short intervals was very effective. Complete eradication was not achieved, however, presumably because of reinfection. The female proportion among discharged worms tended to increase as the treatment was repeated.