Experimental Oesophagostomum bifurcum in monkeys

Oesophagostomum bifurcum larvae, cultured from human stools collected in no rthern Ghana, were used to establish experimental infections in monkeys. A patent infection was established in a rhesus monkey (Macaca mulatta) and th is infection was used to generate larvae to inoculate additional monkeys. I n all, 17 animals were inoculated. Thirteen of 15 animals developed antibod ies to the infection between 19 and 62 days post inoculation (PI); two anim als had a positive response before inoculation. Four of ten animals develop ed patent infections between 88 and 134 days and passed eggs in the faeces. Egg shedding was consistent in only one animal, but at low levels of one o r two eggs per 2 mg direct smear, and extended over a 400 day period. In th e other three animals, egg shedding was sporadic and of only 2-4 weeks dura tion. In seven animals necropsied between 19 and 22 days PI, one to 17 earl y fourth-stage larvae were recovered from nodules in the bowel wall; in an eighth animal examined at 314 days, six immature adult worms (early fifth s tage) were recovered from nodules in the bowel wall. The morphological feat ures and growth of these recovered larvae are described. Three animals were inoculated with larvae that had been dried for one week at 28 degreesC; tw o animals began shedding eggs at 128 and 134 days PI, respectively. The pre sent results suggest that the parasite obtained from humans is poorly adapt ed to lower primate hosts, and supports the concept that Oesophagostomum bi furcum found in humans and monkeys in the same geographical region of north ern Ghana and Togo are distinct and that the infections in humans are not l ikely to represent zoonotic infections acquired from monkeys.