Dracunculus medinensis and D. insignis are morphologically indistinguishable. Experiments to test the susceptibility of various mammalian hosts to these two guinea worm species are described. Infective 3rd-stage larvae of D. medinensis were administered to each of four raccoons (Procyon lotor): infective 3rd-stage larvae of D. insignis were administered to a rhesus monkey (Macaca mulatta), two dogs, two ferrets (Mustela putorius furo), and a marten (Martes americana). D. medinensis was not found in the raccoons when necropsies were performed on days 247, 283, 354, and 390 post-infection, respectively. Nine female D. insignis containing eggs, embryos, and motile 1st-stage larvae were found in the rhesus monkey 180 days post-infection. Lesions had not formed and the larvae were presumed to be immature and not yet infective as they were comparatively inactive and attempts to infect suitable copepods failed. D. insignis was not found in the dogs or the marten, although both ferrets were successfully infected. Variations in susceptibility of various mammalian species to the guinea worm are discussed together with comments on variations in migration routes and sites of emergence in hosts which may be partially refractory. D. insignis and D. medinensis may represent physiological strains of a single species, or they may in fact be two distinct species which have evolved in different geographical locations.
Present address: Manitoba Department of Mines, Resources and Environmental Management, 1-139 Tuxedo Boulevard, Box 12, Winnipeg, Manitoba, Canada R3N 0H6.