Hybridization between Brugia malayi and Brugia pahangi from south Kalimantan, Indonesia.

Hybridization experiments were carried out between sub-periodic Brugia malayi and B. pahangi recovered from cats originating from the same area in South Kalimantan (Borneo), Indonesia. Five to six week-old immature males and females of both species from Mongolian gerbil (Meriones unguiculatus) intraperitoneal infections were inoculated into the peritoneal cavity of other gerbils. Mating occurred between the species and microfilariae developed into infective third-stage larvae in mosquitoes. Larvae from the mosquitoes developed into adults in the peritoneal cavity of gerbils but microfilariae were not produced since the males were sterile. Back-crossing between hybrids and males and females of the parental species were also done and female hybrids produced microfilariae when crossed with parental males but females from the parental species did not produce microfilariae when mated with the hybrid males. This confirmed that the males were sterile but the females were not. If these species are hybridized in nature and humans are exposed to hybrid third-stage larvae, could this lead to occult filarial infection? These results confirmed previous hybridization experiments of these species orginating from other geographic areas.

Susceptibility of Oncomelania hupensis subspecies to infection with geographic strains of Schistosoma japonicum.

Subspecies of Oncomelania hupensis were exposed to infection with zoophilic and anthropophilic strains of Schistosoma japonicum. The snails were Philippine O. h. quadrasi from the islands of Bohol, Leyte and Mindanao, O. h. formosana from Changhua and Ilan, and O. h. chiui from Taiwan, O. h. hupensis from China, O. h. nosophora from Japan and O. h. lindoensis from Indonesia. Anthropophilic strains of S. japonicum were from Bohol and Leyte in the Philippines, China, Japan and Indonesia. The zoophilic strains were from Changhua and Ilan, Taiwan. All geographic strains of the parasite developed exceptionally well and produced cercariae in 32-50% of O. h. chiui and 5-43% of the natural snail hosts. Development in other subspecies of snails with geographic strains of the parasite were variable. Only a few O. h. formosana (Changhua) could be infected with the parasites from other geographic areas and only one O. h. quadrasi each from Mindanao became infected with the Bohol and Changhua strains of S. japonicum.