Schistosoma japonicum in the black rat, Rattus rattus mindanensis, from Leyte, Philippines in relation to Oncomelania snail colonies with reference to other endoparasites.

This study examined the prevalence of Schistosoma japonicum infections in field rats, Rattus rattus mindanensis, according to different trapping locations. Between October 1995 and January 1996, traps were set in the municipality of Palo, Leyte, Philippines to determine the correlation of rats infected with schistosomiasis to the proximity of the intermediate snail host, Oncomelania hupensis quadrasi, colonies. Of the 22 rats that were caught within a snail colony, 21 (95.5%) were positive for schistosomiasis. Of the 23 rats that were caught 100 meters from a snail colony, 13 (56.5%) were positive for schistosomiasis. Of the 17 rats that were caught approximately 1 km from a snail colony, zero (0%) were positive for schistosomiasis. Infection rates were highest within the habitat of the intermediate host and lowest in rats captured far from snail colonies. Captured rats were also examined for the presence of other endoparasites. Infections of the following were found: Angiostrongylus cantonensis, Gonylonema neoplasticum, Hymenolepis diminuta, Nippostrongylus muris, Strongyloides ratti, Syphacia obvelata, Taenia crassicollis and Trichuris muris, but there was no correlation between trapping location and prevalence. None of the rats were infected with Moniliformis moniliformis, Trichinella spiralis, Trypanosoma lewisi or Vampirolepis nana.