Experimental transmission of Capillaria philippinensis to birds.

Capillaria philippinensis larvae from fish and adult and larval forms of the parasite from gerbil intestines established parent infections when given a stomach tube to several species of birds from Taiwan. Adult males, oviparous and larviparous females and larval stages were found in Nycticorax nycticorax, Bubulcus ibis, Ixobrychus sinensis, Gallinula chloropus and Amaurornis phoenicurus. C. philippinensis also developed in pigeons, Rostratula benghalensis, a few Anas spp. and chickens. Some birds died of the infection while others recovered; most could not be re-infected after repeated exposure. Autoinfection also occurred in most birds. Eggs from an egret hatched and the larvae developed in fish intestines. This is the first group of animals indigenous to the endemic area that could be infected with C. philippinensis and although no naturally infected birds have been found in the area, fish-eating birds should be suspected as potential reservoir hosts. A fish-bird life-cycle is thought to be occurring throughout Asia but intestinal capillariasis is reported only in areas where the human population eats raw freshwater fish.