A mallophaga, Trinoton anserinum, as a cyclodevelopmental vector for a heartworm parasite of waterfowl.

The biting louse Trinoton anserinum serves as the intermediate host in the life cycle of the filarial heartworm, Sarconema eurycerca. Microfilariae, second-, and third-stage larvae were dissected from 39 of 89 lice infesting whistling swans, Cygnus columbianus columbianus, in North America and mute swans, Cygnus olor, in the Black Sea, U.S.S.R. Infective third-stage larvae obtained from lice collected from heartworm-parasitized whistling swans were injected subcutaneously into each of two hand-reared, nonparasitized mute swan cygnets. Both of these birds developed heartworm infections, one becoming microfilaremic at 14 weeks. The results of this study provide conclusive evidence that a mallophagan serves as a natural cyclodevelopmental vector of a filarial parasite.