Investigation of the life cycle and adult morphology of the avian blood fluke Austrobilharzia variglandis (Trematoda: Schistosomatidae) from Connecticut.

This study was undertaken to expand the current knowledge of the life cycle and adult morphology of the avian schistosome Austrobilharzia variglandis, which causes a marine cercarial dermatitis in New England. The specific objectives were to: (1) investigate the seasonality of the infection in the molluscan intermediate host, Ilyanassa obsoleta; (2) determine which bird species are acting as natural definitive hosts for the parasite; and (3) characterize the morphology of the parasite using scanning electron microscopy (SEM). One-thousand individuals of I. obsoleta were collected each month for 14 consecutive months and examined for the parasite. Ten to 15 specimens of each of the following avian species, Larus argentatus, Larus delawarensis, Larus marinus, Phalacrocorax auritus, and Branta canadensis, and 2 individuals of Larus atrilla, were collected and examined for schistosomes. Twenty adult male and 10 adult female specimens of A. variglandis were processed for SEM. Ilyanassa obsoleta was found to maintain a relatively low prevalence of infection (0.7-5.1%) throughout the 14-mo study, but no fully developed cercaria were visible in sporocysts recovered from snails collected in winter months. The Larus species had both the highest prevalence (85-92.8%) and highest mean intensity (12.1-34.5 male worms) of infection with A. variglandis. These data suggest that overwintering snail populations can harbor viable infections and in the spring infect shore birds (or humans) with cercaria. The snail and definitive host data suggest that A. variglandis is a year-round resident of the state.(ABSTRACT TRUNCATED AT 250 WORDS)