Dynamics of parasitic infections at four sites within lesser snow geese (Chen caerulescens caerulescens) from the breeding colony at La Pérouse Bay, Manitoba, Canada.

We enumerated parasite burdens within the blood, gizzard, ceca, and kidneys of adult female lesser snow geese Chen caerulescens caerulescens collected from the breeding colony at La Pérouse Bay, Manitoba, Canada, in 1989. We observed 5 species of nematodes, 1 species of digenean, 1 species of protozoan, and an unidentified microfilaria in these geese. We compared parasite burdens between geese collected during the incubation (2-14 June) and brood-rearing (1-5 August) periods. There was a significant decrease in the prevalence and intensity of the gizzard nematode Amidostomum spatulatum and a significant increase in the prevalence of the renal coccidium Eimeria truncata between the 2 collection periods. We suggest that the changes concerning A. spatulatum reflect transmission conditions some 6 months earlier when the geese were on the wintering grounds. Changes involving E. truncata reflected transmission conditions within the previous month. Consequently, it would appear that breeding colonies are the foci for transmission of E. truncata, a significant pathogen of adults and goslings.