Evaluating Sub-lethal Infections of Sphaeridiotrema Spp. and Cyathocotyle Bushiensis Trematodes in Captive Lesser Scaup

During spring and fall migrations throughout the upper Midwest, US, thousands of lesser scaup (Aythya affinis) die from Cyathocotyle bushiensis (Cb) and Sphaeridiotrema spp. (Ss) (Class: Trematoda) intestinal infections after consuming exotic faucet snails (Bithynia tentaculata). Lesser scaup serve as a final host for Cb and Ss while faucet snails serve as the first and second intermediate hosts for the trematodes. As recommended by previous studies, this experimental study will evaluate the potential effects of sub-lethal infections of trematode parasites on the immunological response, body condition, and survival of migrating lesser scaup across the Upper Mississippi River System. Female lesser scaup will be captured at key mid-latitude stopover sites (Pool 19 of the Mississippi River and Emiquon Preserve) and held at Forbes Biological Station, Havana, IL. Faucet snails will be collected by hand from Pool 7 of the Mississippi River and dissected to recover mature Cb and Ss metacercariae. The captive lesser scaup will undergo repeated or single dose trematode infections and will be euthanized 16 days post-infection to gather information that will provide data to evaluate temporal changes in health along a continuum from initial infection to shedding eggs to point of euthanasia. Addressing basic questions related to physiological responses of lesser scaup to infection with trematodes may aid in formulating potential management strategies to minimize co-occurrence of lesser scaup and infected faucet snails.