Auriel Fournier
Joseph D. Lancaster
Douglas C. Osborne
Rebecca A. Cole
Heath M. Hagy
Christopher N. Jacques
C.R Beach
2026
<p><span>Thousands of Lesser Scaup (</span><i>Aythya affinis</i><span>) die annually in the Upper Mississippi River System, USA, from intestinal infections after birds consume exotic faucet snails, </span><i>Bithynia tentaculata</i><span>, infected with introduced parasites, </span><i>Cyathocotyle bushiensis</i><span> and </span><i>Sphaeridiotrema pseudoglobulus</i><span>. To date, the low frequency (biannual) and magnitude of mortality events from intestinal infections likely prevents trematode mortalities from being a major contributor to Lesser Scaup population declines. However, questions remain regarding the role sublethal infections may have on Lesser Scaup fitness along with the potential for carryover effects in the following breeding season. We examined the impact of a single sublethal </span><i>C. bushiensis</i><span> and </span><i>S. pseudoglobulus</i><span> infection on select physiological parameters in Lesser Scaup over a 10-day period post inoculation through three trials, each involving three experimental groups: baseline control, trial control, and treatment (</span><i>n</i><span> = 96 scaup). We found that male Lesser Scaup that were in better body condition before the trial had fewer </span><i>C. bushiensis</i><span> and </span><i>Sphaeridiotrema pseudoglobulus</i><span> recovered from their intestines at necropsy. Individuals with the highest numbers of </span><i>C. bushiensis</i><span> and </span><i>S. pseudoglobulus</i><span> in their intestines lost the largest amounts of body mass during the trial. We found that blood urea nitrogen and triglycerides were lower when </span><i>C. bushiensis</i><span> and </span><i>S. pseudoglobulus</i><span> were present. Triglycerides and glucose declined from Day 0 to Day 5 but stabilized on Day 10 of the trial. Our results highlight changes in physiological metrics in Lesser Scaup from a sublethal infection with </span><i>C. bushiensis</i><span> and </span><i>S. pseudoglobulus</i><span> under experimental conditions. Changes in Lesser Scaup health parameters indicated that scaup surviving a single sublethal trematode infection may have reduced body condition, which could lead to negative health implications in the following breeding season.</span></p>
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10.1080/15594491.2025.2597098
en
Taylor & Francis
Physiological impacts of sublethal Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus infections in captive Lesser Scaup (Aythya affinis)
article