A merganser die-off associated with larval Eustrongylides.

Although several species of Eustrongylides have been reported from mergansers, there is only one report in the North American literature of merganser losses due to nematodes of this genus. Giltner (4) included a report by J. E. Shillinger, U.S. Bureau of Biological Survey, which mentioned losses due to Eustrongylides mergorum among these fish-eating ducks (species not given) on several lakes in British Columbia. The worms were described as causing a great amount of tissue proliferation in the affected organs, with resultant loss of function.