How can you be sure that common mergansers play such an important role as bird hosts on so many lakes in Michigan?
First, on most lakes where swimmer’s itch is an annual problem, nearly all of the common mergansers are infected. Second, common mergansers usually harbor heavy infections compared to other species of bird hosts. For example, the average number of miracidia that hatch from a gram of feces from common mergansers is more than 300. Mallards, Canada geese and wood ducks usually have less than 25% infected and only a couple of miracidia per gram of feces. Furthermore, the cercariae from the species of schistosomes that cycle through common mergansers, are much larger than average and emerge only from lymnaeid snails, particularly Stagnicola emarginata. Can a relatively few common mergansers have an important swimmer’s itch impact on a large recreational lake? Absolutely, because mergansers are heavily infected and because there is a high prevalence of infections in them. In addition, one must consider the dynamics of the life cycle. For example, if one miracidium infects a snail, that inter
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- How can you be sure that common mergansers play such an important role as bird hosts on so many lakes in Michigan?
- How can one be sure that common mergansers play such an important role as bird hosts on so many lakes in Michigan?
