By Sarah A. Orlofske, PhD, University of Wisconsin – Stevens Point

This article originally appeared in Wisconsin Waterfowl Association’s March, 2024 Newsletter edition.

Many hunters are familiar with waterfowl diseases like Avian Influenza, including the recent outbreak with Highly Pathogenic Avian Influenza (HPAI), and other infections like Avian Cholera, Duck Plague, or even Rice-Breast. However, ducks have another group of pathogens that are less familiar but just as important. Normally when we think of malaria, we think of a human disease we get in hot, humid, tropical areas from mosquito bites. What we may not realize is that these parasites are actually one of the most common and widely studied groups of parasites infecting birds. Indeed, before malaria was found in rodents, it was bird malaria that was used to study the human disease (Fecchio et al. 2020).

What does that have to do with ducks and your hunting experience? The ducks that you are hunting have the potential to be infected with not just one or two, but actually three main types of malaria parasites in both their white and red blood cells (Fecchio et al. 2020, figure 1 and 2). But the research on these parasites in ducks is extremely limited. In fact, 75% of the genetic information scientists know about avian malaria is from songbirds (Bell et al. 2020). Among waterfowl, the knowledge is greater for dabblers than divers and sea ducks. This gap in our knowledge is concerning because historical research suggests that infection with avian malaria can be harmful to waterfowl (Khan and Fallis 1968, Herman et al. 1975). More recently, in the Mississippi River area of Wisconsin and Illinois, researchers used DNA analysis to detect avian malaria in spring migrating lesser scaup and found that the higher percentage of infected birds was associated with lower body condition (Merrill et al. 2018). This may not seem like much at first, but when you add the stress of migration and then the breeding season this may have important consequences for individual birds and the overall population. More studies are needed across a wider range of waterfowl species and locations to be able to monitor the overall health of waterfowl populations and the impact of this important disease.

WWA members have been instrumental in donating carcasses for parasite and disease research and avian malaria is among the parasites we monitor. We hope to share the results of our new research soon and in the meantime will continue to expand our research efforts with plans to share those results widely so they can inform management decisions.