Detection, prevalence, and transmission of avian hematozoa in waterfowl at the Arctic/sub-Arctic interface : co-infections, viral interactions, and sources of variation / Brandt W. Meixell, Todd W. Arnold, Mark S. Lindberg, Matthew M. Smith, Jonathan A. Runstadler, and Andrew M. Ramey.

Includes bibliographical references.

Background: The epidemiology of avian hematozoa at high latitudes is still not well understood, particularly in
sub-Arctic and Arctic habitats, where information is limited regarding seasonality and range of transmission,
co-infection dynamics with parasitic and viral agents, and possible fitness consequences of infection. Such information
is important as climate warming may lead to northward expansion of hematozoa with unknown consequences to
northern-breeding avian taxa, particularly populations that may be previously unexposed to blood parasites.
Methods: We used molecular methods to screen blood samples and cloacal/oropharyngeal swabs collected from
1347 ducks of five species during May-August 2010, in interior Alaska, for the presence of hematozoa, Influenza A Virus
(IAV), and IAV antibodies. Using models to account for imperfect detection of parasites, we estimated seasonal variation
in prevalence of three parasite genera (Haemoproteus, Plasmodium, Leucocytozoon) and investigated how co-infection
with parasites and viruses were related to the probability of infection.
Results: We detected parasites from each hematozoan genus in adult and juvenile ducks of all species sampled.
Seasonal patterns in detection and prevalence varied by parasite genus and species, age, and sex of duck hosts. The
probabilities of infection for Haemoproteus and Leucocytozoon parasites were strongly positively correlated, but
hematozoa infection was not correlated with IAV infection or serostatus. The probability of Haemoproteus infection was
negatively related to body condition in juvenile ducks; relationships between Leucocytozoon infection and body
condition varied among host species.
Conclusions: We present prevalence estimates for Haemoproteus, Leucocytozoon, and Plasmodium infections in
waterfowl at the interface of the sub-Arctic and Arctic and provide evidence for local transmission of all three parasite
genera. Variation in prevalence and molecular detection of hematozoa parasites in wild ducks is influenced by seasonal
timing and a number of host traits. A positive correlation in co-infection of Leucocytozoon and Haemoproteus suggests
that infection probability by parasites in one or both genera is enhanced by infection with the other, or that encounter
rates of hosts and genus-specific vectors are correlated. Using size-adjusted mass as an index of host condition, we did
not find evidence for strong deleterious consequences of hematozoa infection in wild ducks.