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Mosquito vectors play a crucial role in the distribution of avian Plasmodium parasites worldwide. At northern latitudes, where climate warming is most pronounced, there are questions about possible changes in the abundance and distribution of Plasmodium parasites, their vectors, and their impacts to avian hosts. To better understand the transmission of Plasmodium among local birds and to gather baseline data on potential vectors, we sampled a total of 3,909 mosquitoes from three locations in south-central Alaska during the summer of 2016. We screened mosquitoes for the presence of Plasmodium parasites using molecular techniques and estimated Plasmodium infection rates per 1,000 mosquitoes using maximum likelihood methods. We found low estimated infection rates across all mosquitoes (1.28 per 1,000), with significantly higher rates in Culiseta mosquitoes (7.91 per 1,000) than in Aedes mosquitoes (0.57 per 1,000). We detected Plasmodium in a single head/thorax sample of Culiseta, indicating potential for transmission of these parasites by mosquitoes of this genus. Plasmodium parasite DNA isolated from mosquitoes showed a 100% identity match to the BT7 Plasmodium lineage that has been detected in numerous avian species worldwide. Additionally, microscopic analysis of blood smears collected from black-capped chickadees (Poecile atricapillus) at the same locations revealed infection by parasites preliminarily identified as Plasmodium circumflexum. Results from our study provide the first information on Plasmodium infection rates in Alaskan mosquitoes and evidence that Culiseta species may play a role in the transmission and maintenance of Plasmodium parasites in this region., (© 2019 The Society for Vector Ecology.)

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. [ABSTRACT FROM AUTHOR]