Assessment of variation in the detection and prevalence of blood parasites among sympatrically breeding geese in western Alaska

Abstract

Haemosporidian parasites may impact avian health and are subject to shifts in distribution and abundance with changing ecological conditions. Therefore, understanding variation in parasite prevalence is important for evaluating biologically meaningful changes in infection patterns and associated population level impacts. Previous research in western Alaska indicated a possible increase in Leucocytozoon infection between emperor geese (Anser canagicus) sampled in 1996 (<1%, n=134), and during 2011-2012 (19.9%, 95% CI: 3.0-36.8%, n=77); however, different detection methods were used for these estimates. Prior research in this same region identified a lack of Leucocytozoon parasites (0%, n=117) in sympatrically breeding cackling geese (Branta hutchinsii minima) in 2011. In this study, we molecularly screened blood samples collected from sympatrically breeding emperor and cackling geese in western Alaska during additional breeding seasons to better assess temporal and species-specific variation in the prevalence of blood parasites. We found similar prevalence estimates for Leucocytozoon parasites in emperor goose blood samples collected in 1998 and 2014, suggesting consistent infection of emperor geese with blood parasites at these time points. Using samples from sympatric geese sampled during 2014, we found evidence for higher incidence of Leucocytozoon parasites among emperor geese (20.3%, 95% CI: 11.8-32.7%) as compared to cackling geese (3.6%, 95% CI: 1.1-11.0%) reinforcing the previous finding of species-specific differences in infection. Furthermore, we detected Leucocytozoon, Haemoproteus, and Plasmodium blood parasites in unflighted goslings of both species, supporting the possible transmission of these parasites at western Alaska breeding grounds. Our results help to clarify that prevalence of Leucocytozoon parasites have likely remained consistent among emperor geese breeding in western Alaska since the late 1990s and that this species may disproportionally harbor Leucocytozoon parasites as compared to sympatrically breeding cackling geese.