Dear Malaria: Deer Have Malaria! Prevalence of<i>Plasmodium odocoilei</i> Infection in White-tailed deer in Pennsylvania

Abstract Background To combat antimalarial treatment resistance, better understanding of malaria pathogenesis is needed, but existing animal model have various limitations. Notably, prevailing murine models require laboratory infection of non-natural host species. In 2016, the parasite Plasmodium odocoilei was identified in white-tailed deer (Odocoileus virginianus). This was the first non-human mammalian malaria parasite identified in North America, representing a novel naturally occurring model system that allows for integrated examination of host, vector, and systems parasite biology. In addition, sickle hemoglobinopathy is exceptionally common among white-tailed deer, occurring in up to 60% of apparently healthy animals. In humans, the prevalence of sickle hemoglobinopathy in individuals with ancestry from malaria-endemic regions is due to the protective effects of sickle trait against severe malaria. Thus, the white-tailed deer-P. odocoilei system represents the only known naturally occurring model of the association between malaria parasite biology and sickle cell disease. Pennsylvania white-tailed deer have not previously been surveyed for infection. In this study, we determined P. odocoilei prevalence in a sample of 170 Pennsylvania white-tailed deer. Methods We amplified the CytB gene of P. odocoilei by nested PCR from DNA extracted from homogenized white-tailed deer tongue tissue obtained from the PennVet Wildlife Futures Program. We confirmed samples screening positive on gel electrophoresis via unprimed sequencing (Plasmidsaurus, USA) and NCBI-BLAST analysis. Results We estimate the prevalence of P. odocoilei infection in Pennsylvania white-tailed deer to be 0.6% (1 of 170 samples). Sequencing of the positive sample revealed a 621-bp sequence with close sequence identity to previous North American isolates of P. odocoilei (query cover 91-100%, percent identity 99.34-100.00%). Biobank metadata showed the positive sample originated from a roadkilled yearling male picked up at GPS coordinates (40.8423, -79.0409) on August 15, 2022. Conclusion P. odocoilei is endemic to Pennsylvania white-tailed deer. Our future directions include screening of additional samples, determination of host hemoglobin allele frequencies, detailed parasite genetic studies, and entomologic studies to elucidate vector biology. In addition, granular sample metadata collected by the PennVet Wildlife Futures Program will allow us to analyze the effects of geographic, demographic, and temporal variables on epidemiology. In sum, our survey data empowers future Pennsylvania-based studies to take advantage of the only known naturally occurring animal model of sickling and its association with protozoan infection.