A highly invasive malaria parasite has expanded its range to non-migratory birds in North America

Parasite range expansions are a direct consequence of globalization and are an increasing threat to biodiversity. Here we report a recent range expansion of the SGS1 strain of a highly invasive parasite, Plasmodium relictum, to two non-migratory passerines in North America. Plasmodium relictum is considered one of the world’s most invasive parasites and causes the disease avian malaria: this is the first reported case of SGS1 in wild birds of Western North America and wild non-migratory birds on the continent. Using a long-term database where researchers report avian malaria parasite infections, we summarized our current understanding of the geographic range of SGS1 and its known hosts. We also identified the most likely geographic region of this introduction event using the MSP1 allele. We hypothesize that this introduction resulted from movements of captive birds and subsequent spillover to native bird populations, via ecological fitting. Further work should be conducted to determine the extent to which SGS1 has spread following its introduction in North America.

Methods
This data was collected across a time period spanning 4 years (2017-2020) in Boulder County, Colorado. DNA extractions were conducted on all blood samples. We conducted a nested PCR protocol on all DNA extractions to amplify a region of the cytb gene for Plasmodium parasites. In brief– we used primers HAEMNF1 and HAEMNR3 followed by the nested set of primers HAEMF and HAEMR2. Infections were further verified by an alternative set of primers– 983R and 621F. We further identified the Pr2 variant for the SGS1 infecting chickadees using an additional nested PCR protocol with primers MSP1-3F and MSP1-3R followed by the nested set of primers MSP1-3FN and MSP1-3RN.