First record of Culex pipiens (Diptera: Culicidae) in Alberta: expanding distributions and ecotype patterns in a western Canadian province.

Culex pipiens is an invasive mosquito found in temperate regions globally. It is considered among the most important disease vectors worldwide and is responsible for the transmission of a range of pathogens, including West Nile virus, avian malaria, Saint Louis encephalitis, and filarial worms. Throughout its northern temperate range, this mosquito is found in 2 ecotypes: form pipiens and form molestus. In Canada, this mosquito was previously thought restricted to the Pacific coast of British Columbia and the eastern provinces of Ontario, Quebec, and the Maritimes. Through routine mosquito surveillance and targeted trapping for Cx. pipiens, we detected this mosquito in 2 Albertan municipalities earlier than suggested by species distribution modeling based on climate change data. We confirmed the identity of putative Cx. pipiens specimens using DNA sequencing and found that alleles associated with form molestus were present, but at a low frequency compared to alleles associated with form pipiens. Furthermore, we compared the frequency of ecotype-related alleles in Alberta to elsewhere in North America and found a general trend of increased form pipiens in more northern latitudes, similar to previously reported results. We discuss our findings in the context of vector-borne disease activity in Canada, particularly West Nile virus.