Updated distribution maps of predominant Culex mosquitoes across the Americas

Abstract

Background Estimates of the geographical distribution of Culex mosquitoes in the Americas have been limited to state and provincial levels in the United States and Canada and based on data from the 1980s. Since these estimates were made, there have been many more documented observations of mosquitoes and new methods have been developed for species distribution modeling. Moreover, mosquito distributions are affected by environmental conditions, which have changed since the 1980s. This calls for updated estimates of these distributions to understand the risk of emerging and re-emerging mosquito-borne diseases. Methods We used contemporary mosquito data, environmental drivers, and a machine learning ecological niche model to create updated estimates of the geographical range of seven predominant Culex species across North America and South America: Culex erraticus, Culex nigripalpus, Culex pipiens, Culex quinquefasciatus, Culex restuans, Culex salinarius, and Culex tarsalis. Results We found that Culex mosquito species differ in their geographical range. Each Culex species is sensitive to both natural and human-influenced environmental factors, especially climate and land cover type. Some prefer urban environments instead of rural ones, and some are limited to tropical or humid areas. Many are found throughout the Central Plains of the USA. Conclusions Our updated contemporary Culex distribution maps may be used to assess mosquito-borne disease risk. It is critical to understand the current geographical distributions of these important disease vectors and the key environmental predictors structuring their distributions not only to assess current risk, but also to understand how they will respond to climate change. Since the environmental predictors structuring the geographical distribution of mosquito species varied, we hypothesize that each species may have a different response to climate change. Graphical abstract

West Nile virus: another emerging arboviral risk for travelers?

“…Consequently, as global warming progresses, the rate at which Culex populations multiply and become infected with WNV may increase in temperate regions. Evidence of this is already present in the Americas, where increasing temperatures have permitted Culex species to expand northward, with C. pipiens reaching southern Canada [ 74 ]. In Southern Europe, this phenomenon has been observed with an increase in temperature, showing positive association with the circulation of WNV and lengthening the vector’s season [ 27 ••].…”

Bayesian time-varying occupancy model for West Nile virus in Ontario, Canada

“…On the other hand, baiting for potential WNV vectors could have affected the viral testing. For example, the Culex genus is especially relevant to WNV transmission (Turell et al 2005) and widespread throughout Ontario (Gorris et al 2021). Zero inflation was a concern as well at finer spatial resolutions.…”

“…We focused on agricultural and urban land types with a downstream application in mind of relating WNV in mosquito populations to human WNV cases. These land types carry great significance as well because they are habitats frequented by Culex species (Gorris et al 2021). Population density from the 2016 census was strongly correlated with urban land type, so we did not use it in our models.…”

“…Mosquitoes carry the potential to transmit pathogens maintained in reservoir hosts to humans and other animals. Culex mosquitoes, in particular, have been documented as potent disease vectors for West Nile virus (WNV), Eastern equine encephalitis virus (EEV), Zika virus, and other pathogens (Gorris et al 2021). Turell et al (2005) confirmed through laboratory experiments that Culex species could spread WNV efficiently as enzootic or bridge vectors.…”

“…This trend is true for mosquitoborne pathogens because the mosquito life cycle depends on local weather and land use conditions (Bartlow et al 2019). For instance, Gorris et al (2021) inferred northward range expansions for several Culex mosquito species in updating the original maps of Darsie and Ward (1981). They found that abiotic factors like warm temperatures, water availability, terrain, and land cover characterized ecological niches for these mosquitoes.…”