Modeling host-feeding preference and molecular systematics of mosquitoes in different ecological niches in Canada

Highlights

• This is the first work to analyze the host-feeding pattern of different mosquito species in Canada via molecular techniques.

• We found 34 different mosquito taxa in Canada by combining morphological and molecular identification approaches.

• Our data showed that the 201 blood-fed mosquitos were spread over 20 taxa who fed on 10 mammalian species, and three bird species.

• The majority of all analysed mosquito taxa fed on humans (24.3%) followed by pigs (21.8%).

• In our study, seven mosquito species with both ornithophilic and anthropophilic biting habit could function as potential bridge vectors.

Abstract

Several mosquito-borne viruses (mobovirus) cause infections in Canada. Ecological data on mosquito species and host range in Canada remains elusive. The main aim of the current study is to determine the host range and molecular systematics of mosquito species in Canada. Mosquitoes were collected using BG-Sentinel traps and aspirators at 10 trapping sites in Canada during 2018 and 2019. Mosquitoes collected were identified via morphology and molecular techniques. Mosquito sequences were aligned by MUSCLE algorithm and evolutionary systematics were drawn using MEGA and SDT software. Moreover, the source of blood meals was identified using a DNA barcoding technique. A total of 5,708 female mosquitoes over 34 different taxa were collected. DNA barcodes and evolutionary tree analysis confirmed the identification of mosquito species in Canada. Of the total collected samples, 201 specimens were blood-fed female mosquitoes in 20 different taxa. Four mosquito species represented about half (51.47%) of all collected blood-fed specimens: Aede cinereus (39 specimens, 19.11%), Aedes triseriatus (23, 11.27%), Culex pipiens (22, 10.78%), and Anopheles punctipennis (21, 10.29%). The most common blood meal sources were humans (49 mosquito specimens, 24% of all blood-fed mosquito specimen), pigs (44, 21.5%), American red squirrels (28, 13.7%), white-tailed deers (28, 13.7%), and American crows (16, 7.8%). Here, we present the first analysis of the host-feeding preference of different mosquito species in Canada via molecular techniques. Our results on mosquito distribution and behavior will aid in the development of effective mitigation and control strategies to prevent or reduce human/animal health issues in regards to moboviruses.

Introduction

Mosquitoes are important vectors for several pathogens, including viruses and parasites (Chinikar et al., 2013). Virus transmission from a reservoir to a susceptible host can occur through the feeding habits of female mosquitoes, which act as a vector (Takken and Verhulst, 2013). Several moboviruses are currently circulating in Canada, including West Nile virus (WNV) and St Louis encephalitis viruses (SLEV), Eastern Equine Encephalitis virus (EEEV), Cache Valley virus (CVV), La Crosse virus (LCV), Jamestown Canyon virus (JCV) and Snowshoe Hare virus (SSHV) (Artsob and Spence, 1991; Evans and Peterson, 2019; Giordano et al., 2017).

Only female mosquitoes bite, as they need blood proteins to produce eggs. While female mosquitoes search for blood in vertebrate hosts including humans (anthropophilic), non-human mammals (mammalophilic), birds (ornithophilic), and reptiles (herpetophilic) (Ng et al., 2011), some mosquito species show different preferential behavior toward hosts. Mosquitoes are known to discriminate between their hosts beyond the level of host classes (Burkett-Cadena et al., 2008).

Several extrinsic and intrinsic factors drive host-feeding preference. Inherent factors are determined by genetic selection, while extrinsic factors include adaptation to the environment, mediated by the abundance and location of potential host species (Takken and Verhulst, 2013). Mosquitoes can detect their hosts by several sensory systems, including vision, thermoreception, hygroreception, and gustation (Wolff and Riffell, 2018). Therefore, the preference of mosquitoes to certain host species means that many of the pathogens transmitted by mosquitoes are host specific. Hence, host preference by mosquitoes has a profound impact on disease transmission (Takken and Verhulst, 2013).

Steadily increasing international travel and projected climate changes may cause introduction or northward spread of exotic mosquito species into Canada, which consequently might alter the composition of mosquito populations and associated diseases (Shahhosseini et al., 2020). In order to identify potential vector species for mobovirus transmission, it is fundamental to know mosquito biodiversity and their host preference since many mosquitoes feed on multiple species and thus represent a potential vectorial route between species (Kramer and Ciota, 2015). Once this knowledge is attained, species-specific control measurements can be implemented (Kramer and Ciota, 2015).

In Canada, the mosquito fauna is diverse, including 10 genera (Cywinska et al., 2006; Giordano et al., 2015; Scudder and Cannings, 2006), with at least 83 species considering the recent introduction of Ae. aegypti in southern Ontario (the main vector for Dengue fever virus) (Chinikar et al., 2013; Giordano et al., 2020). The DNA typing assay provides information on mosquito biting patterns, which subsequently will provide new insights into host preference in mosquito species. This will ultimately help close the knowledge gaps in Canadian mosquito host range and will contribute to a deeper understanding of the transmission cycles and dynamics of moboviruses.

To cover different ecological niches in a surveillance study, it is important to choose a variety of habitats including natural, suburban and urban sites. Moreover, sampling methodology is a critical factor in presenting the most realistic scenario of mosquito host-feeding preference in an ecosystem (Giordano et al., 2020). As such, we have chosen to utilize the BG-Sentinel trap, which attracts a diverse range of mosquito species through two elements for attraction; CO₂ and lure (odor of animal/ human body) (Lühken et al., 2014).

There are several published studies that have utilized molecular techniques to determine the source of a blood meal in mosquito species (Molaei et al., 2008; Tomazatos et al., 2019), but there is no such study on Canadian mosquitoes. The objectives of the current study are to identify hosts of Canadian mosquitoes through DNA typing assay and confirm the identification of mosquito species through DNA barcodes in different ecological niches in Canada.