Understanding the role of mosquito community composition in West Nile virus transmission

INTRODUCTION The composition of mosquito communities plays a pivotal role in the transmission of vector-borne pathogens, including West Nile virus (WNV). WNV is a zoonotic emerging pathogen (arbovirus) that is increasing in both incidence and distribution worldwide. It is maintained in an enzootic cycle involving birds as primary host and mosquitoes as vectors. While humans can become infected through mosquito bites, they act as dead-end hosts and cannot transmit the infection further. Surveillance efforts, aimed at detecting WNV circulation in hosts and vectors, are ongoing in endemic countries, but the complexity of WNV epidemiological cycle, coupled with the involvement of numerous species in its maintenance, poses challenges for accurate prediction of WNV outbreaks. Culex pipiens and Cx. perexiguus have emerged as key vectors responsible for the transmission of WNV in both the United States and Europe, although their role in the transmission of WNV is still unclear. These mosquito species differ in their habitat requirements and feeding preferences, and this divergence may impact WNV spread. MATERIALS AND METHODS We developed a set of mathematical models, based on the SEIR (Susceptible-Exposed-Infectious-Recovered) framework, to investigate the impact on WNV dynamics of the differences in habitat requirements and feeding preferences of mosquito species. The models incorporate two vector species (Cx. pipiens and Cx. perexiguus), as well as two vertebrate hosts (birds, as amplifying hosts, and humans, as dead-end hosts), and account for the influence of climatic variables on mosquito abundance and epidemiological parameters. We generated different scenarios of WNV transmission to test the effects of different abundances and of different feeding preferences of the two mosquito species. For each scenario, we predicted the daily number of infected mosquitoes as a proxy of human infection risk. RESULTS AND CONCLUSIONS Our analyses revealed that a feeding preference of mosquitoes on birds increases the number of infected mosquitoes. Additionally, when the two mosquito species have same preference for birds, they contribute equally to the spread of the infection. If mosquito species differ in feeding preference instead, they contribute differently to the spread of the infection and their relative abundance plays a central role in driving WNV dynamics. Our findings enhance the need to improve current vector surveillance and control programs by identifying specific vector species in particular environments, particularly those most susceptible to environmental shifts. The proposed model can be developed to fit data collected on field to test the hypotheses produced, furthermore, given the generalizability of the framework, it can be adapted to investigate other mosquito-borne infections.