Vector competence of Culex quinquefasciatus from Santiago Island, Cape Verde, to West Nile Virus: exploring the potential effect of the vector native Wolbachia

Abstract

Background: Culex quinquefasciatus plays a crucial role as a vector of West Nile virus (WNV). This mosquito species is widely distributed in Cape Verde, being found in all inhabited islands of the archipelago. However, no data are currently available on the susceptibility of the local mosquito population to WNV. This study aimed to assess the vector competence of Cx. quinquefasciatus mosquitoes from Santiago Island, Cape Verde, for WNV and to explore the potential impact of its native Wolbachia on virus transmission.

Methods: Wolbachia-infected and uninfected Cx. quinquefasciatus female mosquitoes were exposed to WNV lineage 1 PT6.39 strain using a Hemotek membrane feeding system. Mosquito samples, including the body, legs, wings and saliva, were collected at days 7, 14 and 21 post-infection (dpi) to assess WNV infection through one-step quantitative real-time PCR (RT-qPCR).

Results: Culex quinquefasciatus from Cape Verde exhibited high susceptibility to the tested strain of WNV. Also, treated females without their native Wolbachia exhibited significantly higher WNV load in their bodies and greater dissemination rate at 7 dpi than their wild-type counterparts carrying Wolbachia.

Conclusions: The high susceptibility to WNV of Cx. quinquefasciatus from Cape Verde poses a potential risk for virus transmission in the archipelago. However, Wolbachia infection in this mosquito species seems to confer protection against WNV dissemination in the early stages of viral infection. Additional research is required to uncover the mechanisms driving this protection and its potential impact on WNV transmission.

Keywords: Culex quinquefasciatus; Wolbachia; Cape Verde; Vector competence; West Nile virus.

Fig. 1

Wolbachia detection in Culex quinquefasciatus from Santiago Island, Cape Verde, based on the Wolbachia surface protein gene (wsp). a Wolbachia prevalence in F1 and F7 generations of wild-type mosquitoes, as well as in the F7 generation group treated with tetracycline (n = 200 per group), analyzed using conventional and real-time PCR. b Wolbachia density on a linear scale relative to the Cx. quinquefasciatus 18S ribosomal gene, as estimated by quantitative real-time PCR. The difference in Wolbachia density between the F1 and F7 generations was assessed using the Mann–Whitney test. Error bars represent 95% confidence intervals from three biological replicates, each containing DNA from a pool of 5 females

Fig. 2

West Nile virus RNA copies in Culex quinquefasciatus body (a), legs + wings (b) and saliva samples (c) at different days post-infection for wPip⁺ and wPip^- colonies. At each time point, 30 mosquito bodies were screened for WNV. Error bars represent the median with 95% confidence intervals. Statistical significance at P < 0.05 was determined by the Mann–Whitney U-test at each day post-infection. dpi, Day post-infection; WNV, West Nile virus; wPip⁻/wPip⁺, mosquitoes treated with tetracycline hydrochloride to clear Wolbachia/untreated mosquitoes