Insecticide Resistance Mutations, Enzymatic Activity, and Pathogen Infection in Culex quinquefasciatus from Haiti

Haiti is a Caribbean country of about 11 million people with a high burden of mosquito-transmitted disease and limited vector control, thereby making effective operational mosquito control of high importance. Previous studies have examined vector-borne disease burden and insecticide resistance markers in Haitian <i>Aedes</i> and <i>Anopheles</i> mosquitoes, but not <i>Culex</i> species. In this study, we examined collections of <i>Culex quinquefasciatus</i> from 12 locations in northern and southern Haiti for the presence of markers of insecticide resistance (using a variety of target-site mutations and biochemical assays) and pathogens (using a deep-sequencing microbiome workflow). The metagenomic analysis identified <i>Wolbachia</i>, <i>Rhabdoviridae</i>, and <i>Plasmodium</i> infections in all sample pools at relatively high levels, along with less frequent detections of other potential pathogens. Insecticide resistance marker examination identified variable frequencies of knockdown resistance and acetylcholinesterase resistance mutations, as well as variation in resistance-associated enzymatic activities in these populations. These findings indicate that insecticide resistance to pyrethroid and organophosphate insecticides is likely. Although there was variation among <i>Culex</i> mosquito populations and no clear activity pattern, enzymatic activity was significantly higher at the southern sites than at the northern sites. Similar findings in <i>Cx. quinquefasciatus</i> populations in other locations in the Americas strongly suggest that vector control with pyrethroid and organophosphate adulticides may be of limited efficacy.