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

## TL;DR

This study finds that Culex mosquitoes in Haiti show signs of insecticide resistance and carry various pathogens, suggesting current control methods may be ineffective.

## Contribution

The study is the first to examine insecticide resistance and pathogens in Culex mosquitoes from Haiti.

## Key findings

- Cx. quinquefasciatus mosquitoes in Haiti show signs of pyrethroid and organophosphate resistance.
- Southern locations near Port-au-Prince had higher insecticide resistance markers.
- Mosquitoes were ubiquitously infected with bacteria, viruses, and avian malaria.

## Abstract

Haiti has a high burden of mosquito-transmitted diseases and very limited vector control activities. Therefore, effective operational mosquito control is important. Previous studies have examined insecticide resistance in Haitian Aedes and Anopheles mosquitoes, but not Culex species. In this study, we examined collections of Culex quinquefasciatus from 12 locations in northern and southern Haiti for markers of insecticide resistance and pathogens. Metagenome analysis identified ubiquitous infection of these Cx. quinquefasciatus with symbiotic bacteria, insect-specific viruses, and avian malaria. The presence of target-site insecticide resistance markers and elevated enzymatic activities in these mosquito populations indicates insecticide resistance is likely. We also found that these insecticide resistance markers were generally higher in southern locations near the capital, Port-au-Prince. The findings suggest that Cx. quinquefasciatus mosquito control with pyrethroid and organophosphate adulticides may be of limited efficacy.

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 Aedes and Anopheles mosquitoes, but not Culex species. In this study, we examined collections of Culex quinquefasciatus 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 Wolbachia, Rhabdoviridae, and Plasmodium 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 Culex mosquito populations and no clear activity pattern, enzymatic activity was significantly higher at the southern sites than at the northern sites. Similar findings in Cx. quinquefasciatus populations in other locations in the Americas strongly suggest that vector control with pyrethroid and organophosphate adulticides may be of limited efficacy.