Insecticide resistance mutations, enzymatic activity and pathogen infection in Culex quinquefasciatus from Haiti

Authors: TANACHAIWIWAT, PRIMROSE - University Of Florida; Sanscrainte, Neil; OKECH, BERNARD - Uniformed Services University; Estep Iii, Alden

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2026
Publication Date: 3/18/2026
Citation: Tanachaiwiwat, P., Sanscrainte, N.D., Okech, B.A., Estep Iii, A.S. 2026. Insecticide resistance mutations, enzymatic activity and pathogen infection in Culex quinquefasciatus from Haiti. Insects. 17(3):331. https://doi.org/10.3390/insects17030331.
DOI: https://doi.org/10.3390/insects17030331

Interpretive Summary: Haiti has a high burden of mosquito transmitted disease and very limited vector control activities, so 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, USDA CMAVE scientists and collaborators examined collections of Culex quinquefasciatus from 12 locations in northern and southern Haiti for the presence of 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 indicate insecticide resistance is likely. We also found that these insecticide resistance markers were generally higher in the southern locations near the capital of Port-au-Prince. The findings suggest that Cx. quinquefasciatus mosquito control with pyrethroid and organophosphate adulticides may be of limited efficacy.

Technical Abstract: Haiti is a Caribbean country of about 11 million people with a high burden of mosquito-transmitted disease and limited vector control, so effective operational mosquito control is important. 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 mutation and biochemical assays) and pathogens (using a deep sequencing microbiome workflow). The metagenome analysis identified Wolbachia, Rhabdoviridae and Plasmodium infection in all sample pools at relatively high levels along with less frequent findings of other potential pathogens. 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, which indicate that insecticide resistance to the primary pyrethroid and organophosphate insecticides is likely. Though there was variation between Culex mosquito populations and no clear activity pattern, enzymatic activity was significantly higher in the southern sites compared to 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.