Entomological Investigations During Early Stages of A Chikungunya Outbreak In the United States Virgin Islands, 2014.

During the 2014 chikungunya (CHIK) outbreak in the Caribbean, we performed entomological surveys on 3 United States Virgin Islands (USVI): St. Croix, St. Thomas, and St. John. We aimed to evaluate the potential for chikungunya virus (CHIKV) transmission in the USVI. The surveys took place between June 19, 2014, and June 29, 2014, during the dry season in USVI. A total of 1,929 adult mosquitoes belonging to 4 species- Culex quinquefasciatus (68.4%), Aedes aegypti (29.7%), Ae. mediovittatus (1.3%), and Ae. sollicitans (<1%)-were detected. Environmental investigations showed that between 73% and 87% of the homes had containers that could serve as mosquito larval habitats. In addition, 47% of the homes did not have air conditioning and between 69% and 79% of homes showed evidence of frequent outdoor activity exhibited by residents. Taken together, these observations suggest a high potential for CHIKV transmission in USVI. The relative abundance of Ae. aegypti on St. John's, St. Thomas, and St. Croix was 21.0, 11.0, and 3.0 mosquitoes/trap per day, respectively, suggesting that the former 2 islands were at the highest risk of CHIKV outbreaks. Insecticide resistance testing detected high levels of resistance to malathion and permethrin in several local populations of Ae. aegypti on St. Croix Island, which suggested that these 2 insecticides should not be used during CHIK outbreaks.