Aedes Mosquitoes in Alabama – Population Dynamics and Sensitivity to Insecticides

Abstract

The Asian tiger mosquito, Aedes albopictus, is one of the most notorious day-biting species of mosquito in the world and can transmit approximately 26 diseases, including dengue, of which more than 50 million cases occur each year; chikungunya, which has spread to 40 countries located in Asia, Africa, Europe, and America and caused more than 1,500,000 cases in 2006; and yellow fever, which has caused several serious outbreaks in Bolivia, Peru, Ecuador, Brazil, and Africa. Insecticides are still the most efficient way to combat and prevent mosquito-borne diseases and control mosquito populations among several approaches. However, intensive and inappropriate use of insecticide results in insecticide resistance, which is a major barrier to the development of a management strategy to control mosquito populations. Plenty of papers have reported insecticide resistance in different mosquito species, and Aedes aegypti populations from around the world have been confirmed be resistant to a variety of insecticides, such as temephos, malathion, deltamethrin, permethrin, DDT and propoxur. Aedes albopictus, which is less resistant than Aedes aegypti, is still resistant to several insecticides, such as chlorpyrifos, pyrethroids, and carbamates. Insensitive targets, the overexpression of detoxifying enzymes, penetration resistance, behavioral avoidance, and so on have been confirmed to play roles in insecticide resistance. Mutations can change the properties of the target site, affecting insecticide binding to the target, and gene overexpression of detoxifying enzymes can generate more detoxifying enzymes to degrade more toxins. Surveillance of the mosquito population and insecticide resistance are fundamental for controlling mosquito-borne diseases and could be used by the government to optimize the strategy to fight diseases transferred by mosquitoes. In this research, traps used to collect mosquito eggs were placed in several locations scattered across Alabama and were checked every two or three weeks from July 2017 to July 2018. Three species were identified in this survey in Alabama: Aedes albopictus, Aedes triseriatus, and Aedes japonicus. The mosquito population began to emerge in April at approximately 57°F. The suitable temperature range of mosquito is 75°F to 85°F. Aedes albopictus was tested for its resistance level to eight insecticides, chlorpyrifos, deltamethrin, etofenprox, malathion, permethrin resmethrin, fenitrothion, and β-cyfluthrin, in adult and larval bioassays. Resmethrin, permethrin, and fenitrothion were found to allow the mosquitoes to survive longer than the diagnostic time. Mobile is the most suitable city for mosquitoes, with most strains demonstrating insecticide resistance. We suggest that β-cyfluthrin and deltamethrin should replace permethrin and malathion for controlling mosquitoes. Altogether, our study data provide fundamental information for the government to establish a strategy for controlling mosquitoes in the future.