Susceptibility of Culex quinquefasciatus (Diptera: Culicidae) in Southern Louisiana to Larval Insecticides

Abstract

Mosquito control districts conduct rigorous insecticide treatments against both larval and adult Culex quinquefasciatus Say (Diptera: Culicidae), the primary vector of West Nile virus in the southern United States. However, the development of resistant populations of Cx. quinquefasciatus in response to extensive larvicide or adulticide applications has been demonstrated repeatedly across the world. Examining changes in insecticide susceptibility in treated field areas can help inform mosquito control districts as to whether or not their treatments remain effective. We hypothesized that frequent insecticide applications for the control of mosquitoes in East Baton Rouge Parish, Louisiana, lowered susceptibility of wild Cx. quinquefasciatus to larvicides. Larvicide susceptibility was measured using Lysinibacillus sphaericus, spinosad, and temephos in populations of Cx. quinquefasciatus sampled from sites in three Parishes where frequencies of insecticide applications varied, and frequencies of resistance were measured relative to a susceptible reference colony. Susceptibility to these larvicides was widespread, although fourfold resistance to the organophosphate temephos was detected at one site in East Baton Rouge Parish in the spring of 2016, which increased to eightfold resistance by the end of the mosquito season. Activities of esterases were found to be elevated in wild, temephos-resistant mosquitoes, indicating the potential role of these enzymes as a mechanism of resistance. The results of this study provide a baseline of comparison for future measurements of susceptibility in Cx. quinquefasciatus in Louisiana, and may help inform local mosquito control districts as to the effectiveness and sustainability of their insecticide programs.

Characterization of a yeast interfering RNA larvicide with a target site conserved in the synaptotagmin gene of multiple disease vector mosquitoes

“…Given the recent spread of West Nile virus across the continental United States, the existing global disease burden of lymphatic filariasis [3], as well as reported resistance to existing larvicides [48], it is also useful that syt.427 has larvicidal activity in C . quinquefasciatus (Fig 6C).…”

Characterization of a broad-based mosquito yeast interfering RNA larvicide with a conserved target site in mosquito semaphorin-1a genes

“…As a member of a new class of larvicides, sema.460 could help combat resistance to existing insecticides, an ever-growing problem [10–16, 52]. Moreover, through our efforts to build an arsenal of interfering RNA larvicides ([25, 26], this study), we are working to combat resistance that could potentially develop due to a mutation in any one shRNA target site.…”

“…4c). The existing global disease burden of lymphatic filariasis [3], recent spread of West Nile virus across the continental United States, and reported resistance to existing larvicides [52] make the development of new larvicides for control of Culex pipiens complex mosquitoes a vital necessity. Larvicides for control of Culex mosquitoes are often used to treat stormwater catch basins, which are known to be important breeding sites for Culex mosquitoes in urban and suburban regions [60–62].…”

First report of Culex quinquefasciatus Say (Diptera: Culicidae) larvae susceptible to temephos, malathion, cypermethrin, and Deltamethrin in Jakarta, Indonesia: Detoxification enzyme activity and the midgut cell damage

“…This study correlates with previous studies that only used the larval stage of Cx.quinquefasciatus. For example, DeLisi et al [35] in East Baton Parish, Louisiana, only used Cx.quinquefasciatus larvae to assess the susceptibility of Cx.quinquefasciatus to larval insecticides (Lysinibacillus sphaericus, spinosad, and temephos). DeLisi's research results found that Cx.…”