Temephos Resistance Status of Aedes aegypti Populations From Havana, Cuba.

Aedes aegypti chemical control remains an indispensable alternative to prevent dengue, Zika, and chikungunya outbreaks in Havana, Cuba. The city of Havana requires constant surveillance because of its bioecological characteristics that favor the proliferation of mosquito vectors of these viruses, which constitutes a high risk to the health of its inhabitants. The goal of this study was to determine the impact of the stopping of temephos applications during the 2 years of the COVID-19 pandemic on the level of susceptibility of Ae. aegypti in 5 municipalities of Havana, Cuba. Larval susceptibility was evaluated by bioassays as described by the World Health Organization. All Ae. aegypti populations tested showed high resistance to temephos. The National Control Program of Ae. aegypti in Cuba will need to promote insecticide rotation policies to prevent the evolution of temephos resistance in Havana.

First report of natural Wolbachia infections in mosquitoes from Cuba.

Mosquitoes are extensively responsible for the transmission of pathogens. Novel strategies using Wolbachia could transform that scenario, since these bacteria manipulate mosquito reproduction, and can confer a pathogen transmission-blocking phenotype in culicids. Here, we screened the Wolbachia surface protein region by PCR in eight Cuban mosquito species. We confirmed the natural infections by sequencing and assessed the phylogenetic relationships among the Wolbachia strains detected. We identified four Wolbachia hosts: Aedes albopictus, Culex quinquefasciatus, Mansonia titillans, and Aedes mediovittatus (first report worldwide). Knowledge of Wolbachia strains and their natural hosts is essential for future operationalization of this vector control strategy in Cuba.

Characterization of Insecticide Resistance in Aedes aegypti from the Zoological Garden of Havana, Cuba.

Chemical control of Aedes aegypti continues to be an indispensable alternative to preventing dengue, Zika, and chikungunya outbreaks. The Havana Zoological Garden requires constant vigilance because its special characteristics help in the spread of the causal agents of diseases transmitted by mosquitoes, which put the health of visitors at risk. The goals of this study were to determine the level of susceptibility and insecticide resistance mechanisms in the Ae. aegypti population. Temephos susceptibility in larvae was evaluated with bioassays using the World Health Organization's methodology, and susceptibility of adult mosquitoes was determined by the impregnated bottle bioassay, recommended by the Centers for Disease Control and Prevention. Resistance mechanisms were determined with biochemical assays. Mosquito larvae from the Havana Zoo were found resistant to temephos, which was associated with the activity of the enzymes α- and ß-esterases and mixed function oxidases but not glutathione-S-transferase. Adult mosquitoes were susceptible to pyrethroid (lambda-cyhalothrin, deltamethrin, and cypermethrin), organophosphate (chlorpyrifos), and carbamate (bendiocarb). Temephos resistance detected in the mosquito population from the Havana Zoo is an alert for the Vector Control Program, which must take measures to manage their resistance, relying on the surveillance carried out by Cuba's medical entomology laboratories.

Reversal of Resistance to the Larvicide Temephos in an Aedes aegypti (Diptera: Culicidae) Laboratory Strain From Cuba.

The objective of this investigation was to know whether the organophosphate temephos resistance developed in larvae from a laboratory strain of Aedes aegypti (Linnaeus, 1762) from Cuba could be reversed. The resistant laboratory strain of Ae. aegypti, named SAN-F6, was left without temephos selection pressure for 12 generations. The level of temephos resistance was determined using WHO bioassays and mechanisms of metabolic resistance were determined based on enzyme activity levels detected by biochemical assays. Bioassays and biochemical assays were conducted on the SAN-F6 parental strain and every three reversal generations (SANRevF3, SANRevF6, SANRevF9, and SANRevF12) without temephos selection pressure. After 19 yr of keeping the SAN-F6 strain under selection pressure with the LC90 of temephos, the resistance ratio (RR50) was 47.5×. Biochemical assays indicated that esterase and glutathione S-transferase are still responsible for temephos resistance in this strain, but not mixed-function oxidase. Experiments on resistance reversal showed that temephos susceptibility could be recovered as α esterase activity levels decreased. The SAN-F6 strain has provided an essential basis for studies of temephos resistance in Cuba. It was demonstrated that the resistance developed to the larvicide temephos in Ae. aegypti from this Cuban lab strain is a reversible phenomenon, which suggests that similar outcomes might be expected in field populations. As such, the use of temephos alternated with other larvicides recommended by WHO such as Bti or pyriproxyfen is recommended to maintain the effectiveness of temephos and to achieve more effective control of Ae. aegypti.