Resistance to Pyrethroids in the Malaria Vector Anopheles albimanus in Two Important Villages in the Soconusco Region of Chiapas, Mexico, 2022.

Chiapas State comprises the largest malaria foci from Mexico, and 57% of the autochthonous cases in 2021, all with Plasmodium vivax infections, were reported in this State. Southern Chiapas is at constant risk of cases imported due to migratory human flow. Since chemical control of vector mosquitoes is the main entomological action implemented for the prevention and control of vector-borne diseases, this work aimed to investigate the susceptibility of Anopheles albimanus to insecticides. To this end, mosquitoes were collected in cattle in two villages in southern Chiapas in July-August 2022. Two methods were used to evaluate the susceptibility: the WHO tube bioassay and the CDC bottle bioassay. For the latter, diagnostic concentrations were calculated. The enzymatic resistance mechanisms were also analyzed. CDC diagnostic concentrations were obtained; 0.7 µg/mL deltamethrin, 12 µg/mL permethrin, 14.4 µg/mL malathion, and 2 µg/mL chlorpyrifos. Mosquitoes from Cosalapa and La Victoria were susceptible to organophosphates and to bendiocarb, but resistant to pyrethroids, with mortalities between 89% and 70% (WHO), and 88% and 78% (CDC), for deltamethrin and permethrin, respectively. High esterase levels are suggested as the resistance mechanism involved in the metabolism of pyrethroids in mosquitoes from both villages. Mosquitoes from La Victoria might also involve cytochrome P450. Therefore, organophosphates and carbamates are suggested to currently control An. albimanus. Its use might reduce the frequency of resistance genes to pyrethroids and vector abundance and may impede the transmission of malaria parasites.

Acceptance of a sterile male releases pilot project to reduce Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae) populations and its associated factors: A community-based cross-sectional survey in South Chiapas, Mexico.

Worldwide, vector-transmitted diseases account for more than 17% of all infectious diseases and cause more than 700,000 deaths annually. The primary strategy to control the transmission of dengue, chikungunya and Zika focuses on the control of their vectors. Vector control programs depend mainly on the use of insecticides. However, these measures have failed to yield the desired results because the lack of proper control decreases their effectiveness over time. Also, the effect of insecticide use on non-target organisms, environmental contamination, and the development of insecticide resistance impose continuous challenges for insecticide-dependant control programs. The sterile insect technique, on the other hand, is a non-polluting and environment-friendly technique. The use of sterile insects is generally well established in agriculture, but human health interventions often require a consensus that combines social perceptions with scientific evidence. Factors associated with acceptance of the releases of sterile male Aedes aegypti mosquitoes were assessed with logistic regression models for two communities (Rio Florido and Hidalgo) in Tapachula, Chiapas, Mexico. The favourable opinion of the respondents about the project workers, and the fact that the releases of sterile mosquitoes would be managed by the Secretaría de Salud, were found to be factors that supported the acceptance of sterile mosquito releases. Factors associated with disapproval were community (Rio Florido and Hidalgo) and the misbelief that sterile male mosquitoes can bite. The differences observed between the communities included in this study might be the result of experiences with the releases, of social and community organisation, and of leadership by social actors.