Background: There is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS. Methods: We evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify “delayed mortality”. Results: Mean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80–97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months). Conclusions: Chlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.

Aedes aegypti and Aedes albopictus vector dengue, chikungunya and Zika viruses. With both species expanding their global distributions at alarming rates, developing effective surveillance equipment is a continuing priority for public health researchers. Sound traps have been shown, in limited testing, to be highly species-specific when emitting a frequency corresponding to a female mosquito wingbeat. Determining male mosquito capture rates in sound traps based on lure frequencies in endemic settings is the next step for informed deployment of these surveillance tools. We field-evaluated Male Aedes Sound Traps (MASTs) set to either 450 Hz, 500 Hz, 550 Hz or 600 Hz for sampling Aedes aegypti and/or Aedes albopictus and compared catch rates to BG-Sentinel traps within Pacific (Madang, Papua New Guinea) and Latin American (Molas, Mexico and Orange Walk Town, Belize) locations. MASTs set to 450–550 Hz consistently caught male Ae. aegypti at rates comparable to BG-Sentinel traps in all locations. A peak in male Ae. albopictus captures in MASTs set at 550 Hz was observed, with the lowest mean abundance recorded in MASTs set to 450 Hz. While significantly higher abundances of male Culex were sampled in MASTs emitting lower relative frequencies in Molas, overall male Culex were captured in significantly lower abundances in the MASTs, relative to BG-Sentinel traps within all locations. Finally, significant differences in rates at which male Aedes and Culex were positively detected in trap-types per weekly collections were broadly consistent with trends in abundance data per trap-type. MASTs at 550 Hz effectively captured both male Ae. aegypti and Ae. albopictus while greatly reducing bycatch, especially male Culex, in locations where dengue transmission has occurred. This high species-specificity of the MAST not only reduces staff-time required to sort samples, but can also be exploited to develop an accurate smart-trap system—both outcomes potentially reducing public health program expenses.

El loxoscelismo es ocasionado cuando el veneno dermonecrótico producido por las arañas del género Loxosceles, conocidas como “arañas violinistas”, ingresa al organismo de una persona a través de su mordida. En México ocurre un subregistro de los casos de loxoscelismo por la ausencia de pruebas de laboratorio para su diagnóstico y la dificultad del cuadro clínico. El objetivo de este trabajo es describir un caso de loxoscelismo cutáneo ocasionado por mordedura de Loxosceles yucatana en un residente de Yucatán, México. El loxoscelismo cutáneo es el tipo más frecuente y menos severo. El presente caso se diagnosticó por medio de la sintomatología registrada en la historia clínica, la lesión inicial y la identificación de arañas L. yucatana. Este trabajo representa la primera descripción de un caso de loxoscelismo cutáneo con resolución favorable en Yucatán.

Background: Triatoma dimidiata, the main vector of Trypanosoma cruzi throughout South Mexico and Central America, infest domiciles and peridomestic ecotopes of rural and semi-rural communities. This study reports the effect of the residual application of the organophosphate pirimiphos-methyl in a microencapsulated formulation (Actellic 300CS) for the control of intradomiciliary and peridomestic T. dimidiata in the community of Tekik de Regil (hereafter Tekik) in Yucatan, Southeast Mexico. Methods: From March to October 2022, a two-arm, unblinded entomological trial was performed in Tekik. Timed Manual Collections (TMC) characterized house and peridomicile infestation by T. dimidiata prior (baseline) and after the residual spraying (RS) (post-intervention) of a microencapsulated formulation. A total of 120 premises were surveyed (60 positive and 60 negative for T. dimidiata), randomly allocated 1:1 to treatment (RS with Actellic 300CS) and control (no RS) arms. Monthly post-spraying entomological surveys (May-October) with TMC were carried out in a random sample of ten houses from each arm. We analyzed the association between the treatment and post-intervention infestations using chi-square contingency tables. The estimated efficacy of the intervention with the 95% Confidence Intervals (CI) was calculated with the efficacy formula, using the Odds Ratio (OD) calculated from a binomial Generalized Linear Mixed Model (GLMM) from the positive premises in the baseline survey and post-intervention, using time as a random effect. Results: Domestic infestations post-intervention were only detected in the control group (2/60 houses, 3.3%). Cumulative peridomestic infestation was significantly higher in the control arm (31.7%; 19/60) compared to the treatment arm (11.7%; 7/60) (X² = 0.007, p < 0.01). The cumulative 6-month estimated efficacy of the intervention (% reduction in treatment versus control arm) was 65% (95% CI: 14%-79%). Conclusions: A single application of Actellic 300CS reduced T. dimidiata infestations by more than 60% for up to 6 months and provides evidence of an alternative formulation suitable for triatomine control in Mexico.