First national-scale evaluation of temephos resistance in Aedes aegypti in Peru

Widespread Resistance to Temephos in Aedes aegypti (Diptera: Culicidae) from Mexico

Organic synthetic insecticides continue to be part of the arsenal for combating vector-borne diseases in Mexico. Larvicides are a fundamental part of the process in programs for mosquito control, temephos being one of the most widely used in Mexico. In the present study, we analyzed the frequency of temephos resistance in twenty-three Aedes aegypti populations using the discriminating concentration (DC) of 0.012 mg/L. We also tested 5× DC (0.6 mg/L) and 10× DC (0.12 mg/L) of temephos. The resistance distribution to temephos was interpolated to unsampled sites using the inverse distance weighting (IDW) method. The populations of Ae. aegypti showed a high frequency of resistance (1× DC) with mortality rates below 93% in 22 of the 23 populations analyzed. Moderate resistance intensity (5× DC) was found in 78% of the populations, and high intensity (10× DC) in 30%. Predicted mortality was below 60% in the populations of the Pacific Coast, along the Gulf of Mexico, and in the state of Coahuila in Northeastern Mexico in relation to 1× DC; the Pacific Coast and Northeast patterns hold for 5× and 10× DC. The results suggest the need for rotation of the larvicide to effectively control the larval populations of the vector in the country.

Biological evaluation of 1,3-benzodioxole acids points to 3,4-(methylenedioxy) cinnamic acid as a potential larvicide against Aedes aegypti (Diptera: Culicidae)

Aedes aegypti serves as the primary vector for viruses like dengue, Chikungunya, Zika, and yellow fever, posing a significant public health challenge in Brazil. Given the absence of approved vaccines for these diseases, effective mosquito control becomes paramount in preventing outbreaks. However, currently available chemical insecticides face issues related to toxicity and the emergence of resistance, necessitating the exploration of new active compounds. Drawing inspiration from natural products, we identified the 1,3-benzodioxole group as a key pharmacophore associated with insecticidal activity. Therefore, this study aimed to synthesize and assess the larvicidal activity of 1,3-benzodioxole acids against Ae. aegypti, as well as their toxicity in mammals. Among the compounds evaluated, 3,4-(methylenedioxy) cinnamic acid (compound 4) demonstrated larvicidal activity. It exhibited LC50 and LC90 values of 28.9 ± 5.6 and 162.7 ± 26.2 μM, respectively, after 24 h of exposure. For reference, the positive control, temephos, displayed both LC50 and LC90 values below 10.94 μM. These findings underline the significance of the 3,4-methylenedioxy substituent on the aromatic ring and the presence of a double bond in the aliphatic chain for biological activity. Furthermore, compound 4 exhibited no cytotoxicity towards human peripheral blood mononuclear cells, even at concentrations up to 5200 μM. Lastly, in mice treated with 2000 mg kg-1, compound 4 showed mild behavioral effects and displayed no structural signs of toxicity in vital organs such as the kidney, liver, spleen, and lungs.

Spent Coffee Grounds and Novaluron Are Toxic to Aedes aegypti (Diptera: Culicidae) Larvae

Aedes aegypti (Diptera: Culicidae) is a vector for mosquito-borne diseases worldwide. Insecticide resistance is a major concern in controlling this mosquito. We investigated the chemical compounds in wet and dry spent coffee grounds (wSCGs and dSCGs) and evaluated the efficacy of dSCGs, wSCGs, and novaluron on the mortality and adult emergence inhibition of Ae. aegypti. We found higher concentrations of chemical compounds in wSCGs than in dSCGs. The wSCGs and dSCGs both contained total phenolic compounds, total flavonoid compounds, caffeic acid, coumaric acid, protocatechuic acid, and vanillic acid. Complete mortality was observed after 48 h of exposure to 50 g/L wSCGs, while similar mortality was found after 120 h of exposure to 10 µg/L of novaluron. The sublethal dose was a concentration of wSCGs (5 g/L) and novaluron (0.01, 0.1, and 1 µg/L) combined that resulted in a larval mortality lower than twenty percent (at 72 h) to determine their synergistic effects. The death rate of larvae exposed in sublethal combination of wSCGs and novaluron was significantly higher than that of its stand-alone. The findings indicate that the combination of wSCGs and novaluron at sublethal concentrations had synergistic effects on the mortality of Ae. aegypti larvae and could be applied as an alternative control measure.

Laboratory Evaluation and Field Feasibility of Micro-Encapsulated Insecticide Effect on Rhodnius prolixus and Triatoma dimidiata Mortality in Rural Households in Boyacá, Colombia

Chagas disease is a neglected vector-borne zoonosis caused by the parasite Trypanosoma cruzi that is primarily transmitted by insects of the subfamily Triatominae. Although control efforts targeting domestic infestations of Rhodnius prolixus have been largely successful, with several regions in Boyacá department certified free of T. cruzi transmission by intradomicile R. prolixus, novel native species are emerging, increasing the risk of disease. Triatoma dimidiata is the second most important species in Colombia, and conventional control methods seem to be less effective. In this study we evaluated the efficacy and usefulness of micro-encapsulated insecticide paints in laboratory conditions and its applicability in rural communities to avoid triatomine domiciliation. Laboratory conditions measured mortality at 6 months and 12 months, with an average mortality between 93-100% for T. dimidiata and 100% for R. prolixus. Evaluation of triatomine infestation in rural households was measured after one year, with an overall perception of effectiveness in reducing household domiciliation. Although triatomines were still spotted inside and around the homes, our findings demonstrate the ability of micro-encapsulated insecticide to prevent colonization inside the households when comparing infestation rates from previous years. Current control measures suggest insecticide spraying every six months, which implies great economic cost and logistical effort. Complementary triatomine control measures with insecticide spraying and micro-encapsulated insecticide paint would make public health efforts more efficient and reduce the frequency of treatment.