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Simple Summary: The role of mosquito eggs in disease transmission is not well understood, despite reports of virus vertical transmission and their ability to survive dry periods in a dormant stage. Additionally, field evidence shows that new generations of mosquitoes often reappear weeks or months later in certain city areas. This may be because both species follow an "R strategy" reproduction pattern, laying many eggs to ensure survival in a harsh environment. This study was conducted in southern Mexico in 2023 and focused on the egg-laying activity of Ae. aegypti and Ae. albopictus mosquitoes during the dry inter-epidemic season. Ovitraps were used in the backyards of the houses to identify egg species, and further larval containers were surveyed. Most of the larval habitats were containers smaller than 1 L, commonly not treated as they were considered trash. Even though homeowners volunteer to remove them during government cleaning community-based campaigns, city waste disposal trucks transporting these containers do not take any measures to destroy the tiny eggs. We conclude with the urgent need to develop an egg-killing treatment, which could significantly enhance vector reduction and achieve a total stage strategy within the Integrated Vector Control Programs. Although integrated management and control programs implement intense control measures for adult, pupal, larval, and breeding sites during outbreaks, there is a lack of studies to understand the role of the vector egg stage in disease dynamics. This study aimed to assess the dry season quiescent Aedes aegypti and Aedes albopictus egg populations in houses and backyards in Tapachula, southern Mexico. Two hundred and fifty ovitraps were placed in 125 homes in the Las Americas neighborhood. A total of 7290 eggs were collected from 211 (84.4%) ovitraps. Only 5667 (77.7%) hatched under insectary water immersion and food supply conditions, with 4031 (71.1%) identified as Ae. aegypti, and 1636 (28.8%) as Ae. albopictus, respectively. The remaining 1623 (22.3%) did not hatch due to Delayed Hatching and/or quiescence tropical stage. Eighty-three larval containers were sampled with desiccated eggs during the dry season; most of them were described as trash waste because larvicides are only used for larger containers of 5–10 L. Evolutionary characteristics for the two species including partial egg hatching, ambient-regulated quiescence, the ability of the embryo to survive for a more extended period intra-seasonally, the egg sticking to inner container walls, demands urgent operational research to achieve successful egg-proof larval container methods. [ABSTRACT FROM AUTHOR]

Although having five different ways of transmission the vector‐borne is the principal way of transmission of Chagas disease, which involves insects of the subfamily Triatominae (Hemiptera: Reduviidae). Nineteen of the 31 species that occur in Mexico are associated with humans, and all are capable of transmitting the disease. Pyrethroids are the insecticides recommended for the control of these vectors in Mexico. We determined the susceptibility to the pyrethroids deltamethrin and permethrin of peridomestic populations of Triatoma mazzottii Usinger and two populations of Triatoma longipennis Usinger in comparison with a reference strain for each species. Bioassays were performed for the determination of the LD50 for both field populations and reference strains. A maximum of 27 fold resistance to deltamethrin was observed in T. mazzottii, meanwhile, for permethrin, T. longipennis from Jalisco show the highest value of 3.19 fold. There was significantly increased activity of esterases in field populations in comparison with their corresponding reference strain. The results of the search of kdr mutations related to the resistance to deltamethrin and permethrin in the evaluated species show the presence of mutations in the field populations, as is the case with individuals of T. mazzottii, for which the mutation was found A943V, and for the two populations of T. longipennis included in this study, we report the presence of the kdr mutation K964R. Evaluation of the various mechanisms involved in resistance to pyrethroids in triatomines from Mexico could guide us to the real justification for insecticide resistance monitoring. [ABSTRACT FROM AUTHOR]

The L1014F mutation in the voltage-sodium channel gene has been associated with resistance to DDT and pyrethroids in various arthropod species including mosquitoes. We determined the frequency of the L1014F kdr mutation in 16 field populations of Culex quinquefasciatus from Northeastern Mexico collected between 2008 and 2013. The L1014F was present in all populations analyzed with the lowest frequency (3.33%) corresponding to the population from Monclova collected in 2012, and the highest frequency (63.63%) from the Monterrey population collected in 2012. The presence of a kdr mutation in populations of Cx. quinquefasciatus from northeastern Mexico provides evidence of pyrethroid resistance. This requires a special attention, considering that pyrethroid-based insecticides are commonly used in vector-control campaigns, especially against Aedes aegypti (L.). [ABSTRACT FROM AUTHOR]

Enzymatic mechanisms indicating resistance were determined in the southern house mosquito, Culex quinquefasciatus Say, from Nuevo Leon, northeastern Mexico, after exposure to pyrethroids: trans-permethrin (92% trans-6% cis) 0.75%, bifenthrin (99%) 0.1%, cypermethrin (99%) 0.1%, deltamethrin (99%) 0.5%, and lambda-cyhalothrin (99.1%) 0.5%. Mosquitoes were collected from four municipalities in the north and center of the state of Nuevo Leon. Four groups of 25 female mosquitoes, 24 hours of age were exposed to insecticide doses pre-evaluated. After 50% of the mosquitoes had died, individuals were divided into alive and dead categories. With the individuals selected and a group of 100, 1-day old adult females from each location without exposure to the pyrethroids, biochemical tests were used to determine resistance-related activities of enzymes alpha- and beta-esterases, glutathione S-transferases, and mixed-function oxidases. The results were compared with those from a susceptible strain of southern house mosquito obtained after rearing for 25 generations in a laboratory. Biochemical assays showed elevated glutathione S-transferases and esterases, enzymes associated with resistance to pyrethroids. [ABSTRACT FROM AUTHOR]

Potato purple top and zebra chip diseases are transmitted by potato psyllid, Bactericera cockerelli (Sulc), to tomato, Solanum lycopersicum L., and potato, Solanum tuberosum L., crops. The aim of this study was to characterize and quantify vitellogenin receptor in potato psyllid. We obtained partial characterization of the receptor by end-point PCR and sequencing using capillary electrophoresis. Relative quantification by real-time PCR was used to determine expression levels of the receptor in females and males. Similarity in vitellogenin sequence obtained in a laboratory was 89% compared with the sequence of the entire transcriptome of the species reported in GenBank. Expression analysis showed the vitellogenin receptor significantly expressed in potato psyllid females compared with males from potato plants. Further study of the vitellogenin receptor of potato psyllid is needed to determine its complete sequence and potential target to control the pest. [ABSTRACT FROM AUTHOR]

Rhipicephalus microplus is the most important tick in veterinary medicine, given its repercussions on animal production. The principal strategy to avoid adverse effects associated with R. microplus is the chemical control of tick populations through organosynthetic acaricides. Therefore, monitoring susceptibility to acaricides is paramount in any control program. This study aimed to analyze the resistance status of 2 populations of R. microplus from northeastern Mexico to the organochlorine (OC) lindane, organophosphates (OP) coumaphos, chlorfenvinphos, diazinon, and chlorpyrifos, and the synthetic pyrethroids (SPs) flumethrin, deltamethrin, and cypermethrin. Discriminating doses (DD) of each acaricide were used in the larval packet bioassay (LPT). Additionally, the presence of the knockdown resistance (kdr) mutation T2134A associated with pyrethroid resistance was evaluated using allele-specific polymerase chain reaction (PCR). The populations of R. microplus showed a high frequency of resistance to SP, with mortality rates of less than 5%; they also showed resistance to the OPs (diazinon and chlorpyrifos) with mortality rates ranging from 1.29% to 34.62%; meanwhile, they were susceptible to coumaphos and chlorfenvinphos. Mortality rates higher than 66% were observed for lindane, indicating susceptibility. The mutant allele of the kdr mutation T2134A was detected in 75% and 100% of the pools analyzed. The populations studied presented a highly resistant profile to pyrethroids, with the presence of the kdr mutant allele A2134. The susceptibility to the organophosphates such as coumaphos and chlorfenvinphos of R. microplus from northeastern Mexico should be noted., (Copyright © 2023 by The American Mosquito Control Association, Inc.)

Aedes aegypti (L.) is the primary vector of the viruses that cause dengue, Zika, and chikungunya, for which effective vaccines and drugs are still lacking. Current strategies for suppressing arbovirus outbreaks based on insecticide use pose a challenge because of the rapid increase in resistance. The widespread and excessive use of pyrethroid-based insecticides has created a large selection pressure for a kdr-type resistance, caused by mutations in the para gene of the voltage-gated sodium channel (vgsc). Our objective was to evaluate the allelic frequency of natural populations of Ae. aegypti of Mexico at codon 410 of the para gene. Twenty-six Ae. aegypti populations from east and southern Mexico were genotyped for the codon 410 using allele-specific PCR. The frequencies of the L410 allele in Ae. aegypti ranged from 0.10 to 0.99; however, most of the frequencies were in the range of 0.36 to 0.64. The highest frequencies were found in three populations from the state of Veracruz, namely, Minatitlan with 0.99, Poza Rica with 0.82, and Jose Cardel with 0.97, along with populations from Cancun in Quintana Roo with 0.93, Frontera in Tabasco with 0.91, and Ciudad del Carmen in Campeche with 0.86. The frequency of the L410 allele was high in all populations of Ae. aegypti with higher values in populations of the southeast of the country. The knowledge of specific substitutions in vgsc and their interaction to confer resistance is essential to predict and develop future strategies for resistance management in Ae. aegypti in Mexico., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)