Gustavo Ponce-Garcia

GONOTROPHIC CYCLE AND SURVIVORSHIP OF CULEX QUINQUEFASCIATUS (DIPTERA: CULICIDAE) USING STICKY OVITRAPS IN MONTERREY, NORTHEASTERN MEXICO

ABSTRACT Mark–release–recapture experiments were conducted to determine the length of the gonotrophic cycle and rate of survivorship of Culex quinquefasciatus Say in Monterrey, northeastern Mexico. A total of 2,352 field-caught Cx. quinquefasciatus females were marked and released at 8–12 h postemergence in 2 field trials. Sticky ovitraps were used to recapture marked gravid females. One hundred and ten (4.6%) marked females were recaptured during a 12-day sampling period. Recapture rates for the 2 individual trials were 6.4% and 3.5%. The length of the gonotrophic cycle, calculated as the average time between the initial blood meal and the time of recapture of gravid females, was 2–3 days. The first blood-fed mosquitoes were recaptured on the 2nd day postrelease. Gravid egg-laying females were most commonly recaptured at 2–3 days postfeeding. Daily survival estimates for the 2 release dates were of 0.871 and 0.883, respectively.

Local Evolution of Pyrethroid Resistance Offsets Gene Flow among Aedes aegypti Collections in Yucatan State, Mexico

The mosquito Aedes aegypti is the major vector of the four serotypes of dengue virus (DENV1-4). Previous studies have shown that Ae. aegypti in Mexico have a high effective migration rate and that gene flow occurs among populations that are up to 150 km apart. Since 2000, pyrethroids have been widely used for suppression of Ae. aegypti in cities in Mexico. In Yucatan State in particular, pyrethroids have been applied in and around dengue case households creating an opportunity for local selection and evolution of resistance. Herein, we test for evidence of local adaptation by comparing patterns of variation among 27 Ae. aegypti collections at 13 single nucleotide polymorphisms (SNPs): two in the voltage-gated sodium channel gene para known to confer knockdown resistance, three in detoxification genes previously associated with pyrethroid resistance, and eight in putatively neutral loci. The SNPs in para varied greatly in frequency among collections, whereas SNPs at the remaining 11 loci showed little variation supporting previous evidence for extensive local gene flow. Among Ae. aegypti in Yucatan State, Mexico, local adaptation to pyrethroids appears to offset the homogenizing effects of gene flow.

Susceptibility to insecticides and resistance mechanisms in Aedes aegypti from the Colombian Caribbean Region

We determined the susceptibility to insecticides and the biochemical and molecular mechanisms involved in resistance in nine populations of Aedes aegypti (L.) of the Colombian Caribbean region. Bioassays were performed on larvae for susceptibility to temephos and on adults to the insecticides malathion, fenitrothion, pirimiphos-methyl, permethrin, deltamethrin, λ-cyhalothrin and cyfluthrin. The resistance ratio (RR) for each insecticide in the populations was determined, using the susceptible Rockefeller strain as a susceptible control. Additionally, we evaluated the response of the populations to the diagnostic dose (DD) of the organochlorine pesticide DDT. The following biochemical mechanisms associated with resistance were studied: α-esterases, β-esterases, mixed-function oxidases (MFO), glutathione s-transferases (GST) and insensitive acetylcholinesterase (iAChE) as well as the presence of kdr I1,016 mutation and its frequency. All populations studied showed susceptibility to the organophosphates evaluated (RR < 5-fold), except for the Puerto Colombia and Soledad populations which showed high resistance (RR 15-fold) and moderate resistance (RR 5-fold) to temephos, respectively, and Sincelejo (Sucre) with moderate resistance to pirimiphos-methyl (RR 5-fold). All populations evaluated with DD of DDT were found to be resistant with 2-28% of mortality. Variability was observed in the resistance to pyrethroids: permethrin (RR 1.2- to 30.8-fold), deltamethrin RR 0.9- to 37.8-fold), λ-cyalothrin (RR 3.4- to 83-fold) and cyfluthrin (RR 0.3- to 33.8-fold). Incipiently α-esterases and MFO levels were found in the Valledupar population; MFO showed the same profile in Cienaga and GST in the Sincelejo population, all other populations showed unaltered profiles of the enzymes evaluated. The kdr I1,016 mutation was found in all populations evaluated with variability in its allelic and genotypic frequencies.

Host-feeding preference of Culex quinquefasciatus in Monterrey, northeastern Mexico.

ABSTRACT Studies were conducted to determine the host selection patterns of Culex quinquefasciatus in the municipalities of Guadalupe and Escobedo near Monterrey, northeastern Mexico. Mosquitoes were captured inside and outside houses. Chickens and humans were the most common blood sources for all Cx. quinquefasciatus females, accounting for nearby 70% of blood meals. Human blood was detected by enzyme-linked immunosorbent assay in 36.4% and 28.4% of engorged females resting inside houses in Guadalupe and Escobedo, respectively. The proportions of indoor resting females fed on chicken blood were 38.7% and 56.7%, respectively. The weighted and unweighted human blood index (HBI) values were calculated, by using indoor and outdoor data, from the proportions of humanfed mosquitoes. Weighted means (HBI) estimates for Guadalupe and Escobedo were 23.0% and 15.4%, respectively. The forage ratios (FRs) for humans were <1.0 (with or without chicken populations); consequently, it seems that these mosquitoes feed on humans with less frequency in comparison with chickens, horses, and pigs. The FRs for chickens were the highest of all available hosts (1.7 and 3.2), and they were the most abundant hosts in Escobedo, and the second most abundant in Guadalupe, indicating a selective bias of Cx. quinquefasciatus for chickens (i.e. ornithophagic).

Knockdown Resistance Mutations in Aedes aegypti (Diptera: Culicidae) From Puerto Rico.

Abstract Permethrin resistance is widespread in Aedes aegypti (L.), the main dengue, zika, and chikungunya virus vector in Latin America and the Caribbean. A common mechanism of resistance to pyrethroids—knockdown resistance (kdr)—is conferred through mutations in the insects voltage-dependent sodium channel. In this mosquito, around 10 replacement substitutions in the voltage-gated sodium channel gene (vgsc) have been reported in pyrethroid-resistant strains. Two of these mutations, named Ile1,016 and Cys1,534, are widespread in mosquito populations from Latin America and the Caribbean. This study assessed the levels of permethrin resistance and the frequency of two kdr mutations in eight Ae. aegypti populations collected in Puerto Rico in 2013. Permethrin resistance factors ranged from 33–214-fold relative to the New Orleans reference strain. The frequency of kdr mutation Ile1,016 ranged from 0.65 to fixation (1.0), and for Cys1,534 frequencies varied from 0.8 to fixation. Alarmingly, two populations—Carolina and Caguas—reached fixation at both loci. Our results suggest that permethrin effectiveness for Ae. aegypti control is compromised in these collections from Puerto Rico.

Assessing the effect of selection with deltamethrin on biological parameters and detoxifying enzymes in Aedes aegypti (L.)

BACKGROUND Resistance to insecticides through one or several mechanisms has a cost for an insect in various parameters of its biological cycle. The present study evaluated the effect of deltamethrin on detoxifying enzymes and biological parameters in a population of Aedes aegypti selected for 15 generations. The enzyme activities of alpha- and beta-esterases, mixed-function oxidases and glutathione-S-transferases were determined during selection, along with biological parameters. RESULTS Overexpression of mixed-function oxidases as a mechanism of metabolic resistance to deltamethrin was found. There were decreases in percentages of eggs hatching, pupation and age-specific survival and in total survival at the end of the selection (F16 ). Although age-specific fecundity was not affected by selection with deltamethrin, total fertility, together with lower survival, significantly affected gross reproduction rate, gradually decreasing due to deltamethrin selection. Similarly, net reproductive rate and intrinsic growth rate were affected by selection. CONCLUSION Alterations in life parameters could be due to the accumulation of noxious effects or deleterious genes related to detoxifying enzymes, specifically those coding for mixed-function oxidases, along with the presence of recessive alleles of the V1016I and F1534C mutations, associating deltamethrin resistance with fitness cost in Ae. aegypti.

Reference values for amino acids and acylcarnitines in peripheral blood in Quarter horses and American Miniature horses

AbstractBackgroundFree amino acids and acylcarnitines circulating in the blood can be used for diagnosis for metabolic illness and imbalances. To date, the normal reference ranges of amino acids and acylcarnitines in horse peripheral blood have not been established. In this study, the concentrations of 12 amino acids and 26 acylcarnitines were determined by tandem mass spectrometry in complete blood from 100 healthy horses (50 Quarter horses (QH) [23 males and 27 females] and 50 American Miniature horses (AMH) [15 males and 35 females]) with no signs of metabolic disease. The means and standard deviations were determined and data statistically analyzed.FindingsConcentrations of short, medium, and long chain acylcarnitines were significantly higher in male AMH than in male QH. The concentrations of the amino acids alanine, arginine, glycine, proline (glycogenic), and leucine (ketogenic) were higher in the QH than in the AMH. Female AMH had higher concentrations of propionylcarnitine, leucine, proline, arginine, and ornithine than female QH.ConclusionsNormal reference ranges of amino acids and acylcarnitines were established for AMH and QH. Significant differences were found in concentration of these compounds between breeds and gender.

Profiles of Amino Acids and Acylcarnitines Related with Insecticide Exposure in Culex quinquefasciatus (Say).

Culex quinquefasciatus Say is a vector of many pathogens of humans, and both domestic and wild animals. Personal protection, reduction of larval habitats, and chemical control are the best ways to reduce mosquito bites and, therefore, the transmission of mosquito-borne pathogens. Currently, to reduce the risk of transmission, the pyrethroids, and other insecticide groups have been extensively used to control both larvae and adult mosquitoes. In this context, amino acids and acylcarnitines have never been associated with insecticide exposure and or insecticide resistance. It has been suggested that changes in acylcarnitines and amino acids profiles could be a powerful diagnostic tool for metabolic alterations. Monitoring these changes could help to better understand the mechanisms involved in insecticide resistance, complementing the strategies for managing this phenomenon in the integrated resistance management. The purpose of the study was to determine the amino acids and acylcarnitines profiles in larvae of Cx. quinquefasciatus after the exposure to different insecticides. Bioassays were performed on Cx. quinquefasciatus larvae exposed to the diagnostic doses (DD) of the insecticides chlorpyrifos (0.001 μg/mL), temephos (0.002 μg/mL) and permethrin (0.01 μg/mL). In each sample, we analyzed the profile of 12 amino acids and 31 acylcarnitines by LC-MS/MS. A t-test was used to determine statistically significant differences between groups and corrections of q-values. Results indicates three changes, the amino acids arginine (ARG), free carnitine (C0) and acetyl-carnitine (C2) that could be involved in energy production and insecticide detoxification. We confirmed that concentrations of amino acids and acylcarnitines in Cx. quinquefasciatus vary with respect to different insecticides. The information generated contributes to understand the possible mechanisms and metabolic changes occurring during insecticide exposure.

Mining the Alkhumra Hemorrhagic Fever Virus Genomes in 2015

Abstract. Alkhurma hemorrhagic fever virus was first isolated at Jeddah, Saudi Arabia, in the early 1990s, and identified as a member of the Flaviviridae family. The virus has been confirmed only in the sand tampan tick, Ornithodoros savignyi (Audouin), and camel tick, Hyalomma dromedarii Koch. Symptoms of infection include headache, joint and muscle pain, vomiting, and thrombocytopenia, leading to hemorrhagic fever, which can cause death. The purpose of this article was to make a genomic-mined Alkhurma hemorrhagic fever virus from the genomic sequences previously reported in GenBank of NCBI. Genomes were divided into peptides, and different evolutionary parameters were derived using bioinformatics tools. The individual behavior of each of the peptides encoded in the genome of Alkhurma hemorrhagic fever virus is specific; the rate of change indicates different kinds of evolutionary pressure. Complete genome and NS3 protein are under positive selection (dN > dS, p < 0.05), while purifying selection is the main force that drives the evolution of envelope and NS5 proteins (dN < dS, p < 0.05). The spread of viruses such as Alkhurma hemorrhagic fever virus can be catastrophic if they affect the global population without antibodies. Genomic mining of Alkhurma hemorrhagic fever virus provides a powerful tool to design new strategies focused on variable regions of the genome in case of spread.

Current Status of the Insecticide Resistance in Aedes aegypti (Diptera: Culicidae) from Mexico

The mosquito Aedes aegypti (Diptera: Culicidae) is the primary vector of dengue in Mexi‐ co and lately virus Chikungunya, although Aedes albopictus is widely distributed; its role in both diseases’ transmission has not been confirmed. The control of mosquitoes in Mex‐ ico includes source reduction consisting in the elimination of containers that are favorable sites for oviposition and development of the aquatic stage. The use of insecticides is to control larvae and adulticides as outdoor ultra-low volume applications and indoor re‐ sidual spray and more recently impregnated materials. The health department regulates the use of insecticides, and such regulations are revised and adapted over time. Since 1999, the vector control regulations gave preference to the use of pyrethroids, a perme‐ thrin-based formulation to control adult forms. This insecticide was used as the only adulticide in Mexico for more than 10 years. The consequences of this actions have evolved in a widespread and strong resistance to other insecticides, mainly pyrethroids. We include in this revision evidence of resistance reported in Ae. aegypti in Mexico.