Molecular Evidence of Ehrlichia canis (Rickettsiales: Anaplasmataceae) in Ticks (Ixodida: Ixodidae) Associated with Dogs (Carnivora: Canidae) from Nuevo Leon, Mexico.

Background: Ehrlichia canis is transmitted by ticks causing Canine monocytic ehrlichiosis, which is considered one of the most critical tickborne pathogens. Materials and Methods: This study aimed to identify by PCR technique E. canis in ticks associated with dogs from urban and rural homes in Nuevo Leon, Mexico. The study was conducted at 13 localities in eight municipalities from 2012 to 2021. Results: A total of 1873 ticks of three species were captured: Amblyomma tenellum, Dermacentor variabilis, and Rhipicephalus sanguineus s.l. The overall infection rate of E. canis in ticks was 59.12% (149/252). Of the 15 sequences, three haplotypes were identified. Conclusion: The urban transmission cycle of canine ehrlichiosis is demonstrated, where the potential vector is the tick R. sanguineus s.l.

Species diversity, barcode, detection of pathogens and blood meal pattern in Phlebotominae (Diptera: Psychodidae) from northeastern Mexico.

More than 90 species of phlebotomines are vectors of parasites, bacteria, and viruses, which cause disease in animals and humans. Therefore, their study is necessary to establish prevention and control strategies. Mexico is an endemic country for leishmaniasis, mostly in the center and southern regions of the country, yet only few studies have been conducted in the northern part of the country. The present study aims to: (a) assess the alpha diversity of Phlebotominae in an annual cycle, (b) to correlate climatic variables with abundance, (c) to generate barcodes of these insects as part of the integrative taxonomy, and (d) to detect Leishmania, Wolbachia and blood sources in an area close to where a case of autochthonous leishmaniasis has been detected in Nuevo Leon, Mexico. A systematic sampling was conducted during three consecutive nights from 17:00 to 22:00 h., placing Shannon traps, CDC traps with incandescent light, and BG Sentinel 2 + BG Lure traps. A total catch effort of 660 nights/traps/hours was achieved, in which a total number of 707 phlebotomines (58% female and 42% male) of six species were collected and identified. The most abundant species were Psathyromyia cratifer (57%) and Psathyromyia shannoni sensu stricto (26%). The highest abundance (72%; 507/707) was collected during March, April and May 2021. Barcodes were generated for four species of phlebotomines, which represent new records for Mexico. For the molecular detection of microorganisms, 302 specimens were analyzed, although no specimens were positive for Leishmania spp. Wolbachia strains were detected in phlebotomines with an infection rate of 1.32% (4/302) and found in Pa. cratifer and Lu. cruciata. Likewise, human DNA was identified in female Lu. cruciata and Pa. cratifer phlebotomines. These findings indicate the presence of potential vector species of the parasite Leishmania spp. This result shows the need for further entomological surveillance to elucidate the transmission mechanisms in these northern areas of the country.

Evidencia molecular de Rickettsia ricketsii y Rickettsia felis en garrapatas colectadas en ganado bovino en la costa de Chiapas.

OBJETIVO: Estimar la diversidad de garrapatas, la prevalencia de infestación y tasa de infección de Rickettsia spp. en ganado bovino en la costa del estado de Chiapas. Material y métodos. Se realizó un estudio transversal de octubre de 2021 a marzo de 2022, que incluyó la extracción de garrapatas de 297 vacas pertenecientes a 5 municipios. Se calcularon los índices de diversidad. El diagnóstico de Rickettsia spp en las garrapatas se realizó mediante PCR anida. RESULTADOS: Se encontró una baja diversidad de especies. Las especies Rhipicephalus microplus, Amblyomma cajennense y Rhipicephalus sanguineus hembra adultas fueron positivas a Rickettsia spp. Los municipios de Pijijiapan y Tonalá presentaron la TMI más alta con 7.5 y 7.2%. Conclusión. Este es primer estudio México que reporta infección de Rickettsia spp, en garrapatas colectadas de ganado bovino, lo cual indica un riesgo de salud pública.

Design and Evaluation of a Sticky Attractant Trap for Intra-Domiciliary Surveillance of Aedes aegypti Populations in Mexico.

Surveillance consists of systematic data collection, analysis, and interpretation and is essential for planning and implementing control activities. The lack of success in the control and surveillance of the Ae. aegypti mosquito elsewhere demands the development of new accessible and effective strategies. This work aimed to develop and evaluate an adhesive lure trap for household indoor surveillance of Ae. aegypti. Based on a bibliographic review, four compounds that have significant attraction percentages for Ae. aegypti were considered. Our more effective blend was determined through preliminary bioassays using the high-throughput screening system (HITSS) and 90 × 90 cm mosquito cages. We designed a low-cost, pyramid-shaped, sticky cardboard trap to incorporate the selected blend. Semi-field 2 × 2 m cages and field tests were utilized to evaluate its effectiveness through mosquito capture percentages. In laboratory tests, blend number 2 presented an attraction percentage of 47.5 ± 4.8%; meanwhile, in semi-field cages, a 4-inch, 110 v powered fan was used to disperse the attractants, and then a similar capture percentage of 43.2 ± 4.0% was recorded. Results were recorded during the field evaluation of the at-house indoor environment and were compared with those recorded with the golden-standard BG-Sentinel trap, i.e., our prototype trapped an average of 6.0 ± 1.5 mosquitoes versus 10.0 ± 2.6. In most Latin American countries, there is a lack of formal and accessible strategies for monitoring adult populations of Ae. Aegypti; therefore, we must develop tools that reinforce entomological surveillance methods.

Molecular and Serological Identification of Anaplasma marginale and Borrelia burgdorferi in Cattle and Ticks from Nuevo Leon, Northern Mexico.

Ticks and tick-borne diseases affect livestock productivity and cause significant economic losses. Therefore, surveillance of these pathogens and vectors is paramount to reducing these effects in livestock. This study aimed to identify Anaplasma marginale and Borrelia burgdorferi sensu lato in ticks collected from cattle. Molecular biology techniques were utilized to identify A. marginale for both types of samples, i.e., ticks and bovine blood. Serology of cattle using indirect immunofluorescence assay (IFA) was conducted to determine antibodies to B. burgdorferi s.l. from seven locations in Nuevo Leon, Mexico, between 2015 and 2017. From 404 bovines, 2880 ticks were collected: Rhipicephalus microplus (2391 females and 395 males), Amblyomma spp. (51 females and 42 males) and Dermacentor variabilis (1 female). Rhipicephalus microplus represented the largest specimens captured, with 96.7% within the seven study sites. PCR processed only 15% (442) of tick samples to identify A. marginale. Field genera proportions were followed to select testing tick numbers. Results showed that 9.9% (44/442) of A. maginale infected the pooled tick species, whereas the highest percent corresponded to 9.4% (38/404) in R. microplus. Regarding the molecular analysis of blood samples, 214 of 337 (63.5%) were positive for A. maginale. In each of the seven locations, at least one bovine sample tested positive for A. maginale. Borrelia burgdorferi s.l. was not found either in the ticks or serum samples. Two A.marginale DNA nucleotide sequences obtained in this study were deposited in the GenBank with the following accession numbers OR050501 cattle, and OR050500 R.microplus tick. Results of this work point to current distribution of bovine anaplasmosis in northern Mexico.

Occurrence of scorpion sting and associated factors in a highly marginalized municipality in Guerrero, Mexico: A cross-sectional study.

BACKGROUND: Scorpion sting is a neglected public health problem, despite a global estimate of 1.2 million scorpion stings and some 3,250 deaths annually. METHODS: This cross-sectional study estimates the occurrence of scorpion stings and identifies associated factors in seven communities in the highly marginalized municipality of Chilapa, in the Mexican state of Guerrero. After informed consent, 1,144 households provided information on 4,985 residents. The questionnaire collated sociodemographic data, characteristics of the dwelling, efforts to avoid scorpion stings, and individual information of scorpion stings suffered in the last year. Cluster-adjusted (acl), bivariate and multivariate analysis relied on the Mantel-Haenszel procedure. RESULTS: The overall period prevalence of scorpion stings in the year prior to the study was 4.4% (218/4985), 5.4% in men (126/2320), and 3.5% in women (92/2665), p<0.01. The majority occurred at home 68.3% (149/218), followed by agricultural fields 26.6% (58/218), street 2.8% (6/218), and work 2.3% (5/218). Factors associated with scorpion sting were carrying firewood (OR 2.1; CI95%acl 1.40-3.09), keeping free-range hens around of the home (OR 1.9; CI95%acl 1.19-2.85), residing in a rural area (OR 1.7; CI95%acl 1.04-2.78), being male (OR 1.6; CI95%acl 1.18-2.28), and helping with housework (OR 1.6; CI95%acl 1.04-2.40). CONCLUSION: This study confirms scorpion bites are a public health problem in these marginalized communities in Guerrero State, with risk factors related to living conditions and the work process at home and in the fields. Almost all risk factors identified could be reduced with low-cost interventions implemented by the communities themselves.

Determination of Knockdown Resistance (kdr) Allele Frequencies (T929I mutation) in Head Louse Populations from Mexico, Canada, and Peru.

The head louse Pediculus humanus capitis (De Geer) is a hematophagous ectoparasite that inhabits the human scalp. The infestations are asymptomatic; however, skin irritation from scratching occasionally may cause secondary bacterial infections. The present study determined the presence and frequency of the knockdown resistance (kdr) mutation T929I in 245 head lice collected from Mexico, Peru, and Canada. Head lice were collected manually using a comb in the private head lice control clinic. Allele mutation at T9291 was present in 100% of the total sampled populations (245 lice) examined. In addition, 4.89% of the lice were homozygous susceptible, whereas 6.93% heterozygous and 88.16% homozygous were resistant, respectively. This represents the second report in Mexico and Quebec and fist in Lima.

Comparison of Ground Release and Drone-Mediated Aerial Release of Aedes aegypti Sterile Males in Southern Mexico: Efficacy and Challenges.

Sterile males of Aedes aegypti were released once a week for 8 weeks to evaluate the dispersal efficiency of ground and aerial drone release methods in a rural village of 26 Ha in southern Mexico. Indoor and outdoor BG-Sentinel traps were placed in 13−16 houses distributed throughout the village. The BG traps were activated 48 h after the release of the sterile males and functioned for a 24 h period following each release. Over the 8-week period of simultaneous ground and aerial releases, an average of 85,117 ± 6457 sterile males/week were released at ground level and 86,724 ± 6474 sterile males/week were released using an aerial drone. The ground release method resulted in higher numbers of captured males (mean = 5.1 ± 1.4, range 1.1−15.7 sterile males/trap) compared with the aerial release method (mean = 2.6 ± 0.8, range 0.5−7.3 sterile males/trap) (p < 0.05). Similarly, the prevalence of traps that captured at least one sterile male was significantly higher for ground release compared to the aerial release method (p < 0.01). The lower numbers of sterile males captured in the aerial release method could be due to mortality or physical injury caused by the chilling process for immobilization, or the compaction of these insects during transport and release. However, aerial releases by a two-person team distributed insects over the entire village in just 20 min, compared to ~90 min of work for a five-person team during the ground release method. Ground release also resulted in higher aggregations of males and some villagers reported feeling discomfort from the presence of large numbers of mosquitoes in and around their houses. We conclude that modifications to the handling and transport of sterile males and the design of containers used to store males are required to avoid injury and to improve the efficiency of aerial releases for area-wide SIT-based population suppression programs targeted at mosquito vectors of human disease.

Assessing the Impact of Insecticide Resistance on Vector Competence: A Review.

The primary strategy to avoid adverse impacts from insect-mediated pathogen transmission is the chemical control of vector populations through insecticides; its continued use has led to insecticide resistance and unknown consequences on vector competence. This review aims to systematically analyze and synthesize the research on the influence of insecticide resistance (IR) on vector competence (VC). Thirty studies met the inclusion criteria. Twenty studies, conducted either in laboratory or field settings, described the influence of phenotypic insecticide resistance and mechanisms on VC in vectors of human pathogens. Seven studies showed the effect of exposure to insecticides on VC in vectors of human pathogens. Three studies reported the influence of phenotypic resistance and mechanisms on VC in crop pests. The evidence shows that IR could enhance, impair, or have no direct effect on VC in either field or laboratory-designed studies. Similar positive and negative trends are found in pest vectors in crops and studies of insecticide exposure and VC. Even though there is evidence that exposure to insecticides and IR can enhance VC, thus increasing the risk of pathogen transmission, more investigations are needed to confirm the observed patterns and what implications these factors could have in vector control programs.

Molecular Characterization of Associated Pathogens in Febrile Patients during Inter-Epidemic Periods of Urban Arboviral Diseases in Tapachula Southern Mexico.

Emerging and re-emerging vector-borne infections are a global public health threat. In endemic regions, fever is the main reason for medical attention, and the etiological agent of such fever is not usually identified. In this study, non-specific febrile pathogens were molecularly characterized in serum samples from 253 patients suspected of arbovirus infection. The samples were collected in the southern border region of Mexico from April to June 2015, and February to March 2016. ZIKV, CHIKV, DENV, leptospirosis, and rickettsiosis were detected by qPCR and nested PCR to identify flavivirus and alphavirus genera. The results indicated that 71.93% of the samples were positive for CHIKV, 0.79% for ZIKV, and 0.39% for DENV, with the number positive for CHIKV increasing to 76.67% and those positive for ZIKV increasing to 15.41% under the nested PCR technique. Leptospira Kmetyi was identified for the first time in Mexico, with a prevalence of 3.16%. This is the first report of ZIKV in Mexico, as well the first detection of the virus in early 2015. In conclusion, the etiological agent of fever was determined in 94% of the analyzed samples.

Field Effectiveness of Drones to Identify Potential Aedes aegypti Breeding Sites in Household Environments from Tapachula, a Dengue-Endemic City in Southern Mexico.

Aedes aegypti control programs require more sensitive tools in order to survey domestic and peridomestic larval habitats for dengue and other arbovirus prevention areas. As a consequence of the COVID-19 pandemic, field technicians have faced a new occupational hazard during their work activities in dengue surveillance and control. Safer strategies to monitor larval populations, in addition to minimum householder contact, are undoubtedly urgently needed. Drones can be part of the solution in urban and rural areas that are dengue-endemic. Throughout this study, the proportion of larvae breeding sites found in the roofs and backyards of houses were assessed using drone images. Concurrently, the traditional ground field technician's surveillance was utilized to sample the same house groups. The results were analyzed in order to compare the effectiveness of both field surveillance approaches. Aerial images of 216 houses from El Vergel village in Tapachula, Chiapas, Mexico, at a height of 30 m, were obtained using a drone. Each household was sampled indoors and outdoors by vector control personnel targeting all the containers that potentially served as Aedes aegypti breeding sites. The main results were that the drone could find 1 container per 2.8 found by ground surveillance; however, containers that were inaccessible by technicians in roofs and backyards, such as plastic buckets and tubs, disposable plastic containers and flowerpots were more often detected by drones than traditional ground surveillance. This new technological approach would undoubtedly improve the surveillance of Aedes aegypti in household environments, and better vector control activities would therefore be achieved in dengue-endemic countries.

Population Dynamics of Aedes aegypti and Aedes albopictus in Two Rural Villages in Southern Mexico: Baseline Data for an Evaluation of the Sterile Insect Technique.

Indoor and outdoor ovitraps were placed in 15 randomly selected houses in two rural villages in Chiapas, southern Mexico. In addition, ovitraps were placed in five transects surrounding each village, with three traps per transect, one at the edge, one at 50 m, and another at 100 m from the edge of the village. All traps were inspected weekly. A transect with eight traps along a road between the two villages was also included. Population fluctuations of Aedes aegypti and Ae. albopictus were examined during 2016-2018 by counting egg numbers. A higher number of Aedes spp. eggs was recorded at Hidalgo village with 257,712 eggs (60.9%), of which 58.1% were present in outdoor ovitraps and 41.9% in indoor ovitraps, compared with 165,623 eggs (39.1%) collected in the village of Río Florido, 49.0% in outdoor and 51.0% in indoor ovitraps. A total of 84,047 eggs was collected from ovitraps placed along transects around Río Florido, compared to 67,542 eggs recorded from transects around Hidalgo. Fluctuations in egg counts were associated with annual variation in precipitation, with 2.3 to 3.2-fold more eggs collected from ovitraps placed in houses and 4.8 to 5.1-fold more eggs in ovitraps from the surrounding transects during the rainy season than in the dry season, respectively. Aedes aegypti was the dominant species during the dry season and at the start of the rainy season in both villages. Aedes albopictus populations were lower for most of the dry season, but increased during the rainy season and predominated at the end of the rainy season in both villages. Aedes albopictus was also the dominant species in the zones surrounding both villages. The numbers of eggs collected from intradomiciliary ovitraps were strongly correlated with the numbers of eggs in peridomiciliary ovitraps in both Río Florido (R2 adj = 0.92) and Hidalgo (R2 adj = 0.94), suggesting that peridomiciliary sampling could provide an accurate estimate of intradomiciliary oviposition by Aedes spp. in future studies in these villages. We conclude that the feasibility of sterile insect technique (SIT)-based program of vector control could be evaluated in the isolated Ae. aegypti populations in the rural villages of our baseline study.

Temporal Viability of Aedes aegypti and Aedes albopictus Eggs Using Two Hygroscopic Substances as Preservatives under a Sterile Insect Technique (SIT) Program in Southern Mexico.

Dengue and other Aedes-borne diseases have dramatically increased over the last decades. The Sterile Insect Technique (SIT) has been successfully used as part of integrated pest strategies to control populations of insect-plant and livestock pests and is currently being tested as a potential method to reduce mosquito populations in an environmentally friendly approach. However, during the mass rearing steps needed to produce millions of mosquitoes, egg storage and preservation are essential for a certain amount of time. Eggs of Aedes aegypti have a chorionic pad that functions as a sticky substance to glue them onto the inner walls of larval breeding sites. The chorionic pad is chemically made of hyaluronic acid, a hygroscopic compound, responsible to protect them from desiccation over time. Two commercial products with hygroscopic properties, hydrolyzed collagen, and Hyalurosmooth®, both were tested to assess their ability to prolong egg life storage for A. aegypti and A. albopictus. Results showed that 85-95% of Ae. aegypti eggs were able to hatch up to week 8 after being treated with both hydrophilic compounds, compared with the control 66.3%. These two substances showed promising effects for keeping Ae. aegypti eggs viable during prolonged storage in mass rearing insect production focused on vector control SIT programs.

Pediculosis Affects Mexican Children from Different Socioeconomic Status Equally: A Cross-Sectional Study.

The prevalence of pediculosis in Mexican children was studied in San Nicolas and Tapachula, Mexico. A cross-sectional study included 888 students between six and 12 years old from two urban communities with an unequal socioeconomic status between September 2015 and March 2016. A Pearson χ2 and multivariate logistic analysis were carried out to associate risk factors to pediculosis. The overall prevalence of pediculosis from both localities was 23.9%. The female gender; long and medium hair; living with someone infested; previously infested by head lice and curling hair were variables linked to a significantly higher prevalence of pediculosis (p < 0.01). Nevertheless, no significant differences were observed in the age groups, localities and socioeconomic status for human lice infection. Socioeconomic variables such as numbers of inhabitants, floors of house, beds and rooms; and parents' qualification did not show a significative association for pediculosis. Health education in schools is needed for pediculosis prevention and remove the stigmatization of this disease related to poverty.

Respuesta de Aedes aegypti L. (Diptera: Culicidae) a transflutrina y linalol impregnados en diferentes tipos de tela / Response of Aedes aegypti L. (Diptera: Culicidae) to transfluthrin and linalool impregnated in different of fabric types

Resumen: Objetivo: Evaluar el efecto de repelencia espacial contra Ae. aegypti de dos compuestos químicos impregnados en diferentes tipos de telas. Material y métodos: El estudio se realizó en el periodo 2015-2016 en el Centro Regional de Investigación en Salud Pública, del Instituto Nacional de Salud Pública. Se utilizó el Sistema de Procesamiento de Alto-rendimiento para evaluar la respuesta de Ae. aegypti a transflutrina y linalol, impregnados individualmente a diferentes concentraciones en popelina, algodón y poliéster. También se determinó el efecto de sus mezclas, lavado sobre la residualidad y porcentaje de protección. Resultados: La mayor respuesta de repelencia espacial fue para el tratamiento linalol-algodón al 0.1% (RE= 70 ± 5.77%). La mezcla de linalol 0.1% y transflutrina 0.001% presentó un porcentaje de repelencia espacial similar para los tres tipos de tela. El tratamiento transflutrina-popelina 0.001% mantuvo una residualidad de cinco días. El linalol al 0.1% produjo 62.50% de protección en presencia de un estímulo de atracción. Conclusión: Se sugiere la impregnación de linalol al 0.1% en ropa como medida de protección de las picaduras de Ae. aegypti.

Abstract: Objective: Evaluate the effect of spatial repellency against Ae. aegypti of two chemical compounds impregnated in different types of fabrics. Materials and methods: The study was carried out in the year 2015-2016 in the Centro Regional de Investigación en Salud Pública, del Instituto Nacional de Salud Pública. The high-throughput screening system was used to evaluate the response of Ae. aegypti to transfluthrin and linalool, impregnated individually at different concentrations in poplin, cotton and polyester. The effect of their mixtures was also determined, washing on residuality and percentage of protection. Results: The highest spatial repellency response was for 0.1% linalool-cotton treatment (RE = 70 ± 5.77%). The mixture of 0.1% linalool and 0.001% transfluthrin presented a similar spatial repellence percentage for the three types of fabric. The transfluthrin-poplin treatment 0.001% maintained a residual of five days. 0.1% linalool produced a 62.50% protection in the presence of an attraction stimulus. Conclusion: It is suggested the impregnation of 0.1% linalool in clothing as a protection measure for Ae. aegypti.

Nebulización térmica intradomiciliar de la mezcla de flupyradifurona y transflutrina en mosquitos Aedes aegypti susceptibles y resistentes a piretroides en el Sur de México / Indoor thermal fogging of the mixture of flupyradifurone and transflutrin on Aedes aegypti mosquitoes susceptible and resistant to pyrethroids in southern Mexico

Resumen: Objetivo: Evaluar la efectividad de la mezcla de flupyradifurona 26.3 g/L y transflutrina 52.5 g/L aplicada como niebla térmica a mosquitos Aedes vectores de virus dengue, Zika y chikungunya. Material y métodos: Se colocaron grupos de 15 mosquitos de Ae. aegypti (susceptibles y resistentes a piretroides) dentro de jaulas, en sala, recámara y cocina. Posteriormente, se aplicó la mezcla de flupyradifurona y transflutrina dentro de las viviendas a una dosis de 2 y 4 mg/m3, respectivamente. Resultados: La mezcla de flupyradifurona y transflutrina causó mortalidades de 97 a 100% sobre las cepas de mosquitos Aedes y su efectividad fue la misma en los diferentes compartimentos de las viviendas. Conclusiones: La mezcla de flupyradifurona y transflutrina, aplicada en niebla térmica, es una herramienta prometedora para el control de poblaciones de mosquitos Aedes independientemente de su estado de resistencia a insecticidas.

Abstract: Objective: To evaluate the efficacy of thermal fogging of a mixture of flupyrafirudone (26.3 g/L) and transfluthrin (52.5 g/L) against dengue, Zika y chikungunya Aedes mosquito vectors. Materials and methods: Groups of 15 caged Ae. aegypti (susceptible and pyrethroid resistant) mosquitoes were placed in living room, kitchen and bedroom inside houses, after which a dose of 2 and 4 mg/m3 of flupyradifurone and transfluthrine, respectively, was applied as thermal fog. After one hour of exposure mosquitoes were transferred to the laboratory and mortality was recorded after 24 h. Results: The mixture killed 97 to 100% of mosquitoes from the strains and the efficacy was similar independently of their place within the premises. Conclusions: The mixture of flupyrafirudone and transfluthrin applied as thermal fog is a promising tool to control Aedes mosquito populations independently of the pyrethroid-insecticide resistance status.

[Response of Aedes aegypti L. (Diptera: Culicidae) to transfluthrin and linalool impregnated in different of fabric types.] / Respuesta de Aedes aegypti L. (Diptera: Culicidae) a transflutrina y linalol impregnados en diferentes tipos de tela.

OBJECTIVE: Evaluate the effect of spatial repellency against Ae. aegypti of two chemical compounds impregnated in different types of fabrics. MATERIALS AND METHODS: The study was carried out in the year 2015-2016 in the Centro Regional de Investigación en Salud Pública, del Instituto Nacional de Salud Pública. The high-throughput screening system was used to evaluate the response of Ae. aegypti to transfluthrin and linalool, impregnated individually at different concentrations in poplin, cotton and polyester. The effect of their mixtures was also determined, washing on residuality and percentage of protection. RESULTS: The highest spatial repellency response was for 0.1% linalool-cotton treatment (RE = 70 ± 5.77%). The mixture of 0.1% linalool and 0.001% transfluthrin presented a similar spatial repellence percentage for the three types of fabric. The transfluthrin-poplin treatment 0.001% maintained a residual of five days. 0.1% linalool produced a 62.50% protection in the presence of an attraction stimulus. CONCLUSIONS: It is suggested the impregnation of 0.1% linalool in clothing as a protection measure for Ae. aegypti.

OBJETIVO: Evaluar el efecto de repelencia espacial contra Ae. aegypti de dos compuestos químicos impregnados en diferentes tipos de telas. MATERIAL Y MÉTODOS: El estudio se realizó en el periodo 2015-2016 en el Centro Regional de Investigación en Salud Pública, del Instituto Nacional de Salud Pública. Se utilizó el Sistema de Procesamiento de Alto-rendimiento para evaluar la respuesta de Ae. aegypti a transflutrina y linalol, impregnados individualmente a diferentes concentraciones en popelina, algodón y poliéster. También se determinó el efecto de sus mezclas, lavado sobre la residualidad y porcentaje de protección. RESULTADOS: La mayor respuesta de repelencia espacial fue para el tratamiento linalol-algodón al 0.1% (RE= 70 ± 5.77%). La mezcla de linalol 0.1% y transflutrina 0.001% presentóun porcentaje de repelencia espacial similar para los tres tipos de tela. El tratamiento transflutrina-popelina 0.001%N mantuvo una residualidad de cinco días. El linalol al 0.1% produjo 62.50% de protección en presencia de un estímulo de atracción. CONCLUSIONES: Se sugiere la impregnación de linalol al 0.1% en ropa como medida de protección de las picaduras de Ae. aegypti.

[Indoor thermal fogging of the mixture of flupyradifurone and transflutrin on Aedes aegypti mosquitoes susceptible and resistant to pyrethroids in southern Mexico]. / Nebulización térmica intradomiciliar de la mezcla de flupyradifurona y transflutrina en mosquitos Aedes aegypti susceptibles y resistentes a piretroides en el Sur de México.

OBJECTIVE: To evaluate the efficacy of thermal fogging of a mixture of flupyrafirudone (26.3 g/L) and transfluthrin (52.5 g/L) against dengue, Zika y chikungunya Aedes mosquito vectors. MATERIALS AND METHODS: Groups of 15 caged Ae. aegypti (susceptible and pyrethroid resistant) mosquitoes were placed in living room, kitchen and bedroom inside houses, after which a dose of 2 and 4 mg/m3 of flupyradifurone and transfluthrine, respectively, was applied as thermal fog. After one hour of exposure mosquitoes were transferred to the laboratory and mortality was recorded after 24 h. RESULTS: The mixture killed 97 to 100% of mosquitoes from the strains and the efficacy was similar independently of their place within the premises. CONCLUSIONS: The mixture of flupyrafirudone and transfluthrin applied as thermal fog is a promising tool to control Aedes mosquito populations independently of the pyrethroid-insecticide resistance status.

OBJETIVO: Evaluar la efectividad de la mezcla de flupyradifurona 26.3 g/L y transflutrina 52.5 g/L aplicada como niebla térmica a mosquitos Aedes vectores de virus dengue, Zika y chikungunya. MATERIAL Y MÉTODOS: Se colocaron grupos de 15 mosquitos de Ae. aegypti (susceptibles y resistentes a piretroides) dentro de jaulas, en sala, recámara y cocina. Posteriormente, se aplicó la mezcla de flupyradifurona y transflutrina dentro de las viviendas a una dosis de 2 y 4 mg/m3, respectivamente. RESULTADOS: La mezcla de flupyradifurona y transflutrina causó mortalidades de 97 a 100% sobre las cepas de mosquitos Aedes y su efectividad fue la misma en los diferentes compartimentos de las viviendas. CONCLUSIONES: La mezcla de flupyradifurona y transflutrina, aplicada en niebla térmica, es una herramienta prometedora para el control de poblaciones de mosquitos Aedes independientemente de su estado de resistencia a insecticidas.

Genetic risk for dengue hemorrhagic fever and dengue fever in multiple ancestries.

BACKGROUND: Genetic risk factors for dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) and dengue fever (DF) are limited, in particular there are sparse data on genetic risk across diverse populations. METHODS: We conducted a genome-wide association study (GWAS) in a derivation and validation sample of 7, 460 participants of Latin American, South Asian, and South East Asian ancestries. We then developed a weighted polygenic risk score (PRS) for each participant in each of the validation cohorts of the three ancestries to predict the risk of DHF/DSS compared to DF, DHF/DSS compared to controls, and, DF compared to controls. FINDINGS: The risk of DHF/DSS was significantly increased, odds ratio [OR] 1.84 (95%CI 1.47 to 2.31) (195 SNPs), compared to DF, fourth PRS quartile versus first quartile, in the validation cohort. The risk of DHF/DSS compared to controls was increased (OR=3.94; 95% CI 2.84 to 5.45) (278 SNPs), as was the risk of DF compared to controls (OR=1.97; 95%CI 1.63 to 2.39) (251 SNPs). Risk increased in a dose-dependent manner with increase in quartiles of PRS across comparisons. Significant associations persisted for PRS built within ancestries and applied to the same or different ancestries as well as for PRS built for one outcome (DHF/DSS or DF) and applied to the other. INTERPRETATION: There is a strong genetic effect that predisposes to risk of DHF/DSS and DF. The genetic risk for DHF/DSS is higher than that for DF when compared to controls, and this effect persists across multiple ancestries.

Vertical transmission of dengue virus in Aedes aegypti and its role in the epidemiological persistence of dengue in Central and Southern Mexico.

BACKGROUND: Aedes aegypti and Aedes albopictus are the main mosquito species responsible for dengue virus (DENV) transmission to humans in the tropical and subtropical regions of the world. The role of vertical transmission in the epidemiology of dengue and the maintenance of this arbovirus in nature during interepidemic periods remain poorly understood, and DENV vertical transmission could sustain the existence of virus reservoirs within Aedes populations. METHODS: Between April 2011 and October 2012, we monitored vertical transmission of DENV in Ae. aegypti and Ae. albopictus in 9 cities of 4 Mexican states. Aedes eggs were collected in ovitraps, then adults were reared under laboratory conditions and their heads were used to infect C6/36 cells. The presence of flavivirus was detected by immunofluorescence assays (IFA), and DENV infection was confirmed by RT-PCR. RESULTS: About 96% of reared adults were Ae. aegypti and 4.0% were Ae. albopictus. No infection was detected in Ae. albopictus, whereas 54 of 713 (7.8%) of Ae. aegypti pools tested positive. A minimum infection rate (MIR) of 2.52 per 1000 mosquitoes was estimated for Ae. aegypti. DENV-1, DENV-2 & DENV-3 serotypes were detected even during interepidemic periods. CONCLUSIONS: This study reports the evidence of vertical transmission of dengue virus with viral isolation and molecular confirmation in Ae. aegypti eggs collected in four endemic regions of Central and Southern Mexico. Vertical transmission may play a role as a reservoir mechanism during mosquito dormancy in interepidemic periods but with minor participation in transmission during epidemic periods.

TRANSMISSION VERTICALE DU VIRUS DE LA DENGUE CHEZ AEDES AEGYPTI ET SON RÔLE DANS LA PERSISTANCE ÉPIDÉMIOLOGIQUE DE LA DENGUE DANS LE CENTRE ET LE SUD DU MEXIQUE: OBJECTIF: Aedes aegypti et Aedes albopictus sont les principales espèces de moustiques responsables de la transmission du virus de la dengue (DENV) à l'homme dans les régions tropicales et subtropicales du monde. Le rôle de la transmission verticale dans l'épidémiologie de la dengue et le maintien de cet arbovirus dans la nature pendant les périodes d'inter-épidémiques restent mal compris, et la transmission verticale du DENV pourrait maintenir l'existence de réservoirs de virus au sein des populations d'Aedes. Notre objectif était d'évaluer la transmission verticale du DENV au Mexique. MÉTHODES: Entre avril 2011 et octobre 2012, nous avons surveillé la transmission verticale du DENV chez Ae. aegypti et Ae. albopictus dans 9 villes de 4 états mexicains. Les œufs d'Aedes ont été collectés dans des ovitraps, puis les adultes ont été élevés dans des conditions de laboratoire et leur tête a été utilisée pour infecter les cellules C6/36. La présence de flavivirus a été détectée par des tests d'immunofluorescence (IFA) et l'infection par DENV a été confirmée par RT-PCR. RÉSULTATS: 96% des adultes élevés étaient Ae. aegypti et 4,0% étaient Ae. albopictus. Aucune infection n'a été détectée chez Ae. albopictus, alors que 54 des 713 (7,8%) des pools d'Ae. aegypti ont été testés positifs. Un taux d'infection minimum (MIR) de 2,52 pour 1000 moustiques a été estimé pour Ae. aegypti. Les sérotypes DENV-1, DENV-2 et DENV-3 ont été détectés même pendant les périodes inter-épidémiques. CONCLUSIONS: Cette étude rapporte les preuves de transmission verticale du virus de la dengue avec isolement viral et confirmation moléculaire dans les œufs d'Ae. Aegypti collectés dans quatre régions d'endémie du centre et du sud du Mexique. La transmission verticale pourrait jouer un rôle de mécanisme réservoir lors de la dormance des moustiques en période inter-épidémique, mais avec une participation mineure à la transmission en période d'épidémie.