A numbers game: Mosquito-based arbovirus surveillance in two distinct geographic regions of Latin America.

Aedes mosquitoes, as vectors of medically important arthropod-borne viruses (arboviruses), constitute a major public health threat that requires entomological and epidemiological surveillance to guide vector control programs to prevent and reduce disease transmission. In this study, we present the collaborative effort of one year of mosquito-based arbovirus surveillance in two geographically distinct regions of Latin America (Nicaragua and Ecuador). Adult female mosquitoes were collected using backpack aspirators in over 2,800 randomly selected households (Nicaragua, Ecuador) and 100 key sites (Nicaragua) from eight distinct communities (Nicaragua: 2, Ecuador: 6). A total of 1,358 mosquito female pools were processed for RNA extraction and viral RNA detection using real-time RT-PCR. Ten positive dengue virus (DENV) pools were detected (3 in Nicaragua and 7 in Ecuador), all of which were found during the rainy season and matched the serotypes found in humans (Nicaragua: DENV-1 and DENV-4; Ecuador: DENV-2). Infection rates ranged from 1.13 to 23.13, with the Nicaraguan communities having the lowest infection rates. Our results demonstrate the feasibility of detecting DENV-infected Aedes mosquitoes in low-resource settings and underscore the need for targeted mosquito arbovirus sampling and testing, providing valuable insights for future surveillance programs in the Latin American region.

Adoption of community-based strategies for sustainable vector control and prevention.

Community engagement strategies provide tools for sustainable vector-borne disease control. A previous cluster randomized control trial engaged nine intervention communities in seven participatory activities to promote management of the domestic and peri-domestic environment to reduce risk factors for vector-borne Chagas disease. This study aims to assess the adoption of this innovative community-based strategy, which included chickens' management, indoor cleaning practices, and domestic rodent infestation control, using concepts from the Diffusion of Innovations Theory. We used questionnaires and semi-structured interviews to understand perceptions of knowledge gained, intervention adoption level, innovation attributes, and limiting or facilitating factors for adoption. The analysis process focused on five innovation attributes proposed by the Diffusion of Innovations Theory: relative advantage, compatibility, complexity, trialability, and observability. Rodent management was highly adopted by participants, as it had a relative advantage regarding the use of poison and was compatible with local practices. The higher complexity was reduced by offering several types of trapping systems and having practical workshops allowed trialability. Observability was limited because the traps were indoors, but information and traps were shared with neighbors. Chicken management was not as widely adopted due to the higher complexity of the method, and lower compatibility with local practices. Using the concepts proposed by the Diffusion of Innovations Theory helped us to identify the enablers and constraints in the implementation of the Chagas vector control strategy. Based on this experience, community engagement and intersectoral collaboration improve the acceptance and adoption of novel and integrated strategies to improve the prevention and control of neglected diseases.

The unreachable doorbells of South Texas: community engagement in colonias on the US-Mexico border for mosquito control.

Mosquitoes and the diseases they transmit continue to place millions of people at risk of infection around the world. Novel methods of vector control are being developed to provide public health officials with the necessary tools to prevent disease transmission and reduce local mosquito populations. However, these methods will require public acceptance for a sustainable approach and evaluations at local settings. We present our efforts in community engagement carried out in colonias of the Lower Rio Grande Valley in south Texas for mosquito surveillance, control, and ecological projects. Along the US-Mexico border the term colonia refers to impoverished communities that are usually inhabited by families of Hispanic heritage. The different engagements were carried out from September 2016 to February 2019; during this time, we had three distinct phases for community engagement. In Phase 1 we show the initial approach to the colonias in which we assessed security and willingness to participate; in Phase 2 we carried out the first recruitment procedure involving community meetings and house-to-house recruitment; and in Phase 3 we conducted a modified recruitment procedure based on community members' input. Our findings show that incorporating community members in the development of communication materials and following their suggestions for engagement allowed us to generate culturally sensitive recruitment materials and to better understand the social relationships and power dynamics within these communities. We were able to effectively reach a larger portion of the community and decrease the dropout rate of participants. Progress gained with building trust in the communities allowed us to convey participant risks and benefits of collaborating with our research projects. Community engagement should be viewed as a key component of any local vector control program as well as for any scientific research project related to vector control. Even in the face of budgetary constraints, small efforts in community engagement go a long way.

Diel activity patterns of two distinct populations of Aedes aegypti in Miami, FL and Brownsville, TX.

The diel biting activity of Aedes (Stegomyia) aegypti (L) populations was extensively investigated in the early 1900s to gain more information on the biology of Ae. aegypti, and this information was used to devise effective approaches to controlling populations of this species and protect the human population from widespread arbovirus outbreaks. However, few contemporary studies are available regarding the diel activity patterns of Ae. aegypti. To assess the diel activity patterns of Ae. aegypti in southern Florida and Texas, we conducted 96-h uninterrupted mosquito collections once each month from May through November 2019 in Miami, Florida, and Brownsville, Texas, using BG-Sentinel 2 Traps. The overall diel activity pattern in both cities was bimodal with morning and evening peak activity between 7:00 and 8:00 and between 19:00 and 20:00. There were significant daily, monthly, seasonal, and site-specific differences in activity patterns, but these differences did not affect the overall peak activity times. These differences suggest daily, monthly, seasonal, and site-specific variations in human exposure to Ae. aegypti. Our observations can be used in planning and executing Ae. aegypti vector control activities in southern Florida and southern Texas, specifically those targeting the adult mosquito populations.

Public Acceptance of and Willingness to Pay for Mosquito Control, Texas, USA.

Mosquito control is essential to reduce vectorborne disease risk. We surveyed residents in Harris, Tarrant, and Hidalgo Counties, Texas, USA, to estimate willingness-to-pay for mosquito control and acceptance of control methods. Results show an unmet demand for expanded mosquito control that could be funded through local taxes or fees.

Variable coverage in an Autocidal Gravid Ovitrap intervention impacts efficacy of Aedes aegypti control.

Control of the arboviral disease vector Aedes aegypti has shown variable levels of efficacy around the globe. We evaluated an Autocidal Gravid Ovitrap (AGO) intervention as a stand-alone control tool for population suppression of A. aegypti in US communities bordering Mexico.We conducted a cluster randomized crossover trial with weekly mosquito surveillance of sentinel households from July 2017 to December 2018. The intervention took place from August to December of both years. Multilevel models (generalized linear and additive mixed models) were used to analyse the changes in population abundance of female A. aegypti.We observed that female populations were being suppressed 77% (2018) and four times lower outdoor female abundance when AGO coverage (number of intervention AGO traps that surrounded a sentinel home) was high (2.7 AGOs/house). However, we also observed that areas with low intervention AGO coverage resulted in no difference (2017) or slightly higher abundance compared to the control. These results suggest that coverage rate might play a critical role on how populations of female A. aegypti are being modulated in the field. The lack of larval source habitat reduction and the short duration of the intervention period might have limited the A. aegypti population suppression observed in this study. Synthesis and applications. The mosquito, A. aegypti, is a public health concern in most tropical and subtropical regions. With the rise of insecticide resistance, the evaluation of non-chemical tools has become pivotal in the fight against arboviral disease transmission. Our study shows that the AGO intervention, as a stand-alone control tool, is limited by its coverage in human settlements. Vector control programmes should consider, that if the target coverage rate is not achieved, measures will be ineffective unless coupled with other control approaches. Although our multilevel modelling was focused on A. aegypti and the AGO, the approach can be applied to other mosquito vector species.

Susceptibility of South Texas Aedes aegypti to Pyriproxyfen.

An integral part to integrated mosquito management is to ensure chemical products used for area-wide control are effective against a susceptible population of mosquitoes. Prior to conducting an intervention trial using an insect growth regulator, pyriproxyfen, in South Texas to control Aedes aegypti, we conducted a larval bioassay to evaluate baseline levels of susceptibility. We used seven serially-diluted doses ranging from 2.5 ppb to 6.3 × 10-4 ppb. We observed 100% inhibition emergence (IE) at even the lowest dose of 6.3 × 10-4 ppb in our susceptible reference colony of Ae. aegypti Liverpool. In our field strain of Ae. aegypti (F5 colonized from South Texas) we observed 79.8% IE at 6.3 × 10-4 ppb, 17.7% IE at 1.25 × 10-3 ppb, 98.7% IE at 1.25 × 10-2 ppb, and 100% emergence inhibition for the remainder of the doses. Given that commercial pyriproxyfen products are labeled for doses ranging to 50 ppb, we conclude that the field population sampled by this study are susceptible to this insect growth regulator.

Global patterns of aegyptism without arbovirus.

The world's most important mosquito vector of viruses, Aedes aegypti, is found around the world in tropical, subtropical and even some temperate locations. While climate change may limit populations of Ae. aegypti in some regions, increasing temperatures will likely expand its territory thus increasing risk of human exposure to arboviruses in places like Europe, Northern Australia and North America, among many others. Most studies of Ae. aegypti biology and virus transmission focus on locations with high endemicity or severe outbreaks of human amplified urban arboviruses, such as dengue, Zika, and chikungunya viruses, but rarely on areas at the margins of endemicity. The objective in this study is to explore previously published global patterns in the environmental suitability for Ae. aegypti and dengue virus to reveal deviations in the probability of the vector and human disease occurring. We developed a map showing one end of the gradient being higher suitability of Ae. aegypti with low suitability of dengue and the other end of the spectrum being equal and higher environmental suitability for both Ae. aegypti and dengue. The regions of the world with Ae. aegypti environmental suitability and no endemic dengue transmission exhibits a phenomenon we term 'aegyptism without arbovirus'. We then tested what environmental and socioeconomic variables influence this deviation map revealing a significant association with human population density, suggesting that locations with lower human population density were more likely to have a higher probability of aegyptism without arbovirus. Characterizing regions of the world with established populations of Ae. aegypti but little to no autochthonous transmission of human-amplified arboviruses is an important step in understanding and achieving aegyptism without arbovirus.

The Eco-Bio-Social Factors That Modulate Aedes aegypti Abundance in South Texas Border Communities.

Aedes aegypti control requires dedicated resources that are usually scarce, limiting the reach and sustainability of vector control programs. This generates a need to focus on areas at risk of disease transmission and also understand the factors that might modulate local mosquito abundance. We evaluated the eco-bio-social factors that modulate indoor and outdoor relative abundance of female Ae. aegypti in communities of South Texas. We conducted housing quality and Knowledge Attitudes and Practices surveys in households that were part of a weekly mosquito surveillance program in November of 2017 and 2018. Our results showed widespread knowledge of mosquitoes and Zika virus by our participants. However, less than 35% considered them as serious problems in this region. The presence of window-mounted air conditioning units increased the risk of female mosquito relative abundance indoors. An increase in outdoor relative abundance was associated with larger properties and a higher number of children between 6 to 17 years of age. Interestingly, we observed that an increasing number of children <5 years of age modulated both indoor and outdoor relative abundance, with a 52% increase indoors and 30% decrease outdoors. The low perception of mosquito and disease risk highlights engagement needs for vector-borne disease prevention in this region. The identified risk factors can help guide public health officials in their efforts to reduce human and vector contact.

Desbridamiento apropiado y técnica de "pie crusting" en el manejo de herida traumática / Adequate debridement and pie-crusting technique in the management of traumatic injuries

Las heridas crónicas de origen traumático, con exposición de tejidos, requieren de un desbridamiento adecuado, lavado y una pronta cubierta para evitar la infección y la desecación. A veces, incluso deben ser ampliadas para realizar un adecuado desbridamiento quirúrgico; por lo que, al intentar una cobertura completa, el resultado es una herida a tensión, que se complica con inflamación, infección y la dehiscencia que se acentúa aún más si está en una zona de flexión, como la rodilla. Se presenta el caso de una paciente de 28 años, que acudió a emergencias con un antecedente de herida traumática en la rodilla derecha, signos de retraso de la cicatrización, tejido de granulación friable, exposición de la rótula, abundante secreción serosa y dolor al movimiento con rango limitado. Se la trató en un solo tiempo quirúrgico con desbridamiento, irrigación y cobertura completa de la herida mediante la técnica de "pie-crusting". Nivel de Evidencia: IV

Chronic wounds of traumatic origin, with tissue exposure, require adequate debridement, lavage and prompt coverage to prevent infection and desiccation. Wounds may even require to be enlarged in order to perform an adequate surgical debridement. Enlarged wound attempts to perform a complete coverage may result in tension wound closures, which are complicated by inflammation, infection, and dehiscence and aggravated when located on flexure areas, such as on the knee. We report the case of a 28-year female patient, who presented to the Emergency Department with a history of traumatic wound in the right knee and signs of delayed healing, friable granulation tissue, exposed patella, increased serous drainage, and painful limited range of motion. She underwent a single surgical time procedure with debridement, irrigation, and complete coverage of the wound with the help of the pie-crusting technique. Level of Evidence: IV

Cell fusing agent virus (Flavivirus) infection in Aedes aegypti in Texas: seasonality, comparison by trap type, and individual viral loads.

South Texas has experienced local transmission of Zika virus and of other mosquito-borne viruses such as chikungunya virus and dengue virus in the last decades. Using a mosquito surveillance program in the Lower Rio Grande Valley (LRGV) and San Antonio, TX, from 2016 to 2018, we detected the presence of an insect-specific virus, cell fusing agent virus (CFAV), in the Aedes aegypti mosquito population. We tested 6,326 females and 1,249 males from the LRGV and 659 females from San Antonio for CFAV by RT-PCR using specific primers. Infection rates varied from 0 to 261 per 1,000 mosquitoes in the LRGV and 115 to 208 per 1,000 in San Antonio depending on the month of collection. Infection rates per 1,000 individuals appeared higher in females collected from BG Sentinel 2 traps compared to Autocidal Gravid Ovitraps, but the ratio of the percentage of infected pools did not differ by trap type. The natural viral load in individual males ranged from 1.25 x 102 to 5.50 x 106 RNA copies and in unfed females from 5.42 x 103 to 8.70 x 106 RNA copies. Gravid females were found to harbor fewer viral particles than males and unfed females.

Dispersal of female and male Aedes aegypti from discarded container habitats using a stable isotope mark-capture study design in South Texas.

Aedes aegypti is the main vector of arboviral diseases such as dengue, chikungunya and Zika. A key feature for disease transmission modeling and vector control planning is adult mosquito dispersal. We studied Ae aegypti adult dispersal by conducting a mark-capture study of naturally occurring Ae. aegypti from discarded containers found along a canal that divided two residential communities in Donna, Texas, USA. Stable isotopes were used to enrich containers with either 13C or 15N. Adult mosquitoes were collected outdoors in the yards of households throughout the communities with BG Sentinel 2 traps during a 12-week period. Marked mosquito pools with stable isotopes were used to estimate the mean distance travelled using three different approaches (Net, Strip or Circular) and the probability of detecting an isotopically marked adult at different distances from the larval habitat of origin. We consistently observed, using the three approaches that male (Net: 220 m, Strip: 255 m, Circular: 250 m) Ae. aegypti dispersed further in comparison to gravid (Net: 135 m, Strip: 176 m, Circular: 189 m) and unfed females (Net: 192 m, Strip: 213 m, Circular: 198 m). We also observed that marked male capture probability slightly increased with distance, while, for both unfed and gravid females, such probability decreased with distance. Using a unique study design documenting adult dispersal from natural larval habitat, our results suggest that Ae. aegypti adults disperse longer distances than previously reported. These results may help guide local vector control authorities in their fight against Ae. aegypti and the diseases it transmits, suggesting coverage of 200 m for the use of insecticides and innovative vector control tools.

High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas.

Mosquito-borne viruses are emerging or re-emerging globally, afflicting millions of people around the world. Aedes aegypti, the yellow fever mosquito, is the principal vector of dengue, Zika, and chikungunya viruses, and has well-established populations across tropical and subtropical urban areas of the Americas, including the southern United States. While intense arboviral epidemics have occurred in Mexico and further south in the Americas, local transmission in the United States has been minimal. Here, we study Ae. aegypti and Culex quinquefasciatus host feeding patterns and vertebrate host communities in residential environments of South Texas to identify host-utilization relative to availability. Only 31% of Ae. aegypti blood meals were derived from humans, while 50% were from dogs and 19% from other wild and domestic animals. In Cx. quinquefasciatus, 67% of blood meals were derived from chicken, 22% came from dogs, 9% from various wild avian species, and 2% from other mammals including one human, one cat, and one pig. We developed a model for the reproductive number, R0, for Zika virus (ZIKV) in South Texas relative to northern Mexico using human disease data from Tamaulipas, Mexico. We show that ZIKV R0 in South Texas communities could be greater than one if the risk of human exposure to Ae. aegypti bites in these communities is at least 60% that of Northern Mexico communities. The high utilization of non-human vertebrates and low risk of human exposure in South Texas diminishes the outbreak potential for human-amplified urban arboviruses transmitted by Ae. aegypti.

Sugar Feeding Patterns for Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) Mosquitoes in South Texas.

Effective mosquito surveillance and management depend on a thorough understanding of the biology and feeding patterns unique to species and sex. Given that a propensity to sugar feed is necessary for some mosquito surveillance and newer control strategies, we sought to document the amount of total sugar in wild Aedes aegypti (L.) and Culex quinquefasciatus (Say) captured from five different locations in the Lower Rio Grande Valley (LRGV) of South Texas over 2 yr. We used Biogents Sentinel 2 (BGS2) traps in year 1 and aspirators, BGS2, and CDC resting traps in years 2 and 3 to collect adult mosquitoes. The hot anthrone test was used to quantify total sugar content in each mosquito. Additionally, the cold and hot anthrone tests were used to distinguish fructose content from total sugars for mosquitoes captured in 2019. Overall, Ae. aegypti females had significantly lower total sugar content than Ae. aegypti males as well as both sexes of Cx. quinquefasciatus. However, the percentage of Ae. aegypti positive for fructose consumption was four to eightfold higher than Ae. aegypti previously reported in other regions. The difference between locations was significant for males of both species, but not for females. Seasonality and trapping method also revealed significant differences in sugar content of captured mosquitoes. Our results reinforce that sugar feeding in female Ae. aegypti is less than Cx. quinquefasciatus, although not absent. This study provides necessary data to evaluate the potential effectiveness of sugar baits in surveillance and control of both Ae. aegypti and Cx. quinquefasciatus mosquitoes.

Stable Isotope Marking of Laboratory-Reared Aedes aegypti (Diptera: Culicidae).

The use of stable isotope enrichment to mark mosquitoes has provided a tool to study the biology of vector species. In this study, we evaluated isotopic marking of Aedes aegypti (L.) (Diptera: Culicidae) in a laboratory setting. We determined the optimal dosage for marking adult Ae. aegypti mosquitoes with 13C and 15N. Additionally, Ae. aegypti mosquitoes were single and dually marked with 13C and 15N for up to 60 d postemergence without changes to adult body size or transgenerational marking. This report adds to the growing literature that explores the use of alternative marking methods for ecological and vector biology studies.

From Surveillance To Control: Evaluation of A Larvicide Intervention Against Aedes aegypti In Brownsville, Texas.

South Texas is recognized as a potential area for the emergence and re-emergence of mosquito-borne diseases due to recent circulation of Zika, chikungunya, and dengue viruses. During 2017, high Aedes aegypti abundance found in the city of Brownsville, TX, in combination with the previous year's local transmission of Zika virus, triggered the activation of the Texas Department of State Health Services Emergency Mosquito Control Contingency Contract. A contract with the Clarke Environmental and Mosquito Control was a response to control Ae. aegypti, using a ground-based wide-area larvicide spray (WALS™) containing Bacillus thuringiensis israelensis. The WALS application was evaluated through a field-based bioassay and by comparing surveillance data pre- and post-WALS application. The WALS application bioassay demonstrated that the larvicide was effective up to 60 m into the target properties. Additionally, the number of Ae. aegypti captured in traps decreased in the WALS intervention areas compared with the untreated control areas, with an estimated 29% control.

Surveillance of Aedes aegypti indoors and outdoors using Autocidal Gravid Ovitraps in South Texas during local transmission of Zika virus, 2016 to 2018.

The yellow fever mosquito, Aedes aegypti, has facilitated the re-emergence of dengue virus (DENV) and emergence of chikungunya virus (CHIKV) and Zika virus (ZIKV) in the Americas and the Caribbean. The recent transmission of these arboviruses in the continental United States has been limited, to date, to South Florida and South Texas despite Ae. aegypti occurring over a much larger geographical region within the country. The main goal of our study was to provide the first long term longitudinal study of Ae. aegypti and enhance the knowledge about the indoor and outdoor relative abundance of Ae. aegypti as a proxy for mosquito-human contact in South Texas, a region of the United States that is at high risk for mosquito-borne virus transmission. Here, the relative abundance of indoors and outdoors mosquitoes of households in eight different communities was described. Surveillance was done weekly from September 2016 to April 2018 using the CDC Autocidal Gravid Ovitraps in low- and middle-income communities. A total of 69 houses were included in this survey among which 36 were in the low-income communities (n = 11 for Donna, n = 15 for Progresso, n = 5 for Mesquite, n = 5 for Chapa) and 33 in middle-income communities (n = 9 for La Feria, n = 8 for Weslaco, n = 11 for McAllen, and n = 5 for Rio Rico). Overall, Ae. aegypti was the dominant species (59.2% of collections, n = 7255) followed by Culex spp. mosquitoes (27.3% of collections, n = 3350). Furthermore, we demonstrated for Ae. aegypti that 1) outdoor relative abundance was higher compared to indoor relative abundance, 2) low-income communities were associated with an increase in mosquito relative abundance indoors when compared to middle-income communities, 3) no difference was observed in the number of mosquitoes collected outdoors between low-income and middle-income communities, and 4) warmer months were positively correlated with outdoor relative abundance whereas no seasonality was observed in the relative abundance of mosquitoes indoors. Additionally, Ae. aegypti mosquitoes collected in South Texas were tested using a specific ZIKV/CHIKV multiplex real-time PCR assay, however, none of the mosquitoes tested positive. Our data highlights the occurrence of mosquitoes indoors in the continental United States and that adults are collected nearly every week of the calendar year. These mosquito data, obtained concurrently with local ZIKV transmission of 10 locally acquired cases in nearby communities, represent a baseline for future studies in the Lower Rio Grande Valley (LRGV) including vector control interventions relying on the oviposition behavior to reduce mosquito populations and pathogen transmission.

A decade of vector control activities: Progress and limitations of Chagas disease prevention in a region of Guatemala with persistent Triatoma dimidiata infestation.

INTRODUCTION: Chagas disease, a neglected tropical disease that affects millions of Latin Americans, has been effectively controlled in Guatemala after multiple rounds of indoor residual insecticide spraying (IRS). However, a few foci remain with persistent Triatoma dimidiata infestation. One such area is the municipality of Comapa, Department of Jutiapa, in the southeastern region of Guatemala, where control interventions appear less effective. We carried out three cross sectional entomological and serological surveys in Comapa to evaluate a decade of vector control activities. Baseline serological (1999) and entomological (2001-2) surveys were followed by three rounds of insecticide applications (2003-2005) and intermittent focal spraying of infested houses, until approximately 2012. Household inspections to determine entomological indices and construction materials were conducted in 2001, 2007 and 2011. Seroprevalence surveys were conducted in school-age children in 1999, 2007 and 2015, and in women of child bearing age (15-44 years) only in 2015. After multiple rounds of indoor residual sprayings (IRS), the infestation index decreased significantly from 39% (2001-2) to 27% (2011). Household construction materials alone predicted <10% of infested houses. Chagas seroprevalence in Comapa declined in school-aged children by 10-fold, from 10% (1999) to 1% (2015). However, seroprevalence in women of child bearing age remains >10%. CONCLUSION: After a decade of vector control activities in Comapa, there is evidence of significantly reduced transmission. However, the continued risk for vector-borne and congenital transmission pose a threat to the 2022 Chagas disease elimination goal. Systematic integrated vector control and improved Chagas disease screening and treatment programs for congenital and vector-borne disease are needed to reach the elimination goal in regions with persistent vector infestation.

The Chagas disease domestic transmission cycle in Guatemala: Parasite-vector switches and lack of mitochondrial co-diversification between Triatoma dimidiata and Trypanosoma cruzi subpopulations suggest non-vectorial parasite dispersal across the Motagua valley.

Parasites transmitted by insects must adapt to their vectors and reservoirs. Chagas disease, an American zoonosis caused by Trypanosoma cruzi, is transmitted by several species of triatomines. In Central America, Triatoma dimidiata is a widely dispersed vector found in sylvatic and domestic habitats, with distinct populations across the endemic region of Guatemala. Our aim was to test the strength of association between vector and parasite genetic divergence in domestic environments. Microsatellite (MS) loci were used to characterize parasites isolated from T. dimidiata (n=112) collected in domestic environments. Moderate genetic differentiation was observed between parasites north and south of the Motagua Valley, an ancient biogeographic barrier (FST 0.138, p=0.009). Slightly reduced genotypic diversity and increased heterozygosity in the north (Allelic richness (Ar)=1.00-6.05, FIS -0.03) compared to the south (Ar=1.47-6.30, FIS 0.022) suggest either a selective or demographic process during parasite dispersal. Based on parasite genotypes and geographic distribution, 15 vector specimens and their parasite isolates were selected for mitochondrial co-diversification analysis. Genetic variability and phylogenetic congruence were determined with mitochondrial DNA sequences (10 parasite maxicircle gene fragments and triatomine ND4+CYT b). A Mantel test as well as phylogenetic, network and principal coordinates analyses supported at least three T. dimidiata haplogroups separated by geographic distance across the Motagua Valley. Maxicircle sequences showed low T. cruzi genetic variability (π nucleotide diversity 0.00098) with no evidence of co-diversification with the vector, having multiple host switches across the valley. Sylvatic Didelphis marsupialis captured across the Motagua Valley were found to be infected with T. cruzi strains sharing MS genotypes with parasites isolated from domiciliated triatomines. The current parasite distribution in domestic environments can be explained by multiple parasite-host switches between vector populations and selection or bottleneck processes across the Motagua Valley, with a possible role for didelphids in domestic transmission.

Development of a community-based intervention for the control of Chagas disease based on peridomestic animal management: an eco-bio-social perspective.

BACKGROUND: Integrated vector management strategies depend on local eco-bio-social conditions, community participation, political will and inter-sectorial partnership. Previously identified risk factors for persistent Triatoma dimidiata infestation include the presence of rodents and chickens, tiled roofs, dirt floors, partial wall plastering and dog density. METHODS: A community-based intervention was developed and implemented based on cyclical stakeholder and situational analyses. Intervention implementation and evaluation combined participatory action research and cluster randomized pre-test post-test experimental designs. The intervention included modified insecticide application, education regarding Chagas disease and risk factors, and participatory rodent control. RESULTS: At final evaluation there was no significant difference in post-test triatomine infestation between intervention and control, keeping pre-test rodent and triatomine infestations constant. Knowledge levels regarding Chagas disease and prevention practices including rodent control, chicken management and health service access increased significantly only in intervention communities. The odds of nymph infection and rat infestation were 8.3 and 1.9-fold higher in control compared to intervention communities, respectively. CONCLUSION: Vector control measures without reservoir control are insufficient to reduce transmission risk in areas with persistent triatomine infestation. This integrated vector management program can complement house improvement initiatives by prioritizing households with risk factors such as tiled roofs. Requirement for active participation and multi-sectorial coordination poses implementation challenges.