Vector competence of lambda-cyhalothrin resistant Aedes aegypti strains for dengue-2, Zika and chikungunya viruses in Colombia.

Aedes aegypti is the primary vector of dengue, Zika, and chikungunya viruses. Studies have shown that insecticide resistance affects vector competence (VC) of some mosquito species. This study evaluates the effect of resistance to lambda-cyhalothrin and kdr V1016I mutation genotypes on the VC of Ae. aegypti strains for DENV-2, ZIKV, and CHIKV. Three Ae. aegypti strains with gradual lambda-cyhalothrin resistance (susceptible, resistant, and highly resistant) were infected with DENV-2, ZIKV, and CHIKV. Individual mosquitoes were tested to detect virus infection in the abdomen and head-salivary glands, using RT-PCR, and genotypes for V1016I mutations using allele-specific PCR. Recorded VC variables were midgut infection rate (MIR), dissemination rate (DIR), and dissemination efficiency (DIE). Lambda-cyhalothrin resistance affects differentially VC variables for ZIKV, DENV-2, and CHIKV. For ZIKV, an apparent gradual increase in DIR and DIE with the increase in insecticide resistance was observed. For DENV-2 the MIR and DIE were higher in insecticide resistant strains. For CHIKV, only MIR could be evaluated, this variable was higher in insecticide resistance strains. The presence of kdr V1016I mutation on mosquito resistant strains did not affect VC variables for three study viruses.

Integration of phlebotomine ecological niche modelling, and mapping of cutaneous leishmaniasis surveillance data, to identify areas at risk of under-estimation.

INTRODUCTION: Passive surveillance systems are thought to under-estimate the true incidence of American cutaneous leishmaniasis (ACL) by two- to five-fold. Ecological niche models based on remotely sensed data can identify environmental factors which favor phlebotomine vectors. Here we report an integrated approach to identifying areas at risk of cutaneous leishmaniasis by applying spatial analysis methods to niche model results, and local surveillance data, in two locations in Colombia with differing vector ecology. The objective was to identify townships in which later phases of the project could implement community-based surveillance to obtain direct estimates of under-reporting. MATERIALS AND METHODS: The study was carried out in one municipality in each of two departments of the Andean region of Colombia: Pueblo Rico in Risaralda, and Rovira in Tolima. Niche mapping by maximum entropy, based on published and unpublished existing locations of Pintomyia (Pifanomyia) longiflocosa and Psychodopygus panamensis, and using variables on land cover, climate and elevation. Field catches were done in each municipality to test predictions of high relative probability of presence. The niche model results were included as a predictor in a conditional autoregressive spatial model, in which the outcome variable was the number of cases by township, as detected by passive surveillance. RESULTS: Having rarefied 173 geolocated records, 46 of Pi. longiflocosa and 57 of Ps. panamensis were used for the niche modelling. At the national level, both species had high relative probability of presence on parts of the slopes of the three Andean cordilleras. Pi. longiflocosa also has a high relative probability of presence in the higher parts of the Magdalena valley, as does Ps. panamensis in some areas close to the Caribbean coast. At the local level, field catches confirmed that Pi. longiflocosa was the most abundant species in Rovira, and likewise Ps. panamensis in Pueblo Rico. The spatial regression showed that the incidence of ACL, according to surveillance, was positively, but not statistically significantly, associated with the relative probability of presence from the risk model. CONCLUSIONS: These niche maps bring together published and unpublished results on phlebotomine species which are important vectors in Colombia. Maps of the fitted values of incidence were used to guide the selection of townships in which further phases of the study will attempt to quantify the extent of under-estimation of ACL incidence.

Transcriptome comparison of dengue-susceptible and -resistant field derived strains of Colombian Aedes aegypti using RNA-sequencing.

BACKGROUND: Forty percent of the world's population live in areas where they are at risk from dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Dengue viruses are transmitted primarily by the mosquito Aedes aegypti. In Cali, Colombia, approximately 30% of field collected Ae. aegypti are naturally refractory to all four dengue serotypes. OBJECTIVES: Use RNA-sequencing to identify those genes that determine refractoriness in feral mosquitoes to dengue. This information can be used in gene editing strategies to reduce dengue transmission. METHODS: We employed a full factorial design, analyzing differential gene expression across time (24, 36 and 48 h post bloodmeal), feeding treatment (blood or blood + dengue-2) and strain (susceptible or refractory). Sequences were aligned to the reference Ae. aegypti genome for identification, assembled to visualize transcript structure, and analyzed for dynamic gene expression changes. A variety of clustering techniques was used to identify the differentially expressed genes. FINDINGS: We identified a subset of genes that likely assist dengue entry and replication in susceptible mosquitoes and contribute to vector competence. MAIN CONCLUSIONS: The differential expression of specific genes by refractory and susceptible mosquitoes could determine the phenotype, and may be used to in gene editing strategies to reduce dengue transmission.

Transcriptome comparison of dengue-susceptible and -resistant field derived strains of Colombian Aedes aegypti using RNA-sequencing

BACKGROUND Forty percent of the world's population live in areas where they are at risk from dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Dengue viruses are transmitted primarily by the mosquito Aedes aegypti. In Cali, Colombia, approximately 30% of field collected Ae. aegypti are naturally refractory to all four dengue serotypes. OBJECTIVES Use RNA-sequencing to identify those genes that determine refractoriness in feral mosquitoes to dengue. This information can be used in gene editing strategies to reduce dengue transmission. METHODS We employed a full factorial design, analyzing differential gene expression across time (24, 36 and 48 h post bloodmeal), feeding treatment (blood or blood + dengue-2) and strain (susceptible or refractory). Sequences were aligned to the reference Ae. aegypti genome for identification, assembled to visualize transcript structure, and analyzed for dynamic gene expression changes. A variety of clustering techniques was used to identify the differentially expressed genes. FINDINGS We identified a subset of genes that likely assist dengue entry and replication in susceptible mosquitoes and contribute to vector competence. MAIN CONCLUSIONS The differential expression of specific genes by refractory and susceptible mosquitoes could determine the phenotype, and may be used to in gene editing strategies to reduce dengue transmission.

Land use in relation to composition and abundance of phlebotomines (Diptera: Psychodidae) in five foci of domiciliary transmission of cutaneous leishmaniasis in the Andean region of Colombia.

American cutaneous leishmaniasis is a public health concern in Colombia, its incidence being sustained or focally increased principally by the emergence of domestic transmission concomitantly with the adaptation of the phlebotomine vectors to habitat transformation around households. The objective of the study is to scale up a rapid characterization methodology for evaluating the relationship of land use around the house to the composition and abundance of phlebotomines. Five sites with a history of domestic leishmaniasis transmission in the Andean area of Colombia were selected. The peri-domestic habitat was evaluated at 10 m intervals along eight radial transects, centered on each house, at 45° intervals using a web pattern. Phlebotomines were captured by placing three CDC light traps over two nights both indoors and outdoors (10 m from the house). Blood source and infection were determined by PCR. Spearman rank correlation coefficients and negative binomial regression were used to quantify associations between the phlebotomine abundance and habitat categories. The study demonstrated that the vectors were largely anthropophagic (62% of 79 were human blood) and that a single species in each site was favored by the pertaining agriculture monoculture. Specifically, Pintomyia (Pifanomyia) quasitownsendi was associated with sugar cane in Novillero and La Esmeralda; while Pi. (Pif.) longiflocosa was associated with coffee plantations in Agua Bonita and El Cucal. Honda Alta had a more diverse array of land use and forest coverage with a lower number of specimens but higher species diversity. In terms of distance from the house to an area of a given land use, the abundance of Pi. (Pif.) quasitownsendi was inversely related to the distance to sugar cane plantation (Spearman correlation coefficient, ρ = -0.56, p < 0.001 for outdoor catches, and ρ = -0.50, p < 0.001 indoors). A similar inverse relationship was observed for Pi. (Pif.) longiflocosa with regard to technified coffee (ρ = -0.51, p < 0.001 outdoors, and ρ = -0.48, p < 0.001 indoors). This rapid characterization methodology could guide public heath decision makers in identifying those houses at higher risk of domestic transmission, and also educate farmers to increase the distance between their crops and any neighboring houses.

VECTOS: An Integrated System for Monitoring Risk Factors Associated With Urban Arbovirus Transmission.

In Colombia, as in many Latin American countries, decision making and development of effective strategies for vector control of urban diseases such as dengue, Zika, and chikungunya is challenging for local health authorities. The heterogeneity of transmission in urban areas requires an efficient risk-based allocation of resources to control measures. With the objective of strengthening the capacity of local surveillance systems to identify variables that favor urban arboviral transmission, a multidisciplinary research team collaborated with the local Secretary of Health officials of 3 municipalities in Colombia (Giron, Yopal, and Buga), in the design of an integrated information system called VECTOS from 2015 to 2018. Information and communication technologies were used to develop 2 mobile applications to capture entomological and social information, as well as a web-based system for the collection, geo-referencing, and integrated information analysis using free geospatial software. This system facilitates the capture and analysis of epidemiological information from the Colombian national surveillance system (SIVIGILA), periodic entomological surveys-mosquito larvae and pupae in premises and peridomestic breeding sites-and surveys of knowledge, attitudes, and practices (KAP) in a spatial and temporal context at the neighborhood level. The data collected in VECTOS are mapped and visualized in graphical reports. The system enables real-time monitoring of weekly epidemiological indicators, entomological indices, and social surveys. Additionally, the system enables risk stratification of neighborhoods, using selected epidemiological, entomological, demographic, and environmental variables. This article describes the VECTOS system and the lessons learned during its development and use. The joint analysis of epidemiological and entomological data within a geographic information system in VECTOS gives better insight to the routinely collected data and identifies the heterogeneity of risk factors between neighborhoods. We expect the system to continue to strengthen vector control programs in evidence-based decision making and in the design and enhanced follow-up of vector control strategies.

Immune response-related genes associated to blocking midgut dengue virus infection in Aedes aegypti strains that differ in susceptibility.

Aedes (Stegomyia) aegypti, the principal global vector of dengue viruses, has differences in its susceptibility to dengue virus infection. We compared the global expression of genes in the midguts of Colombian Ae. aegypti dengue-susceptible (Cali-S) and dengue-refractory (Cali-MIB) field derived strains after ingesting either a sugarmeal, a bloodmeal, or a bloodmeal containing dengue virus serotype 2 (DENV-2). Microarray-based transcriptome analysis among treatments indicated a total of 4725 transcripts with differential expression between the two strains. Eleven genes were selected from different functional groups based on their significant up or down expression levels as well as reports in the literature suggesting they are associated with dengue virus elimination. We measured mRNA abundance of these 11 genes at 0, 8, 24, and 36 h postinfection using quantitative real time PCR (qPCR) to confirm the microarray results and assess any temporal patterns. Four genes were selected (Gram-negative binding protein-GNBP [AAEL009176], Niemann Pick Type-C2-NPC2 [AAEL015136], Keratinocyte lectin [AAEL009842], and Cathepsin-b [AAEL007585]) for knockdown experiments using RNA interference (RNAi) methodology to determine the phenotype (DENV-2 susceptible or refractory). Silencing GNBP, Cathepsin-b and Keratinocyte lectin reduced the percentage of mosquitoes with disseminated virus in the Cali-S strain to 8%, 20%, and 12% respectively compared with 96% in the controls. Silencing of NPC2 increased the percentage of mosquitos with disseminated virus infections in Cali-MIB to 66% compared with 35% in the controls. This study provides insight into genes that may contribute to the Cali-S susceptible and Cali-MIB refractory phenotypes in Ae. aegypti.

Mechanisms of pyrethroid resistance in Aedes (Stegomyia) aegypti from Colombia.

In Colombia Aedes (Stegomyia) aegypti is the main vector of urban arboviruses such as dengue, chikungunya and Zika. This urban mosquito has a well-established capacity to develop insecticide resistance to different types of insecticides (pyrethroids, organochlorides, organophosphates), using multiple resistance mechanisms. An understanding of ongoing resistance mechanisms is critical to determining the activities of vector control programs. In order to identify the biochemical and molecular mechanisms associated with pyrethroid resistance in Colombia, three laboratory-selected strains resistant to DDT, Propoxur and lambdacyhalothrin, and 7 field-collected strains were evaluated. CDC bioassays were performed to measure the susceptibility status to pyrethroid type I (permethrin) and II (deltamethrin and lambdacyhalothrin), and potential cross-resistance to different types of insecticides; organochlorine (DDT), carbamates (propoxur) and organophosphates (malathion). The enzymatic activity of esterases, glutathione S-transferases (GST) and P450 monooxygenases were biochemically determined. Frequencies of kdr mutations Val1016Ile and Phe1534cys were determined through real-time PCR. The Rockefeller strain of Aedes (Stegomyia) aegypti was used as the susceptible control. The laboratory-selected strains "propoxur" and "lambdacyhalothrin" and one field population (Medellín (BF) F2 were resistant to all evaluated pyrethroids. Six of the seven field populations as well as the laboratory- selected "DDT" strain were resistant to permethrin. All the evaluated strains were resistant to DDT. Cross-resistance between lambdacyhalothrin and propoxur was observed in the laboratory-selected strains; however, all field-collected strains were susceptible to propoxur and no evidence of malathion resistance was found. The main biochemical mechanism for resistance observed in the field-collected strains was related to the enzyme GST. Further, the frequencies of kdr mutations alleles associated with insecticide resistance were high and ranged from 0.02 to 0.72 for Ile1016 and from 0.44 to 0.99 for Cys1534. Strains with high frequencies of both kdr mutations were resistant to both type I and II pyrethroids. These results suggest that Ae. aegypti from Colombia have developed multiple resistance mechanisms associated with pyrethroid resistance; therefore a resistance management strategy against these field populations of Ae. Aegypti, incorporating these findings is strongly recommended.

The Composition of Midgut Bacteria in Aedes aegypti (Diptera: Culicidae) That Are Naturally Susceptible or Refractory to Dengue Viruses.

The composition, abundance, and diversity of midgut bacteria in mosquitoes can influence pathogen transmission. We used 16S rRNA microbiome profiling to survey midgut microbial diversity in pooled samples of laboratory colonized dengue-refractory, Cali-MIB, and dengue-susceptible, Cali-S Aedes aegypti (Linnaeus). The 16S rRNA sequences from the sugar-fed midguts of adult females clustered to 63 amplicon sequence variants (ASVs), primarily from Proteobacteria, Firmicutes, Flavobacteria, and Actinobacteria. An average of five ASVs dominated the midguts, and most ASVs were present in both Cali-MIB and Cali-S midguts. No differences in abundance were noted at any phylogenetic level (Phylum, Class, Order, Family, Genus) by analysis of composition of microbiome (w = 0). No community diversity metrics were significantly different between refractory and susceptible mosquitoes. These data suggest that phenotypic differences in the susceptibility to dengue virus between Cali-MIB and Cali-S are not likely due to major differences in midgut bacterial communities.

Changing paradigms in Aedes control: considering the spatial heterogeneity of dengue transmission / Cambio de paradigma en el control de Aedes: consideración de la heterogeneidad espacial de la transmisión del dengue

Current dengue vector control strategies, focusing on reactive implementation of insecticide- based interventions in response to clinically apparent disease manifestations, tend to be inefficient, short-lived, and unsustainable within the worldwide epidemiological scenario of virus epidemic recrudescence. As a result of a series of expert meetings and deliberations, a paradigm shift is occurring and a new strategy, using risk stratification at the city level in order to concentrate proactive, sustained efforts in areas at high risk for transmission, has emerged. In this article, the authors 1) outline this targeted, proactive intervention strategy, within the context of dengue epidemiology, the dynamics of its transmission, and current Aedes control strategies, and 2) provide support from published literature for the need to empirically test its impact on dengue transmission as well as on the size of disease outbreaks. As chikungunya and Zika viruses continue to expand their range, the need for a science-based, proactive approach for control of urban Aedes spp. mosquitoes will become a central focus of integrated disease management planning.

Las estrategias actuales de control de vectores del dengue, centradas en la ejecución reactiva de intervenciones con insecticidas en respuesta a la aparición de cuadros clínicos evidentes de la enfermedad, suelen ser ineficientes, de duración limitada e insostenibles en el contexto epidemiológico mundial, caracterizado por la recrudescencia de las epidemias virales. Como resultado de una serie de reuniones y deliberaciones entre expertos, está en proceso un cambio de paradigma y ha surgido una nueva estrategia, que consiste en estratificar el riesgo de cada ciudad para concentrar y mantener los esfuerzos proactivos donde hay un alto riesgo de transmisión. En este artículo, los autores 1) describen esta estrategia de intervención específica y proactiva dentro del contexto de las características epidemiológicas del dengue, la dinámica de su transmisión y las estrategias actuales de control de Aedes y 2) fundamentan con fuentes bibliográficas la necesidad de demostrar empíricamente las repercusiones de esta estrategia sobre la transmisión del dengue y el tamaño de los brotes. Dado que los virus del chikunguña y el Zika siguen ampliando su alcance, uno de los objetivos primordiales de la planificación de la atención integrada de estas enfermedades estará determinado por la necesidad de adoptar un enfoque científico y proactivo del control urbano de los mosquitos del género Aedes.

Changing paradigms in Aedes control: considering the spatial heterogeneity of dengue transmission.

Current dengue vector control strategies, focusing on reactive implementation of insecticide-based interventions in response to clinically apparent disease manifestations, tend to be inefficient, short-lived, and unsustainable within the worldwide epidemiological scenario of virus epidemic recrudescence. As a result of a series of expert meetings and deliberations, a paradigm shift is occurring and a new strategy, using risk stratification at the city level in order to concentrate proactive, sustained efforts in areas at high risk for transmission, has emerged. In this article, the authors 1) outline this targeted, proactive intervention strategy, within the context of dengue epidemiology, the dynamics of its transmission, and current Aedes control strategies, and 2) provide support from published literature for the need to empirically test its impact on dengue transmission as well as on the size of disease outbreaks. As chikungunya and Zika viruses continue to expand their range, the need for a science-based, proactive approach for control of urban Aedes spp. mosquitoes will become a central focus of integrated disease management planning.

Las estrategias actuales de control de vectores del dengue, centradas en la ejecución reactiva de intervenciones con insecticidas en respuesta a la aparición de cuadros clínicos evidentes de la enfermedad, suelen ser ineficientes, de duración limitada e insostenibles en el contexto epidemiológico mundial, caracterizado por la recrudescencia de las epidemias virales. Como resultado de una serie de reuniones y deliberaciones entre expertos, está en proceso un cambio de paradigma y ha surgido una nueva estrategia, que consiste en estratificar el riesgo de cada ciudad para concentrar y mantener los esfuerzos proactivos donde hay un alto riesgo de transmisión. En este artículo, los autores 1) describen esta estrategia de intervención específica y proactiva dentro del contexto de las características epidemiológicas del dengue, la dinámica de su transmisión y las estrategias actuales de control de Aedes y 2) fundamentan con fuentes bibliográficas la necesidad de demostrar empíricamente las repercusiones de esta estrategia sobre la transmisión del dengue y el tamaño de los brotes. Dado que los virus del chikunguña y el Zika siguen ampliando su alcance, uno de los objetivos primordiales de la planificación de la atención integrada de estas enfermedades estará determinado por la necesidad de adoptar un enfoque científico y proactivo del control urbano de los mosquitos del género Aedes.

Changing paradigms in Aedes control: considering the spatial heterogeneity of dengue transmission / Cambio de paradigma en el control de Aedes: consideración de la heterogeneidad espacial de la transmisión del dengue

ABSTRACT Current dengue vector control strategies, focusing on reactive implementation of insecticide-based interventions in response to clinically apparent disease manifestations, tend to be inefficient, short-lived, and unsustainable within the worldwide epidemiological scenario of virus epidemic recrudescence. As a result of a series of expert meetings and deliberations, a paradigm shift is occurring and a new strategy, using risk stratification at the city level in order to concentrate proactive, sustained efforts in areas at high risk for transmission, has emerged. In this article, the authors 1) outline this targeted, proactive intervention strategy, within the context of dengue epidemiology, the dynamics of its transmission, and current Aedes control strategies, and 2) provide support from published literature for the need to empirically test its impact on dengue transmission as well as on the size of disease outbreaks. As chikungunya and Zika viruses continue to expand their range, the need for a science-based, proactive approach for control of urban Aedes spp. mosquitoes will become a central focus of integrated disease management planning.

RESUMEN Las estrategias actuales de control de vectores del dengue, centradas en la ejecución reactiva de intervenciones con insecticidas en respuesta a la aparición de cuadros clínicos evidentes de la enfermedad, suelen ser ineficientes, de duración limitada e insostenibles en el contexto epidemiológico mundial, caracterizado por la recrudescencia de las epidemias virales. Como resultado de una serie de reuniones y deliberaciones entre expertos, está en proceso un cambio de paradigma y ha surgido una nueva estrategia, que consiste en estratificar el riesgo de cada ciudad para concentrar y mantener los esfuerzos proactivos donde hay un alto riesgo de transmisión. En este artículo, los autores 1) describen esta estrategia de intervención específica y proactiva dentro del contexto de las características epidemiológicas del dengue, la dinámica de su transmisión y las estrategias actuales de control de Aedes y 2) fundamentan con fuentes bibliográficas la necesidad de demostrar empíricamente las repercusiones de esta estrategia sobre la transmisión del dengue y el tamaño de los brotes. Dado que los virus del chikunguña y el Zika siguen ampliando su alcance, uno de los objetivos primordiales de la planificación de la atención integrada de estas enfermedades estará determinado por la necesidad de adoptar un enfoque científico y proactivo del control urbano de los mosquitos del género Aedes.

Reduction in dengue cases observed during mass control of Aedes (Stegomyia) in street catch basins in an endemic urban area in Colombia.

Dengue incidence continues to increase globally and, in the absence of an efficacious vaccine, prevention strategies are limited to vector control. It has been suggested that targeting the most productive breeding sites instead of all water-holding containers could be a cost-effective vector control strategy. We sought to identify and continuously control the most productive Aedes (Stegomyia) breeding site in an endemic urban area in Colombia and followed the subsequent incidence of dengue. In the urban area of Guadalajara de Buga, southwestern Colombia, potential breeding sites inside and outside houses were first characterized, and local personnel trained to assess their productivity based on the pupae/person index. Simultaneously, training and monitoring were implemented to improve the dengue case surveillance system. Entomological data and insecticide resistance studies were used to define the targeted intervention. Then, a quasi-experimental design was used to assess the efficacy of the intervention in terms of the positivity index of the targeted and non- targeted breeding sites, and the impact on dengue cases. Street catch basins (storm drains) were the potential breeding site most frequently found containing Aedes immature stages in the baseline (58.3% of 108). Due to the high resistance to temephos (0% mortality after 24h), the intervention consisted of monthly application of pyriproxyfen in all the street catch basins (n=4800). A significant decrease in catch basins positivity for Aedes larvae was observed after each monthly treatment (p<0.001). Over the intervention period, a reduction in the dengue incidence in Buga was observed (rate ratio 0.19, 95% CI 0.12-0.30, p<0.0001) after adjusting for autocorrelation and controlling with a neighboring town, Palmira, This study highlights the importance of street catch basins as Aedes breeding sites and suggests that their targeted control could help to decrease dengue transmission in such areas.

Differential expression of apoptosis related genes in selected strains of Aedes aegypti with different susceptibilities to dengue virus.

Aedes aegypti is the principal vector of Dengue viruses worldwide. We identified field collected insects with differential susceptibility to Dengue-2 virus (DENv-2) and used isofemale selection to establish susceptible and refractory strains based on midgut infection barriers. Previous experiments had identified higher expression of apoptosis-related genes in the refractory strain. To identify potential molecular mechanisms associated with DENv susceptibility, we evaluated the differential expression of Caspase-16, Aedronc, Aedredd, Inhibitor of apoptosis (AeIAP1) and one member of the RNAi pathway, Argonaute-2 in the midguts and fat body tissues of the selected strains at specific times post blood feeding or infection with DENv-2. In the refractory strain there was significantly increased expression of caspases in midgut and fatbody tissues in the presence of DENv-2, compared to exposure to blood alone, and significantly higher caspase expression in the refractory strain compared with the susceptible strain at timepoints when DENv was establishing in these tissues. We used RNAi to knockdown gene expression; knockdown of AeIAP1 was lethal to the insects. In the refractory strain, knockdown of the pro-apoptotic gene Aedronc increased the susceptibility of refractory insects to DENv-2 from 53% to 78% suggesting a contributing role of this gene in the innate immune response of the refractory strain.

Phlebotomine vector ecology in the domestic transmission of American cutaneous leishmaniasis in Chaparral, Colombia.

Phlebotomine vector ecology was studied in the largest recorded outbreak of American cutaneous leishmaniasis in Colombia in 2004. In two rural townships that had experienced contrasting patterns of case incidence, this study evaluated phlebotomine species composition, seasonal abundance, nocturnal activity, blood source, prevalence of Leishmania infection, and species identification. CDC miniature light traps were used to trap the phlebotomines. Traps were set indoors, peridomestically, and in woodlands. Natural infection was determined in pools by polymerase chain reaction-Southern blot, and blood sources and species identification were determined by sequencing. Large differences were observed in population abundance between the two townships evaluated. Lutzomyia longiflocosa was the most abundant species (83.1%). Abundance was higher during months with lower precipitation. Nocturnal activity was associated with human domestic activity. Blood sources identified were mainly human (85%). A high prevalence of infection was found in L. longiflocosa indoors (2.7%) and the peridomestic setting (2.5%). L. longiflocosa was responsible for domestic transmission in Chaparral.

Comparison of the efficacy of long-lasting insecticidal nets PermaNet® 2.0 and Olyset® against Anopheles albimanus under laboratory conditions.

Insecticide-treated nets provide a reduction in human-vector contact through physical barrier, mortality and/or repellent effects that protect both users and non-users, thereby protecting the wider community from vector-borne diseases like malaria. Long-lasting insecticide-treated nets (LLINs) are the best alternative. This study evaluated the bioefficacy of LLINs PermaNet® 2.0 and Olyset® under laboratory conditions with Anopheles albimanus. The laboratory strain was evaluated for insecticide susceptibility with selected insecticides used for malarial control. Regeneration time and wash resistance were evaluated with the standard bioassay cone technique following WHO guidelines. Heat assistance was used for Olyset® nets; the nets were exposed to four different temperatures to speed the regeneration process. The regeneration study of PermaNet® 2.0 showed that efficacy was fully recovered by 24 h after one and three washes and wash resistance persisted for 15 washes. Regeneration of Olyset® nets was not observed for nets washed three times, even with the different temperature exposures for up to seven days. Thus, for Olyset® the wash resistance evaluation could not proceed. Differences in response between the two LLINs may be associated with differences in manufacturing procedures and species response to the evaluated LLINs. PermaNet® 2.0 showed higher and continuous efficacy against An. albimanus.

Comparison of the efficacy of long-lasting insecticidal nets PermaNet® 2.0 and Olyset® against Anopheles albimanus under laboratory conditions

Insecticide-treated nets provide a reduction in human-vector contact through physical barrier, mortality and/or repellent effects that protect both users and non-users, thereby protecting the wider community from vector-borne diseases like malaria. Long-lasting insecticide-treated nets (LLINs) are the best alternative. This study evaluated the bioefficacy of LLINs PermaNet® 2.0 and Olyset® under laboratory conditions with Anopheles albimanus. The laboratory strain was evaluated for insecticide susceptibility with selected insecticides used for malarial control. Regeneration time and wash resistance were evaluated with the standard bioassay cone technique following WHO guidelines. Heat assistance was used for Olyset® nets; the nets were exposed to four different temperatures to speed the regeneration process. The regeneration study of PermaNet® 2.0 showed that efficacy was fully recovered by 24 h after one and three washes and wash resistance persisted for 15 washes. Regeneration of Olyset® nets was not observed for nets washed three times, even with the different temperature exposures for up to seven days. Thus, for Olyset® the wash resistance evaluation could not proceed. Differences in response between the two LLINs may be associated with differences in manufacturing procedures and species response to the evaluated LLINs. PermaNet® 2.0 showed higher and continuous efficacy against An. albimanus.

Leishmania (Viannia) infection in the domestic dog in Chaparral, Colombia.

Peridomestic transmission of American cutaneous leishmaniasis is increasingly reported and dogs may be a reservoir of Leishmania (Viannia) in this setting. We investigated the prevalence of infection in dogs in Chaparral County, Colombia, the focus of an epidemic of human cutaneous leishmaniasis caused by Leishmania (Viannia) guyanensis. Two (0.72%) of 279 dogs had lesions typical of cutaneous leishmaniasis that were biopsy positive by kinetoplast DNA polymerase chain reaction-Southern blotting. Seroprevalence was 2.2% (6 of 279) by enzyme-linked immunosorbent assay. Buffy coat and ear skin biopsy specimens were positive by polymerase chain reaction-Southern blotting in 7.3% (10 of 137) and 11.4% (12 of 105) of dogs, respectively. Overall 20% of dogs (21 of 105) showed positive results for one or more tests. Amplification and sequencing of the Leishmania 7SL RNA gene identified L. guyanensis in one dog and L. braziliensis in two dogs. No association was identified between the risk factors evaluated and canine infection. Dogs may contribute to transmission but their role in this focus appears to be limited.