Increased threat of urban arboviral diseases from Aedes aegypti mosquitoes in Colombia.

Objectives: Our study targets the potential of the local urban mosquito Aedes aegypti to experimentally transmit chikungunya virus (CHIKV), dengue virus (DENV), yellow fever virus (YFV), and Zika virus (ZIKV). Methods: We collected eggs and adults of Ae. aegypti in Medellín, Colombia (from February to March 2020) for mosquito experimental infections with DENV, CHIKV, YFV and ZIKV and viral detection using the BioMark Dynamic arrays system. Results: We show that Ae. aegypti from Medellín was more prone to become infected, to disseminate and transmit CHIKV and ZIKV than DENV and YFV. Conclusions: Thus, in Colombia, chikungunya is the most serious threat to public health based on our vector competence data.

wMel Wolbachia alters female post-mating behaviors and physiology in the dengue vector mosquito Aedes aegypti.

Globally invasive Aedes aegypti disseminate numerous arboviruses that impact human health. One promising method to control Ae. aegypti populations is transinfection with Wolbachia pipientis, which naturally infects ~40-52% of insects but not Ae. aegypti. Transinfection of Ae. aegypti with the wMel Wolbachia strain induces cytoplasmic incompatibility (CI), allows infected individuals to invade native populations, and inhibits transmission of medically relevant arboviruses by females. Female insects undergo post-mating physiological and behavioral changes-referred to as the female post-mating response (PMR)-required for optimal fertility. PMRs are typically elicited by male seminal fluid proteins (SFPs) transferred with sperm during mating but can be modified by other factors, including microbiome composition. Wolbachia has modest effects on Ae. aegypti fertility, but its influence on other PMRs is unknown. Here, we show that Wolbachia influences female fecundity, fertility, and re-mating incidence and significantly extends the longevity of virgin females. Using proteomic methods to examine the seminal proteome of infected males, we found that Wolbachia moderately affects SFP composition. However, we identified 125 paternally transferred Wolbachia proteins, but the CI factor proteins (Cifs) were not among them. Our findings indicate that Wolbachia infection of Ae. aegypti alters female PMRs, potentially influencing control programs that utilize Wolbachia-infected individuals.

Evidence of two mitochondrial lineages and genetic variability in forensically important Lucilia eximia (Diptera: Calliphoridae) in Colombia.

Lucilia eximia (Wiedemann, 1819) (Diptera: Calliphoridae) is a blowfly with medical and forensic importance that shows genetic and color variation, however, these variations have not justified the description of new species. But in forensic entomology an accurate identification of species and subpopulations is crucial. We explored the genetic variation of L. eximia from eight localities, in five natural regions in Colombia using two mitochondrial fragments, including the standard locus for insect identification COI and the Cytb-tRNA-Ser-ND1 region. We found significant differentiation at COI and Cytb-tRNA-Ser-ND1 level, characterizing two lineages and revealing a deep and significant genetic split. High values of FST and genetic distances supported the two lineages. The origin of the divergence of L. eximia remains to discover. Examining whether the lineages have diverse ecological and biological behaviors could be a significant impact on the use of L. eximia in forensic and medical science. Our results could have relevant implications for the use of post-mortem interval estimation based on insect evidence, as well as our sequences improve the database used in DNA-based methods for identifying forensically important flies.

Local-scale virome depiction in Medellín, Colombia, supports significant differences between Aedes aegypti and Aedes albopictus.

Aedes spp. comprise the primary group of mosquitoes that transmit arboviruses such as dengue, Zika, and chikungunya viruses to humans, and thus these insects pose a significant burden on public health worldwide. Advancements in next-generation sequencing and metagenomics have expanded our knowledge on the richness of RNA viruses harbored by arthropods such as Ae. aegypti and Ae. albopictus. Increasing evidence suggests that vector competence can be modified by the microbiome (comprising both bacteriome and virome) of mosquitoes present in endemic zones. Using an RNA-seq-based metataxonomic approach, this study determined the virome structure, Wolbachia presence and mitochondrial diversity of field-caught Ae. aegypti and Ae. albopictus mosquitoes in Medellín, Colombia, a municipality with a high incidence of mosquito-transmitted arboviruses. The two species are sympatric, but their core viromes differed considerably in richness, diversity, and abundance; although the community of viral species identified was large and complex, the viromes were dominated by few virus species. BLAST searches of assembled contigs suggested that at least 17 virus species (16 of which are insect-specific viruses [ISVs]) infect the Ae. aegypti population. Dengue virus 3 was detected in one sample and it was the only pathogenic virus detected. In Ae. albopictus, up to 11 ISVs and one plant virus were detected. Therefore, the virome composition appears to be species-specific. The bacterial endosymbiont Wolbachia was identified in all Ae. albopictus samples and in some Ae. aegypti samples collected after 2017. The presence of Wolbachia sp. in Ae. aegypti was not related to significant changes in the richness, diversity, or abundance of this mosquito's virome, although it was related to an increase in the abundance of Aedes aegypti To virus 2 (Metaviridae). The mitochondrial diversity of these mosquitoes suggested that the Ae. aegypti population underwent a change that started in the second half of 2017, which coincides with the release of Wolbachia-infected mosquitoes in Medellín, indicating that the population of wMel-infected mosquitoes released has introduced new alleles into the wild Ae. aegypti population of Medellín. However, additional studies are required on the dispersal speed and intergenerational stability of wMel in Medellín and nearby areas as well as on the introgression of genetic variants in the native mosquito population.

Distance to public transit predicts spatial distribution of dengue virus incidence in Medellín, Colombia.

Dengue is a growing global threat in some of the world's most rapidly growing landscapes. Research shows that urbanization and human movement affect the spatial dynamics and magnitude of dengue outbreaks; however, precise effects of urban growth on dengue are not well understood because of a lack of sufficiently fine-scaled data. We analyzed nine years of address-level dengue case data in Medellin, Colombia during a period of public transit expansion. We correlate changes in the spread and magnitude of localized outbreaks to changes in accessibility and usage of public transit. Locations closer to and with a greater utilization of public transit had greater dengue incidence. This relationship was modulated by socioeconomic status; lower socioeconomic status locations experienced stronger effects of public transit accessibility and usage on dengue incidence. Public transit is a vital urban resource, particularly among low socioeconomic populations. These results highlight the importance of public health services concurrent with urban growth.

Blood Meals With Active and Heat-Inactivated Serum Modifies the Gene Expression and Microbiome of Aedes albopictus.

The Asian "tiger mosquito" Aedes albopictus is currently the most widely distributed disease-transmitting mosquito in the world. Its geographical expansion has also allowed the expansion of multiple arboviruses like dengue, Zika, and chikungunya, to higher latitudes. Due to the enormous risk to global public health caused by mosquitoes species vectors of human disease, and the challenges in slowing their expansion, it is necessary to develop new and environmentally friendly vector control strategies. Among these, host-associated microbiome-based strategies have emerged as promising options. In this study, we performed an RNA-seq analysis on dissected abdomens of Ae. albopictus females from Manhattan, KS, United States fed with sugar and human blood containing either normal or heat-inactivated serum, to evaluate the effect of heat inactivation on gene expression, the bacteriome transcripts and the RNA virome of this mosquito species. Our results showed at least 600 genes with modified expression profile when mosquitoes were fed with normal vs. heat-inactivated-containing blood. These genes were mainly involved in immunity, oxidative stress, lipid metabolism, and oogenesis. Also, we observed bacteriome changes with an increase in transcripts of Actinobacteria, Rhodospirillaceae, and Anaplasmataceae at 6 h post-feeding. We also found that feeding with normal blood seems to particularly influence Wolbachia metabolism, demonstrated by a significant increase in transcripts of this bacteria in mosquitoes fed with blood containing normal serum. However, no differences were observed in the virome core of this mosquito population. These results suggest that heat and further inactivation of complement proteins in human serum may have profound effect on mosquito and microbiome metabolism, which could influence interpretation of the pathogen-host interaction findings when using this type of reagents specially when measuring the effect of Wolbachia in vector competence.

Entomovirological Surveillance in Schools: Are They a Source for Arboviral Diseases Transmission?

Surveillance and control activities for virus-transmitting mosquitoes have primarily focused on dwellings. There is little information about viral circulation in heavily trafficked places such as schools. We collected and analyzed data to assess the presence and prevalence of dengue, chikungunya, and Zika viruses in mosquitoes, and measured Aedes indices in schools in Medellín (Colombia) between 2016-2018. In 43.27% of 2632 visits we collected Aedes adults, creating 883 pools analyzed by RT-PCR. 14.27% of pools yielded positive for dengue or Zika (infection rates of 1.75-296.29 for Aedes aegypti). Ae. aegypti was more abundant and had a higher infection rate for all studied diseases. Aedes indices varied over time. There was no association between Aedes abundance and mosquito infection rates, but the latter did correlate with cases of arboviral disease and climate. Results suggest schools are important sources of arbovirus and health agencies should include these sites in surveillance programs; it is essential to know the source for arboviral diseases transmission and the identification of the most population groups exposed to these diseases to research and developing new strategies.

Transcriptome of the Aedes aegypti Mosquito in Response to Human Complement Proteins.

Aedes aegypti is the primary mosquito vector of several human arboviruses, including the dengue virus (DENV). Vector control is the principal intervention to decrease the transmission of these viruses. The characterization of molecules involved in the mosquito physiological responses to blood-feeding may help identify novel targets useful in designing effective control strategies. In this study, we evaluated the in vivo effect of feeding adult female mosquitoes with human red blood cells reconstituted with either heat-inactivated (IB) or normal plasma (NB). The RNA-seq based transcript expression of IB and NB mosquitoes was compared against sugar-fed (SF) mosquitoes. In in vitro experiments, we treated Aag2 cells with a recombinant version of complement proteins (hC3 or hC5a) and compared transcript expression to untreated control cells after 24 h. The transcript expression analysis revealed that human complement proteins modulate approximately 2300 transcripts involved in multiple biological functions, including immunity. We also found 161 upregulated and 168 downregulated transcripts differentially expressed when human complement protein C3 (hC3) and human complement protein C5a (hC5a) treated cells were compared to the control untreated cells. We conclude that active human complement induces significant changes to the transcriptome of Ae. aegypti mosquitoes, which may influence the physiology of these arthropods.

Surveillance of Zika virus in field-caught Aedes aegypti and Aedes albopictus suggests important role of male mosquitoes in viral populations maintenance in Medellín, Colombia.

Due to the rapid spread of Zika virus (ZIKV) infection after its emergence in the Americas in 2015 and its relationship with birth defects, it became declared a Public Health Emergency of International Concern (WHO). The main mechanism by which this virus circulates in nature is horizontal transmission between vectors and humans. However, it has been suggested that vertical transmission (parent to offspring infection) or venereal mosquito-mosquito transmission may have an important role in viral populations maintenance during inter-epidemic periods. In this study we evaluate the presence of ZIKV in males and females of Aedes aegypti and Ae. albopictus in Medellín, Colombia, throughout the post-epidemic period of 2017 and 2018. A total of 7986 mosquitoes Aedes sp. resting within houses were captured and grouped in 2768 pools; 146 of these were RT-PCR positive for ZIKV, of which 38 (26%) were male mosquito pools (36 of Ae. aegypti and 2 of Ae. albopictus). The partial NS5 gene was sequenced in all ZIKV PCR-positive pools to confirm the ZIKV presence throughout spatial and temporal sampling. The results suggest a vector role of ZIKV by Ae. Albopictus; and because it is well known that male mosquitoes are not hematophagous, the high rate detection of ZIKV in male Aedes mosquitoes pools supports the existence of vertical or venereal transmission in Medellín, which can contribute to ZIKV maintenance during low transmission periods. This study provides a better understanding of the population dynamics of ZIKV in an endemic region during an inter-epidemic period and supports alternative transmission pathways as a mechanism to maintain endemism of this arbovirus.

Natural infection of Aedes aegypti, Ae. albopictus and Culex spp. with Zika virus in Medellin, Colombia / Infección natural de Aedes aegypti, Ae. albopictus y Culex spp. con virus Zika en Medellín, Colombia

Abstract Introduction: The Zika virus has generated serious epidemics in the different countries where it has been reported and Colombia has not been the exception. Although in these epidemics Aedes aegypti traditionally has been the primary vector, other species could also be involved in the transmission. Methods: Mosquitoes were captured with entomological aspirators on a monthly ba sis between March and September of 2017, in four houses around each of the 250 entomological surveillance traps installed by the Secretaria de Sa lud de Medellin (Colombia). Additionally, 70 Educational Institutions and 30 Health Centers were visited each month. Results: 2 504 mosquitoes were captured and grouped into 1045 pools to be analyzed by RT-PCR for the detection of Zika virus. Twenty-six pools of Aedes aegypti, two pools of Ae. albopictus and one for Culex quinquefasciatus were positive for Zika virus. Conclusion: The presence of this virus in the three species and the abundance of these species in the different sectors of the city, suggests that the control strategies should be addressed to all species that could be potential vec tors until the vectorial role of Ae. albopictus and Culex quinquefasciatus is completely elucidated in the transmission of the Zika virus.

Resumen Introducción: El virus Zika ha generado serias epidemias en los diferentes países en donde se ha reportado, Colombia no ha sido la excepción. Aunque en estas epidemias el vector presuntamente involucrado ha sido Aedes aegypti, otras especies también podrían estar implicadas en su transmisión. Meto dología: en el marco del Programa de vigilancia virológica en mosquitos de la Secretaría de Salud de Medellín (Colombia). Resultados: entre marzo y septiembre de 2017 se capturaron 2 504 mosquitos en predios visitados durante los levantamientos de índices entomológicos. El material entomo lógico fue agrupado en 1 045 pooles para ser analizados por RT-PCR para la detección de virus Zika. Resultaron positivos para virus Zika 26 pooles de Aedes aegypti, dos pooles de Ae. albopictus y uno para Culex quinquefasciatus. Conclusión: la presencia de este virus en las tres especies y su abundancia en los distintos sectores de la ciudad sugieren que las estrategias de control deban dirigirse a todos los potenciales vectores, hasta tanto no se dilucide comple tamente el papel vectorial de Ae. albopictus y Cx. quinquefasciatus en la transmisión del virus Zika.

A new approach to improve acoustic trapping effectiveness for Aedes aegypti (Diptera: Culicidae).

Monitoring mosquito populations is essential to designing and implementing control strategies. Recent strategies based on releasing biologically modified mosquitoes have increased the need to effectively monitor mosquito abundance. Unfortunately, existing surveillance traps are of limited value due to their high cost and low capture rates. Here, we report the results of experiments designed to evaluate the effectiveness of an acoustic trap prototype. Stimuli synthesized from recordings of Ae. aegypti wingbeat signals and pure tones were evaluated as attractants to males in indoor and semi-field conditions. Overall, the acoustic trap´s efficacy differed significantly between indoor and semi-field conditions. After two hours of indoor recapture, ∼69% of males were collected from acoustic traps broadcasting pure tones while ∼78% of males were collected using synthesized wingbeat signals. Under semi-field conditions, however, acoustic traps collected less than ∼1.7% of the males released. Increasing the intensity of the signals up to 90 dB (SPL re. 20 uPa at 1 m from the trap) did not improve the capture rate under semi-field conditions. Overall, our results indicate that acoustic signals synthesized from recordings of wingbeats can be used to enhance capture of male Ae. aegypti.

Barriers that limit the implementation of thermal fogging for the control of dengue in Colombia: a study of mixed methods.

BACKGROUND: Thermal fogging of Insecticides is a vector control strategy used by the Medellin Secretary of Health to combat dengue. This method is employed during outbreaks to curb populations of potentially infectious adult mosquitoes and interrupt transmission cycles. While this strategy has been used in Medellin since 2007, in some years it has not reduced dengue cases as expected. Difficulties in the implementation of fumigation strategies, such as lack of opportunity for treatment and public perception may be factors that limit its utility. The objective of this study was to identify barriers that hinder the implementation of thermal fogging, as well as attitudes and beliefs that prevent its acceptance. METHODS: We used a cross-sectional observational study of mixed methods carried out in neighborhoods prioritized for fumigation treatment in Medellin, Colombia. First, we assessed the timeliness of treatment by determining the latency period between reported dengue cases and the implementation of fumigation in response to those cases. Next, we administered structured questionnaires to residents in the area of fumigation treatments (n = 4455 homes) to quantify acceptance and rejection, as well as factors associated with rejection. RESULTS: The median time between notification and treatment was 25 days (IQR 20.0-36.5). Fumigators were only able to treat 53.7% of total households scheduled for treatment; 9.6% rejected treatment, and treatment teams were unable to fumigate the remaining 36.7% of homes due to absent residents, no adults being present, and other reasons. The most frequent causes for rejection were residents being busy at the time of treatment (33.1%) and no interest in the treatment (24.5%). Other reasons for rejection include the perceptions that fumigation does not control pests other than mosquitoes (4.3%), that no mosquitoes were present in the home (3.3%), and that fumigation affects human health (3.1%). CONCLUSIONS: The high percentage of houses where it was not possible to perform fumigation limits control of the vector. Future strategies should consider more flexible treatment schedules and incorporate informational messages to educate residents about the safety and importance of treatment.

[Knowledge of malaria and long-lasting insecticidal net use practices in two departments of colombia]. / Conocimientos sobre malaria y prácticas de uso de mosquiteros insecticidas de larga duración en dos departamentos de Colombia.

OBJECTIVES: To determine the knowledge about malaria and use practice of insecticide-treated mosquito nets in the departments of Antioquia and Chocó in Colombia, 2013. MATERIALS AND METHODS: Cross-sectional and descriptive study with probability sampling of clusters, stratified and two-staged. The head of household survey was developed using ten questions on knowledge, transmission, symptoms and preventive measures against malaria, used in the questionnaires of the 2007 National Health Survey in Colombia, as well as 13 questions on long-lasting insecticidal nets, tenure, use, reasons for non-use, short-term health side effects, washing and drying. RESULTS: 2078 residents responded to the survey. 89% (95% CI: 87.5-89.9) in Antioquia and 94% (95% CI: 93.0-94.0) in Chocó recognized the causes, symptoms, treatment and prevention methods. In Antioquia, 86% (95% CI: 84.9-87.3) had at least one mosquito net and 72% (95% CI: 70.0-73.4) used it daily; and for the department of Chocó, it was 93% (95% CI: 92.2-94.4) and 73% (95% CI: 72.0-74.4), respectively. CONCLUSIONS: There are high levels of knowledge about malaria; however, the care of the mosquito nets does not follow the recommendations to increase their useful life, therefore, specific social strategies are required for each department.

Objetivos. Determinar los conocimientos sobre malaria y prácticas del uso de mosquiteros tratados con insecticidas en los departamentos de Antioquia y Chocó en Colombia, 2013. Materiales y métodos. Estudio transversal y descriptivo con muestreo probabilístico de conglomerados, estratificado y bietápico. La encuesta dirigida a jefes de hogar se elaboró usando diez preguntas sobre conocimientos, transmisión, síntomas y medidas preventivas contra la malaria, utilizado en los cuestionarios de la Encuesta Nacional de Salud en Colombia 2007, e involucrando 13 preguntas sobre los mosquiteros insecticidas de larga duración (MILD), tenencia, uso, motivos de no uso, efectos secundarios sobre la salud a corto plazo, lavado y secado. Resultados. 2078 residentes respondieron la encuesta. El 89% (IC 95%: 87,5-89,9) en Antioquia y el 94% (IC 95%: 93,0-94,0) en Chocó reconoce las causas, síntomas, tratamiento y métodos de prevención. En Antioquia el 86% (IC 95%: 84,9-87,3) tuvo al menos un mosquitero y 72% (IC 95%: 70,0-73,4) lo usó diariamente, y para el departamento de Chocó fue de 93% (IC 95%: 92,2-94,4) y 73% (IC 95%: 72,0-74,4) respectivamente. Conclusiones. Hay altos niveles de conocimiento sobre malaria; sin embargo, el cuidado de los mosquiteros no está de acuerdo a lo recomendado para aumentar su vida útil, por lo tanto, se requieren estrategias sociales propias para cada departamento.

Knowledge, practices and entomological aspects of dengue in Medellín, Colombia: A comparative study of neighborhoods with high and low incidence

Introduction: Dengue, mainly transmitted by Aedes aegypti, is a very important viral disease in terms of public health. Colombia is an endemoepidemic country for dengue and, in cities like Medellín, there are neighborhoods with high and low incidence. The disease dynamics in the neighborhoods might be determined by differences in the knowledge, practices and entomological aspects of the vector among the communities. Objective: To identify the knowledge and practices of residents of neighborhoods with high and low incidence of dengue, and to explore the entomological aspects related to the presence of the vector. Materials and methods: We conducted a cross-sectional study comparing two neighborhoods with high incidence and two with low incidence during the triennium of 2013-2015. A random sample of 100 houses per neighborhood was selected in order to evaluate the knowledge, practices and entomological aspects related to dengue. In addition, descriptive, bivariate and multivariate analyses (logistic regression) were performed. Results: In neighborhoods with high incidence, participants had not attended school or had only a primary school level of education (OR=1.69; 95% CI: 1.09-2.63). Additionally, they did not have health coverage or belonged to the subsidized regime (OR=2.16; 95% CI: 1.41-3.32). In contrast, they had a greater knowledge of the vector (OR=1.53; 95% CI: 1.00-2.35). In terms of practices, there was a greater chance of finding houses where water was stored (OR=1.69; 95% CI: 1.11-2.57) and regarding the entomological aspects, more houses with adult mosquitoes were found (OR=2.13 95% CI: 1.29-3.50). Conclusions: We found important differences among the neighborhoods regarding knowledge, practices, and the presence of adult stages of the vector, which helps to explain the epidemiology of dengue in these sites.

Conocimientos sobre malaria y prácticas de uso de mosquiteros insecticidas de larga duración en dos departamentos de Colombia / Knowledge of malaria and long-lasting insecticidal net use practices in two departments of colombia

RESUMEN Objetivos. Determinar los conocimientos sobre malaria y prácticas del uso de mosquiteros tratados con insecticidas en los departamentos de Antioquia y Chocó en Colombia, 2013. Materiales y métodos. Estudio transversal y descriptivo con muestreo probabilístico de conglomerados, estratificado y bietápico. La encuesta dirigida a jefes de hogar se elaboró usando diez preguntas sobre conocimientos, transmisión, síntomas y medidas preventivas contra la malaria, utilizado en los cuestionarios de la Encuesta Nacional de Salud en Colombia 2007, e involucrando 13 preguntas sobre los mosquiteros insecticidas de larga duración (MILD), tenencia, uso, motivos de no uso, efectos secundarios sobre la salud a corto plazo, lavado y secado. Resultados. 2078 residentes respondieron la encuesta. El 89% (IC 95%: 87,5-89,9) en Antioquia y el 94% (IC 95%: 93,0-94,0) en Chocó reconoce las causas, síntomas, tratamiento y métodos de prevención. En Antioquia el 86% (IC 95%: 84,9-87,3) tuvo al menos un mosquitero y 72% (IC 95%: 70,0-73,4) lo usó diariamente, y para el departamento de Chocó fue de 93% (IC 95%: 92,2-94,4) y 73% (IC 95%: 72,0-74,4) respectivamente. Conclusiones. Hay altos niveles de conocimiento sobre malaria; sin embargo, el cuidado de los mosquiteros no está de acuerdo a lo recomendado para aumentar su vida útil, por lo tanto, se requieren estrategias sociales propias para cada departamento.

ABSTRACT Objectives. To determine the knowledge about malaria and use practice of insecticide-treated mosquito nets in the departments of Antioquia and Chocó in Colombia, 2013. Materials and Methods. Cross-sectional and descriptive study with probability sampling of clusters, stratified and two-staged. The head of household survey was developed using ten questions on knowledge, transmission, symptoms and preventive measures against malaria, used in the questionnaires of the 2007 National Health Survey in Colombia, as well as 13 questions on long-lasting insecticidal nets, tenure, use, reasons for non-use, short-term health side effects, washing and drying. Results. 2078 residents responded to the survey. 89% (95% CI: 87.5-89.9) in Antioquia and 94% (95% CI: 93.0-94.0) in Chocó recognized the causes, symptoms, treatment and prevention methods. In Antioquia, 86% (95% CI: 84.9-87.3) had at least one mosquito net and 72% (95% CI: 70.0-73.4) used it daily; and for the department of Chocó, it was 93% (95% CI: 92.2-94.4) and 73% (95% CI: 72.0-74.4), respectively. Conclusions. There are high levels of knowledge about malaria; however, the care of the mosquito nets does not follow the recommendations to increase their useful life, therefore, specific social strategies are required for each department.

Monitoring and Predicting Net Longevity by Measuring Surface Levels of Insecticide: Implementing a Faster, Cost Effective, Nondestructive, and Field-Ready Alternative to the World Health Organization Cone Test Bioassay.

An important component of malaria control programs is the ability to assess the effectiveness of the insecticide in insecticide-treated nets (ITNs) during normal usage. The standard technique to measure insecticidal activity is the World Health Organization (WHO) cone test, which in many circumstances, may be difficult to implement. We have evaluated an alternative technique, the colorimetric field test (CFT) on a group of 24-month-old Permanet® 2.0 (Vestergaard-Frandsen, Denmark) nets collected in Colombia. The CFT, which measures surface levels (SL) of deltamethrin is compared with standard high-performance liquid chromatography (HPLC) and the WHO cone test. Effective concentrations of deltamethrin for 80% mortality (EC80) were determined from the CFT and HPLC results. Distribution of insecticide SL after 24 months of use reveal that sampling of the midsection best represents the condition of the entire net. We conclude that the CFT is a practical alternative to the WHO cone test for assessing ITN efficacy.

Conocimientos, prácticas y aspectos entomológicos del dengue en Medellín, Colombia: un estudio comparativo entre barrios con alta y baja incidencia / Knowledge, practices and entomological aspects of dengue in Medellín, Colombia: A comparative study of neighborhoods with high and low incidence

Introducción. El dengue, transmitido principalmente por Aedes aegypti, es una enfermedad viral de gran importancia en salud pública. Colombia es un país endemoepidémico para el dengue y, en ciudades como Medellín, hay barrios con alta y baja incidencia. Las diferencias en cuanto a los conocimientos, las prácticas y los aspectos entomológicos podrían estar determinando la dinámica de la enfermedad en los barrios. Objetivo. Determinar los conocimientos y prácticas en torno al dengue de los habitantes de barrios con alta y baja incidencia y explorar los aspectos entomológicos relacionados con la presencia del vector. Materiales y métodos. Se hizo un estudio transversal y se compararon dos barrios con alta incidencia y dos con baja incidencia durante el trienio de 2013 a 2015. Se seleccionó una muestra aleatoria de 100 viviendas por barrio para evaluar los conocimientos, las prácticas y los aspectos entomológicos. Se hicieron el análisis descriptivo, el bivariado y el multivariado (regresión logística). Resultados. En los barrios con alta incidencia, los participantes se caracterizaron por no haber realizado estudios o haber cursado únicamente primaria (odds ratio, OR=1,69; IC95%=1,09-2,63), así como por pertenecer al régimen subsidiado del sistema de seguridad social en salud o no estar afiliado (OR=2,16; IC95% 1,41-3,32) y, además, presentaron un mayor conocimiento del vector (OR=1,53; IC95% 1,00-2,35). En cuanto a las prácticas, la posibilidad de encontrar viviendas en donde se almacenaba el agua fue mayor (OR=1,69; IC95% 1,11-2,57) y, en lo relacionado con los aspectos entomológicos, se encontraron más viviendas con mosquitos adultos (OR=2,13; IC95% 1,29-3,50). Conclusiones. En este estudio se encontraron diferencias importantes entre los barrios en cuanto a los conocimientos, las prácticas y la presencia de estados adultos del vector, lo cual contribuye a explicar la epidemiología del dengue en estos lugares.

Introduction: Dengue, mainly transmitted by Aedes aegypti, is a very important viral disease in terms of public health. Colombia is an endemoepidemic country for dengue and, in cities like Medellín, there are neighborhoods with high and low incidence. The disease dynamics in the neighborhoods might be determined by differences in the knowledge, practices and entomological aspects of the vector among the communities. Objective: To identify the knowledge and practices of residents of neighborhoods with high and low incidence of dengue, and to explore the entomological aspects related to the presence of the vector. Materials and methods: We conducted a cross-sectional study comparing two neighborhoods with high incidence and two with low incidence during the triennium of 2013-2015. A random sample of 100 houses per neighborhood was selected in order to evaluate the knowledge, practices and entomological aspects related to dengue. In addition, descriptive, bivariate and multivariate analyses (logistic regression) were performed. Results: In neighborhoods with high incidence, participants had not attended school or had only a primary school level of education (OR=1.69; 95% CI: 1.09-2.63). Additionally, they did not have health coverage or belonged to the subsidized regime (OR=2.16; 95% CI: 1.41-3.32). In contrast, they had a greater knowledge of the vector (OR=1.53; 95% CI: 1.00-2.35). In terms of practices, there was a greater chance of finding houses where water was stored (OR=1.69; 95% CI: 1.11-2.57) and regarding the entomological aspects, more houses with adult mosquitoes were found (OR=2.13 95% CI: 1.29-3.50). Conclusions: We found important differences among the neighborhoods regarding knowledge, practices, and the presence of adult stages of the vector, which helps to explain the epidemiology of dengue in these sites.

Mosquito (Diptera: Culicidae) grouping based on larval habitat characteristics in high mountain ecosystems of Antioquia, Colombia.

Information about mosquito ecology in the high mountain ecosystems of the Neotropical region is sparse. In general, few genera and species have been reported in these ecosystems and there is no information available on habitats and the mosquitoes occupying them. In the present study, specimens collected from NW Colombia in HME were grouped using larval habitat data via an Operational Taxonomic Unit (OTU) determination. A total of 719 mosquitoes was analyzed belonging to 44 OTUs. The analysis considered habitat features and clustered the specimens into six groups from A-F. Five of these included species from different genera, suggesting common habitat requirements. Group E with four genera, seven subgenera, and six species occupied the highest areas (above 3,000 m), whereas three groups (B, D, F) were detected at lower altitudes (1,960-2,002 m). Bromeliads were the most common larval habitat, with 47% (335/719) of the specimens; five genera, six subgenera, and eight species were identified and classified into 66% (29/44) of the OTUs. This work showed some similarities to the habitat requirements and provides a grouping system that constitutes an important baseline for the classification of mosquito fauna from high mountain ecosystems according to altitude and larval habitat.

Virological surveillance of Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus as support for decision making for dengue control in Medellín.

INTRODUCTION: Dengue represents an important public health problem in Colombia. No treatment is available and the vaccine has not been approved in all countries, hence, actions should be strengthened to mitigate its impact through the control of Aedes aegypti, the vector mosquito. In Colombia, surveillance is done using entomological indexes and case notification, which is usually informed late, leading to untimely interventions. Viral detection in urban mosquitoes using molecular techniques provides more accurate entomological information for decision-making. OBJECTIVE: To report results of virological surveillance in Aedes specimens collected during routine entomological activities of the Secretaría de Salud de Medellín. MATERIALS AND METHODS: Specimens were collected during two periods in each of which we selected 18 dwellings around each one of the 250 larva traps arranged for mosquitoe surveillance, as well as 70 educational institutions and 30 health centers. Specimens were identified morphologically, and divided in pools for viral detection using reverse transcription polymerase chain reaction (RT-PCR). We calculated the minimum infection rate and the adult infestation index for each group. RESULTS: We collected 1,507 adult mosquitoes, 10 of which were identified as A. albopictus. Out of the 407 pools, 132 (one of them Ae. albopictus) were positive, and 14.39% were A. aegypti males. The minimum infection rates for Ae. aegypti were 120.07 and 69,50 for the first and second periods, respectively, and the adult infestation index was higher in educational institutions (23.57%). CONCLUSIONS: Using RT-PCR we identified natural infectivity and vertical transmission of dengue virus in A. aegypti and A. albopictus. We suggest the use of molecular techniques in arbovirosis surveillance and control programs in Colombia.