Surveillance for Leishmania asymptomatic infection in endemic foci of cutaneous leishmaniasis in Venezuela: a combination of leishmanin skin test and PCR using blood clots improves detection and enables identification of species.

BACKGROUND: Little is known about the prevalence of asymptomatic leishmaniasis in Venezuela. The objective of this study was to quantify Leishmania asymptomatic infection in six endemic foci of cutaneous leishmaniasis (CL) in Portuguesa State, Venezuela, where no previous data were available. METHODS: Study of the prevalence of Leishmania asymptomatic infection was carried out in 841 individuals from six endemic foci of CL in the municipalities Sucre and Ospino, Portuguesa State. We applied the leishmanin skin test (LST) and the internal transcribed spacer 1 (ITS1) PCR to DNA from sera and blood clots of all LST-positive and 20% of LST-negative patients. RESULTS: Of 841 inhabitants tested by LST, 197 returned a positive reaction (23.42%); all of the LST-positives (197) and 121 negatives were screened by nested PCR using serum and blood clots. Among the LST-positive group, 2.54% were PCR-positive with sera, while 44.67% were positive with blood clots. In the LST-negative group, PCR was positive in 2.48% of serum samples and in 38.84% of blood clots. CONCLUSIONS: It is recommended that LST and PCR on blood clots are used together to detect exposure and asymptomatic infection and for identification of the Leishmania species.

Vital Statistics of Triatominae (Hemiptera: Reduviidae) Under Laboratory Conditions: IV. Panstrongylus geniculatus.

A cohort of 100 eggs of Panstrongylus geniculatus (Latreille) was reared in the laboratory under constant conditions (temperature 26 ± 1°C, 60 ± 10% RH), with mortality and fecundity data recorded weekly. We calculated stage-specific development times, age-specific mortality and fecundity (18.4 eggs/♀/wk), and stage-specific and total preadult mortality (31.6%), and the weekly intrinsic rate of natural increase (r(o) = 0.096), the finite population growth rate (λ = 1.109), the net reproductive rate (R(0) = 60.45), and the generation time (T = 46.34 wk). Elasticity analysis showed that the dominant life-history trait determining λ was survival (particularly the adult female's survival). Adult females dominated the stage-specific reproductive value, and the egg stage dominated the stable stage distribution (SSD). The damping ratio (ρ = 1.096) suggests a relatively rapid period of recovery to a disturbed SSD. Results were compared with one previous study and conform relatively well, considering that environmental conditions were not the same. We estimated the colonizing ability of P. geniculatus, using as a criterion the ro/b index, and obtained the value of 0.74, an indicator of a good colonizer, and similar to well-known invasive species such as Rhodnius prolixus and Triatoma infestans. The life history traits and demographic parameters here presented for P. geniculatus are discussed in terms of their usefulness for evolutionary studies and vector control activities.

Genetic and Morphometric Variability of Triatoma sordida (Hemiptera: Reduviidae) from the Eastern and Western Regions of Paraguay.

Triatoma sordida is widely distributed throughout the Chaco and the Eastern Region of Paraguay. It is associated to palm trees and artificial ecotopes located in peridomestic environments. The aim of this work was to determine genetic and morphometric variability and feeding behavior among population of T. sordida captured in domicile and peridomicile areas of Paraguay. Feeding contents and levels of genetic and morphometric variation were determined in 124 T. sordida from domicile and peridomicile populations of San Pedro and Paraguarí departments of the Eastern Region and Boquerón and Presidente Hayes departments of the Western region using Double Diffusion Gel, random amplified polymorphic DNA (RAPD), and head and wings morphometry. Morphometric analysis revealed isolation of populations by geographic region and larger size in triatomine populations from the Western Region. RAPD showed no specific patterns for domicile and peridomicile populations. The estimator of diversity (F ST; 0.08) and high gene flow obtained (N m; 5.7) did not allow the establishment of genetic differentiation within the same region. The blood meal source showed that poultry feeding was 38% of host preferences, and human blood was the second feeding preference (24%) in the insects from the Eastern Region while poultry feeding was predominant in those from the Western Region (30%). This work showed homogeneity between T. sordida populations of the same region and between domicile and peridomicile. The genetic diversity was determined among T. sordida populations of both geographical regions suggesting differentiation associated to eco-geographical isolation by distance. It is important to notice that pattern feedings were different between the two regions. Further studies should be focused on how phenetic and genetic variations could be related to the adaptation capacity of these triatomine populations to domicile, increasing their vector potentiality in the transmission of Chagas disease.

Leishmaniasis en Venezuela: Situación actual, acciones y perspectivas para el control vectorial en el marco de un programa de control multisectorial / Leishmaniasis in Venezuela: Current status, actions and prospects for vector control in the context of a multi-sectorial control program

El Programa de Control de Leishmaniasis en Venezuela, a cargo del Servicio Autónomo Instituto de Biomedicina (IB) del Ministerio del Poder Popular para la Salud (MPPS), ha sido reforzado en los últimos años a través del fortalecimiento de la asistencia médica, en especial la consolidación de la base diagnóstica y una mayor interacción con los Servicios de Zoonosis para la LV. Sin embargo, indicadores entomológicos y epidemiológicos de la dispersión y en algunos casos urbanización, de la leishmaniasis cutánea (LC) y visceral (LV) han resaltado la necesidad del control antivectorial para un abordaje sistémico y transdisciplinario de este problema de salud, en el marco de la protección ambiental. Se presenta en este documento una revisión de los datos epidemiológicos, de los conocimientos sobre las especies de flebótomos incriminadas en la transmisión, su respuesta a los insecticidas y los ensayos de control conducidos en el país. Como perspectiva factible a corto plazo se propone un programa multisectorial en el cual concurran en primera instancia el IB, la Dirección General de Salud Ambiental (DGSA) y el Sector Educativo en una acción concertada para el control de leishmaniasis y Enfermedad de Chagas y leishmaniasis-malaria en áreas de co-endemicidad. Se hace especial énfasis en la necesidad de buenos programas educativos de salud que deben aplicarse antes de la selección de las medidas de control, de acuerdo a las características epidemiológicas y socio-culturales de la zona. Es importante tener en cuenta los conocimientos, actitudes y prácticas (CAP) de la población de riesgo con el fin de promover la aceptación del programa y de la participación comunitaria en la prevención de estas "enfermedades desatendidas", a través de la gestión ambiental y la protección personal. Sobre la base de estas premisas, estas acciones de lucha integrada, concertadas en un programa multisectorial, en el marco del enfoque Ecosalud conducirían hacia la optimización de los recursos y la sostenibilidad del programa en sí.

The Leishmaniasis Control Program in Venezuela, directed by the Institute of Biomedicine (IB) of the Ministry of Popular Power for Health (MPPH) has been strengthened in recent years by the improvement of health care, especially with regard to the establishment of diagnostic procedures and for Visceral Leishmaniasis (VL), tighter relations with the Zoonosis Department of the MPPH. However, entomological and epidemiological indicators of the dispersion, and in some cases urbanization, of cutaneous and visceral leishmaniasis (CL and VL, respectively) have highlighted the need for vector control in order to approach this health problem from a transdisciplinary systemic perspective in the context of environmental protection. We present a review of epidemiological data, our knowledge about the species of phlebotomine sand flies incriminated in transmission, and their response to insecticides and control assays undertaken in Venezuela. A multisectorial program managed between the Institute of Biomedicine (MPPH), the General Directorate of Environmental Health (GDEH) (MPPH) and the Education Sector (MPPE) for the control of leishmaniasis-Chagas disease and leishmaniasis-malaria in co-endemic areas, has been proposed as a feasible short term strategy. The need for high quality health education programs implemented according to the epidemiological and socio-cultural features of the regions, before control measures are selected, is also emphasized. It is important to take into account the knowledge, attitudes and practices (KAP) of the population at risk in order to a) ensure acceptance of the program and b) promote community participation, through environmental management and personal protection, for the prevention of these "neglected diseases". Based on this approach, these integrated control actions within a multi-sectorial program would lead towards the optimization of resources and the sustainability of the program itself.

Geographical distribution of Trypanosoma cruzi genotypes in Venezuela.

Chagas disease is an endemic zoonosis native to the Americas and is caused by the kinetoplastid protozoan parasite Trypanosoma cruzi. The parasite is also highly genetically diverse, with six discrete typing units (DTUs) reported TcI - TcVI. These DTUs broadly correlate with several epidemiogical, ecological and pathological features of Chagas disease. In this manuscript we report the most comprehensive evaluation to date of the genetic diversity of T. cruzi in Venezuela. The dataset includes 778 samples collected and genotyped over the last twelve years from multiple hosts and vectors, including nine wild and domestic mammalian host species, and seven species of triatomine bug, as well as from human sources. Most isolates (732) can be assigned to the TcI clade (94.1%); 24 to the TcIV group (3.1%) and 22 to TcIII (2.8%). Importantly, among the 95 isolates genotyped from human disease cases, 79% belonged to TcI - a DTU common in the Americas, however, 21% belonged to TcIV- a little known genotype previously thought to be rare in humans. Furthermore, were able to assign multiple oral Chagas diseases cases to TcI in the area around the capital, Caracas. We discuss our findings in the context of T. cruzi DTU distributions elsewhere in the Americas, and evaluate the impact they have on the future of Chagas disease control in Venezuela.

Comparative microsatellite typing of new world leishmania infantum reveals low heterogeneity among populations and its recent old world origin.

Leishmania infantum (syn. L. chagasi) is the causative agent of visceral leishmaniasis (VL) in the New World (NW) with endemic regions extending from southern USA to northern Argentina. The two hypotheses about the origin of VL in the NW suggest (1) recent importation of L. infantum from the Old World (OW), or (2) an indigenous origin and a distinct taxonomic rank for the NW parasite. Multilocus microsatellite typing was applied in a survey of 98 L. infantum isolates from different NW foci. The microsatellite profiles obtained were compared to those of 308 L. infantum and 20 L. donovani strains from OW countries previously assigned to well-defined populations. Two main populations were identified for both NW and OW L. infantum. Most of the NW strains belonged to population 1, which corresponded to the OW MON-1 population. However, the NW population was much more homogeneous. A second, more heterogeneous, population comprised most Caribbean strains and corresponded to the OW non-MON-1 population. All Brazilian L. infantum strains belonged to population 1, although they represented 61% of the sample and originated from 9 states. Population analysis including the OW L. infantum populations indicated that the NW strains were more similar to MON-1 and non-MON-1 sub-populations of L. infantum from southwest Europe, than to any other OW sub-population. Moreover, similarity between NW and Southwest European L. infantum was higher than between OW L. infantum from distinct parts of the Mediterranean region, Middle East and Central Asia. No correlation was found between NW L. infantum genotypes and clinical picture or host background. This study represents the first continent-wide analysis of NW L. infantum population structure. It confirmed that the agent of VL in the NW is L. infantum and that the parasite has been recently imported multiple times to the NW from southwest Europe.

Ciencia, tecnología y acción sanitaria a través de los 50 años del Boletín de Malariología y Salud Ambiental / Science, technology and health action trough the 50 years of the Boletín de Malariología y Salud Ambiental

El Boletín de Malariología y Salud Ambiental es una de las revistas más antiguas de Venezuela en el área de la Salud Pública. Durante 50 años de publicación ininterrumpida, sus páginas reflejan la ciencia, tecnología y acción sanitaria, que han contribuido a la prevención y control de las parasitosis y arbovirosis de mayor impacto en la población venezolana. Se reseñan autores y acontecimientos, que en las diferentes décadas han incidido en el devenir de esta revista. En los últimos años, su especificidad, pertinencia social y calidad científica la han hecho acreedora de inclusión en importantes índices internacionales, como Global Health, SciELO Venezuela y el WEB Science Citation Index ExpandedTM 2010. Por ende, gracias a la moderna tecnología de la comunicación, esta revista ha logrado una mayor participación a nivel ibero-americano y mayor visibilidad internacional. Dentro de este marco, se aprecia un renovado apoyo de la comunidad científica venezolana y del órgano patrocinador, Instituto de Altos Estudios "Dr. Arnoldo Gabaldon", en pro del Boletín de Malariología y Salud Ambiental, revista que ha contribuido a poner al alcance de todo el mundo, un importante acervo científico venezolano, de alto compromiso social en el ámbito de la Salud Pública.

The Boletín de Malariología y Salud Ambiental is one of Venezuela’s oldest journals in the area of Public Health. During 50 years of uninterrupted publication, its pages reflect the science, technology and environmental sanitation that have contributed to the prevention and control of parasitic and arborviral diseases with a greatest impact on the Venezuelan population. Authors and events are outlined, which, over the decades, have influenced the evolution of this journal. In recent years, high specificity, social relevance and scientific quality have earned its inclusion in major indexes such as Global Health, SciELO Venezuela and the WEB Science Citation Index ExpandedTM 2010. Thus, thanks to the modern communication technology, this magazine has achieved a greater participation of the Ibero-American scientists and wider visibility. Within this framework, we see a renewed support of the Venezuelan scientific community and its sponsor, the "Instituto de Altos Estudios Dr. Arnoldo Gabaldon" with the Boletin de Malariología y Salud Ambiental magazine, that has contributed to making available worldwide, a major Venezuelan scientific heritage, with high social commitment in the field of Public Health!.

Control de la enfermedad de chagas en Venezuela: Logros pasados y retos presentes / Chagas disease control program in Venezuela: Past successes and current challenges / Control da doença de chagas na Venezuela: Sucessos passados e actuais desafios

La Enfermedad de Chagas es una "enfermedad desatendida" que afecta a millones de personas en América Latina. En este trabajo se hace una revisión de los logros pasados y retos actuales del Programa de Control de la Enfermedad de Chagas (PCECh) en Venezuela, presentándose resultados de investigaciones recientes. Implementado en la década de 1960 con el objetivo de interrumpir la transmisión intradoméstica mantenida por Rhodnius prolixus, el PCECh se basó en el uso en gran escala de insecticidas de acción residual, la implementación del Programa de Vivienda Rural y el Programa de Mejoramiento de la Vivienda Campesina (MIVICA), y la introducción del examen rutinario de Trypanosoma cruzi utilizando la técnica de ELISA en los bancos de sangre. Tras cuatro décadas se ha logrado una reducción drástica del índice de prevalencia de la infección a nivel nacional de 44,5% a 8,9%. Sin embargo, la presión de la reinfestación por R. prolixus selváticos y la tendencia a la domiciliación de especies silvestres como Panstrongylus geniculatus han dado lugar a nuevos escenarios epidemiológicos que plantean nuevos retos. Frente a estas situaciones, es imperiosa la necesidad de reorientar sobre bases científicas las acciones de monitoreo, prevención y control. Mejorar la atención médica al paciente chagásico e incrementar los esfuerzos para incorporar la participación comunitaria a la vigilancia entomológica, aspectos no abordados en el pasado, deben ser además considerados como una prioridad urgente dentro de una política integral del PCECh en Venezuela.

Chagas disease is a "neglected disease" affecting millions of people in Latin America. A review is made of the past successes and current challenges of the Chagas disease Control Program in Venezuela (PCECh), and results of recent research are presented. Officially implemented in the decade of 1960 with the aim of interrupting the intra-domestic transmission maintained by Rhodnius prolixus, the PCECh was mainly based on the large-scale use of insecticide spraying, the construction or improving of rural houses and the introduction of routine screening in public hospital blood banks for Trypanosoma cruzi using the ELISA test. After four decades, a drastic reduction of the prevalence of infection from 44.5% to 8.9% has been achieved. However, the pressure of house re-infestation by sylvan R. prolixus, and trends of domestication of other sylvan species, such as Panstrongylus geniculatus, have given rise to new epidemiological scenarios that pose new challenges. Because of this situation, re-examining how best to target monitoring and control efforts on scientific bases is of great urgency. Additionally, efforts to improve health education and community participation for a more efficient epidemiological surveillance as well as medical attention to Chagas patients, not undertaken in the past, are currently considered as a new and urgent priority of a comprehensive Chagas disease Control Program policy in Venezuela.

A doença de Chagas é uma "doença negligenciada" que afecta milhões de pessõas na América Latina e na Venezuela. Neste trabalho faz-se uma revisão dos sucessos do passado e os desafios actuais do Programa de Controlo da Doença de Chagas na Venezuela (PCECh). Mais ainda, apresentam-se resultados de investigações recentes. Este programa foi implementado oficialmente em 1960, com o objectivo de interromper a transmissão intra-doméstica mantida por Rhodnius prolixus, baseou-se principalmente no uso em grande escala de insecticidas de acção residual, construção ou melhoramento das habitações rurais e introdução em todos os bancos de sangue dos Hospitais públicos como rotina, a pesquisa da infecção por Trypanosoma cruzi utilizando a técnica de ELISA. Quarenta anos depois do início do PCECh, obteve-se uma redução drástica da prevalência da infecção de 44,5% para 8,9%. Contudo, a pressão da re-infestação por R. prolixus silváticos e a tendência para a domiciliação de outras espécies silvestres, como Panstrongylus geniculatus, levaram ao aparecimento de novos cenários epidemiológicos. Analisar novamente como melhor dirigir sobre bases científicas, as acções de monitorização e controlo es agora uma prioridade. Também devem-se estimular os esforços para melhorar a educação para a saúde e a participação comunitária para uma vigilância epidemiológica mais eficiente. Mas, a atenção médica integrada ao paciente chagásica não abordada no passado, es agora considerada como uma necessidade urgente dentro de uma política integral do Programa de Controlo da Doença de Chagas.

On the genus Panstrongylus Berg 1879: evolution, ecology and epidemiological significance.

The genus Panstrongylus is currently composed of 13 species, several of which are involved in the transmission of Trypanosoma cruzi to humans in South and Central America. Some species exhibit minor morphological differences possibly associated with adaptation to different silvatic ecotopes or domestic environments. We present a distillation of past and recent literature pertaining to the biology of this group. In particular, we summarise the current status of the genus according to systematic and recent phylogenetic studies. In light of recent evidence suggesting polyphyly/paraphyly of the genus we have investigated the possible mechanisms of morphological convergence/divergence. By assessing postembryonic ontogeny we reveal that the distinctive head shape of Panstrongylus can be derived from a Triatoma-like head late in development. A comprehensive phylogenetic study is therefore required to elucidate their relationship with Triatoma spp., and other genera of the tribe Triatomini. We also present a comparative summary of biology, ecology and epidemiological significance for each species in the genus. This reveals that knowledge of many species is fragmentary or lacking. This is mainly due to the fact that, except for few species with synanthropic traits (P. megistus and P. lignarius [formerly P. herreri]), important vectors of Chagas disease in Brazil and Peru, the majority are sylvatic species, associated with a wide variety of habitats and wild animals (many of them reservoirs of Trypanosoma cruzi). However, trends to invade human dwellings and to establish domestic colonies have been observed in several species in the genus (P. geniculatus, P. rufotuberculatus, P. lutzi, P. chinai), while others are opportunistic species (e.g. P. lignarius in the Amazon basin flying from wild ecotopes to houses on occasion without colonizing). Nevertheless, they can play some role in the transmission of sylvatic T. cruzi to humans. Research on the genus Panstrongylus requires some focus on investigating the natural ecology of these species. This knowledge would add to our understanding of their evolutionary potential and may assist in predicting new epidemiological scenarios, for which new control strategies need to be devised.

Risk factors for Trypanosoma cruzi human infection in Barinas State, Venezuela.

This study attempted to quantify the transmission of Trypanosoma cruzi in children less than 15 years of age in Barinas State, Venezuela and investigate risk factors for infection. Among 3,296 children, 4 (0.12%) were seropositive. The mother of one child also was also seropositive, which suggested that congenital transmission is a possible risk factor for Chagas disease in this area. Seroprevalence among the dwellers of 10 localities was 3.3%. Rhodnius prolixus was detected in 7 localities and in 8% of 125 dwellings. A multivariate logistic regression model showed that infection was associated with age, a dirt floor, and distance from houses to palm trees. The risk of infection is increased by the presence of adventitious sylvatic R. prolixus and transient or residual colonies. Insecticide spraying does not seem justified in this scenario, a finding that was also observed in other Latin American countries. New methods are therefore needed for Chagas disease control programs.

Morphometric evidence for a possible role of Rhodnius prolixus from palm trees in house re-infestation in the State of Barinas (Venezuela).

The main vector of Chagas disease in Venezuela is Rhodnius prolixus. Specimens of Rhodnius sp., identified elsewhere as R. prolixus by molecular tools, were collected in Barinas State (Venezuela) before insecticide application, and compared by morphometric techniques with post-spraying, re-infesting insects after control. Geometric morphometry was applied, allowing separate analyses of shape and size. The idea of a single species sharing silvatic and domestic/peri-domestic ecotopes was supported, suggesting new evolutionary scenarios for the controversial R. prolixus origins. The same data allowed to understand the possible mechanisms of villages re-infestation after a control campaign, either recolonization by local recovery of survivors or re-infestation by external migrants. Both mechanisms were apparent. Although shape properties could distinguish very close subpopulations such as insects from houses and insects from peri-domestic shelters, they were unable to identify the insects from palm trees as a distinct subpopulation. This strongly suggested that human environment could receive immigrants from palm trees. The pattern of size variation supported the hypothesis of a one-way exchange from silvatic to human environments, but did not support the reverse movement. Thus, morphometric data indicated that a silvatic population of the local vector is probably responsible for re-infesting villages after insecticide application, and they also pointed to the existence of re-infestation by local recovery of survivors. According to this interpretation, new epidemiological scenarios must be considered to improve Chagas disease control in Venezuela.

Esculpido exocoriónico del huevo de dos poblaciones de Lutzomyia longipalpis s.l. (Diptera: Psychodidae) de Venezuela / Chorionic sculpturing in eggshells from two populations of Lutzomyia longipalpis (Diptera: Psychodidae) from Venezuela

Estudios de los patrones del exocorión en insectos, utilizando microscopia electrónica de barrido (MEB), refieren que las diferencias entre éstos son marcadores taxonómicos útiles para separar especies relacionadas. En el presente trabajo se examinó el patrón del exocorión del huevo de dos poblaciones venezolanas de Lutzomyia longipalpis s.l., principal vector de la leishmaniasis visceral americana, una procedente del Estado Trujillo y la otra del Estado Guárico. El esculpido del exocorión del material estudiado estuvo caracterizado por un patrón de crestas paralelas, pero el huevo de la población de Trujillo presentó irregularidades y crestas conectadas, mientras que en la población del Guárico, las crestas son más regulares y no se observaron conexiones. Siendo L. longipalpis un complejo de especies, es necesario realizar estudios comparativos con otras poblaciones del complejo de diferentes paises neotropicales, incluyendo Lutzomyia pseudolongipalpis, la primera especie descrita en el complejo, para tratar de dilucidar el significado de estas diferencias y su utilidad como herramienta taxonómica para este complejo.

Leishmania and sand flies: proximity to woodland as a risk factor for infection in a rural focus of visceral leishmaniasis in west central Venezuela.

OBJECTIVE: To relate entomological, epidemiological and geographical data to understand the transmission dynamics of visceral leishmaniasis (VL) in a closed focus in western Venezuela. METHODS: Spatial and temporal patterns of Lutzomyia pseudolongipalpis, the most prevalent phlebotomine sand fly species (99.7%), were studied in El Brasilar, Curarigua, Lara State, Venezuela, a small rural community of 20 dwellings and 118 inhabitants. The sand fly population was monitored using Centers for Disease Control light traps monthly throughout 1 year in the domestic and sylvatic habitats and for 3 months in all inhabited houses. RESULTS: Temporal variation followed the yearly bimodal pattern of precipitation with the highest population densities in April and December. Infection with flagellates suggestive of Leishmania spp. was detected in 0.01% of 10,026 dissected females of L. pseudolongipalpis, which proved to be highly endophilic. Prevalence of Leishmania infection in people, as measured by the leishmanin skin test, was correlated with distance of the houses from the woodland and with sand fly abundance. A logistic regression model showed that for people who live in the village, the proximity to the woodland (linear) should be considered a risk factor for Leishmania infection (binary) (z = -2.02, P = 0.04, OR = 0.98, 95% CI = 0.97-0.99). This was consistent with the association between the proportion of VL infection and the log of sand fly abundance, which was negatively correlated with distance from the woodland. CONCLUSION: We discuss strategies that might be useful in controlling VL transmission in this endemic focus.

Could the Chagas disease elimination programme in Venezuela be compromised by reinvasion of houses by sylvatic Rhodnius prolixus bug populations?

The Andean Pact Initiative (1997) committed Andean countries to eliminate vectorial transmission of Chagas disease by 2010 via widespread residual insecticide spraying. In Venezuela, this aim could be compromised by reinvasion of houses by palm tree populations of the major vector Rhodnius prolixus. To test this hypothesis, a multivariate logistic regression was undertaken of risk factors for triatomine infestation and colonization in 552 houses and 1068 peri-domestic outbuildings in Barinas State. After adjusting for other risk factors, including palm roofs, R. prolixus infestation and colonization of outbuildings (and, to some extent, houses) was significantly associated with proximity to high densities of Attalea butyracea palm trees. House infestation and/or colonization was also positively associated with bug density in peri-domestic outbuildings, the presence of pigsties and nests. Hence, R. prolixus populations in ineffectively sprayed outbuildings could also provide an important source of house re-infestations. The secondary vector Triatoma maculata was mainly found associated with the presence of hens nesting both indoors and outdoors.

Analysis of antenal sensilla patterns of Rhodnius prolixus from Colombia and Venezuela

Antennal sensilla patterns were used to analyze population variation of domestic Rhodnius prolixus from six departments and states representing three biogeographical regions of Colombia and Venezuela. Discriminant analysis of the patterns of mechanoreceptors and of three types of chemoreceptors on the pedicel and flagellar segments showed clear differentiation between R. prolixus populations east and west of the Andean Cordillera. The distribution of thick and thin-walled trichoids on the second flagellar segment also showed correlation with latitude, but this was not seen in the patterns of other sensilla. The results of the sensilla patterns appear to be reflecting biogeographic features or population isolation rather than characters associated with different habitats and lend support to the idea that domestic R. prolixus originated in the eastern region of the Andes.

Male sex pheromones and the phylogeographic structure of the Lutzomyia longipalpis species complex (Diptera: Psychodidae) from Brazil and Venezuela.

Lutzomyia longipalpis, a sibling complex, is the main vector of Leishmania chagasi/infantum. Discriminating between siblings is important as they may differ in vectorial capacity. Lutzomyia longipalpis populations display distinct male sex pheromone chemotypes. We investigated the phylogeographic pattern of variation at microsatellite loci from 11 populations from Brazil and Venezuela related to their male pheromone. Temporal genetic differentiation was mostly not significant at the same site. Spatial genetic differentiation was, however, strong, although there was only a weak relationship between genetic differentiation and the geographic distance separating the samples (r2 < 0.10); geographic separation explained a much greater (54-97%) percentage of the genetic differences among populations when samples with the same pheromone type were analyzed separately. A cluster analysis showed five groups: Lu. cruzi (Brazil) and Lu. pseudolongipalpis (Venezuela) as separate species, two (mostly 9-methyl-germacrene-B) Venezuelan and Brazilian groups, and a very distinct cluster of Brazilian cembrene populations.

Risk of Trypanosoma cruzi I (Kinetoplastida: Trypanosomatidae) transmission by Panstrongylus geniculatus (Hemiptera: Reduviidae) in Caracas (Metropolitan District) and neighboring States, Venezuela.

The collection of Panstrongylus geniculatus bugs by inhabitants of dwellings in Caracas city (Metropolitan District) and in the neighboring Miranda and Vargas Sates, Venezuela, allowed for the gathering of data on the potential role of this sylvatic triatomine bug as a vector of Chagas disease in this area. The natural infection by Trypanosoma cruzi was recorded by examining fresh and stained faeces of the bugs. Additionally, a random amplification of polymorphic DNA technique for parasite identification and group typing was employed. A dot-ELISA test was used to identify the gut content of the triatomine bugs with the aim of assessing and quantifying the vector-human contact. Sixty-seven specimens (76.1%) were positive to T. cruzi (identified as T. cruzi I) and 60.2% (53/88) gave a positive reaction to the human antiserum. The human blood-positive samples included mixed blood meals with domestic animals (dog, pig and cow) (9.4%) and with mouse (3.8%). The overall Human Blood Index, measured as the percentage of bugs whose gut contents reacted with human antiserum on the total numbers of bugs that reacted with all the antisera tested, was 98.1%. Almost 41% of the bugs that had fed on humans were also positive for T. cruzi. These data show that the feeding of P. geniculatus on humans does not seem to be accidental and that its rate of infection by T. cruzi is high in this area which is not regarded as endemic for Chagas disease by the National Control Programme. This situation is particularly striking because it occurs in and around Caracas, the capital city, where 20% of the whole population of Venezuela live, human migrations from endemic areas are continuous, people in the crowded shantytown as well as people living in high-quality country houses are equally at risk and the epidemiological cycle Didelphis marsupialis/Rattus rattus-P. geniculatus-human does appear to occur successfully.