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.
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.
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 (ro = 0.096), the finite population growth rate (λ = 1.109), the net reproductive rate (R0 = 60.45), and the generation time (T = 46.34 wk). Elasticity analysis showed that the dominant lifehistory 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.
Abstract
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.
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.
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.
Summary
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.
Objectifs Rapporter des données entomologiques, épidémiologiques et géographiques pour la compréhension de la dynamique de transmission de la leishmaniose viscérale dans foyer délimitée dans l'ouest du Venezuela.
Méthodes Les profils spatiaux et temporaux de Lutzomyia pseudolongipalpis, l'espèce de phlébotomie la plus prévalente (99.7%) ont étéétudiés à El Brasilar à Curarigua dans l’état de Lara au Venezuela, une petite communauté rurale constituée de 20 habitations et de 118 habitants. La population de phlébotomes a été suivie mensuellement en utilisant des pièges lumineux CDC pendant une année dans les habitats domestiques et sylvatiques et pendant 3 mois dans toutes les maisons inhabitées.
Résultats Les variations temporelles ont suivi le profil bimodal annuel des précipitations avec la population la plus dense en avril et décembre. L'infection par des flagellées suggestive de Leishmania spp a été détectée chez 0.01% des 10026 femelles disséquées de L. pseudolongipalpis qui s'est révélée fortement endophilique. La prévalence de l'infection leishmania mesurée par le test cutanée à la leishmanine corrélait avec la distance des maisons aux bois et à l'abondance des phlébotomes. Un modèle de régression logistique a montré que pour les personnes vivant dans le village, la proximité des bois devrait être considérée comme facteur de risque pour l'infection leishmania. Cette observation était consistante avec l'association entre la proportion d'infection leishmania et le log de l'abondance des phlébotomes, qui corrélait négativement avec la distance aux bois.
Conclusion Nous discutons de stratégies qui pourraient être utiles dans le contrôle de la transmission de la leishmaniose viscérale dans ce foyer endémique.
Objetivo Relacionar datos entomológicos, epidemiológicos y geográficos para entender la dinámica de transmisión de la leishmaniasis visceral (LV) en un foco cerrado de Venezuela.
Métodos Se estudiaron los patrones espaciales y temporales de Lutzomyia pseudolongipalpis, la especie de flebótomo predominante (99.7%), en El Brasilar, Curarigua, estado de Lara, Venezuela, una pequeña comunidad rural de 20 domicilios y 118 habitantes. Se monitorizó la población de flebótomos, utilizando trampas de luz CDC mensuales durante 1 año en hábitats domésticos y selváticos, y durante 3 meses en todas las casas habitadas.
Resultados La variación temporal siguió el patrón bimodal de precipitación anual, con las mayores densidades de población en Abril y Diciembre. Se detectó infección con sugestivos de Leishmania spp en 0.01% de 10,026 hembras disecadas de L. pseudolongipalpis disectadas, que resultó ser altamente endofílico. La prevalencia de infección por Leishmania, medida mediante la prueba cutánea con leishmanina, estaba correlacionada con la distancia de las casas al bosque y con la abundancia de flebótomos. Un modelo de regresión logística mostró que para las personas que viven en el poblado, la proximidad al bosque (linear) debería considerarse como un factor de riesgo de infección por Leishmania (binaria) (z = −2.02, P = 0.04, OR = 0.98, IC 95% = 0,.97–0.99). Esto era consistente con la asociación entre la proporción de infección por LV y el logaritmo de la abundancia de los flebótomos, que estaba a su vez correlacionada con la distancia al bosque.
Conclusión Se discuten estrategias que podrían ser útiles en el control de la transmisión de LV en este foco endémico.
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.
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.
Summary
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.
Le Pacte d'Initiative Andain (1997) engageaient les pays Andains dans l’éradication du vecteur de transmissions de la maladie de Chagas d'ici 2010 via l'utilisation massive d'insecticides. Au Venezuela, ce but pourrait être compromis par la ré‐invasion des maisons par le vecteur majeur Rhodonius prolixus infestant les palmiers. Pour vérifier cette hypothèse, une régression logistique multivariée a été entreprise sur les facteurs de risques d'infestation et de colonisation par la triatomine dans 552 maisons et 1068 annexes peri‐domestiques dans l’état de Barinas. Après ajustement sur les autres facteurs de risques, y compris les toits en palmier, l'infestation et la colonisation des constructions extérieures par R. prolixus(et, dans certains cas, des maisons) étaient associées significativement à la proximité de grande densité de palmiers Attalea butyracea. L'infestation et/ou la colonisation des maisons étaient aussi associées significativement avec la densité en punaise des annexes peri‐domestiques, la présence de porcheries et de nids. Par conséquent, les populations de prolixus de R. dans des annexes inefficacement pulvérisées pourraient également être une source importante de re‐infestations des maisons. Le second vecteur T. maculataétait fortement associéà la présence de poules nichant aussi bien à l'intérieur qu’à l'extérieur.
La Iniciativa del Pacto Andino (1977) comprometió a los países andinos a eliminar la transmisión vectorial del mal de Chagas para 2020 a través de una extensiva fumigación de insecticida residual. En Venezuela, este objetivo podría estar comprometido por la reinvasión de las casas por poblaciones en palmeras del mayor vector de Rhodnius prolixus. Para comprobar esta hipótesis, se realizó una regresión logística multivariable de factores de riesgo de infestación de triatominos y colonización en 552 casas y en 1068 construcciones anexas en el estado de Barinas. Luego de realizar ajustes de otros factores de riesgo, incluyendo techos de palmeras, la infestación y colonización de construcciones anexas (y hasta cierto punto, de las casas) fue asociada significativamente la proximidad de una alta densidad de palmeras Attalea butyracea. La infestación y/o colonización en las casas fue también positivamente asociada con la densidad de insectos en las construcciones anexas a esas casas, así como la presencia de porquerizas y nidos. Consecuentemente, las poblaciones de R. prolixus en las construcciones anexas ineficazmente fumigadas podría proporcionar también un importante origen para la re‐infestación de las casas. El vector secundario T. maculata se encontró principalmente asociado a la presencia de nidos de gallinas, tanto fuera como dentro de las casas.
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