Measuring mosquito diversity patterns in an Amazonian terra firme rain forest.

We reanalyzed a dataset consisting of approximately 10,700 crepuscular and night-biting female mosquitoes (Culicidae) collected over 12 mo in the canopy and understorey of primary Amazonian rain forest. We investigate whether vertical habitat stratification and rainfall modified major ecological parameters of this mosquito ensemble, combining descriptive and hypothesis-testing statistics with species richness and diversity metrics in the analyses. A total of 31 species was recorded. Contrary to expectations, the host-seeking mosquito fauna was less diverse in the forest canopy than in the understorey. In particular, species diversity and evenness were higher in understorey samples, whereas species richness estimates were similar in both habitats. Only two out of 12 species tested for vertical stratification were clearly acrodendrophilic, and five preferred understorey habitats. The mosquito fauna was more diverse in the rainy than in the dry season. We propose the hypothesis that female mosquito density and host defensive behavior may promote host seeking in nonpreferred habitats by acrodendrophilic mosquito species. These results may be particularly relevant for understanding the dynamics of Plasmodium malariae/brasilianum and arboviral infections in Amazonian forested landscapes.

Field ecology of sylvatic Rhodnius populations (Heteroptera, Triatominae): risk factors for palm tree infestation in western Ecuador.

Most Rhodnius species (Triatominae) are primarily associated with palm trees. They maintain enzootic Trypanosoma cruzi transmission and are responsible for human infection (causing Chagas disease) through the Neotropics. Assessing whether individual palm traits (ecological and/or botanical) may increase the risk of palm infestation by triatomines is relevant in areas where bugs invade houses flying from peridomestic palms. We developed a novel fieldwork approach with that objective, and applied it to study infestation by sylvatic Rhodnius ecuadoriensis in 110 tagua palms (Phytelephas aequatorialis). Palm infestation (23% overall) was non-randomly distributed in our sample. Palms located in anthropic landscapes were frequently infested (>27%, n=92), whereas no bugs were collected from palms surveyed within forest remnants (n=18; P=0.01). The presence of abundant decaying vegetable matter (P=0.001) and (to a lesser extent) epiphytic plants (P=0.049) on palm crowns and stems increased the probability of infestation and was positively correlated with the apparent density of bug colonies (R2=0.68). A trend towards higher infestation rates in male palms (34% vs. 18%) could relate to female palm management (removal of infrutescences and vegetable debris) in areas where palm seeds are harvested. An outline of 'risk palm ecotopes' and environmental management-based strategies for the control of peridomestic, palm tree-living vector populations are proposed.

Observations on the domestic ecology of Rhodnius ecuadoriensis (Triatominae).

Rhodnius ecuadoriensis infests peridomiciles and colonises houses in rural southern Ecuador. Six out of 84 dwellings (7%) surveyed in a rural village were infested (78 bugs/infested domicile; 279 bugs were collected in a single dwelling). Precipitin tests revealed R. ecuadoriensis fed on birds (65%), rodents (31%), marsupials (8%), and humans (15%) - mixed bloodmeals detected in 37.5% of individual samples. Trypanosoma cruzi from opossums and rodents may thus be introduced into the domestic cycle. Wasp parasitoidism was detected in 6.5% of 995 R. ecuadoriensis eggs (only in peridomestic habitats). Control strategies should integrate insecticide spraying (indoors and peridomestic), better management of poultry, and housing improvements. A possible inefficacy of Malathion is reported.

Observations on the domestic ecology of Rhodnius ecuadoriensis (Triatominae)

Rhodnius ecuadoriensis infests peridomiciles and colonises houses in rural southern Ecuador. Six out of 84 dwellings (7 percent) surveyed in a rural village were infested (78 bugs/infested domicile; 279 bugs were collected in a single dwelling). Precipitin tests revealed R. ecuadoriensis fed on birds (65 percent), rodents (31 percent), marsupials (8 percent), and humans (15 percent) - mixed bloodmeals detected in 37.5 percent of individual samples. Trypanosoma cruzi from opossums and rodents may thus be introduced into the domestic cycle. Wasp parasitoidism was detected in 6.5 percent of 995 R. ecuadoriensis eggs (only in peridomestic habitats). Control strategies should integrate insecticide spraying (indoors and peridomestic), better management of poultry, and housing improvements. A possible inefficacy of Malathion is reported

Nuclear rDNA ITS-2 sequences reveal polyphyly of Panstrongylus species (Hemiptera: Reduviidae: Triatominae), vectors of Trypanosoma cruzi.

Panstrongylus species are widely distributed throughout the Americas, where they act as vectors of Trypanosoma cruzi, agent of Chagas disease. Their intraspecific relationships, taxonomic position and phylogeny in relation to other Triatomini were explored using ribosomal DNA (rDNA) internal transcribed spacer 2 (ITS-2) sequence polymorphisms and maximum parsimony, distance and maximum likelihood analyses of 10 populations representing six species of the genus (P. megistus, P. geniculatus, P. rufotuberculatus, P. lignarius, P. herreri and P. chinai). At the subspecific level, P. megistus appeared more homogeneous than P. rufotuberculatus and P. geniculatus (both with broader distribution). Several dinucleotide microsatellites were detected in the sequences of given species. Many of these microsatellites (GC, TA, GT and AT) showed different number of repeats in different populations and thus, may be very useful for population differentiation and dynamics analyses in future studies. The sequences of P. lignarius (considered sylvatic) and P. herreri (a major disease vector in Peru) were identical, suggesting that these species should be synonymised. Intrageneric analysis showed a clear separation of P. rufotuberculatus, with closest relationships between P. geniculatus and P. chinai, and P. megistus occupying a separate branch. Genetic distances between Panstrongylus species (0.11585-0.22131) were higher than those between Panstrongylus and other Triatomini (16 species from central and North America and South America) (0.08617-0.11039). The distance between P. megistus and P. lignarius/herreri (0.22131) was the largest so far recorded in the tribe. The pronounced differences in length and nucleotide composition suggest a relatively old divergence of Panstrongylus species. P. rufotuberculatus was closer to Mesoamerican Triatoma, Meccus and Dipetalogaster species than to other Panstrongylus. All Panstrongylus clustered with the Mesoamerican clade; P. rufotuberculatus clustered with the phyllosoma complex and T. dimidiata, with D. maxima and T. barberi in a basal position. The rest of Panstrongylus appeared paraphyletically in the tree. This is evidence suggesting polyphyly within the genus Panstrongylus, whose species may be related to the ancestors giving rise to central and North American Triatomini.

[A model of primary prevention of sexually transmitted diseases and HIV/AIDS in adolescents]. / Un modelo de prevención primaria de las enfermedades de transmisión sexual y del VIH/sida en adolescentes.

OBJECTIVE: To develop, apply, and evaluate an educational model for the primary prevention of sexually transmitted diseases (STDs) and acquired immunodeficiency syndrome (AIDS) that was based on the sexual knowledge, attitudes, and practices (KAPs) of adolescents and on their perceptions and behaviors in this area, with the ultimate goal of helping develop educational tools to prevent infection with STDs and the human immunodeficiency virus (HIV). METHODS: An STD/HIV/AIDS primary prevention model was applied with adolescent schoolchildren (12 to 15 years old) in the canton of Santo Domingo de los Colorados, Ecuador. Two groups with similar characteristics were formed: the experimental group, with 358 students, and the control group, with 288 students. Schools were selected according to inclusion criteria, and adolescents at each school were chosen at random. A discussion guide was applied with 16 focus groups, and the resulting information was used to prepare a KAP survey. After being validated, the KAP survey was applied to the experimental group and to the control group. A prevention education program geared to students and teachers was implemented with the experimental group. Eight months later a second KAP survey was done with the experimental group and the control group. The differences in KAPs before and after the intervention were evaluated using the chi-square test. RESULTS: There were no statistically significant differences between the two groups before the intervention, but afterwards the differences were statistically significant (P = 0.012), with an increase in the knowledge of sexuality and STDs/AIDS in the experimental group, even though the long-term behavior changes have not been evaluated. CONCLUSIONS: This study validated a multifactorial STD/AIDS prevention model adapted to the reality of adolescents, and it suggests the possibility of extrapolating this experience more broadly to contexts similar to those of this Ecuador population.

Biogeography of Triatominae (Hemiptera: Reduviidae) in Ecuador: implications for the design of control strategies.

Chagas disease control strategies strongly depend on the triatomine vector species involved in Trypanosoma cruzi transmission within each area. Here we report the results of the identification of specimens belonging to various species of Triatominae captured in Ecuador (15 species from 17 provinces) and deposited in the entomological collections of the Catholic University of Ecuador (Quito), Instituto Oswaldo Cruz (Brazil), the Natural History Museum London (UK), the London School of Hygiene and Tropical Medicine (UK), the National Institute of Hygiene (Quito), and the Vozandes Hospital (Quito). A critical review of published information and new field records are presented. We analysed these data in relation to the life zones where triatomines occur (11 life zones, excluding those over 2,200 m altitude), and provide biogeographical maps for each species. These records are discussed in terms of epidemiological significance and design of control strategies. Findings relevant to the control of the main vector species are emphasised. Different lines of evidence suggest that Triatoma dimidiata is not native to Ecuador-Peru, and that synanthropic populations of Rhodnius ecuadoriensis in southern Ecuador-northern Peru might be isolated from their sylvatic conspecifics. Local eradication of T. dimidiata and these R. ecuadoriensis populations might therefore be attainable. However, the presence of a wide variety of native species indicates the necessity for a strong longitudinal surveillance system.

The ITS-2 of the nuclear rDNA as a molecular marker for populations, species, and phylogenetic relationships in Triatominae (Hemiptera: Reduviidae), vectors of Chagas disease.

The nucleotide sequences of the rDNA second internal transcribed spacer (ITS-2) of 31 populations of 12 and 3 species of the two main Triatominae tribes Triatomini and Rhodniini, including the most important Chagas disease vectors, were obtained. Sequence comparisons and parsimony, distance, and maximum-likelihood analyses indicate that ITS-2 is a useful marker for resolving supraspecific, specific, subspecific, and even sometimes population-level relationships in Triatominae. Results were markedly different between species of Triatomini and Rhodniini, suggesting polyphyly. Phylogenetic trees support an old divergence between South American and North-Central American Triatomini and query the validity of some genera (Dipetalogaster, Psammolestes). The very low sequence variation between species of the phyllosoma complex suggests that subspecific ranking would be more appropriate. Triatoma dimidiata proves to be a clearly differentiated species, with several populations evidencing a clinal variation along a north-south axis and a population from Yucatan showing differences consistent with specific status.

Natural ecotopes of Triatoma infestans dark morph and other sylvatic triatomines in the Bolivian Chaco.

A survey of natural ecotopes of Triatoma infestans dark morph and other triatomine sylvatic species was performed in an uninhabited area of the Bolivian Chaco. Among the 321 triatomines collected by light trapping, only 4 T. infestans dark morph specimens were identified. Predominant flying species were T. guasayana and T. sordida group 2 (51.7% and 37.1% of capture, respectively). The same species prevailed in terrestrial and epiphytic bromeliads where scarce T. infestans dark morph nymphal instars were also detected. In parrot nests T. delpontei prevailed broadly over other species (90.2% of the capture) and only 4 T. infestans dark morph adults were collected. In contrast, T. infestans dark morph was the predominant species captured in hollow trees (46.0% of the total collected). The abundance of immature forms (88.2% of the collection) shows that hollow trees constitute a favourable ecotope for this species. Of the 421 trees investigated, 33.7% were positive for triatomines. T. infestans dark morph, found inside 15.0% of them, also had higher apparent density than other species (average number of T. infestans in positive trees, 2.0 +/- 1.6 vs 1.3 +/- 0.6 for other species). Light trapping seems to be an efficient method to sample the T. sordida-T. guasayana complex in that it shows a similar distribution to that observed in natural ecotopes; however, this method is ineffective for the assessment of the local abundance of T. infestans dark morph.

Epidemiology of Chagas disease in Ecuador. A brief review.

Chagas disease is a complex public health problem that has been underestimated in Ecuador. Here we review the relevant published information, and present unpublished and new data that help to understand the current Chagas disease epidemiological situation and its evolution in the country. Three main characteristics have been identified: (i) persistence of Trypanosoma cruzi transmission in already known foci; (ii) a marked endemicity in some urban areas of Guayaquil; and (iii) the transformation of new Amazon foci into truly endemic areas. The situation in other suspect areas remains uncertain. Five Triatominae species have been implicated in the transmission of T. cruzi to people in Ecuador (Triatoma dimidiata, Rhodnius ecuadoriensis, R. pictipes, R. robustus and Panstrongylus geniculatus), but some others may also play a role in some areas (P. rufotuberculatus, P. howardi, T. carrioni and P. chinai). Other Triatominae reported seem to have little or no epidemiological relevance (T. venosa, T. dispar, Eratyrus mucronatus, E. cuspidatus, P. lignarius and Cavernicola pilosa). High frequency of acute cases and severe chronic disease has been observed. Although cardiomyopathy is more frequent, serious digestive disease is also present. It is estimated that around 120,000-200,000 people may be infected. 2.2 to 3.8 million people are estimated to live under transmission risk conditions.