Diversity of Anopheles spp. (Diptera: Culicidae) in an Amazonian Urban Area.

The genus Anopheles encompasses several species considered as vectors of human infecting Plasmodium. Environmental changes are responsible for behavior changes in these vectors and therefore the pattern of malaria transmission. To better understand the dynamics of malaria transmission, this study aimed at identify the species of adult anophelines found in a malaria endemic urban area of the Amazon region, Mâncio Lima, located in the Acre State Brazil. Using Shannon-type light traps installed at 11 collection points near fish ponds, a total of 116 anophelines were collected belonging to nine species. Anopheles darlingi Root 1926 and An. albitarsis s.l. Lynch-Arribalzaga 1878 were the most abundant and predominant species. Despite the low number of captured adult anophelines, the occurrence of An. darlingi throughout all urban area and the presence of secondary vectors reinforce the need of a permanent and continuous entomological surveillance.

Frequency of Aedes sp. Linnaeus (Diptera: Culicidae) and Associated Entomofauna in Bromeliads from a Forest Patch within a densely Urbanized Area.

Little is known about the relationship between the presence of Aedes, abiotic factors and the entomofauna existing in phytotelmatas. The aim of this study was to identify biotic and abiotic factors associated with the presence of Aedes in bromeliads sites located in a forest fragment in Rio de Janeiro, Brazil. In the study area, eight bromeliads from the Aechmea genus were chosen and kept in landscape form. Physical and chemical variables were measured. Collected aquatic insects were identified according to the literature. A total of 3102 immature insects were collected. The presence of Aedes aegypti (Linnaeus) (2.29%) was rare. Few specimens were found concentrated in urban-adjacent areas during summer. On the other hand, Aedes albopictus (Skuse) (17.57%) was found throughout the year in 0%-80% of the sites, averaging 1.0 mosq/bromelia. Aedes albopictus was found predominantly in central sites of the forest fragment. The Canonical Correspondence Analysis indicates that most taxa had a moderate association with temperature, dissolved oxygen, and pH. The abiotic variables, such as temperature and dissolved oxygen, affect the distribution of the genus Aedes vectors, while most of the other variables did not.

Spatial Clustering of Aedes aegypti (Diptera: Culicidae) and Its Impact on Entomological Surveillance Indicators.

Spatial clustering of Aedes aegypti (L.) was assessed in 0.25-km2 sampling plots located in three different neighborhoods in the city of Rio de Janeiro, Brazil Monitoring was carried out with two oviposition traps (collecting either. eggs or adult mosquitoes) over a consecutive 80-wk period. Taylor power laws (TPL) were used to assess clustering in both adult and egg collections. The clustering level observed in both TPL models was sufficient to increase by two to three times the sampling effort required to achieve a desired precision of population estimates of egg and adults collections, respectively. The relationship between positivity and density indices was also affected by this clustering level, and virtually no changes in positivity data were observed for variations of adult densities over two mosquitoes per trap. General TPL model parameterizations for dealing with clustering of egg and adult populations of Ae. aegypti are proposed. Accounting for clustering-related issues is necessary for an appropriate design and interpretation of trap-based entomological surveillance data.

Spatial clustering and longitudinal variation of Anopheles darlingi (Diptera: Culicidae) larvae in a river of the Amazon: the importance of the forest fringe and of obstructions to flow in frontier malaria.

Deforestation has been linked to a rise in malaria prevalence. In this paper, we studied longitudinally 20 spots, including forested and deforested portions of a temporary river in a malarigenous frontier zone. Larval habitat parameters influencing distribution of Anopheles darlingi (Diptera: Culicidae) larvae were studied. We observed that larvae were clustered in forested-deforested transitions. For the first time in the literature, it was verified that parameters determining larval distribution varied from deforested to forested areas. The proximity to human dwellings was also a significant factor determining distribution, but larvae was most importantly associated with a previously undescribed parameter, the presence of small obstructions to river flow, such as tree trunks within the river channel, which caused pooling of water during the dry season ('microdams'). In deforested areas, the most important factor determining distribution of larvae was shade (reduced luminance). Larvae were absent in the entire studied area during the wet season and present in most sites during the dry season. During the wet-dry transition, larvae were found sooner in areas with microdams, than in other areas, suggesting that flow obstruction prolongs the breeding season of An. darlingi. Adult mosquito densities and malaria incidence were higher during the dry season. Our data correlate well with the published literature, including the distribution of malaria cases near the forest fringes, and has permitted the creation of a model of An. darlingi breeding, where preference for sites with reduced luminance, human presence and microdams would interact to determine larval distribution.

Temporal distribution of Aedes aegypti in different districts of Rio de Janeiro, Brazil, measured by two types of traps.

Dengue dynamics in Rio de Janeiro, Brazil, as in many dengue-endemic regions of the world, is seasonal, with peaks during the wet-hot months. This temporal pattern is generally attributed to the dynamics of its mosquito vector Aedes aegypti (L.). The objectives of this study were to characterize the temporal pattern of Ae. aegypti population dynamics in three neighborhoods of Rio de Janeiro and its association with local meteorological variables; and to compare positivity and density indices obtained with ovitraps and MosquiTraps. The three neighborhoods are distinct in vegetation coverage, sanitation, water supply, and urbanization. Mosquito sampling was carried out weekly, from September 2006 to March 2008, a period during which large dengue epidemics occurred in the city. Our results show peaks of oviposition in early summer 2007 and late summer 2008, detected by both traps. The ovitrap provided a more sensitive index than MosquiTrap. The MosquiTrap detection threshold showed high variation among areas, corresponding to a mean egg density of approximately 25-52 eggs per ovitrap. Both temperature and rainfall were significantly related to Ae. aegypti indices at a short (1 wk) time lag. Our results suggest that mean weekly temperature above 22-24 degrees C is strongly associated with high Ae. aegypti abundance and consequently with an increased risk of dengue transmission. Understanding the effects of meteorological variables on Ae. aegypti population dynamics will help to target control measures at the times when vector populations are greatest, contributing to the development of climate-based control and surveillance measures for dengue fever in a hyperendemic area.

[Frequency of Aedes aegypti and Aedes albopictus larvae and pupae in traps, Brazil]. / Freqüência de larvas e pupas de Aedes aegypti e Aedes albopictus em armadilhas, Brasil.

OBJECTIVE: To evaluate the monthly frequency of larvae and pupae of Aedes albopictus, Aedes aegypti and other mosquitoe species in tires, and the influence of environmental factors on that. METHODS: The immature stages of mosquitoes were collected monthly from four tires in the municipality of Nova Iguaçu, Brazil, from November 1997 to October 1998. The following variables were measured: rainfall, temperature, water volume, water pH. The tires were arranged in a pyramid, one at the base (tire 1) and 3 others (2,3 e 4) laying over it. RESULTS: Were collected 10,310 larvae and 612 pupae. Aedes albopictus was the most common species in both the larval and pupal stages. Aedes aegypti and Aedes albopictus were collected throughout the year but were more frequent during in the rainy season. The number of Aedes aegypti was significantly correlated with the temperature, rainfall and water volume of the tires. The correlation between water pH and number of larvae was not significant. Aedes albopictus larvae were more frequent in tires left in the shade. CONCLUSIONS: Aedes albopictus was more abundant in tires than Aedes aegypti. Discarded tires seem to be an important source of both Aedes species throughout the year. The favored environmental conditions of the tires, such as water volume and exposure to sunlight differ for Aedes albopictus and Aedes aegypti.

Comparative susceptibility of two members of the Anopheles oswaldoi complex, An. oswaldoi and An. konderi, to infection by Plasmodium vivax.

We compared the susceptibility of Anopheles oswaldoi and An. konderi to infection by Plasmodium vivax based on the proportion of mosquitoes presenting oocysts and sporozoites. Anophelines were captured in the State of Acre and Rondônia, Brazilian Amazon, and used to obtain F1 progenies. After emergence of adults, male genitalia of mosquitoes of each family were dissected in order to identify them as either An. oswaldoi or An. konderi. F1 progenies of field-captured An. oswaldoi, An. konderi and An. darlingi (used as control) were fed simultaneously on P. vivax-infected blood. Mosquitoes were dissected on day 10-12 after feeding and examined for the presence of oocysts and sporozoites. Both An. oswaldoi and An. konderi developed oocysts in the midguts, however, the percentage of oocyst-positive mosquitoes for An. oswaldoi (13.8%) was higher than for An. konderi (3.3%), and only An. oswaldoi developed salivary infection with sporozoites (6.9% of positivity). Infection rates in An. darlingi ranged from 22.5% to 30.0% for both oocysts and sporozoites. These results indicate that An. oswaldoi can transmit P. vivax and suggest that it is more susceptible than An. konderi. Although An. oswaldoi is an exophilic and zoophilic species, it may be involved in malaria transmission as possibly occurred in the State of Acre.

Faunal composition and behavior of anopheline mosquitoes in the Xavánte Indian reservation of Pimentel Barbosa, central Brazil.

Faunal composition and behavior of anopheline mosquitoes were studied in a Xavánte Indian reservation of Central Brazil. Altogether 558 anophelines were collected in three environments (intra, peri, and extra-domiciliary). Anopheles darlingi (30.9%), An. triannulatus s.l. (24.6%) and An. oswaldoi (19.7%) were the most common species. Average capture rates were higher in the rainy season (8.03 per hour) than in the dry season (4.37 per hour). Anophelines exhibited exophilic behavior almost exclusively. It was observed that Xavánte cultural practices facilitate outdoor exposure during peak hours of mosquito activities (e.g., coming to the creek early in the morning for bathing or to draw water, fishing, etc.). The results of this study raise the question of whether or not applying to the Xavánte the more commonly recommended malaria control strategies (e.g., in-house spraying, screening windows, and impregnated bed nets) which aim at hampering human-mosquito contact inside human dwellings may be effective.