ABSTRACT
ABSTRACT The objective of this study was to evaluate the effect of the construction of the Jirau hydroelectric plant on the anopheline species, in Porto Velho, Rondônia, Brazil. For this, sampling was carried out in 23 locations in the pre (2004) and 23 after construction (2018) phases in the hydroelectric dam's coverage area, performed by human landing catch between 6:00 pm and 10:00 pm. We found 14 anopheline species. In the pre-construction phase, An. darlingi (73%) was the most abundant and after construction An. braziliensis (31.5%) was the most abundant. The T test indicated that there were no differences in the indexes - diversity (H '), richness (Sjack 1), equitability (J') and dominance (d) of anophelines species - evaluated between the phases (p > 0.05). The spatio-temporal distribution of An. darlingi proved to be wide, with the highest density values observed in March ( x ¯w = 27.1) in the pre-construction phase and in the months of May ( x ¯w = 4) and July ( x ¯w = 3.1), post-construction. Differences in hematophagic activity peaks were observed between species and between phases. According to the data obtained in this study, the construction of the hydroelectric plant had little influence on the composition of anopheline species, however changes were observed in the spatio-temporal distribution of the An. darlingi and in the pattern of hematophagic activity of the species, which directly influenced the dynamics of malaria in the region.
ABSTRACT
ABSTRACT Mosquitoes belonging to the Anopheles genus are of great relevance in the epidemiology and transmission of malaria, with their larval phase developing in clean waters in the presence of organic matter. However, the human presence in the Amazon has increasingly influenced the emergence of new breeding sites and larval habitats, such as clay pits, fish ponds and dams, among others. The objective of the study was to characterize mosquito larval habitats using the biotic and abiotic parameters in the metropolitan area of Manaus. We collected in 23 artificial larval habitats in Manaus, classified in dams, fish ponds and clay pits. Water samples, Anopheles larvae, aquatic macrophytes and limnological parameters were collected from each artificial larval habitat. The Larvae Index per Man/Hour and canonical correspondence analysis were used for data analysis. Results indicate that artificial larval habitats with characteristics similar to natural sites present higher larval density, displaying a high abundance of An. triannulatus and An. darlingi. More than 90% of the determined limnological parameters were in agreement with the environmental resolution stipulated by the Brazilian environmental resolution, while pH, dissolved oxygen and phosphorus levels were below the established limits at some of the larval habitats. Conductivity, total suspended solids and phosphorus were positively correlated to the presence of An. albitarsis, An. peryassui and An. nuneztovari in fish ponds, and An. trianulatus and An. braziliensis in dams. Thus, the evaluated limnological variables and habitat structure explain Anopheles species distribution in artificial larval habitats in the metropolitan Manaus region.
ABSTRACT
ABSTRACT The aim of this study was to analyze the effectiveness of different control agents of Aedes aegypti and Aedes albopictus associated with ovitraps under laboratory and field conditions. Five treatments were used: grass infusion + Bacillus thuringiensis israelensis (gI + Bti), grass infusion + Saccharopolyspora spinosa (gI + Ss), grass infusion + Pyriproxyfen (gI + P), distilled water + Toxorhynchites haemorrhoidalis (dW + Th), and grass infusion (gI) (control). The highest mean number of eggs of both species were obtained with grass infusion in the laboratory. Among control agents, the lowest mean of A. aegypti eggs occurred with gI + Ss and the lowest mean of A. albopictus eggs occurred with dW + Th. There was no difference between treatments in A. aegypti (P = 0.4320) and A. albopictus (P = 0.7179). In the field, the highest mean number of eggs for both species were obtained with gI + Ss, and the lowest values were obtained with gI + P (P = 0.0124). The treatments can be applied to both the surveillance and the control, but ovitraps with biological larvicide Bti were more effective and safer considering the number of eggs laid and selectivity of pathogens for mosquitoes.
ABSTRACT
ABSTRACTWe analyzed the effects of Bacillus sphaericus on Anopheles larvae and on the associated insect fauna in fish farming ponds. Five breeding sites in the peri-urban area of the city of Manaus, AM, Brazil, were studied. Seven samples were collected from each breeding site and B. sphaericus was applied and reapplied after 15 days. The samples were made at 24 h before application, 24 h post-application and 5 and 15 days post-application. We determined abundance, larval reduction and larval density for Anopheles, and abundance, richness, Shannon diversity index and classified according to the functional trophic groups for associated insect fauna. A total of 904 Anopheles larvae were collected and distributed into five species. Density data and larval reduction demonstrated the rapid effect of the biolarvicide 24 h after application. A total of 4874 associated aquatic insects belonging to six orders and 23 families were collected. Regression analysis of diversity and richness indicated that the application of the biolarvicide had no influence on these indices and thus no effect on the associated insect fauna for a period of 30 days. B. sphaericus was found to be highly effective against the larvae of Anopheles, eliminating the larvae in the first days after application, with no effect on the associated insect fauna present in the fish ponds analyzed.