Parity and gonotrophic discordance of females of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in the city of São Paulo, SP, Brazil.

The objective of this study was to assess the parity, presence of blood in the stomach, and the gonotrophic discordance of females of Aedes aegypti and Aedes albopictus captured in two areas of the city of São Paulo. The captures were undertaken monthly, by aspiration, in the period from January, 2015 to August, 2017. All the females of the two species had their midguts and ovaries dissected to determine the presence of blood and the parity/stage of maturation. With regard to parity, 27% and 34% of the females of Ae. aegypti and Ae. albopictus, respectively, were parous or were in advanced stages of the development of their ovaries (33% and 27%, respectively). The larger part of the females of Ae. aegypti and Ae. albopictus contained blood in their stomachs (77% and 60%, respectively), beyond which 36% and 27% of the females of Ae. aegypti and Ae. albopictus, respectively, were in gonotrophic discordance. Our results indicate favorable conditions in the study areas because of the presence of parous females. Moreover, this frequent and multiple contact of Ae. aegypti and Ae. albopictus females with vertebrate hosts, such as humans, increases the possibility of transmitting the viruses they may be carrying.

Seasonal and spatial distribution of Aedes aegypti and Aedes albopictus in a municipal urban park in São Paulo, SP, Brazil.

Dengue, yellow fever, chikungunya and Zika are important arboviruses present in various countries of the world, the etiological agents of which are transmitted to human-beings by the bite of infected females of Aedes aegypti and Aedes albopictus. Biological aspects of these vectors, such as their distribution and abundance, are influenced by climatic variables such as rainfall and temperature. We assess the spatial and seasonal distribution of Ae. aegypti and Ae. albopictus, during spring 2014 and spring 2015 and autumn 2015 and autumn 2016, in an urban Municipal Park, São Paulo (SP, Brazil), using 36 ovitraps. The Park was divided into three areas: internal, intermediate and peripheral, and 12 geo-referenced ovitraps were randomly installed in each area. We evaluated the association between the environmental variables maximum and minimum temperatures and rainfall with oviposition rates in the park using negative binomial regression models. Further, to estimate the distribution of the species in the three areas during the seasons, we employed the geostatic interpolation method with the use of kriging. Our results show the presence of the two species in the area in both the seasons but with a greater predominance of Ae. albopictus. Both species were significantly more abundant in spring than autumn. However, our results suggested that this seasonal variation was mediated by the maximum and minimum temperatures, which were significantly associated with the oviposition rate of both species, in all regression models. Cumulative rainfall of the week of collection was not associated with the abundance of the vectors in the multiple models. Moreover, regardless of climatic variables, the oviposition of Ae. aegypti was positively associated with the peripheral area of the park compared with the internal area (oviposition rate ratio [ORR]: 4.92; 95% CI: 2.46-9.83). On the other hand, the oviposition of Ae. albopictus was negatively associated with the peripheral area as compared with the internal one (ORR: 0.59; 95% CI: 0.38-0.91). The spatial distribution revealed a pattern of spatial segregation, confirming the ecological preferences of each species. Green areas in urban centers can serve as important habitats for various mosquito species, including especially Ae. albopictus. Thus it is that our study highlights the importance of maintaining surveillance for the targeting of control strategies in green areas as well, since most control strategies are focused on Ae. aegypti and urban residential centers.