Mosquito Fauna and Spatial Distribution in an Atlantic Forest Area in Rio de Janeiro State, Brazil, Reveal a High Risk of Transmission of Yellow Fever and Other Arboviruses.

In 2017-2019, Brazil recorded its most severe outbreak of yellow fever due to the spread of the virus (YFV) in the country's southeast. Here, we investigated mosquito fauna and the spatial distribution of species in a primatology center in the Atlantic Forest bioregion in Rio de Janeiro state to evaluate the risk of YFV transmission in distinct environments. Fortnightly mosquito collections were performed from December 2018 to December 2019 at 12 sites along a disturbance gradient from a modified environment to 400 m inside the forest. We used ovitraps, BG-Sentinel, and protected human attraction (PHA). A total of 9349 mosquitoes of 21 species were collected. The collection method strongly influenced the captured fauna, with species such as Anopheles cruzii, Psorophora ferox, Runchomyia cerqueirai, Wyeomyia incaudata, Wy. theobaldi, Sabethes chloropterus, and Sa. albiprivus only collected via PHA. Collections with ovitraps resulted in low diversity and richness, with Haemagogus leucocelaenus and Hg. janthinomys/capricornii predominating. The diverse local fauna and the abundance and ubiquity of the latter species, which are the primary vectors of YFV, indicated that this area was highly vulnerable to arbovirus transmission, especially yellow fever, highlighting the need for improved surveillance and vaccination coverage in human and captive endangered non-human primates.

Interaction of Haemagogus leucocelaenus (Diptera: Culicidae) and Other Mosquito Vectors in a Forested Area, Rio de Janeiro, Brazil.

The yellow fever (YF) virus has been detected throughout Brazil, with the occurrence of human cases, cyclic epizootics, and its isolation from Haemagogus janthinomys and Hg. leucocelaenus. We assessed the seasonal occurrence, egg abundancy, and oviposition interaction of mosquito vector species captured at a Private Natural Heritage Reserve in the Atlantic Forest biome. A total of 2943 eggs and 1538 mosquito larvae were collected from which 1231 belonged to entomologically important species. Ovitraps were used to collect immature mosquitoes from September 2019 to January 2021. The Mann-Whitney test was used to assess the differences in the abundance of eggs between rainy and dry seasons. Kruskal-Wallis and Dunn's post hoc tests were used to evaluate the significance of the differences in the number of individuals from vector species. The highest percentage of mosquito vector eggs were collected during the rainy season, from December to February. Most eggs recovered from ovitraps belonged to the species Hg. leucocelaenus, representing 85% of all mosquito eggs identified. The other species had lower abundances and percentages: Aedes terrens (7%), Haemagogus janthinomys (5%) and Aedes albopictus (3%). The species that shared breeding sites with a higher frequency were Hg. leucocelaenus and Hg. janthinomys, with a statistically positive correlation (ρ = 0.74). This finding suggests that maybe the presence of Hg. leucocelaenus eggs acted as an attractant for Hg. janthinomys or vice versa. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control approaches directed against specific pathogen vectors of medical and veterinary importance.

Oviposition activity of Haemagogus leucocelaenus (Diptera: Culicidae) during the rainy and dry seasons, in areas with yellow fever virus circulation in the Atlantic Forest, Rio de Janeiro, Brazil.

The present study aims to analyze the effectiveness of ovitraps in the capture of Hg leucocelaenus eggs and evaluate the influence of the dry and rainy seasons on their abundance and hatching rates. The eggs were collected in the Atlantic Forest of State of Rio de Janeiro, Brazil, an area in which the yellow fever virus is known to circulate. We distributed 15 ovitraps in three sampling points, with five ovitraps per point. We distributed 15 ovitraps in three sampling points on trees within a forested area, which were sequentially numbered, monitored, and replaced every two weeks from October 2016 to April 2018. There was a high dominance of Hg. leucocelaenus eggs (98.4%) and a variation in egg hatching rates between the wet and dry seasons. These rates were 1.5 times higher in the rainy season than in the dry season. The rainy season also showed a greater abundance of eggs and higher values of ovitrap positivity and egg density indexes in the installed ovitraps. The abundances of Hg. leucocelaenus eggs were positively correlated with mean monthly temperature and air humidity but not significantly correlated with accumulated precipitation. These results, as well as their implications for the possible use of ovitraps to monitor vector mosquitoes of yellow fever in the study region, are discussed.

Bionomy of Mosquitoes in Bamboo Internodes in an Atlantic Forest Remnant of the State of Rio De Janeiro, Brazil.

Living bamboo stalks are one of the most specialized habitats for mosquito oviposition and immature development. Most of the mosquito species that breed in these habitats are sylvatic, and some are of importance for public health as possible vectors of pathogens. Perforated internodes are a very specialized environment due to the difficulty of access. Furthermore, due to their relatively simple fauna, they represent a valuable model for ecological studies that may be applicable to more complex environments. This study aims to assess the mosquito bionomics of species raised in bamboo internodes. Therefore, the diversity of mosquito species and the influence of abiotic variables (pH and temperature) on the distribution of mosquitoes that breed in this habitat were analyzed. The study area is a fragment of Atlantic Forest within the Association of da Armada (ATA) in Nova Iguaçu, state of Rio de Janeiro, Brazil. Immature mosquitoes were sampled with suction tubes (mouth aspirators) between August 2017 and July 2018. A total of 3,170 larvae were collected in 5 bamboo plants, each with 8 stalks perforated. Of these, 688 larvae reached the adult stage, representing 10 genera and 19 species. The most common species were Culex neglectus (43%), Trichoprosopon digitatum (22%), Culex iridescens (8%), Sabethes identicus (7%), and Orthopodomyia albicosta (7%). The richness of the immatures collected in the ATA was 19 species, with a diversity of 1.10 and Shannon evenness of 0.57. A diverse composition of Culicidae in bamboo stalks was found, although dominance was low.

Evaluation of Mansonia spp. Infestation on Aquatic Plants in Lentic and Lotic Environments of the Madeira River Basin in Porto Velho, Rondônia, Brazil.

The females of Mansonia are voraciously hematophagous. The spiracular apparatus of the immature, larval, and pupal forms is adapted to perforate submerged aquatic vegetation, from whose aeriferous aerenchyma they obtain the oxygen necessary for breathing. The proliferation of aquatic plants, in some cases linked to anthropic modifications that reduce water flow and/or increase organic matter content, may therefore contribute to the spread of these mosquitoes. This study aims to assess the presence of immature individuals of Mansonia in different aquatic plants of the Madeira River basin in 10 lentic and lotic environments and correlate their population density with abiotic factors such as water pH, dissolved O2, conductivity, and temperature. The sampling lasted from February 2016 to June 2018, a 29-month period during which 31,287 specimens belonging to the genus Mansonia were captured. Of the 12 species of macrophytes inspected, Eichhornia crassipes made up 70.1% of the samples. Lentic environments accounted for 58.9% of the samples and lotic environments for 41.1%. Immature individuals were most commonly found on Eichhornia crassipes, with this plant accounting for an average of 96.2% of all individuals, with a percentage ranging between 58.2% and 77.1% in different breeding areas. Only at the Foz do Igarapé Jirau site was a different distribution observed, with the number of aquatic plants more nearly equal: 83.3% of the larvae were found in Eichhornia crassipes, 9.2% in Ceratopteris pteridoides, 3.6% in E. azurea, 2.0% in Salvinia sp., and 1.9% in Pistia sp. The greatest richness was found in Iguapé do Raul. Concerning the larval/plant relationship, although less frequent, E. azurea had a higher larval density of Mansonia spp. It is important to emphasize that this finding may indicate a possible selection for this plant. Egg deposition by Mansonia spp. was more abundant in sample areas with Eichhornia crassipes and Pistia sp. The number of specimens collected was positively correlated with temperature, pH, and conductivity. These correlations showed a marked increase in the rainy season. Therefore, we were able to establish preliminary parameters of how environmental changes influence the ecology of this important genus of mosquitoes, the species of which are critical disease vectors.