Microclimate and the vertical stratification of potential bridge vectors of mosquito‑borne viruses captured by nets and ovitraps in a central Amazonian forest bordering Manaus, Brazil

Abstract

In the Americas, some mosquito-borne viruses such as Zika, chikungunya, and dengue circulate among humans in urban transmission cycles, while others, including yellow fever and Mayaro, circulate among monkeys in sylvatic cycles. The intersection of humans and wildlife at forest edges creates risk for zoonotic virus exchange. We built a scaffold tower at the edge of a treefall gap in rainforest bordering Manaus, Brazil, to identify vectors that may bridge transmission between humans and monkeys. We vertically sampled diurnally active, anthropophilic mosquitoes using handheld nets at 0, 5, and 9 m and container-breeding mosquitoes in ovitraps at 0, 5, 10, and 15 m. Haemagogus janthinomys and Psorophora amazonica were present in high relative abundance in nets at each height sampled, while anthropophilic species were uncommon in ovitraps. Hg. janthinomys was more abundant at elevated heights than at ground level, while Ps. amazonica abundance was not significantly stratified across heights. The presence of each species increased with increasing 7-day rainfall lagged at 1 week, and at 1 and 4 weeks prior to collection, respectively. In addition, Hg. janthinomys was most frequently collected at 29.9 °C, irrespective of height. These data provide insight into the potential role of each species as bridge vectors.

Evaluation of methods for collecting mosquitoes (Culicidae: Diptera) in canopy and ground strata in the Brazilian Savanna.

“…This result differs from several studies in which the species is cited as an acrodendrophile [45,53,55,65,66]. On the other hand, it adds to the results of other studies where variations in this pattern were observed [3,44,56].…”

“…However, in both studies, the hand-net was the technique with greater richness and diversity and lower dominance in both strata, while the indicators of traps using only BG-Lure® demonstrated inefficiency, a result also found for wild diurnal mosquitoes in Brazil by other researchers [55,56]. This shows that the exclusive use of BG-Lure® may be inefficient for wild neotropical species.…”

“…It is worth mentioning that there are few attractants available for commercial use, as can be seen in many studies carried out in Brazil to evaluate the performance of mosquito collection with automatic traps [23][24][25][26][27]30,[55][56][57][58][59][60][61]. This suggests the need to develop in situ studies using olfactometry to discover different substances that present selective attractiveness for each species of interest, according to the biome where it will be used.…”

Towards the Laboratory Maintenance of Haemagogus janthinomys (Dyar, 1921), the Major Neotropical Vector of Sylvatic Yellow Fever

“…Host-seeking female Haemagogus species mosquitoes were collected at the Adolpho Ducke forest reserve bordering Manaus in the Brazilian Amazon between February and April 2022. Approaching mosquitoes were collected with handheld nets at ground level and on elevated platforms during the daytime (10:00–15:00) at a treefall (02.92537° S, 059.96582° W) [ 36 ]. Captured mosquitoes were transferred to a 16 × 19.5 cm cylindrical cardboard cage and provided with cotton wool soaked with mineral water for hydration.…”

“…Field collected mosquitoes were sampled at a site where >97% of anthropophilic Haemagogus were known to be Hg. janthinomys [ 36 ]. All individually maintained mosquitoes (field collected and F 2 adult females) were morphologically identified using a stereomicroscope and relevant taxonomic keys [ 2 , 37 , 38 , 39 ].…”