Anopheline species (Diptera: Culicidae) from the Maracá Ecological Station, Roraima State, Brazil

Anopheline species were sampled in different ecotones at Maracá Ecological Station and in Cantá municipality, both in Roraima State, Brazil, in June 2016. Nine species were recorded. Six species belong to the subgenus Nyssorhynchus and three species to the subgenus Anopheles. The most abundant species collected were Anopheles triannulatus s.l., Anopheles nuneztovari s.l. and Anopheles oswaldoi species B. The remaining species had frequencies lower than 10%. While A. triannulatus s.l. was the most frequent and the most widely distributed species in the studied area, Anopheles darlingi Root, the main malaria vector in the Brazilian Amazon region, was captured in two different ecotones and in low frequency. Our findings suggest that the risk of malaria outbreaks at Maracá Ecological Station may be low. This study also describes the first record of Anopheles costai Fonseca & Ramos in Maracá Ecological Station, Roraima State, increasing the distribution range of this taxon.

Multiple Novel Clades of Anopheline Mosquitoes Caught Outdoors in Northern Zambia

Residual vector populations that do not come in contact with the most frequently utilized indoor-directed interventions present major challenges to global malaria eradication. Many of these residual populations are mosquito species about which little is known. As part of a study to assess the threat of outdoor exposure to malaria mosquitoes within the Southern and Central Africa International Centers of Excellence for Malaria Research, foraging female anophelines were collected outside households in Nchelenge District, northern Zambia. These anophelines proved to be more diverse than had previously been reported in the area. In order to further characterize the anopheline species, sequencing and phylogenetic approaches were utilized. Anopheline mosquitoes were collected from outdoor light traps, morphologically identified, and sent to Johns Hopkins Bloomberg School of Public Health for sequencing. Sanger sequencing from 115 field-derived samples yielded mitochondrial COI sequences, which were aligned with a homologous 488 bp gene segment from known anophelines (n = 140) retrieved from NCBI. Nuclear ITS2 sequences (n = 57) for at least one individual from each unique COI clade were generated and compared against NCBI’s nucleotide BLAST database to provide additional evidence for taxonomical identity and structure. Molecular and morphological data were combined for assignment of species or higher taxonomy. Twelve phylogenetic groups were characterized from the COI and ITS2 sequence data, including the primary vector species Anopheles funestus s.s. and An. gambiae s.s. An unexpectedly large proportion of the field collections were identified as An. coustani and An. sp. 6. Six phylogenetic groups remain unidentified to species-level. Outdoor collections of anopheline mosquitoes in areas frequented by people in Nchelenge, northern Zambia, proved to be extremely diverse. Morphological misidentification and underrepresentation of some anopheline species in sequence databases confound efforts to confirm identity of potential malaria vector species. The large number of unidentified anophelines could compromise the malaria vector surveillance and malaria control efforts not only in northern Zambia but other places where surveillance and control are focused on indoor-foraging and resting anophelines. Therefore, it is critical to continue development of methodologies that allow better identification of these populations and revisiting and cleaning current genomic databases.

The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia

Background Irrigation schemes may result in subsequent changes in malaria disease dynamics. Understanding the mechanisms and effects of irrigation on malaria vector bionomics and transmission intensity is essential to develop new or alternative surveillance and control strategies to reduce or control malaria risk. This study was designed to assess the effect of rice irrigation on malaria vector bionomics and transmission intensity in the Gambella Region, Ethiopia. Methods Comparative cross-sectional study was conducted in Abobo District of the Gambella Region, Ethiopia. Accordingly, clusters (kebeles) were classified into nearby and faraway clusters depending on their proximity to the irrigation scheme. Adult mosquito survey was conducted in February, August and November 2018 from three nearby and three faraway clusters using Centers for Disease Control and Prevention (CDC) light traps (LTs). During the November survey, human landing catch (HLC) and pyrethrum spray catch (PSC) were also conducted. The collected mosquitoes were morphologically identified to species and tested for Plasmodium infection using circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA). Furthermore, species-specific polymerase chain reaction (PCR) was performed to identify member species of the Anopheles gambiae complex. Chi-square and t-tests were used to analyze the data using the SPSS version 20 software package. Results A total of 4319 female anopheline mosquitoes comprising An. gambiae sensu lato, An. funestus group, An. pharoensis, An. coustani complex and An. squamosus were collected. Overall, 84.5% and 15.5% of the anopheline mosquitoes were collected from the nearby and faraway clusters, respectively. Anopheles gambiae s.l. was the predominant (56.2%) anopheline species in the area followed by An. pharoensis (15.7%). The density of anopheline mosquitoes was significantly higher in the nearby clusters in both HLCs [t(3) = 5.14, P = 0.0143] and CDC LT catches [t(271.97) = 7.446, P < 0.0001). The overall sporozoite rate of anopheline species from the nearby clusters was 10-fold higher compared to the faraway clusters. Conclusions Significantly higher mosquito population density was observed in areas close to the irrigation sites. Sporozoite infection rate in the mosquito population was also markedly higher from the nearby clusters. Therefore, the irrigation scheme could increase the risk of malaria in the area. Graphical abstract