Mosquitoes (Diptera: Culicidae) From the Southwestern Brazilian Amazon: Liberdade and Gregório Rivers

Efficiency of four trap types and human landing catch in the sampling of Mansonia (Diptera, Culicidae) in Porto Velho, Rondônia, Brazil

Entomological surveillance plays a crucial role in designing and implementing mosquito control measures. In this context, developing more effective collection strategies is essential to accurately estimate the entomological parameters necessary for effective control. In this study, we investigated the effectiveness of four traps: CDC light trap, MosqTent, BG-Sentinel, and SkeeterVac, compared to human landing catch (HLC) in the collection of Mansonia mosquitoes, known to cause discomfort to riverside populations along the Madeira River in the District of Jaci Paraná, Porto Velho, in Rondônia state, Brazil. Sampling was conducted, during three periods corresponding to two seasons, dry and rainy, over five consecutive days for each period. The captures using HLC and the installation of the traps took place on the grounds of five selected residences from 6 to 10 pm. Rotational exchanges between houses ensured that all traps and the HLC were used in each of the five residences, following a predetermined Latin square pattern. A total of 7,080 mosquitoes were collected, of which 90.5% belonged to the Mansonia genus, distributed in four species: Mansonia titillans (75.97%), Mansonia humeralis (18.91%), Mansonia amazonensis (1.90%), and Mansonia indubitans (1.37%). HLC captured the highest number of Mansonia mosquitoes (58.1%), followed by SkeeterVac (21.8%) and MosqTent (18.9%). CDC and BG-Sentinel showed a very low performance (0.92 and 0.23%, respectively). Although HLC performed better in capturing Mansonia, our results suggest that SkeeterVac and MosqTent can serve as valuable additional tools to entomological inventories or sentinels for detecting invasive species in areas with high epidemiological vulnerability, thereby providing evidence-based recommendations for improving mosquito control measures and entomological surveillance.

First Description of Loreto Virus in Three Culicidae Species from the Atlantic Forest, Bahia, Brazil

Loreto virus (LORV) is an insect-specific virus classified into the proposed taxon Negevirus. It was originally described in Iquitos, Peru, in 1977. Here, we describe three novel LORV genomes obtained from the isolates of three pooled samples of Trichoprosopon digitatum, Aedes (Ochlerotatus) fulvus, and Limatus durhamii collected in Ilhéus-Bahia, 2014. Samples were submitted to RNA sequencing on the Illumina platform to recover the LORV genome. The genomes presented, on average, 81.5% nucleotide identity and 92.6% global amino acid identity with the LORV reference genome (NC_034158). Subsequently, phylogenetic analysis was performed based on a multiple sequence alignment of the concatenated amino acid sequences predicted for the three ORFs of the Negevirus genomes, and the target sequences were clustered within the LORV clade. The taxon Negevirus is in constant expansion of its species content and host range. New data about insect specific negeviruses are important for virus evolution studies, along with those approaching interactions with the hosts and their influence in the transmission of arboviruses. Also, the assessment of these data may allow the development of biologic control strategies for arboviral vectors. This is the original report of the identification of LORV in Brazil, infecting three Culicidae species hosts native to the Atlantic Forest biome.

Change in the faunal composition of mosquitoes (Diptera: Culicidae) along a heterogeneous landscape gradient in the Brazilian Amazon

This study aimed to evaluate the influence of different anthropic landscape profiles on the diversity and distribution of mosquito species in a rural settlement of the Brazilian Amazon. Eight field collections were conducted at 18 sampling points interspersed throughout 2020-2021. Plastic containers, bamboo internodes, and tires were used as traps to capture immature mosquitoes in three distinct habitats: forest, forest edge, and peridomicile. A total of 15,547 individuals, distributed in 26 species of culicids, were collected. The most abundant species were Culex urichii (8,376 specimens), Culex (Melanoconion) (2,473 specimens), and Aedes albopictus (1,252 specimens). Forest habitat showed the highest abundance, and forest edge showed the highest species richness. Different types of environments influenced both the abundance and richness of mosquitoes. The species composition was also significantly different between the analyzed sites, mainly between forest and peridomicile environments. The change in species dominance could largely explain this change in mosquito community composition. Haemagogus janthinomys, an important sylvatic arbovirus vector, was found in peridomicile habitats and Ae. albopictus, a vector associated with human environments, was found in forest habitats, thus providing evidence of species spillover. Our results indicated that landscape changes affect mosquito communities, influencing their richness and abundance. These changes may have implications for future arboviral outbreaks in this rural settlement due to the possible establishment of sylvatic vector species in anthropic environments.

Nondestructive Methods of Pathogen Detection: Importance of Mosquito Integrity in Studies of Disease Transmission and Control

Mosquitoes are vectors of many pathogens, including viruses, protozoans, and helminths, spreading these pathogens to humans as well as to wild and domestic animals. As the identification of species and the biological characterization of mosquito vectors are cornerstones for understanding patterns of disease transmission, and the design of control strategies, we conducted a literature review on the current use of noninvasive and nondestructive techniques for pathogen detection in mosquitoes, highlighting the importance of their taxonomic status and systematics, and some gaps in the knowledge of their vectorial capacity. Here, we summarized the alternative techniques for pathogen detection in mosquitoes based on both laboratory and field studies. Parasite infection and dissemination by mosquitoes can also be obtained via analyses of saliva- and excreta-based techniques or of the whole mosquito body, using a near-infrared spectrometry (NIRS) approach. Further research should be encouraged to seek strategies for detecting target pathogens while preserving mosquito morphology, especially in biodiversity hotspot regions, thus enabling the discovery of cryptic or new species, and the determination of more accurate taxonomic, parasitological, and epidemiological patterns.

First Isolation and Genome Sequence Analysis of West Nile Virus in Mosquitoes in Brazil

West Nile virus is a flavivirus transmitted by mosquitoes, mainly of the genus Culex. In Brazil, serological studies have already indicated the circulation of the virus since 2003, with the first human case detected in 2014. The objective of the present paper is to report the first isolation of WNV in a Culex (Melanoconion) mosquito. Arthropods were collected by protected human attraction and CDC light bait, and taxonomically identified and analyzed by viral isolation, complement fixation and genomic sequencing tests. WNV was isolated from samples of Culex (Melanoconion) mosquitoes, and the sequencing analysis demonstrated that the isolated strain belonged to lineage 1a. The finding of the present study presents the first evidence of the isolation and genome sequencing of WNV in arthropods in Brazil.

Vector Competence of Culex quinquefasciatus from Brazil for West Nile Virus

West Nile virus is characterized as a neurotropic pathogen, which can cause West Nile fever and is transmitted by mosquitoes of the genus Culex. In 2018, the Instituto Evandro Chagas performed the first isolation of a WNV strain in Brazil from a horse brain sample. The present study aimed to evaluate the susceptibility of orally infected Cx. quinquefasciatus from the Amazon region of Brazil to become infected and transmit the WNV strain isolated in 2018. Oral infection was performed with blood meal artificially infected with WNV, followed by analysis of infection, dissemination, and transmission rates, as well as viral titers of body, head, and saliva samples. At the 21st dpi, the infection rate was 100%, the dissemination rate was 80%, and the transmission rate was 77%. These results indicate that Cx. quinquefasciatus is susceptible to oral infection by the Brazilian strain of WNV and may act as a possible vector of the virus since it was detected in saliva from the 21st dpi.

Revision of the Educator Group of Culex (Melanoconion) (Diptera, Culicidae)

The Educator Group of the Melanoconion Section of Culex (Melanoconion) (Diptera, Culicidae) is reviewed. Currently, the group includes the following valid species: Culex (Melanoconion) aphyllusTalaga, 2020, Culex (Melanoconion) cristovaoi Duret, 1968, Culex (Melanoconion) educatorDyar & Knab, 1906, Culex (Melanoconion) eknomiosForattini & Sallum, 1992, Culex (Melanoconion) inadmirabilisDyar, 1928, Culex (Melanoconion) rachoui Duret, 1968, Culex (Melanoconion) theobaldi (Lutz), 1904, Culex (Melanoconion) vaxusDyar, 1920, Culex (Melanoconion) angularis Sá & Sallum n. sp., Culex (Melanoconion) spiniformis Sá & Hutchings n. sp., Culex (Melanoconion) longistriatus Sá & Hutchings n. sp., Culex (Melanoconion) anelesDyar & Ludlow, 1922, Culex (Melanoconion) apeteticus Howard, Dyar & Ludlow, 1913, and Culex (Melanoconion) bibulusDyar, 1920. The last three species were resurrected from synonymy of either Cx. educator or Cx. vaxus. Descriptions, differential diagnoses, bionomics, and geographical data are provided for each species when available.

Seasonality and Biting Behavior of Mansonia (Diptera, Culicidae) in Rural Settlements Near Porto Velho, State of Rondônia, Brazil

Mansonia (Diptera: Culicidae) are known to cause discomfort to the local populations of Amazon. Considering the fact that the effective control of these mosquitoes can only be obtained by understanding their ecology and behavior, entomological monitoring becomes essential. In view of this, mosquitoes of the genus Mansonia were collected by human landing catches (HLC) from 2015 to 2019, in four locations of Porto Velho, Rondônia, Brazil. The collections were performed inside and outside the homes, once in every four months, uninterrupted for 24 hr. Human bite indices/hour was used to analyze the hourly activity of the species for different seasons and environment (indoor and outdoor). Moreover, nonparametric Mann-Whitney tests were conducted to indicate if there were differences between exophagic and endophagic behavior. The seasonality of Mansonia species was also analyzed. Overall, 96,766 specimens were collected over five years of sampling. Mansonia titillans (Walker) was found to be the most abundant species (76.9%). The highest percentage of mosquitoes was collected in February (48.4%), followed by October (39.6%) and June (12.0%). The biting activity of the two most abundant species showed peak host seeking activity/behavior during twilight and night, more perceptible in the outdoor environment (peridomiciliary). In general, seasonality showed a tendency towards a reduction in the abundance of Mansonia in the years after 2015. Our results will be essential in the formulation of effective control methodology for Mansonia in the studied area.

Vector role and human biting activity of Anophelinae mosquitoes in different landscapes in the Brazilian Amazon

BACKGROUND

Environmental disturbance, deforestation and socioeconomic factors all affect malaria incidence in tropical and subtropical endemic areas. Deforestation is the major driver of habitat loss and fragmentation, which frequently leads to shifts in the composition, abundance and spatial distribution of vector species. The goals of the present study were to: (i) identify anophelines found naturally infected with Plasmodium; (ii) measure the effects of landscape on the number of Nyssorhynchus darlingi, presence of Plasmodium-infected Anophelinae, human biting rate (HBR) and malaria cases; and (iii) determine the frequency and peak biting time of Plasmodium-infected mosquitoes and Ny. darlingi.

METHODS

Anopheline mosquitoes were collected in peridomestic and forest edge habitats in seven municipalities in four Amazon Brazilian states. Females were identified to species and tested for Plasmodium by real-time PCR. Negative binomial regression was used to measure any association between deforestation and number of Ny. darlingi, number of Plasmodium-infected Anophelinae, HBR and malaria. Peak biting time of Ny. darlingi and Plasmodium-infected Anophelinae were determined in the 12-h collections. Binomial logistic regression measured the association between presence of Plasmodium-infected Anophelinae and landscape metrics and malaria cases.

RESULTS

Ninety-one females of Ny. darlingi, Ny. rangeli, Ny. benarrochi B and Ny. konderi B were found to be infected with Plasmodium. Analysis showed that the number of malaria cases and the number of Plasmodium-infected Anophelinae were more prevalent in sites with higher edge density and intermediate forest cover (30-70%). The distance of the drainage network to a dwelling was inversely correlated to malaria risk. The peak biting time of Plasmodium-infected Anophelinae was 00:00-03:00 h. The presence of Plasmodium-infected mosquitoes was higher in landscapes with > 13 malaria cases.

CONCLUSIONS

Nyssorhynchus darlingi, Ny. rangeli, Ny. benarrochi B and Ny. konderi B can be involved in malaria transmission in rural settlements. The highest fraction of Plasmodium-infected Anophelinae was caught from midnight to 03:00 h. In some Amazonian localities, the highest exposure to infectious bites occurs when residents are sleeping, but transmission can occur throughout the night. Forest fragmentation favors increases in both malaria and the occurrence of Plasmodium-infected mosquitoes in peridomestic habitat. The use of insecticide-impregnated mosquito nets can decrease human exposure to infectious Anophelinae and malaria transmission.