Forest edge landscape context affects mosquito community composition and risk of pathogen emergence

Forest edges, where humans, mosquitoes, and wildlife interact, may serve as a nexus for zoonotic arbovirus exchange. Although often treated as uniform interfaces, the landscape context of edge habitats can greatly impact ecological interactions. Here, we investigated how the landscape context of forest edges shapes mosquito community structure in an Amazon rainforest reserve near the city of Manaus, Brazil, using hand-nets to sample mosquitoes at three distinct forest edge types. Sampling sites were situated at edges bordering urban land cover, rural land cover, and natural treefall gaps, while sites in continuous forest served as controls. Community composition differed substantially among edge types, with rural edges supporting the highest species diversity. Rural edges also provided suitable habitat for forest specialists, including key sylvatic vectors, of which Haemagogus janthinomys was the most abundant species sampled overall. Our findings emphasize the importance of landscape context in assessing pathogen emergence risk at forest edges.

Phylogeographic inference for Bichromomyia flaviscutellata sensu stricto (Diptera: Psychodidae: Phebotominae) from the Brazilian Amazon rainforest, based on the 3' region of the COI gene

Bichromomyia flaviscutellata (Mangabeira, 1942) sensu stricto (Diptera: Psychodidae) has been recognized as the main vector of Leishmania amazonensis in the Brazilian Amazon. For this reason, it is of paramount importance to understand the distribution of genetic diversity of populations of this vector, particularly the genetic structure and gene flow, for its management and control efforts. This study investigated the phylogeographic structure of five B. flaviscutellata s.s. populations from the central Brazilian Amazon region by analyzing 1,141 bp fragment of the 3' region of the COI gene. A total of 85 specimens of B. flaviscutellata s.s. were sequenced from Manaus (14), Rio Preto da Eva (10), Pitinga (14), Novo Airão (21), and Autazes (26); all in the state of Amazonas. The dataset yielded 59 haplotypes, most of them connected to each other in the main network. There were high levels of intrapopulation genetic variability (h = 0.945 ± 0.035 - 0.978 ± 0.054). The genetic distance values among populations varied from moderate (0.0873) to very high (0.3535), and all comparisons were significant, as well as the hierarchical analysis (ΦST = 0.2145). In contrast, these comparisons revealed a high number of shared sites (Ss = 6-34) and no difference in fixed sites (Sf = 0) among populations indicating absence of historical isolation. The Mantel test indicated that 67.92% (r = 0.6792; P = 0.06) of the genetic structure observed in B. flaviscutellata s.s. cannot be explained by the isolation-by-distance (IBD) model. This genetic structure, weakly explained by the IBD, may be due mainly by the forest habitat fragmentation and the low dispersal (flight) capacity of sand flies. Both factors could lead to population fragmentation and isolation, which promote genetic differentiation. Taken together, these findings suggest that the genetic structure observed in the studied populations of B. flaviscutellata s.s. is likely generated by microevolutionary processes acting at the population level at the present time and, therefore, evolutionary lineages were not recognized among the populations analyzed.

Bioecological Aspects of Species of the Subgenus Mansonia (Mansonia) (Diptera: Culicidae) Prior to the Installation of Hydroelectric Dams on the Madeira River, Rondônia State, Brazil

The objective of this study was to evaluate ecological aspects of Mansonia species before the construction of hydroelectric plants on the Madeira River, and thus enable the assessment of the impact of these projects on mosquitoes. A total of 199 samplings were carried out between November 2003 and August 2004, using the technique of attraction with protection. Temporal distribution was evaluated from monthly incidence values obtained from the bite index per man/hour. Relative abundance was subsequently calculated to evaluate the spatial distribution of species, according to land use and municipal districts; furthermore, the pattern of hematophagous activity was evaluated from 12-h and 4-h samplings. The data were analyzed according to the negative binomial distribution and generalized linear models to estimate the influence of environmental factors on the presence and abundance of Mansonia. A total of 1479 specimens were collected, distributed among four species-Mansonia titillans (87%), Mansonia humeralis (6.3%), Mansonia amazonensis (6%), and Mansonia indubitans (0.5%), and spatial distribution analysis showed Ma. titillans to be dominant. Hematophagous activity had peaks between 6:00 p.m. and 8:00 p.m. and species incidence was higher during the rainy season and in areas where domestic animals are raised. Therefore, the region studied presented characteristics favorable to the reproduction of Mansonia even before the construction of the hydroelectric plants and after construction, these conditions were enhanced, due to the increase in the availability of breeding sites for immatures and blood sources for females, as a consequence of changes in the environment.

Bionomics and population dynamics of anopheline larvae from an area dominated by fish farming tanks in northern Brazilian Amazon

BACKGROUND

In Brazilian Amazon, deforestation and other anthropogenic activities as a consequence of human occupation have created new and artificial larval habitats for anopheline mosquitoes, providing conditions for oviposition, development and expansion of malaria vector populations.

OBJECTIVES

This study aimed to structurally characterize and describe the entomological and limnological parameters of Anopheles larval habitats from a malaria region in northern Brazilian Amazon.

METHODS

Fifty-two larval habitats were investigated in the District of Ilha de Santana, in the Brazilian state of Amapá, comprising fish farming tanks, ponds, and streams. For entomological parameters, the immature larvae were collected monthly from July 2019 to June 2020. For limnological parameters, the water samples were collected from 20 larval habitats during the sampling period. The data were analyzed using Generalized Linear Models, Multivariate analyses, and Kruskal-Wallis tests.

RESULTS

Fifty habitats were positive for Anopheles larvae and a total of nine species were collected. The fish farming tanks had the highest abundance of larvae compared with ponds and streams. Anopheles darlingi, Anopheles nuneztovari s.l. and Anopheles triannulatus were collected in 94% of the larval habitats and showed the highest positivity index. The degree of shade and the type of water of the breeding sites were important factors for the presence of the main malaria vector, A. darlingi. This species was the most affected by pH, total dissolved solids, electrical conductivity, and nitrate.

CONCLUSIONS

Our findings indicate that fish farming tanks are major contributors to vector anopheline abundance and malaria transmission. Vector control strategies focused on these habitats are urgently needed.

Detection of Zika Virus in Aedes aegypti and Aedes albopictus Mosquitoes Collected in Urban Forest Fragments in the Brazilian Amazon

Zika virus (ZIKV) is an RNA flavivirus (Flaviviridae family) endemic in tropical and subtropical regions that is transmitted to humans by Aedes (Stegomyia) species mosquitoes. The two main urban vectors of ZIKV are Aedes aegypti and Aedes albopictus, which can be found throughout Brazil. This study investigated ZIKV infection in mosquito species sampled from urban forest fragments in Manaus (Brazilian Amazon). A total of 905 non-engorged female Ae. aegypti (22 specimens) and Ae. albopictus (883 specimens) were collected using BG-Sentinel traps, entomological hand nets, and Prokopack aspirators during the rainy and dry seasons between 2018 and 2021. All pools were macerated and used to inoculate C6/36 culture cells. Overall, 3/20 (15%) Ae. aegypti and 5/241 (2%) Ae. albopictus pools screened using RT-qPCR were positive for ZIKV. No supernatants from Ae. aegypti were positive for ZIKV (0%), and 15 out of 241 (6.2%) Ae. albopictus pools were positive. In this study, we provide the first-ever evidence of Ae. albopictus naturally infected with ZIKV in the Amazon region.

Where boundaries become bridges: Mosquito community composition, key vectors, and environmental associations at forest edges in the central Brazilian Amazon

Risk of spillover and spillback of mosquito-borne viruses in the neotropics, including yellow fever, dengue, Zika (Flaviviridae: Flavivirus), chikungunya, and Mayaro (Togaviridae: Alphavirus) viruses, is highest at ecotones where humans, monkeys, and mosquitoes coexist. With a view to identifying potential bridge vectors, we investigated changes in mosquito community composition and environmental variables at ground level at distances of 0, 500, 1000, and 2000 m from the edge of a rainforest reserve bordering the city of Manaus in the central Brazilian Amazon. During two rainy seasons in 2019 and 2020, we sampled 9,467 mosquitoes at 244 unique sites using BG-Sentinel traps, hand-nets, and Prokopack aspirators. Species richness and diversity were generally higher at 0 m and 500 m than at 1000 m and 2000 m, while mosquito community composition changed considerably between the forest edge and 500 m before stabilizing by 1000 m. Shifts in environmental variables mainly occurred between the edge and 500 m, and the occurrence of key taxa (Aedes albopictus, Ae. scapularis, Limatus durhamii, Psorophora amazonica, Haemagogus, and Sabethes) was associated with one or more of these variables. Sites where Ae. aegypti and Ae. albopictus were detected had significantly higher surrounding mean NDBI (Normalized Difference Built-up Index) values than sites where they were not detected, while the opposite was true for Sabethes mosquitoes. Our findings suggest that major changes in mosquito communities and environmental variables occur within 500 m of the forest edge, where there is high risk for contact with both urban and sylvatic vectors. By 1000 m, conditions stabilize, species diversity decreases, and forest mosquitoes predominate. Environmental variables associated with the occurrence of key taxa may be leveraged to characterize suitable habitat and refine risk models for pathogen spillover and spillback.

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

Haemagogus (Haemagogus) janthinomys (Dyar, 1921), the major neotropical vector of sylvatic yellow fever virus, is notoriously difficult to maintain in captivity. It has never been reared beyond an F1 generation, and almost no experimental transmission studies have been performed with this species since the 1940s. Herein we describe installment hatching, artificial blood feeding, and forced-mating techniques that enabled us to produce small numbers of F3 generation Hg. janthinomys eggs for the first time. A total of 62.8% (1562/2486) F1 generation eggs hatched during ≤10 four-day cycles of immersion in a bamboo leaf infusion followed by partial drying. Hatching decreased to 20.1% (190/944) in the F2 generation for eggs laid by mosquitoes copulated by forced mating. More than 85% (79/92) female F2 mosquitoes fed on an artificial blood feeding system. While we were unable to maintain a laboratory colony of Hg. janthinomys past the F3 generation, our methods provide a foundation for experimental transmission studies with this species in a laboratory setting, a critical capacity in a region with hyper-endemic transmission of dengue, Zika, and chikungunya viruses, all posing a risk of spillback into a sylvatic cycle.

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

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.

Anopheles (Nyssorhynchus) tadei: A new species of the Oswaldoi-konderi complex (Diptera, Anophelinae) and its morphological and molecular distinctions from An. konderi sensu stricto

The Oswaldoi-konderi Complex (Anopheles, Nyssorhynchus) is composed of five species that have been distinguished and delimited using DNA sequences of mitochondrial and nuclear genes. At least two species of the complex have been formally described, namely Anopheles oswaldoi s.s. and An. konderi; however, the identity of An. konderi s.s. is unclear because two morphologically similar species co-exist in the type-locality in the municipality of Coari, Amazonas state, Brazil. Moreover, the study of resurrection and designation of the neotype of An. konderi s.s. included a mixture of both forms. In the present study, mosquitoes were collected in Coari to establish the molecular identity of An. konderi s.s. and describe a new species based on morphological and molecular data. Six females were collected and separated individually for oviposition. The parental progenies were obtained from field collected females, fourth-instar larva, pupa, and female and male were employed for morphological characterization. Genomic DNA from one fourth-instar larva of each progeny was extracted and sequenced for the mtDNA COI barcode region, CAD gene, and the ITS2 rDNA nuclear region to establish the molecular identity of the two morphological forms of An. konderi s.l. The An. konderi neotype was re-examined. The morphological and molecular analyses revealed two distinct groups: the first group was identical to the neotype of An. konderi s.s., whereas the second was found to belong to the group informally referred to as An. sp. near konderi or An. konderi B, herein described as Anopheles tadei n. sp.

Scanning Electron Microscopy and Geometric Contour Morphometry for Identifying Eggs of Three Amazonian Species of Mansonia (Diptera: Culicidae)

The eggs of three Amazonian species of the genus Mansonia (Diptera: Culicidae) were analyzed using morphological and morphometric characters. Eggs of Mansonia humeralis Dyar & Knab, 1916 were morphologically different from those of Mansonia titillans (Walker, 1848) and Mansonia amazonensis (Theobald, 1901), which were more similar to each other according to linear and geometric morphometry. A principal component analysis generated from elliptic Fourier contour data (PC1-92.6% and PC2-2.61%) indicated that Ma. amazonensis and Ma. titillans are more similar to each other than either is to Ma. humeralis. Discriminant multivariate analysis was highly accurate with only four classification errors and a 90% accuracy rate. The results indicate that the three Amazonian species can be precisely distinguished in the egg stage and that geometric morphometry based on elliptic Fourier contours is a promising method for distinguishing eggs of species of Mansonia. An identification key based on egg morphology is provided to distinguish the four Neotropical species.

Exploring deeper genetic structures: Aedes aegypti in Brazil

Aedes aegypti, being the principal vector of dengue (DENV1 to 4), chikungunya and Zika viruses, is considered as one of the most important mosquito vectors. In Brazil, despite regular vector control programs, Ae. aegypti still persists with high urban density in all the states. This study aimed to estimate the intra and inter population genetic diversity and genetic structure among 15 Brazilian populations of Ae. aegypti based on 12 microsatellite loci. A total of 510 specimens were analyzed comprising eight locations from northern (Itacoatiara, Manaus, Novo Airão, Boa Vista, Rio Branco, Porto Velho, Guajará-Mirim and Macapá), three from southeastern (Araçatuba, São José de Rio Preto and Taubaté), one from southern (Foz do Iguaçu), one from central west (Cuiabá) and two from northeastern (Campina Grande and Teresina) regions of Brazil. Genetic distances (pairwise values of F_ST and Nm) and the analysis of molecular variance (AMOVA) were statistically significant, independent of geographic distances among the sites analyzed, indicating that them are under a complex dynamic process that influence the levels of gene flow within and among regions of the country. Bayesian analysis in STRUCTURE revealed the existence of two major genetic clusters, as well as there was genetic substructure within them; these results were confirmed by AMOVA, BAPS and DAPC analyses. This differentiation is the cumulative result of several factors combined as events of multiple introduction, passive dispersal, environmental and climatic conditions, use of insecticides, cycles of extinction and re-colonization followed by microevolutionary processes throughout the country. Isolation by distance also contributed to this differentiation, especially among geographically closer localities. These genetic differences may affect its vector competence to transmit dengue, chikungunya, Zika and the response to vector control programs.

An insight into the sialotranscriptome and virome of Amazonian anophelines

Background

Saliva of mosquitoes contains anti-platelet, anti-clotting, vasodilatory, anti-complement and anti-inflammatory substances that help the blood feeding process. The salivary polypeptides are at a fast pace of evolution possibly due to their relative lack of structural constraint and possibly also by positive selection on their genes leading to evasion of host immune pressure.

Results

In this study, we used deep mRNA sequence to uncover for the first time the sialomes of four Amazonian anophelines species (Anopheles braziliensis, A. marajorara, A. nuneztovari and A. triannulatus) and extend the knowledge of the A. darlingi sialome. Two libraries were generated from A. darlingi mosquitoes, sampled from two localities separated ~ 1100 km apart. A total of 60,016 sequences were submitted to GenBank, which will help discovery of novel pharmacologically active polypeptides and the design of specific immunological markers of mosquito exposure. Additionally, in these analyses we identified and characterized novel phasmaviruses and anpheviruses associated to the sialomes of A. triannulatus, A. marajorara and A. darlingi species.

Conclusions

Besides their pharmacological properties, which may be exploited for the development of new drugs (e.g. anti-thrombotics), salivary proteins of blood feeding arthropods may be turned into tools to prevent and/or better control vector borne diseases; for example, through the development of vaccines or biomarkers to evaluate human exposure to vector bites. The sialotranscriptome study reported here provided novel data on four New World anopheline species and allowed to extend our knowledge on the salivary repertoire of A. darlingi. Additionally, we discovered novel viruses following analysis of the transcriptomes, a procedure that should become standard within future RNAseq studies.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5545-0) contains supplementary material, which is available to authorized users.

Morphology of the eggs surface of ten Brazilian species of phlebotomine sandflies (Diptera: Psychodidae)

The chorionic sculpturing of ten Brazilian sandfly species, Nyssomyia antunesi (Coutinho), N. whitmani (Antunes and Coutinho), Bichromomyia flaviscutellata (Mangabeira), B. olmeca nociva (Young and Arias), Evandromyia walkeri (Newstead), E. williamsi (Antunes and Coutinho), Deanemyia maruaga (Alves, Freitas and Barrett), D. samueli (Deane), Viannamyia furcata (Mangabeira) and Lutzomyia dispar (Martins and Silva), was examined using scanning electron microscopy. Eggs of the last seven species, as well as the genera Deanemyia and Viannamyia, are described for the first time. In total, five patterns of chorionic sculpturing were found: polygonal, connected parallel ridges, unconnected parallel ridges, volcano-like and placoid. The last one is a new chorionic sculpture pattern, which was observed in D. samueli. These structures are illustrated and discussed. These results show that egg morphology can be used in phlebotomine taxonomy, both at generic and specific levels.

Morphological Description of the Immature Stages of Nyssomyia umbratilis (Ward & Frahia) (Diptera: Psychodidae: Phlebotominae), the Main Vector of Leishmania guyanensis Floch (Kinetoplastida: Trypanosomatidae) in the Brazilian Amazon Region

Nyssomyia umbratilis (Ward & Frahia) is the main vector of Leishmania guyanensis in the Brazilian Amazon region, where it is widely distributed. Studies have hypothesized that this phlebotomine is part of a cryptic species complex, spatially delimited by the Amazonian river systems, and with different transmission potential of L. guyanensis. In the present study, the immature stages of N. umbratilis are described from laboratory-reared specimens originating from the states of Amazonas and Pará, Brazil. Based on scanning electron and optical microscopy examinations, fine morphological structures (eggshell, setae, and mouthparts of larvae and pupae) are presented. A new form of sandfly pupae sexing (non-invasive) is also provided. The correct identification of insect is extremely important for the epidemiology of certain diseases. However, only the morphological characters of adult can be insufficient to separate accurately the closely related species. It is expected that the present description may contribute to solve the taxonomic problem involving N. umbratilis.

Molecular taxonomy and evolutionary relationships in the Oswaldoi-Konderi complex (Anophelinae: Anopheles: Nyssorhynchus) from the Brazilian Amazon region

Recent studies have shown that Anopheles oswaldoi sensu lato comprises a cryptic species complex in South America. Anopheles konderi, which was previously raised to synonymy with An. oswaldoi, has also been suggested to form a species complex. An. oswaldoi has been incriminated as a malaria vector in some areas of the Brazilian Amazon, Colombia, Peru and Venezuela, but was not recognized as a vector in the remaining regions in its geographic distribution. The role of An. konderi as a malaria vector is unknown or has been misattributed to An. oswaldoi. The focus of this study was molecular identification to infer the evolutionary relationships and preliminarily delimit the geographic distribution of the members of these complexes in the Brazilian Amazon region. The specimens were sampled from 18 localities belonging to five states in the Brazilian Amazon and sequenced for two molecular markers: the DNA barcode region (COI gene of mitochondrial DNA) and Internal Transcribed Spacer 2 (ITS2 ribosomal DNA). COI (83 sequences) and ITS2 (27 sequences) datasets generated 43 and 10 haplotypes, respectively. Haplotype networks and phylogenetic analyses generated with the barcode region (COI gene) recovered five groups corresponding to An. oswaldoi s.s., An. oswaldoi B, An. oswaldoi A, An. konderi and An. sp. nr. konderi; all pairwise genetic distances were greater than 3%. The group represented by An. oswaldoi A exhibited three strongly supported lineages. The molecular dating indicated that the diversification process in these complexes started approximately 2.8 Mya, in the Pliocene. These findings confirm five very closely related species and present new records for these species in the Brazilian Amazon region. The paraphyly observed for the An. oswaldoi complex suggests that An. oswaldoi and An. konderi complexes may comprise a unique species complex named Oswaldoi-Konderi. Anopheles oswaldoi B may be a potential malaria vector in the extreme north of the Brazilian Amazon, whereas evidence of sympatry for the remaining species in other parts of the Brazilian Amazon (Acre, Amazonas, Pará and Rondônia) precluded identification of probable vectors in those areas.

First record of Anopheles konderi Galvão & Damasceno (Diptera: Culicidae) carrying eggs of Dermatobia hominis (Linnaeus Jr.) (Diptera: Oestridae), from Oriximiná municipality, Pará, Brazil

INTRODUCTION

The muscoid fly Dermatobia hominis causes cutaneous myiases in mammals. Females of this species use a vector to carry their eggs to the host. This note describes Anopheles konderi acting as phoretic vector for D. hominis.

METHODS

A female A. konderi carrying D. hominis was collected using light traps in Oriximiná, Pará, Brazil. The A. konderi specimen was identified at morphological and molecular levels.

RESULTS

Eight eggs of D. hominis were observed on the Anopheles konderi female.

CONCLUSIONS

Anopheles konderi, only the third Anopheles species recorded as a phoretic vector, may be a potential vector of D. hominis.

Behavioral patterns, parity rate and natural infection analysis in anopheline species involved in the transmission of malaria in the northeastern Brazilian Amazon region

The characterization of behavioral patterns allows a better understanding of the transmission dynamics and the design of more effective malaria vector control strategies. This study analyzed the behavioral patterns of the Anopheles species of the Coração district situated in the northeast of the Brazilian Amazon region. The behavioral patterns of the anopheline species were measured based on the 36 collection sites of this district from December 2010 to November 2011. Collections of four hours for three consecutive nights each month and four 12-h collections, comprising two in the rainy season and two in the dry season, were performed. Furthermore, to infer the anthropophily and zoophily indexes, four additional four-hour collections were performed. The samples were also evaluated for parity rate and natural infectivity for Plasmodium spp. A total of 1689 anophelines were captured, comprising of nine species and two subgenera (Nyssorhynchus - six species, and Anopheles - three species). Anopheles darlingi was the most abundant and widely distributed species in the area, followed by A. braziliensis and A.marajoara. Anopheles darlingi and A. marajoara were the only species present in the four collections of 12-h, but only A. darlingi showed activity throughout night. Anopheles darlingi was the most anthropophilic species (AI=0.40), but the zoophily index was higher (ZI=0.60), revealing an eclectic and opportunistic behavior. Of the six most frequent species, A. nuneztovari s.l. was the most zoophilic species (ZI=1.00). All captured species showed predominance towards biting in outdoor environments. Anopheles darlingi and A. braziliensis showed multimodal biting peaks, whereas A. marajoara revealed a stable pattern, with the biting peak after sunset. Using the PCR technique, no anopheline was found infected with the malaria parasite. Since A. darlingi and A. marajoara are recognized as important vectors in this region, the district of Coração may be considered as a highly potent area for transmission of malaria, therefore, the prevention and surveillance measures should be taken constantly to prevent the same. The role of A. braziliensis as malaria vector needs to be urgently investigated.

Evidence of new species for malaria vector Anopheles nuneztovari sensu lato in the Brazilian Amazon region

BACKGROUND

Anopheles nuneztovari sensu lato comprises cryptic species in northern South America, and the Brazilian populations encompass distinct genetic lineages within the Brazilian Amazon region. This study investigated, based on two molecular markers, whether these lineages might actually deserve species status.

METHODS

Specimens were collected in five localities of the Brazilian Amazon, including Manaus, Careiro Castanho and Autazes, in the State of Amazonas; Tucuruí, in the State of Pará; and Abacate da Pedreira, in the State of Amapá, and analysed for the COI gene (Barcode region) and 12 microsatellite loci. Phylogenetic analyses were performed using the maximum likelihood (ML) approach. Intra and inter samples genetic diversity were estimated using population genetics analyses, and the genetic groups were identified by means of the ML, Bayesian and factorial correspondence analyses and the Bayesian analysis of population structure.

RESULTS

The Barcode region dataset (N = 103) generated 27 haplotypes. The haplotype network suggested three lineages. The ML tree retrieved five monophyletic groups. Group I clustered all specimens from Manaus and Careiro Castanho, the majority of Autazes and a few from Abacate da Pedreira. Group II clustered most of the specimens from Abacate da Pedreira and a few from Autazes and Tucuruí. Group III clustered only specimens from Tucuruí (lineage III), strongly supported (97 %). Groups IV and V clustered specimens of A. nuneztovari s.s. and A. dunhami, strongly (98 %) and weakly (70 %) supported, respectively. In the second phylogenetic analysis, the sequences from GenBank, identified as A. goeldii, clustered to groups I and II, but not to group III. Genetic distances (Kimura-2 parameters) among the groups ranged from 1.60 % (between I and II) to 2.32 % (between I and III). Microsatellite data revealed very high intra-population genetic variability. Genetic distances showed the highest and significant values (P = 0.005) between Tucuruí and all the other samples, and between Abacate da Pedreira and all the other samples. Genetic distances, Bayesian (Structure and BAPS) analyses and FCA suggested three distinct biological groups, supporting the barcode region results.

CONCLUSIONS

The two markers revealed three genetic lineages for A. nuneztovari s.l. in the Brazilian Amazon region. Lineages I and II may represent genetically distinct groups or species within A. goeldii. Lineage III may represent a new species, distinct from the A. goeldii group, and may be the most ancestral in the Brazilian Amazon. They may have differences in Plasmodium susceptibility and should therefore be investigated further.

Genetic diversity and population structure in the Leishmania guyanensis vector Lutzomyia anduzei (Diptera, Psychodidae) from the Brazilian Amazon

Lutzomyia (Nyssomyia) anduzei has been recognized as a secondary vector of Leishmania guyanensis in the Brazilian Amazon region. Since L. anduzei is anthropophilic, co-exists in areas of high leishmaniasis transmission and has been found infected with L. guyanensis, the understanding of the vector population structure and of the process responsible for it is paramount to the vector management and control efforts. In this study we analyzed 74 and 67 sequences of the COI and Cytb loci, respectively, from mitochondrial DNA, aiming to estimate the intra-population genetic variability and population structure in six L. anduzei samples from the Brazilian Amazon region. For COI, we found 58 haplotypes, low to high (FST=0.0310-0.4128) and significant (P=0.0033) genetic structure, and reduced gene flow among populations. The haplotype network yielded many reticulations that likely resulted from hypervariability in the locus. For Cytb, we observed 27 haplotypes, low to moderate (FST=0.0077-0.1954) and nonsignificant (P>0.05) genetic structure for the majority of comparisons and extensive gene flow among populations, in line with the haplotypes network data. AMOVA analysis indicated that most of the variation occurred within populations (83.41%, 90.94%); nevertheless, there were significant differences (ΦST=0.0906-0.1659; P=0.00098; P=0.00000) among them for both loci. The Mantel test showed that the genetic structure is not associated to an isolation-by-distance (IBD) model in either of both loci. These data suggest that L. anduzei is genetically very diverse. The genetic structure lacking IBD may be due to adaptation to local habitats and the low dispersal capacity of the sandflies, and both could lead to population fragmentation and geographic isolation. These findings have important implications for epidemiology, surveillance and vector control and may be a first step in understanding the evolutionary history of this species.

New microsatellite markers for the neotropical malaria vector Anopheles nuneztovari sensu lato

Anopheles nuneztovari sensu lato consists of cryptic species and genetic lineages, one of which is an important human malaria vector in the northern part of South America. Population structure and evolutionary genetics studies may help in the definition and delimitation of the species and lineages within this species complex, which is relevant information for organizations involved in malaria control efforts. In this study, 10 new microsatellite markers were isolated from 2 repeat-enriched genomic libraries of A. nuneztovari s.l. and were characterized in 37-48 mosquitoes of this species. All loci were highly polymorphic and encompassed 5-25 alleles per locus. The observed (HO) and expected (HE) heterozygosities ranged from 0.354 to 0.866 and from 0.613 to 0.932, respectively. Six of the 10 new loci showed significant deviations from the Hardy-Weinberg equilibrium, and no linkage disequilibrium was detected. The loci described in this study were more polymorphic than the 18 previously characterized loci and appear to be promising markers for use in investigating the fine-scale population genetic structure and the boundaries of the cryptic species and lineages within the A. nuneztovari complex.

Molecular taxonomy of the two Leishmania vectors Lutzomyia umbratilis and Lutzomyia anduzei (Diptera: Psychodidae) from the Brazilian Amazon

BACKGROUND

Lutzomyia umbratilis (a probable species complex) is the main vector of Leishmania guyanensis in the northern region of Brazil. Lutzomyia anduzei has been implicated as a secondary vector of this parasite. These species are closely related and exhibit high morphological similarity in the adult stage; therefore, they have been wrongly identified, both in the past and in the present. This shows the need for employing integrated taxonomy.

METHODS

With the aim of gathering information on the molecular taxonomy and evolutionary relationships of these two vectors, 118 sequences of 663 base pairs (barcode region of the mitochondrial DNA cytochrome oxidase I - COI) were generated from 72 L. umbratilis and 46 L. anduzei individuals captured, respectively, in six and five localities of the Brazilian Amazon. The efficiency of the barcode region to differentiate the L. umbratilis lineages I and II was also evaluated. The data were analyzed using the pairwise genetic distances matrix and the Neighbor-Joining (NJ) tree, both based on the Kimura Two Parameter (K2P) evolutionary model.

RESULTS

The analyses resulted in 67 haplotypes: 32 for L. umbratilis and 35 for L. anduzei. The mean intra-specific genetic distance was 0.008 (0.002 to 0.010 for L. umbratilis; 0.008 to 0.014 for L. anduzei), whereas the mean interspecific genetic distance was 0.044 (0.041 to 0.046), supporting the barcoding gap. Between the L. umbratilis lineages I and II, it was 0.009 to 0.010. The NJ tree analysis strongly supported monophyletic clades for both L. umbratilis and L. anduzei, whereas the L. umbratilis lineages I and II formed two poorly supported monophyletic subclades.

CONCLUSIONS

The barcode region clearly separated the two species and may therefore constitute a valuable tool in the identification of the sand fly vectors of Leishmania in endemic leishmaniasis areas. However, the barcode region had not enough power to separate the two lineages of L. umbratilis, likely reflecting incipient species that have not yet reached the status of distinct species.

Lutzomyia umbratilis, the main vector of Leishmania guyanensis, represents a novel species complex?

BACKGROUND

Lutzomyia umbratilis is an important Leishmania guyanensis vector in South America. Previous studies have suggested differences in the vector competence between L. umbratilis populations situated on opposite banks of the Amazonas and Negro Rivers in the central Amazonian Brazil region, likely indicating a species complex. However, few studies have been performed on these populations and the taxonomic status of L. umbratilis remains unclear.

METHODOLOGY/PRINCIPAL FINDINGS

Phylogeographic structure was estimated for six L. umbratilis samples from the central Amazonian region in Brazil by analyzing mtDNA using 1181 bp of the COI gene to assess whether the populations on opposite banks of these rivers consist of incipient or distinct species. The genetic diversity was fairly high and the results revealed two distinct clades ( = lineages) with 1% sequence divergence. Clade I consisted of four samples from the left bank of the Amazonas and Negro Rivers, whereas clade II comprised two samples from the right bank of Negro River. No haplotypes were shared between samples of two clades. Samples within clades exhibited low to moderate genetic differentiation (F(ST) = -0.0390-0.1841), whereas samples between clades exhibited very high differentiation (F(ST) = 0.7100-0.8497) and fixed differences. These lineages have diverged approximately 0.22 Mya in the middle Pleistocene. Demographic expansion was detected for the lineages I and II approximately 30,448 and 15,859 years ago, respectively, in the late Pleistocene.

CONCLUSIONS/SIGNIFICANCE

The two genetic lineages may represent an advanced speciation stage suggestive of incipient or distinct species within L. umbratilis. These findings suggest that the Amazonas and Negro Rivers may be acting as effective barriers, thus preventing gene flow between populations on opposite sides. Such findings have important implications for epidemiological studies, especially those related to vector competence and anthropophily, and for vector control strategies. In addition, L. umbratilis represents an interesting example in speciation studies.

Mitochondrial DNA detects a complex evolutionary history with Pleistocene Epoch divergence for the neotropical malaria vector Anopheles nuneztovari sensu lato

Cryptic species and lineages characterize Anopheles nuneztovari s.l. Gabaldón, an important malaria vector in South America. We investigated the phylogeographic structure across the range of this species with cytochrome oxidase subunit I (COI) mitochondrial DNA sequences to estimate the number of clades and levels of divergence. Bayesian and maximum-likelihood phylogenetic analyses detected four groups distributed in two major monophyletic clades (I and II). Samples from the Amazon Basin were clustered in clade I, as were subclades II-A and II-B, whereas those from Bolivia/Colombia/Venezuela were restricted to one basal subclade (II-C). These data, together with a statistical parsimony network, confirm results of previous studies that An. nuneztovari is a species complex consisting of at least two cryptic taxa, one occurring in Colombia and Venezuela and the another occurring in the Amazon Basin. These data also suggest that additional incipient species may exist in the Amazon Basin. Divergence time and expansion tests suggested that these groups separated and expanded in the Pleistocene Epoch. In addition, the COI sequences clearly separated An. nuneztovari s.l. from the closely related species An. dunhami Causey, and three new records are reported for An. dunhami in Amazonian Brazil. These findings are relevant for vector control programs in areas where both species occur. Our analyses support dynamic geologic and landscape changes in northern South America, and infer particularly active divergence during the Pleistocene Epoch for New World anophelines.

Permanent genetic resources added to Molecular Ecology Resources Database 1 February 2011-31 March 2011

This article documents the addition of 111 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Acipenser oxyrinchus desotoi, Anopheles nuneztovari sensu lato, Asellus aquaticus, Calopteryx splendens, Calopteryx virgo, Centaurea aspera, Centaurea seridis, Chilina dombeyana, Proctoeces cf. lintoni and Pyrenophora teres f. teres.

Reduced levels of genetic variation in Aedes albopictus (Diptera: Culicidae) from Manaus, Amazonas State, Brazil, based on analysis of the mitochondrial DNA ND5 gene

Aedes albopictus, a mosquito originally from Southeast Asia, is considered to be one of the main vectors of dengue fever, yellow fever and other arboviruses. We examined the genetic variability and population structure of 68 individuals of Ae. albopictus collected from five neighborhoods of the city of Manaus, based on the mitochondrial gene coding for NADH dehydrogenase subunit 5 (ND5). Two haplotypes were found, separated by a single mutational event (T <--> C), with extremely low levels of genetic variability (h = 0.187 +/- 0.059; pi = 0.00044 +/- 0.00014). Based on AMOVA, we concluded that most of the variation (99.08%) occurred within populations, though the levels of variation were not significant. Neutrality tests (Tajima's D and Fu's Fs) were non-significant, indicating that these populations are in genetic equilibrium. The most frequent haplotype (H1) is restricted to Brazilian populations of Ae. albopictus, while the rarer haplotype (H2) is shared with populations from the United States and Asia. We suggest that the reduced variability and low genetic structure identified in our study is a consequence of the recent introduction of this species in Manaus, possibly through a founder effect, followed by expansion throughout the city neighborhoods. Genetic similarity would therefore be due to insufficient time to have accumulated genetic differences between the populations of Ae. albopictus and not to extensive gene flow among them.

Evidence of two lineages of the dengue vector Aedes aegypti in the Brazilian Amazon, based on mitochondrial DNA ND4 gene sequences

Genetic variation was estimated in ten samples populations of Aedes aegypti from the Brazilian Amazon, by using a 380 bp fragment of the mitochocondrial NADH dehydrogenase subunit 4 (ND4) gene. A total of 123 individuals were analyzed, whereby 13 haplotypes were found. Mean genetic diversity was slightly high (h = 0.666 ± 0.029; π = 0.0115 ± 0.0010). Two AMOVA analyses indicated that most of the variation (~70%-72%) occurred within populations. The variation found among and between populations within the groups disclosed lower, but even so, highly significant values. F(ST) values were not significant in most of the comparisons, except for the samples from Pacaraima and Rio Branco. The isolation by distance (IBD) model was not significant (r = 0.2880; p = 0.097) when the samples from Pacaraima and Rio Branco were excluded from the analyses, this indicating that genetic distance is not related to geographic distance. This result may be explained either by passive dispersal patterns (via human migrations and commercial exchange) or be due to the recent expansion of this mosquito in the Brazilian Amazon. Phylogenetic relationship analysis showed two genetically distinct groups (lineages) within the Brazilian Amazon, each sharing haplotypes with populations from West Africa and Asia.

Population genetics and phylogeography of Aedes aegypti (Diptera: Culicidae) from Brazil

Population genetic analyses were conducted using samples of Aedes aegypti from 14 localities in the north, southeast, northeast, and central regions of Brazil. An 852-bp region of the mitochondrial DNA cytochrome oxidase I (COI) gene was used in the analyses. Ten haplotypes were observed, and cluster analyses revealed 2 groups (lineages) separated by 8 fixed mutations, suggesting that the Brazilian Ae. aegypti populations probably came from East and West Africa, with evidence of multiple introductions, one related to Group 1 and two related to Group 2. Considering all samples, genetic and geographic distances were significantly correlated (r(2) = 0.332; P = 0.038), supporting the isolation by distance (IBD) model, but no correlation was detected for any particular region, which is consistent with human migrations and trade exchanges. Genetic distances (pairwise F(ST) and Nm values), AMOVA, and cluster analyses indicated a deep genetic structure for the Brazilian Ae. aegypti, probably resulting from several factors: multiple introductions associated with distinct lineages, geographic differentiation (IBD), passive dispersal patterns, control activities, extinction and recolonization events, and genetic drift.

Population genetic structure of the major malaria vector Anopheles darlingi (Diptera: Culicidae) from the Brazilian Amazon, using microsatellite markers

The population genetic structure of Anopheles darlingi, the major human malaria vector in the Neotropics, was examined using seven microsatellite loci from nine localities in central and western Amazonian Brazil. High levels of genetic variability were detected (5-25 alleles per locus; H E = 0.519-0.949). There was deviation from Hardy-Weinberg Equilibrium for 59.79% of the tests due to heterozygote deficits, while the analysis of linkage disequilibrium was significant for only two of 189 (1.05%) tests, most likely caused by null alleles. Genetic differentiation (F ST = 0.001-0.095; Nm = 4.7-363.8) indicates that gene flow is extensive among locations < 152 km apart (with two exceptions) and reduced, but not absent, at a larger geographic scale. Genetic and geographic distances were significantly correlated (R(2) = 0.893, P < 0.0002), supporting the isolation by distance (IBD) model. The overall estimate of Ne was 202.4 individuals under the linkage disequilibrium model, and 8 under the heterozygote excess model. Analysis of molecular variance showed that nearly all variation (approximately 94%) was within sample locations. The UPGMA phenogram clustered the samples geographically, with one branch including 5/6 of the state of Amazonas localities and the other branch the Acre, Rondônia, and remaining Amazonas localities. Taken together, these data suggest little genetic structure for An. darlingi from central and western Amazonian Brazil. These findings also imply that the IBD model explains nearly all of the differentiation detected. In practical terms, populations of An. darlingi at distances < 152 km should respond similarly to vector control measures, because of high gene flow.

Molecular differentiation in natural populations of Anopheles oswaldoi sensu lato (Diptera: Culicidae) from the Brazilian Amazon, using sequences of the COI gene from mitochondrial DNA

Anopheles (Nyssorhynchus) oswaldoi (Peryassú, 1922) s. l., which has been incriminated as a potential human malaria vector in Western Brazilian Amazon, may constitute a cryptic species complex. However, the most recent study with isozymes indicated high similarity among samples from the States of Acre, Amazonas and Rondônia in the Brazilian Amazon. In the present study, 45 individuals were sequenced from Sena Madureira (State of Acre), Coari (State of Amazonas), São Miguel (State of Rondônia), and Moju (State of Pará), using the cytochrome oxidase I gene from mitochondrial DNA. Twenty-five haplotypes were identified in the four localities, and no haplotype was shared among them. The lowest haplotype number was detected in the Coari sample. The dendrogram based on maximum parsimony analysis yielded four groups: I) haplotypes 1, 2, 3, 4, and 5 from Sena Madureira and haplotypes 17 and 18 from São Miguel; II) haplotypes 13 to 16 and 19 to 22 from São Miguel; III) haplotypes 23 to 25 from Moju, and IV) haplotypes 6 to 9 from Sena Madureira and haplotypes 10 to 12 from Coari. The genetic distance (uncorrected p) obtained among the four groups ranged from 0.08 to 5.3%, whereas the highest values (4.97 to 5.3%) were found between groups I (Sena Madureira) and III (Moju). Based on male genitalia identification, it was suggested that group I may be A. oswaldoi s. s. whereas group IV may be A. konderi. Groups II and III could constitute other lineages or species within A. oswaldoi s. l., whose taxonomic status remains to be clarified. These results suggest that additional studies are necessary using samples of A. oswaldoi s. l. from a larger geographic area.

Isozyme similarity in Anopheles oswaldoi sensu lato (Diptera: Culicidae) from the Amazon region, Brazil

Isozyme electrophoresis studies were conduced on Anopheles oswaldoi sensu lato from three states in Amazonian (Brazil), including Acre, where this taxon has been incriminated as a potential human malaria vector. The 13 enzymes analyzed yielded a total of 20 loci. Of these, 10 were monomorphic in the three samples. Diagnostic loci were not found. The measures of genetic variability showed mean number of alleles per locus between 1.5 and 2.0, percentage of polymorphic loci of 40%, and mean heterozygosities from 0.031 to 0.062. The inbreeding coefficient F(IS) had a moderate mean value (0.109), which resulted from heterozygote genotype deficiencies and the presence of rare alleles in the homozygote state. Mean F(ST) value (0.0502) and genetic distance values (Nei's genetic similarity values of 0.994-0.997; Roger's genetic similarity values of 0.963-0.968) were very low among the three samples of An. oswaldoi s. l. Preliminary results of identifications of male genitalia indicated that An. oswaldoi s. s. Peryassú and Anopheles konderi Galvão & Damasceno of the An. oswaldoi complex coexist sympatrically in Sena Madureira, Acre, and São Miguel, Rondônia, whereas in the sample from Coari, Amazonas, only An. konderi was identified. The isozyme results do not suggest differences between these species, particularly in areas of sympatry.

Genetic differentiation and diagnostic loci among Anopheles (Nyssorhynchus) rangeli, An. (Nys.) nuneztovari, and An. (Nys.) dunhami (Diptera: Culicidae) in the Brazilian Amazon

Genetic variability and divergence were estimated for populations of Anopheles rangeli Gabaldón, Cova-Garcia & Lopes, Anopheles nuneztovari Gabald6n cytotype A, and Anophels dunhami Causey from the Brazilian Amazon using isozyme electrophoresis. These species are included in the Oswaldoi subgroup, subgenus Nyssorhynchus (Diptera: Culicidae). Thirteen enzymes yielded a total of 22 loci, of which 14 were monomorphic in the three species. Three diagnostic loci (Gpi-1, Hk-1, and Me) and a strong differentiation in the Mdh locus were found between An. rangeli and An. nuneztovari. Five diagnostic loci (Mdh, Gpi-l, Hk-1, Gpd, and Me) separated An. rangeli from An. dunhami, whereas one diagnostic locus (Gpd) separated An. nuneztovari from An. dunhami. Moderate differentiation was observed in the Est-5 and Pgm loci between An. rangeli and An. nuneztovari, and between An. nuneztovari and An. dunhami. Anopheles dunhami had the highest values for three indices of genetic variability, whereas An. rangeli showed the lowest values for mean number of alleles per locus and mean heterozygosity. Nei's genetic distance was highest between An. rangeli and An. dunhami (0.280) and lowest between An. nuneztovari and An. dunhami (0.072). Between An. rangeli and An. nuneztovari the genetic distance was 0.237. Anopheles dunhami and An. nuneztovari are sister species very closely related and may have a recent evolutionary origin. Anopheles rangeli probably diverged before the other two species separated. This is the first record of An. dunhami in Coari (Amazonas, Brazil) and only the third collection site of this species since its description in 1945.

Enzymatic analysis in Anopheles nuneztovari Gabaldón (Diptera, Culicidae)

Enzymatic analysis in Anopheles nuneztovari was made using four populations from the Brazilian Amazon and two from Colombia. The enzymes ME and XDH presented a monomorphic locus in all of the studied populations. EST and LAP presented a higher number of loci. In EST, genetic variation was observed in the five loci; LAP presented four loci, with allec variation in two loci. In IDH, three activity regions were stained, with genetic variation for locus Idh-1 in the Brazilian Amazon populations. A locus for MDH was observed, with genetic variation in the six populations. A region was verified for ACON, with four alleles in Sitronela and three in the other populations. PGM constituted one locus, with a high variability in the Brazilian Amazon populations. A locus was observed for 6-PGD with allelic variation in all of the populations with the exception of Tibú. Enzyme PGI presented two loci, both with genetic variability in the Tucuruí population. The enzyme alpha-GPD showed an activity region with polymorphism in the Tucuruí, Tibú and Sitronela populations. The phenotypic variations detected for these enzymes suggest that four (EST, LAP, ACON and PGM) possess monomeric structures and five (IDH, MDH, 6-PGD, PGI and alpha-GPD) dimeric structures in their proteins. These enzymes constitute in important markers to estimate variability and genetic divergence in natural populations of A. nuneztovari.

Genetic divergence in mitochondrial DNA of Anopheles nuneztovari (Diptera: Culicidae) from Brazil and Colombia

In the present study, we have examined the variability in Anopheles nuneztovari mitochondrial DNA of three populations from the Brazilian Amazon and one from western Colombia (Sitronela), using four restriction endonucleases (BclI, ClaI, HindIII, SstI). The haplotype diversity (h) was slightly elevated in all populations (0.5000 to 0.6765), whereas the nucleotide diversity (pi) was lower in the Sitronela population (0.0029) and higher in populations from the Brazilian Amazon (0.0056 to 0.0098). The degree of sequence divergence (delta) estimated within the Brazilian Amazon and that in Sitronela (0.0329 to 0.0371) suggests that these geographic populations of A. nuneztovari may eventually constitute separate species. The low sequence divergence values among the three Brazilian Amazon populations (0.0012 to 0.0031) indicate that these populations are genetically similar. These results are consistent with those recently reported for allozymes of these same populations.

Population structure and genetic divergence in Anopheles nuneztovari (Diptera: Culicidae) from Brazil and Colombia

Anopheles nuneztovari is considered an important vector of human malaria in several localities in Venezuela and Colombia. Its status as a vector of human malaria is still unresolved in areas of the Brazilian Amazon, in spite of have been found infected with Plasmodium sp.. For a better understanding of the genetic differentiation of populations of A. nuneztovari, electrophoretic analysis using 11 enzymes was performed on four populations from Brazil and two from Colombia. The results showed a strong differentiation for two loci: alpha-glycerophosphate dehydrogenase (alpha-Gpd) and malate dehydrogenase (Mdh) from 16 loci analyzed. Diagnostic loci were not detected. The populations of A. nuneztovari from the Brazilian Amazon showed little genetic structure and low geographic differentiation, based on the F(IS) (0.029), F(ST) (0.070), and genetic distance (0.001-0.032) values. The results of the isozyme analysis do not coincide with the indication of two lineages in the Amazon Basin by analysis of mitochondrial DNA, suggesting that this evolutionary event is recent. The mean F(ST) value (0.324) suggests that there is considerable genetic divergence among populations from the Brazilian Amazon and Colombia. The genetic distance among populations from the Brazilian Amazon and Colombia is ranges from 0.047 to 0.148, with the highest values between the Brazilian Amazon and Sitronela (SIT) (0.125-0.148). These results are consistent with those observed among members of anopheline species complexes. It is suggested that geographic isolation has reduced the gene flow, resulting in the genetic divergence of the SIT population. Dendrogram analysis showed three large groups: one Amazonian and two Colombia, indicating some genetic structuring. The present study is important because it attempted to clarify the taxonomic status of A. nuneztovari and provide a better understanding of the role of this mosquito in transmission of human malaria in northern South America.

Ecologic observations on anopheline vectors of malaria in the Brazilian Amazon

Human intervention in the Brazilian Amazon region promotes contacts between humans and vectors that may favor the propagation of anopheline mosquitoes and the spread of malaria in the absence of planning and infrastructure to control this disease. Vector ecology studies were carried out to determine the risk areas. These data should help in designing appropriate malaria control measures. Data from 14 different regions are reported. Vectors are able to adapt to different environments, which made it necessary to study each area. The parameters studied were Anopheles breeding sites, species distribution, incidence, feeding preferences, hours of maximum activity of adult mosquitoes, seasonality, resting places, and the presence of Plasmodium. Species complexes were also studied. Anopheles darlingi may be responsible for maintaining malaria in human populations in this region. A reduction in the population density of A. darlingi in a particular geographic area can sometimes cause the disappearance of malaria. This species feeds at night but has a peak of activity at the beginning of the evening and another at dawn. Other species are mainly crepuscular and all anophelines demonstrated pronounced exophilia. The timing of feeding activities was found to vary in areas altered by human intervention and also depended on the time of the year and climatic conditions. The larvae were more abundant in the rivers with a less acidic pH and rural areas showed the highest larval index.

[Biology of Amazonian Anopheles. XII. Occurrence of Anopheles species, transmission dynamics and malaria control in the urban area of Ariquemes (Rondônia)]

Dados sobre o grau de incidência e distribuição de espécies Anopheles, em Ariquemes (RO), evidenciaram que a diversidade é maior na periferia da cidade e que Anopheles darlingi é registrada em praticamente todas as localidades de coleta. O inquérito entomológico revelou níveis diferentes de penetração da espécie na área urbana, podendo-se constatar que os Setores 1 e 3 são áreas livres de malária; Setores 2 e 4 mostram riscos na periferia; e a Área Industrial e Setor de Áreas Especiais, Conjunto BNH, Setor 5 e Vila Velha constituem áreas de alto risco da malária. Nestes últimos, os índices de mosquitos por homem/hora foram os mais elevados, observando-se variações no decorrer das amostragens e conforme a localização da área urbana. Medidas de densidade populacional revelaram mudanças estacionais, sendo os menores valores registrados no período de inverno. A transmissão da malária é discutida, considerando-se: 1) o papel da estrutura física da cidade, na época da fundação, 2) os igarapés que margeam a área urbana e suas relações com o ciclo de desenvolvimento dos anofelinos, 3) os padrões comportamentais da atividade de picar das espécies correlacionados a ambientes naturais e às áreas ecologicamente alteradas, e 4) a importância do manuseio ambiental no controle da malária, para redução da densidade populacional. Para conter o processo migratório do vetor é proposto um cinturão de proteção à cidade, constituído de mata não densa, incluindo também proteção biológica para incentivar a zoofilia dos anofelinos. Os resultados de infecção natural, obtidos em áreas de autoctonia da malária, permitem citar A. darlingi como vetor, sendo discutida a possibilidade de que outras espécies estejam envolvidas na transmissão.