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RESEARCH ARTICLE
Year : 2022 | Volume
: 59
| Issue : 4 | Page : 363-374
Dispersion routes of the main vectors of human malaria in the Americas: Genetic evidence from the mitochondrial COI gene
Jean Carlos Sanchez-Rojas, Oscar Alexander Aguirre-Obando
School of Biomathematical Research; Biology Program, Faculty of Basic Sciences and Technologies, Universidad del Quindío. Carrera 15 Calle 12 Norte, Armenia, Colombia
Correspondence Address:
Prof. Oscar Alexander Aguirre-Obando
School of Biomathematical Research, Universidad del Quindío. Carrera 15 Calle 12 Norte, Armenia, Colombia
Colombia
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0972-9062.361173
Background and objectives: In America, of the 44 species of Anopheles, nine are main vectors of malaria and, of these, genetic information exists for seven. Hence, this study sought to know the gene flow and diversity of the seven principal vectors of malaria at the Americas level.
Methods: For the seven species and the sequences of the mitochondrial cytochrome c oxidase I (COI) gene obtained from the GenBank and Bold System, genetic analyzes of populations and genetic structure were performed and haplotype networks and phylogenetic trees were obtained.
Results: For the seven species, 1440 sequences were analyzed and 519 haplotypes were detected. The Hd and π values were higher within a continental context than by countries. Neutrality tests indicated positive and negative values with most of these being significant (p < 0.05). Phylogenetic analyses for all the species recovered three clades with no geographic pattern among them.
Interpretation & conclusion: Studies suggest that native species of Anopheles from the Americas have greater haplotype diversity and low genetic differentiation due to the lack of physical barriers to impede gene flow among these populations. Moreover, all the species are interconnected by roadways. This scenario complicates the epidemiological picture of malaria in the Americas.
Keywords: America; Anopheles; gene flow; haplotype networks; phylogeography
Jean Carlos Sánchez-Rojas & Oscar Alexander Aguirre-Obando. Authors contributed equally
Introduction
Malaria is a disease of medical importance caused by the parasites of genus Plasmodium spp., where mosquitoes of genus Anopheles are their vectors. Female anophelines acquire parasite through the blood of invertebrate hosts infected by Plasmodium spp.[1]. Additionally, it has been observed that it is a competent vector for the Mayaro virus and has the vector capacity for the O’nyong-nyong alphavirus[2]. Malaria is known as the disease of the most vulnerable as it affects children and low-income populations. Globally, malaria is estimated to affect 229 million people annually. In the Americas, between 2010 and 2018, it was estimated that over 680,000 cases occurred annually[3]. The genus Anopheles includes 480 species present all around the world, grouped into eight subgenera. Of these, Anopheles (~190 species), Cellia (~224 species), Kerteszia (~12 species), and Nyssorhynchus (~12 species) have some species vectors for human malaria[4], with 41 being the main vectors of this disease[5].
Of the 41 species, nine are distributed in the American continent. An. (Ano.) pseudopunctipennis is found throughout the continent. In turn, An. (Nys.) aquasalis, An. (Nys.) darlingi, An. (Nys.) marajoara, and An. (Nys.) albimanus are present in Central and South America, with An. (Nys.) albimanus distributed in a small part of North America. The complexes An. (Nys.) albitarsis (~11 species) and An. (Nys.) nuneztovari (~3 species) are distributed in South America; on the contrary, An. (Ano.) freeborni and An. (Ano.) quadrimaculatus (~6 species) are distributed only in North America[5].
For An. (Nys.) albimanus, An. (Nys.) aquasalis, An. (Nys.) darlingi, An. (Nys.) marajoara, An. (Ano.) quadrimaculatus, An. (Nys.) nuneztovari, and An. (Ano.) pseudopunctipennis information exists at the level of some countries within the American continent[6],[8],[9], by countries[10], and in locations of some countries[11],[12] by using molecular markers, like microsatellites, SNPs, and some mitochondrial genes. However, to date, no work exists that compiles and analyzes the genetic information available in open-software databases, like GenBank and BOLD Systems. This type of analysis provides a broader vision about the gene flow among the distinct main vector species of malaria and their populations; thus, permitting to identify their dispersion routes and, consequently, human malaria at the continental scale. Thereby, it could allow vector control programs to implement control strategies regarding the relation among these species.
Material & MethodsA prior search in the GenBank, at genome level and by genes, revealed that the mitochondrial gene cytochrome oxidase unit I (COI; and, consequently, its subsequent search in BOLD Systems – an online COI repository), was available for seven of the principal vector species of Anopheles in America (selecting a representative species for the species complexes) and which additionally cover their natural distribution range. Due to the foregoing, for each of the seven species, the sequences were obtained of the mitochondrial COI gene from the databases mentioned. In GenBank, the search criteria used were “species of Anopheles” AND “COI” OR “cytochrome oxidase I”, while in BOLD Systems, the search only used the name of each species. Moreover, in GenBank it was possible to recover the mitochondrial genomes available for the species by using the search criteria “species of Anopheles” AND “complete mitochondrial genome” OR “complete genome”; this approach permitted broadening the availability of genetic information for the COI in other locations. The sequences from GenBank and BOLD Systems were downloaded and filtered through R Studio platform by using the APE packages version 5.0[13], bold version 1.10. To make sure the downloaded sequences from both databases correspond to the species and the region used in this work, the study used BLAST from NCBI (blast.ncbi.nlm.nih.gov/Blast.cgi).
Upon downloading the sequences, the location was extracted for each species for its geo-referencing in a continental map, hence, only sequences with geographic location were used in the subsequent analyses. In addition, for each species, occurrence data was downloaded, corresponding to the American continent by using QGIS version 3.16.3[14] and the GBIF Occurrence complement. From these, data was found on altitude by employing the online application, GPS Visualizer (www.gpsvisualizer.com/elevation). For all the geographic data and using the layer of coverage for each of the countries of America, the work obtained from Copernicus Global Land Service[15], coverage type was determined (forest, scrub, herbaceous vegetation, herbaceous wetland, mosses and lichens, sparse vegetation, crop lands, construction, ice and bodies of water) from where data was obtained on the presence of each of the species[16]. The maps obtained were edited in Inkscape[17].
Thereafter, for each of the species, all the sequences were aligned using the MAFFT software version 7[18]. Once aligned, for each species, the haplotypes and their frequencies were identified; with the first haplotype (H), H1, being the most frequent, H2, the second-most frequent and so on. With these haplotypes, nuclear mitochondrial (NUMT) DNA presence was identified, genetic information different from the mitochondrial and, thus, different evolutionary histories, by detecting additional stop codons in the alignment[19]. Upon obtaining the haplotypes without NUMT, from these, haplotype networks were elaborated for each species by using the Pegas package version 0.14[20] in the RStudio platform[21], which were implemented to express the genealogical relations in a map.
For each species, genetic diversity (haplotypic (Hd), nucleotide (π)) was estimatedalong with neutrality tests by using the RStudio platform and the Pegas packages version 0.14[13] and StrataG version 2.4.905[22]. In turn, analyses of molecular variance (AMOVA) were performed within a continental context and by countries. All these analyses were performed in the RStudio platform with the hierfstat version 0.5-7[23], ade4 version 1.7-16[24], apex version 1.0.4[25], adegenet version 2.1.3[26] pegas version 0.14[20], mmod version 1.3.3[27], and poppr version 2.8.7[28]. To estimate the genetic population structuring, the fixation index (Fst) and the number of migrants (Nm) were calculated by using the Arlequin program version 3.5[29]. For statistically significant differences, the Bonferroni correction was applied[30]. Each species was tested for isolation through genetic distance (FST) and geographic distance (km) by using Mantel’s test in the RStudio platform[46] with the Vegan package version 2.5-7[31]. Geographic distance was obtained through Google Earth Pro 2021. To infer the evolutionary relations among the populations from each of the seven vector species, phylogenetic reconstructions were conducted by using the maximum likelihood (ML) and Bayesian inference (BI) methods. For this, the model that best fit the data was used through the j Model Test program version 2.1.1 by selecting the model with the lowest value in the Akaike information criterion (AIC)[32].
For ML, RaxML was used with 1,000 boot replicas[33]. Furthermore, the BI analysis was performed through the BEAST2 program version 2.6.3, verifying stabilization of the statistical parameters: subsequent, prior, rateAC, rateAG, rateAT, rateCG, rateGT, gammaShape, and rateCT[34]·. The mosquito Culex quinquefasciatus was used as an outgroup. Finally, the resulting phylogenetic trees were visualized in Figtree version 1.4.4[35] and edited in Inkscape[17].
Ethical statement: Not applicable
ResultsBetween February and April 2021, 1523 sequences of the COI gene were recovered (minimum longitude of 131 bp and maximum longitude of 1234 bp) distributed in the American continent for the seven Anopheles species, of which 1085 were recovered from GenBank (71%) and 438 from BOLD System (29%). After alignment and section of the sequences, it was observed that a single block containing all seven species could not be obtained. Thereby, the prior procedure was carried out separately for each of the species; of which, 1440 sequences were selected and included in subsequent analyses; these were distributed in the following manner: 507 for An. (Nys.) albimanus (35%; 516 bp), 381 for An. (Nys.) darlingi (26%;159 bp), 185 for An. (Nys.) marajoara (13%; 645 bp), 156 for An. (Ano.) quadrimaculatus (11%; 573 bp), 112 for An. (Ano.) pseudopunctipennis (8%; 438 bp), 70 for An. (Nys.) goeldii (5%; 426 bp), and 29 for An. (Nys.) aquasalis (2%; 444 bp).
[Figure 1] and [Figure 2] show for the American continent and each of the species of Anopheles their geographic (obtained from GBIF) and genetic distribution (obtained from GenBank and BOLD System). From these, it may be noted that the species show a similar pattern between their geographic distribution and genetic information available. Species An. (Nys.) albimanus and An. (Ano.) pseudopunctipennis have geographic and genetic distribution in some locations of the American continent. An. (Ano.) quadrimaculatus has geographic and genetic distribution in some locations of North America. An. (Nys.) aquasalis and An. (Nys.) darlingi have geographic and genetic distribution in some locations of Central and South America. An. (Nys.) goeldii and An. (Nys.) marajoara have geographic and genetic distribution in some locations of South America. Additionally, the supplementary material S1 presents ecological, altitude, and coverage data for the geographic coordinates of each of the species. It may be evidenced that all the species have been observed mainly in forest coverages (52% An. (Ano.) quadrimaculatus and 20% An. (Nys.) goeldii), followed by human settlements near to crop zones and herbaceous vegetation (39% An. (Nys.) aquasalis and 18% An. (Nys.) marajoara) and in lower proportion in the other coverages (herbaceous wetland, moss and lichens and bare/sparse vegetation). In addition, these are located in altitudes ranging from 0 m up to 3634 m with species distributed throughout America (An. (Nys.) albimanus, An. (Nys.) albimanus and An. (Ano.) pseudopunctipennis up to 3634 and 3202 m, respectively) or only in the North (An. (Ano.) quadrimaculatus up to 2280 m), in the Center and South (An. (Nys.) darlingi and An. (Nys.) aquasalis up to 2155 and 690 m, respectively) and only in South America (An. (Nys.) marajoara and An. (Nys.) goeldi up to 491 and 147 m, respectively). Also, genetic relationships are shown (and, hence, their gene flow) of each of the species of Anopheles, An. (Nys.) albimanus, and An. (Ano.) pseudopunctipennis have genetic relationships among locations throughout the American continent; An. (Ano.) quadrimaculatus in some locations of North America. An. (Nys) aquasalis and An. (Nys) darlingi in some locations of Central and South America; An. (Nys.) goeldii and An. (Nys) marajoara in some locations of South America.
Figure 1: Geographic distribution (•), genetic distribution (•), Road connections (▬) and gene flow (↔). A. An. (Nys.) albimanus. B. An. (Ano.)pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara.
Figure 2: Geographic distribution (•), genetic distribution (•), Road connections (▬) and gene flow (↔). A. An. (Nys.) albimanus. B. An. (Ano.)pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara.[Figure 3] and [Figure 4] and supplementary material S2 display the distribution and frequency by countries of the haplotypes observed. This work observed 519 haplotypes for the species analyzed, of which 232 correspond for An. (Nys.) albimanus (45%), 73 for An. (Ano.) pseudopuncti-pennis (14%), 80 for An. (Ano.) quadrimaculatus (15%), 23 for An. (Nys.) aquasalis (4%), 15 for An. (Nys.) darlingi (3%), 45 for An. (Nys.) goeldii (9%), and 51 for An. (Nys.) marajoara (10%).
Figure 3: Haplotype networks. A. An. (Nys.) albimanus. B. An. (Ano.) pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara. The area of each circle is proportional to the haplotype frequency, the black circles represent the mutation steps.
Figure 4: Haplotype networks. A. An. (Nys.) albimanus. B. An. (Ano.) pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara. The area of each circle is proportional to the haplotype frequency, the black circles represent the mutation steps.[Figure 5] and [Figure 6] show the phylogenetic reconstruction for the seven Anopheles species under the BI and ML approaches and each of these have the support values with subsequent probability (≥ 0.90) and bootstrap (≥ 50), respectively. For An. (Nys.) albimanus, An. (Ano.) pseudopunctipennis, An. (Ano.) quadrimaculatus, An. (Nys.) aquasalis, An. (Nys.) darlingi, and An. (Nys.) marajoara, both approaches recovered three clades, while for An. (Nys.) goeldii four clades were recovered. In general, the clades did not recover geographic patterns, but they presented mixtures of all the locations, thus, each clade suggests that all the populations are genetically related.
Figure 5: Phylogenetic trees of Bayesian inference (BI) and maximum likelihood (ML). A. An. (Nys.) albimanus. B. An. (Ano.) pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara.
Figure 6: Phylogenetic trees of Bayesian inference (BI) and maximum likelihood (ML). A. An. (Nys.) albimanus. B. An. (Ano.) pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara.[Table 1] shows the results of haplo type diversity (Hd), nucleotide diversity (π), and neutrality test by continent and by countries. In general, the continental Hd for most of the species was ≥ 0.90, except for An. (Nys.) marajoara that was 0.67. In turn, the Hd for most countries was ≥ 0.66, in contrast with An. (Nys.) albimanus and An. (Nys.) darlingi with values of Hd < 0.50. The continental π for all the species was ≤ 0.26, while among countries it was greater for An. (Nys.) albimanus (π = 0.21) in Colombia and ≤ 0.1 for the rest. Tajima’s D and Fu’s F neutrality tests at continental level indicated in both tests positive values for An. (Nys.) albimanus, An. (Ano.) pseudopunctipennis, and An. (Nys.) aquasalis, while An. (Ano.) quadrimaculatus, An. (Nys.) darlingi, An. (Nys.) goeldii, and An. (Nys.) marajoara had negative values. In any of the previous cases, only for An. (Nys.) albimanus, An. (Ano.) pseudopunctipennis, An. (Ano.) quadrimaculatus and An. (Nys.) marajoara were significant values (p < 0.05) obtained.
Table 1: Genetic diversity and neutrality tests of the seven Anopheles species.[Table 2] presents the AMOVA results for the seven species. Of these, the highest percentage of variation was detected in An. (Nys.) albimanus, with the other species showing values between 6.87 (An. (Ano.) pseudopunctipennis) and 1.36 (An. (Ano.) quadrimaculatus). The percentage of variation at country level varied between 88.73 (An. (Ano.) pseudopunctipennis) and 32.84 (An. (Nys.) darlingi). The percentage of variation at population level within the countries varied between 98.64 (An. (Ano.) quadrimaculatus) and 3.73 (An. (Nys.) aquasalis). In general, the AMOVA indicated that at continent level genetic structuring was observed for most of the species (FST ≤ 0.60, p ≤ 0.05) except for An. (Ano.) pseudopunctipennis) (0.96, p > 0.05) and An. (Nys) darlingi (0.36 and p > 0.05). [Table 3] shows the peer-to-peer comparisons between countries after the Bonferroni correction. From such, for An. (Ano.) pseudo punctipennis, genetic structuring is observed in most countries throughout the continent, while in An. (Nys.) darlingi, it was observed in much of the countries of Central and South America. The other species showed genetic structuring only in some countries, as An. (Nys.) aquasalis and An. (Nys.) marajoara in Colombia and Brazil, and An. (Nys.) albimanus in Ecuador, Colombia, and Honduras. Finally, [Figure 7] Mantel’s test for all the species indicated no isolation due to genetic or geographic distance (r= ≥ 0.26, p > 0.05).
Table 3: Peer-to-peer genetic distances by country of six Anopheles species. An. (Nys.) goeldii was only distributed in Brazil
Figure 7: Mantel’s test. A. An. (Nys.) albimanus. B. An. (Ano.) pseudopunctipennis. C. An. (Ano.) quadrimaculatus. D. An. (Nys.) aquasalis. E. An. (Nys.) darlingi. F. An. (Nys.) goeldii. G. An. (Nys.) marajoara. Discussion The distribution patterns observed in this study for each of the seven Anopheles species are quite similar with those suggested through ecological niche modelling by Sinka et al.,[36] with some differences in our study. Thus, in this study, An. (Nys.) albimanus had more occurrence records from Mexico to northern Argentina, as well as in Venezuela and southern Guyana, An. (Ano.) pseudopunctipennis in the United States, Mexico, Central America and some in Venezuela, Peru, and Ecuador; An. (Ano.) quadrimaculatus in western United States, Canada, and Mexico; An. (Nys.) aquasalis in Guadalupe, Dominica, Trinidad and Tobago, French Guyana, and eastern Brazil; and An. (Nys.) goeldii only in northern Brazil. Moreover, our study gathers the altitudinal distribution and types of coverages where these species occur.
Regarding the altitudinal distribution, it was found that An. (Nys.) albimanus (up to 3.634 m), An. (Ano.) pseudopunctipennis (up to 3.202 m), An. (Ano.) quadrimaculatus (up to 2280 m), and An. (Nys.) darlingi (up to 2.155 m) have the greatest geographic distribution and are present at higher altitudes, while An. (Nys.) aquasalis (up to 690 m), An. (Nys.) marajoara (up to 491 m), and An. (Nys.) goeldii (up to 147 m) have the lesser geographic and altitudinal distribution. The literature consulted with respect to this question is scarce, with information that, generally, the genus Anopheles is present in the Americas at altitudes below 500 m37 except for An. (Nys.) albimanus and An. (Ano.) pseudopunctipennis in Ecuador with registries up to 1541 and 3000 m, respectively[38],[39]. Thereby, our study suggests presence of these vectors at altitudes not registered before, indicating the possibility that human activities and climate change could be favoring the expansion of its ecological niche in an altitudinal gradient[40]. Nevertheless, new studies are suggested to corroborate our hypothesis. Furthermore, for our study, the seven species are associated with forest coverages, followed by human settlements (urbans) near to crop zones and herbaceous vegetation, which has been observed in these species[41],[42],[43].
The geographic distribution obtained from the occurrences for each of the species and the genetic information obtained from the databases indicates that these have similar geographic and genetic distribution patterns with lack of genetic information for An. (Nys.) albimanus in Venezuela and southern Guyana, An. (Ano.) pseudopunctipennis in Venezuela and Peru, An. (Ano.) quadrimaculatus in western United States and Mexico, An. (Nys.) aquasalis in Costa Rica, Panama, Venezuela, French Guyana, and Trinidad and Tobago, An. (Nys.) darlingi in México and An. (Nys.) marajoara in French Guyana. Data on altitude and coverages from where the genetic information has been obtained indicates that species with greater or lesser geographic and altitudinal distribution have been sampled up to the maximum altitude where these are present, except for An. (Ano.) quadrimaculatus (up to 519 m) and An. (Nys.) aquasalis (up to 21 m). Genetic data were collected mostly in forest areas (73%) and areas with herbaceous vegetation (24%) for most of the species, except for An. (Nys.) aquasalis in which data concentrate mostly on herbaceous vegetation (60%) and forests (30%). The aforementioned suggests conducting genetic studies that involve species, locations, temperature, and altitudes to better understand the phylogeographic relations within continental and altitudinal contexts[44].
Analyses performed in this work were based on a partial mitochondrial region of the COI gene, with it being used as barcode to identify animal species[45] when conducting phylogeographic studies in Anopheles[46],[47] and other culicids[48],[49]. However, the genetic information retrieved suggests broadening genetic studies in areas where no information is available and perform new analyses by using mitochondrial or nuclear genomes, given that these would allow having a more detailed panorama of the genetic relationships among these species[50].
Haplotype and nucleotide diversity in the American continent for most species was ≥ 0.90 and ≤ 0.23, respectively, except for An. (Nys.) marajoara with an Hd pf 0.67 and π of 0.00. Prior studies suggest that the species in this study are native species because they are only distributed in the American continent[51],[52]. Several studies suggest that native species have greater genetic diversity in their area of native distribution than species outside their distribution range, as, for example, invasive species[53],[54]. A global study on the Asian cosmopolitan mosquito, Aedes albopictus, principal vector of dengue, Zika, and chikungunya viruses in Asia and Europe, observed higher genetic diversity (Hd = 0.94, π = 1.60) in its native area with respect to all the areas it has invaded, therein showing lower diversity indices Hd lowest in Holland (0.059 = π = 0.011) and Hd highest in China (0.946 = π = 1.609)[54].
When the data were analyzed by countries for each of the species, the Hd ≥ 0.66 and π ≥ 0.00 for most countries, unlike An. (Nys.) darlingi with Hd = 0.47 and π = 0.00 in Honduras. Similar values of genetic diversity have been observed for An. (Nys.) albimanus in some countries in the northern neotropics (Hd= 0.91)[55], An. (Nys.) marajoara in Brazil (Hd = 0.828)[56], An. (Nys.) darlingi in Colombia (Hd = 0.650), Panama (Hd = 0.58), and in some countries of South America (Hd = 0.92)[57],[58],[59] and in An. (Ano.) pseudopunctipennis in the Argentine northwest (Hd = 0.547)[60].
Mantel’s test for all the species indicated no isolation due to genetic or geographic distance (r = ≥ 0.26, p > 0.05). Similar patterns have been found for An. (Nys.) albimanus in the northern neotropics[55], An. (Ano.) pseudopunctipennis in Argentina[60], An. (Nys.) darlingi in South and Central America[59], and An. (Nys.) aquasalis in northwestern Brazil[61]. This could be explained given that these species are native of the American continent and, hence, are widely distributed throughout the territory[51], as observed, for example, in another culicid, Ae. albopicus, and in its native distribution range Asia[62].
Tajima’s D and Fu’s F neutrality tests at the continental level indicated negative values for An. (Ano.) quadrimaculatus, An. (Nys.) darlingi, An. (Nys.) goeldii, and An. (w.) marajoara. Exclusively, An. (Ano.) quadrimaculatus and An. (Nys.) marajoara had significant values (p < 0.05). Negative values suggest that these have recently experienced bottlenecks and demographic expansion[63]. This may be due to recent vector control actions and colonizing events, a common phenomenon observed in mosquitoes of medical and veterinary importance[64].
The phylogenetic trees revealed existence of three clades for most of the species and four clades for An. (Nys.) goeldii. All the clades did not recover geographic patterns, but had mixes of all the locations, thus, each clade suggests that all the populations are genetically related. Phylogenetic proposals exist at intraspecific level for An. (Nys.) darlingi in some locations of Central and South America[59], An. (Nys.) aquasalis in some locations of northwestern Brazil[65], and An. (Nys.) goeldii in some locations of Roraima and Pará in Brazil[66]. However, in none of the phylogenies were three clades recovered, but two and in these locations as the individuals were not grouped following a specific geographic pattern, except for An. (Nys.) goeldii.
Haplotype networks for each of the species suggest that all the locations where the species are found are related, this is because these are native species and their evolutionary history has allowed them to disseminate in areas where they are present[51]. Currently, the roadway system connects all the locations from where registries are available for the seven principal vector species for malaria. This connectivity may be favoring gene flow among species and their locations through passive human transport (e.g., land, maritime, air, and riverine transport) phenomenon commonly associated in vector mosquitoes of diseases[67],[68],[69]. Therefore, attention must be paid to this panorama because generation of an epidemiological focus in a location close to a roadway would favor, for example, an infected person travelling a long distance and reaching another place where the same or different species that can be infected exists and, consequently, infect other people.
ConclusionThis research permitted establishing the diversity, structuring, and gene flow of the main seven Anopheles species transmitters of human malaria throughout the Americas. Of these, the species of greatest geographic distribution were those with the highest amount of genetic information and, consequently, greater genetic diversity. All the species are genetically connected between the locations without restrictions of geographic or genetic barriers and phylogenetically related in three and four clades; all these without a grouping pattern among the populations. Due to the genetic and roadway connectivity, constant entomological and epidemiological surveillance is suggested, given that malaria could spread easily in the Americas.
Conflict of interest: None
AcknowledgementsThe authors thank the Vice-rectory of Research at Universidad del Quindío for financial support for expert translation of the manuscript into English.
References
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