Spatial and Temporal Diversity Variation in the Anopheles Communities in Malaria-Endemic Regions of Colombia

This study aimed to evaluate at a temporospatial scale, the influence of anthropogenic land cover changes in the Anopheles species community composition and diversity in two Colombian malaria-endemic regions, Bajo Cauca and Pacific. To determine variations over time, mosquitoes were collected in two time periods; land cover types were characterized on orthorectified aerial photographs, and landscape metrics were estimated for each locality and period. A temporal dissimilarity analysis to evaluated species replacement and the nestedness species loss/gain showed the influence of the species loss or gain component on Anopheles species assemblage (23%). The relationship between land cover variation and Anopheles beta diversity, evaluated by regression analysis, showed the effect of forest variation in the Anopheles community (βsim and forest r2 = 0.9323; βsne and forest r2 = 0.9425). Furthermore, a canonical correspondence analysis showed that the land cover types associated with Anopheles species presence were bare soil, shrub, wet areas, and forest. Results demonstrated the impact of land cover changes attributed to human activities on Anopheles population dynamics, over time; this was evidenced as species loss or gain, which was specific to each locality. Notably, the main malaria vectors were dominant in most localities over time, suggesting their tolerance to anthropogenic transformations; alternatively, the environmental changes are providing adequate ecological conditions for their persistence. Finally, the data generated are relevant for understanding the impact that environmental change may have on the dynamics of the neotropical malaria vectors. Thus, this research has potential implications for vector control interventions.

Entomological parameters and population structure at a microgeographic scale of the main Colombian malaria vectors Anopheles albimanus and Anopheles nuneztovari

Population subdivision among several neotropical malaria vectors has been widely evaluated; however, few studies have analyzed population variation at a microgeographic scale, wherein local environmental variables may lead to population differentiation. The aim of the present study was to evaluate the genetic and geometric morphometric structure of Anopheles nuneztovari and Anopheles albimanus in endemic localities of northwestern Colombia. Genetic and phenetic structures were evaluated using microsatellites markers and wing geometric morphometrics, respectively. In addition, entomological indices of importance in transmission were calculated. Results showed that the main biting peaks of Anopheles nuneztovari were between 20:00 and 22:00, whereas Anopheles albimanus exhibited more variation in biting times among localities. Infection in An. nuneztovari by Plasmodium spp. (IR: 4.35%) and the annual entomological inoculation rate (30.31), indicated high vector exposure and local transmission risk. We did not detect Plasmodium-infected An. albimanus in this study. In general, low genetic and phenetic subdivision among the populations of both vectors was detected using a combination of phenotypic, genetic and environmental data. The results indicated high regional gene flow, although local environmental characteristics may be influencing the wing conformation differentiation and behavioral variation observed in An. albimanus. Furthermore, the population subdivision detected by microsatellite markers for both species by Bayesian genetic analysis provides a more accurate picture of the current genetic structure in comparison to previous studies. Finally, the biting behavior variation observed for both vectors among localities suggests the need for continuous malaria vector surveys covering the endemic region to implement the most effective integrated local control interventions.

New records of Sabethini (Diptera: Culicidae) from Colombia

In the Neotropical Region, the mosquitoes, grouped in the tribe Sabethini (Arthropoda, Insecta, Diptera: Culicidae) are considered of medical importance by the role that some species may have in arbovirus transmission; also, because they are good bioindicators. More than 400 species are currently recognised and are mainly associated with forest areas. The tribe Sabethini is poorly studied and the information about diversity and distribution for species relating to it is scarce. In Colombia, 54 species of the tribe are known; however, several geographical areas have not been included in the studies for this group and data for recent field collections are not available; therefore, the records are outdated.

This study presents the species list of the Sabethini tribe in Colombia, based on a review of previous publications and recent unpublished data. The list includes 68 species of nine genera and 16 subgenera. The genus Wyeomyia has the highest species number (39), followed by Sabethes (14). A total of 29 new records are registered and actualized information related to the local distribution in some Departments is presented, including geographic coordinates. In this paper, the distribution records of Sabethini for Colombia are updated, revealing the high diversity of this group in the country and providing some useful information for species that may need surveillance or control.

Effect of land cover and landscape fragmentation on anopheline mosquito abundance and diversity in an important Colombian malaria endemic region

Landscape structure influences the distribution and abundance of anopheline mosquitoes and has an indirect impact on malaria transmission. This work aimed to determine the effect of land cover and landscape fragmentation on anopheline mosquito abundance and diversity in an important Colombian malaria endemic area, the Bajo Cauca region. Diversity indices were calculated for Anopheles mosquitoes collected in various localities of the region. Land cover types were characterized using orthorectified aerial photographs to estimate landscape metrics. The relationship between landscape fragmentation and species diversity was evaluated by regression analysis. The correlation between species abundance and land cover types was determined using canonical correspondence analyses. Results showed a statistically significant tendency for a lower diversity of the Anopheles community in landscapes with higher patch number, patch density and effective mesh size. For most species, there was evidence of a significant relationship between species abundance and land covers modified by anthropic activities which generate forest loss. These results indicate that activities that modify the landscape structure and land cover composition generate changes that affect the spatial distribution and composition of epidemiologically-important Anopheles species, which may impact malaria distribution in a region. This information is useful to guide control interventions that promote unfavorable landscapes for malaria vector propagation.

Relationship between land cover and Anophelinae species abundance, composition and diversity in NW Colombia

Anthropic activities, mainly deforestation, have produced rapid transformation of land cover types in the Urabá region at northwest Colombia. Land cover alterations impact the abundance and composition of the Anophelinae community, affecting malaria transmission dynamics. Therefore, this study used landscape metrics to evaluate the relationship of land cover types with Anophelinae species abundance, composition and diversity in the important malaria endemic Urabá region, in NW Colombia. Orthorectified aerial photographs were used to identify land cover types in four localities of the region. Landscape metrics were obtained and diversity indices were estimated for both, land covers and Anophelinae species collected. The impact of land cover type on the presence and abundance of Anophelinae species was evaluated using a canonical correspondence analysis. Diversity indices showed differences in the Anophelinae community and land covers. The variables with more influence in the Anophelinae community composition were locality, bare soil and the interaction between forest and bare soil covers. The most abundant and dominant species Nyssorhynchus nuneztovari (former Anopheles nuneztovari), related with impacted environments was associated with grass, shrub and bare soil land covers. In conclusion, land covers derived from anthropic activities favored the presence and abundance of the main malaria vectors; but, regardless of differences in landscape, unknown specific factors varying among localities lead to a unique configuration in each site that directly shaped anopheline community composition locally. This information is essential for the development of malaria risk maps and for the design of integrated vector control interventions that include the recognition of the landscape features favoring human-vector contact.

Discrimination of Anopheles species of the Arribalzagia Series in Colombia using a multilocus approach

The Arribalzagia Series of the Anopheles Subgenus comprises morphologically similar species or members of species complexes which makes correct species identification difficult. Therefore, the aim of this work was to discriminate the morphospecies of the Arribalzagia Series present in Colombia using a multilocus approach based on ITS2, COI and CAD sequences. Specimens of the Arribalzagia Series collected at 32 localities in nine departments were allocated to seven species. Individual and concatenated Bayesian analyses showed high support for each of the species and reinforced the previous report of the Apicimacula species Complex with distribution in the Pacific Coast and northwestern Colombia. In addition, a new molecular operational taxonomic unit-MOTU was identified, herein denominated near Anopheles peryassui, providing support for the existence of a Peryassui species Complex. Further, the CAD gene, just recently used for Anopheles taxonomy and phylogeny, demonstrated its power in resolving phylogenetic relationships among species of the Arribalzagia Series. The divergence times for these species correspond to the early Pliocene and the Miocene. Considering the epidemiological importance of some species of the Series and their co-occurrence in malaria endemic regions of Colombia, their discrimination constitutes an important step for vector incrimination and control in the country.

Population dynamics of Anopheles nuneztovari in Colombia

Anopheles nuneztovari is an important Colombian malaria vector widespread on both sides of the Andean Mountains, presenting morphological, behavioral and genetic heterogeneity throughout the country. The aim of this study was to evaluate whether the population structure and distribution of An. nuneztovari in Colombia are associated with ecological and physical barriers present in a heterogeneous landscape. Further, differences in behavior were addressed. A total of 5392 specimens of An. nuneztovari were collected. Mitochondrial and nuclear marker analyses detected subdivision among the northwest-west, northeast and east populations. For both markers, isolation by distance (~53%) and isolation by resistance (>30%) were determinants of population genetic differentiation. This suggests that physical barriers, geographical distance and ecological differences on both sides of the Andean Mountains promoted the genetic differentiation and population subdivision of An. nuneztovari in Colombia. This species showed the highest biting activity after 20:00h; indoor and outdoor preferences were found in all localities. These results indicated that the most effective interventions for controlling vector populations on both sides of the Andes need to be region-specific.

Behavior and population structure of Anopheles darlingi in Colombia

Anopheles darlingi is a widely distributed and important malaria vector in Colombia. Biogeographical and ecological heterogeneity across the Colombian distribution led to the hypothesis of behavioral and genetic differentiation among A. darlingi populations. A total of 2017 A. darlingi specimens were collected during 222 h of sampling. This vector was the most abundant anopheline species in most of the localities sampled. Subdivision between samples collected west and east of the Andes was indicated by 1) mitochondrial COI and nuclear CAD sequences from NW-W and CE-S populations (COI ΦST=0.48761-0.81974, CAD FST=0.11319-0.21321), 2) a COI haplotype network, and 3) SAMOVA. Endo- and exophagy were detected in populations west of the Andes, whereas exophagy was evident in PTG, a locality east of the Andes. Isolation by resistance was significant for COI and explained 26% of the genetic differentiation. We suggest that at a macrogeographic scale, the Andes influence the differentiation of A. darlingi in Colombia and may drive divergence, and, at a microgeographic scale, ecological differences have a significant impact on structure. These data could constitute a baseline for the design of effective vector interventions, locality-specific for the east and similar for panmictic populations west of the Andes.

Malaria vectors in ecologically heterogeneous localities of the Colombian Pacific region

The Colombian Pacific region is second nationally in number of malaria cases reported. This zone presents great ecological heterogeneity and Anopheles species diversity. However, little is known about the current spatial and temporal distribution of vector species. This study, conducted in three ecologically different localities of the Pacific region, aimed to evaluate the composition and distribution of Anopheles species and characterize transmission intensity. A total of 4,016 Anopheles mosquitoes were collected representing seven species. The composition and dominant species differed in each locality. Three species were infected with malaria parasites: Anopheles darlingi and An. calderoni were infected with Plasmodium falciparum and An. nuneztovari with Plasmodium vivax VK210 and VK247. Annual EIRs varied from 3.5–7.2 infective bites per year. These results confirm the importance of the primary vector An. nuneztovari in areas disturbed by human interventions, of An. darlingi in deforested margins of humid tropical rainforest and An. albimanus and the suspected vector An. calderoni in areas impacted by urbanization and large-scale palm oil agriculture close to the coast. This constitutes the first report in the Colombia Pacific region of naturally infected An. darlingi, and in Colombia of naturally infected An. calderoni. Further studies should evaluate the epidemiological importance of An. calderoni in the Pacific region.