Numerous recent studies have illuminated global distributions of human cases of dengue and other mosquito-transmitted diseases, yet the potential distributions of key vector species have not been incorporated integrally into those mapping efforts. Projections onto future conditions to illuminate potential distributional shifts in coming decades are similarly lacking, at least outside Europe. This study examined the global potential distributions of
Aedes aegypti
and
Aedes albopictus
in relation to climatic variation worldwide to develop ecological niche models that, in turn, allowed anticipation of possible changes in distributional patterns into the future. Results indicated complex global rearrangements of potential distributional areas, which—given the impressive dispersal abilities of these two species—are likely to translate into actual distributional shifts. This exercise also signalled a crucial priority: digitization and sharing of existing distributional data so that models of this sort can be developed more rigorously, as present availability of such data is fragmentary and woefully incomplete.
Chagas disease is one of the most important yet neglected parasitic diseases in
Mexico and is transmitted by Triatominae. Nineteen of the 31 Mexican triatomine
species have been consistently found to invade human houses and all have been found
to be naturally infected with Trypanosoma cruzi. The present paper
aims to produce a state-of-knowledge atlas of Mexican triatomines and analyse their
geographic associations with T. cruzi, human demographics and
landscape modification. Ecological niche models (ENMs) were constructed for the 19
species with more than 10 records in North America, as well as for T.
cruzi. The 2010 Mexican national census and the 2007 National Forestry
Inventory were used to analyse overlap patterns with ENMs. Niche breadth was greatest
in species from the semiarid Nearctic Region, whereas species richness was associated
with topographic heterogeneity in the Neotropical Region, particularly along the
Pacific Coast. Three species, Triatoma longipennis, Triatoma
mexicana and Triatoma barberi, overlapped with the
greatest numbers of human communities, but these communities had the lowest
rural/urban population ratios. Triatomine vectors have urbanised in most regions,
demonstrating a high tolerance to human-modified habitats and broadened historical
ranges, exposing more than 88% of the Mexican population and leaving few areas in
Mexico without the potential for T. cruzi transmission.
Ecological niche models are useful tools to infer potential spatial and temporal distributions in vector species and to measure epidemiological risk for infectious diseases such as the Leishmaniases. The ecological niche of 28 North and Central American sand fly species, including those with epidemiological relevance, can be used to analyze the vector's ecology and its association with transmission risk, and plan integrated regional vector surveillance and control programs. In this study, we model the environmental requirements of the principal North and Central American phlebotomine species and analyze three niche characteristics over future climate change scenarios: i) potential change in niche breadth, ii) direction and magnitude of niche centroid shifts, iii) shifts in elevation range. Niche identity between confirmed or incriminated Leishmania vector sand flies in Mexico, and human cases were analyzed. Niche models were constructed using sand fly occurrence datapoints from Canada, USA, Mexico, Guatemala and Belize. Nine non-correlated bioclimatic and four topographic data layers were used as niche components using GARP in OpenModeller. Both B2 and A2 climate change scenarios were used with two general circulation models for each scenario (CSIRO and HadCM3), for 2020, 2050 and 2080. There was an increase in niche breadth to 2080 in both scenarios for all species with the exception of Lutzomyia vexator. The principal direction of niche centroid displacement was to the northwest (64%), while the elevation range decreased greatest for tropical, and least for broad-range species. Lutzomyia cruciata is the only epidemiologically important species with high niche identity with that of Leishmania spp. in Mexico. Continued landscape modification in future climate change will provide an increased opportunity for the geographic expansion of NCA sand flys' ENM and human exposure to vectors of Leishmaniases.
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