Effect of an altitudinal gradient on the morphology, molecular identification and distribution of Rhipicephalus linnaei in Veracruz, Mexico

Studies of morphological and genetic variation in vector populations across environmental gradients can help researchers to estimate species' responses to climate change scenarios and the potential risk of disease-causing pathogen expansion, which impacts negatively on human health. In this study, we analysed the effect of altitudinal gradients on the phenotypic response of the hard tick of medical and veterinary importance, Rhipicephalus sanguineus sensu lato (s.l.). Specimens of R. sanguineus s.l. were collected from host animals in one of Mexico's regions with high climatic heterogeneity (Veracruz), and geometric morphometric theory was employed to assess the response of three morphological characters to the altitudinal gradient. Additionally, genetic similarity data were provided, and ecological niche models were used to project the climatic distribution in the region. Our results demonstrate that the shape and size of ticks respond to altitude. Molecular identification indicate that all analysed samples correspond to the tropical lineage recently named Rhipicephalus linnaei. According to ecological niche models, the mean annual temperature contributes significantly to the spatial distribution of this tick species, with areas of higher suitability in the mountainous region. These changes in morphological structure and the presence of ticks at higher altitudinal gradients suggest that R. linnaei has a high potential for adaptation. Due to the variability of ecosystems in the state of Veracruz, our results could be valuable in assessing the response of this tick in a changing environment, aiding in predicting future scenarios in the distribution and abundance of this species.

Unraveling the diversity of Trypanosoma species from Central Mexico: Molecular confirmation on the presence of Trypanosoma dionisii and novel Neobat linages

Bats are one of the groups of mammals with the highest number of associated Trypanosoma taxa. There are 50 Trypanosoma species and genotypes infecting more than 75 species of bats across five continents. However, in Mexico, the inventory of species of the genus Trypanosoma associated with bats is limited to only two species (Trypanosoma vespertilionis and Trypanosoma cruzi) even though 140 species of bats inhabit this country. Specifically, 91 bat species have been recorded in the state of Veracruz, but records of trypanosomatids associated with this mammalian group are absent. Due to the complex Trypanosoma-bat relationship, the high diversity of bat species in Veracruz, as well as the lack of records of trypanosomatids associated with bats for this state, the aim of this work was to analyze the diversity of species of the genus Trypanosoma and their presence from a bat community in the central area of the state of Veracruz, Mexico. During the period of January to August 2022 in the Tequecholapa Environmental Management Unit where bats were collected using mist nets and blood samples were obtained from their thumbs. We extracted genetic material and amplified a fragment of 800 bp of the 18S ribosomal gene of the genus Trypanosoma by conventional PCR. The positive amplicons were sequenced, and phylogenetic reconstruction was performed to identify the parasite species. A total of 285 bats (149♀, 136♂) belonging to 13 species from 10 genera and a single family (Phyllostomidae) were collected. Twenty-three specimens from six species tested positive for the presence of Trypanosoma dionisii, Trypanosoma sp. Neobat 4, and a potential novelty species provisionally named as Trypanosoma sp. Neobat 6. The results of the present work increase the number of species of the genus Trypanosoma infecting bats in Mexico and in the Neotropical region.

High climatic ancestral affinity between the lineages of the Leishmania vector Psathyromyia shannoni sensu stricto (Diptera: Phlebotominae)

Psathyromyia (Psathyromyia) shannoni sensu stricto (Dyar) is a vector of Leishmania parasite and the second sandfly of medical importance with a wide geographical but discontinuous distribution in America. Preliminary genetic structure analysis using a mitochondrial marker shows that the species integrated by at least four lineages could be the result of ecological adaptations to different environmental scenarios, but this hypothesis had never been proven. The aim of the present study was to analyse whether the genetic structure that detected Pa. shannoni ss. is associated with divergence or conservatism niche. Using Ecological Niche Models (ENMs) theory, we estimated the potential distribution for each genetic lineage, and then, we evaluated the equivalency niche for assessing whether climatic niche was more different than expected. The ENMs identify different suitable distribution areas but the same climatic or ecological conditions for the genetic lineages of Pa. shannoni (conservatism niche). Our findings allow us to speculate that other potential processes or events could be related to the genetic differentiation of Pa. shannoni. These studies are important because they allow us to identify the factors that could restrict the potential distribution of the different lineages whose vectorial competence is still unknown.

Worldwide comparison between the potential distribution of Rhipicephalus microplus (Acari: Ixodidae) under climate change scenarios

The cattle tick Rhipicephalus microplus (Acari: Ixodidae) has demonstrated its ability to increase its distribution raising spatially its importance as a vector for zoonotic hemotropic pathogens. In this study, a global ecological niche model of R. microplus was built in different scenarios using Representative Concentration Pathway (RCP), Socio-Economic Pathway (SSP), and a climatic dataset to determine where the species could establish itself and thus affect the variability in the presentation of the hemotropic diseases they transmit. America, Africa and Oceania showed a higher probability for the presence of R. microplus in contrast to some countries in Europe and Asia in the ecological niche for the current period (1970-2000), but with the climate change, there was an increase in the ratio between the geographic range preserved between the RCP and SSP scenarios obtaining the greatest gain in the interplay of RCP4.5-SSP245. Our results allow to determine future changes in the distribution of the cattle tick according to the increase in environmental temperature and socio-economic development influenced by human development activities and trends; this work explores the possibility of designing integral maps between the vector and specific diseases.

Comparison of Climate Change Scenarios of Rhipicephalus sanguineus sensu lato (Latreille 1806) from México and the Boarders with Central America and the United States

In America, the presence of Rhipicephalus sanguineus sensu stricto and Rhipicephalus linnaei has been confirmed. Both species are found in sympatry in the southern United States, northern Mexico, southern Brazil, and Argentina. The objective of this work is to evaluate the projection of the potential distribution of the ecological niche of Rhipicephalus sanguineus sensu lato in two climate change scenarios in Mexico and the border with Central America and the United States. Initially, a database of personal collections of the authors, GBIF, Institute of Epidemiological Diagnosis and Reference, and scientific articles was built. The ENMs were projected for the current period and two future scenarios: RCP and SSP used for the kuenm R package, the ecological niche of R. sanguineus s.l. It is distributed throughout the Mexico and Texas (United States), along with the border areas between Central America, Mexico, and the United States. Finally, it is observed that the ecological niche of R. sanguineus s.l. in the current period coincides in three degrees with the routes of human migration. Based on this information, and mainly on the flow of migrants from Central America to the United States, the risk of a greater gene flow in this area increases, so the risk relating to this border is a latent point that must be analyzed.

Similarity but not equivalence: Ecological niche comparison between sandflies from the Pleistocene and future scenarios in Central and South America

Sandfly species (Diptera: Psychodidae) are suspected or proven vectors of Leishmania spp. in the American region. Understanding niche conservatism (NC) in insect vectors allows an understanding of constraints on adaptive responses, and thus implications for disease ecology. Therefore, in this study, the authors evaluated NC in three vector species of leishmaniasis (Lutzomyia gomezi, Psathyromyia shannoni and Pintomyia ovallesi) in Central and South America. For this, the authors performed niche identity and similarity testing through paired comparisons in ENMTools and niche overlap in Niche Analyst. The authors found that species niches were more similar to each other than if the points had been randomly extracted, and they also found extensive similarity between Pa. shannoni and Lu. gomezi niches and in Pa. shannoni niches over different timescales. The authors suggest Pa. shannoni as a priority species due to fundamental niche similarity with phylogenetically related species and also its extensive evolutionary history and ecological plasticity that could affect the emergence and resurgence of leishmaniasis in areas endemic by this vector.

Potential distributions of the parasite Trypanosoma cruzi and its vector Dipetalogaster maxima highlight areas at risk of Chagas disease transmission in Baja California Sur, Mexico, under climate change

Dipetalogaster maxima is a primary vector of Chagas disease in the Cape region of Baja California Sur, Mexico. The geographic distribution of D. maxima is limited to this small region of the Baja California Peninsula in Mexico. Our study aimed to construct the ecological niche models (ENMs) of this understudied vector species and the parasite responsible for Chagas disease (Trypanosoma cruzi). We modelled the ecological niches of both species under current and future climate change projections in 2050 using four Representative Concentration Pathways (RCPs): RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5. We also assessed the human population at risk of exposure to D. maxima bites, the hypothesis of ecological niche equivalency and similarity between D. maxima and T. cruzi, and finally the abundance centroid hypothesis. The ENM predicted a higher overlap between both species in the Western and Southern coastal regions of the Baja California Peninsula. The climate change scenarios predicted a Northern shift in the ecological niche of both species. Our findings suggested that the highly tourist destination of Los Cabos is a high-risk zone for Chagas disease circulation. Overall, the study provides valuable data to vector surveillance and control programs.

Inferring Distributional Shifts of Asian Giant Hornet Vespa mandarinia Smith in Climate Change Scenarios

Vespa mandarinia Smith is a species with native distribution in Asia and with the potential distribution of invasion in the Americas. We use ecological niche models to be able to predict their potential distribution in Asia and their projection in the Americas using KUENM in R in climate change scenarios. The ecological niche of V. mandarinia is potentially distributed in Asia and is expected with invasion potential in the east coast of USA, part of the México, Central America, and South America, while for 2050 it is projected with dispersion in North and Central of USA and rest of the Americas. The realized niche expanded in the Americas. Ecological niche modeling helps us infer the distribution of this species in Asia and its possible establishment of invasion in the USA, México, Central America, and South America.

Composition and abundance of anopheline species according to habitat diversity in Mexico

OBJECTIVE

To determine the abundance and geographic distribution of the main malaria vectors, which are influenced by habitat characteristics and ecological factors that directly impact adult density and the dynamics of malaria transmission in Mexico.

MATERIALS AND METHODS

Samples of larvae were collected from 19 states in Mexico. Each larval habitat was characterized in situ determining the following parameters: water depth, turbidity, percentage of vegetation cover, amount of detritus, presence of algae, light intensity, type of vegetation, amount of predators, habitat stability, altitude, and hydrologic type.

RESULTS

A total of 21 687 larvae corresponding to 13 anopheline species were obtained from 149 aquatic habitats. The most abundant species were Anopheles pseudopunctipennis (52.91%), An. albimanus (39.14%) and An. franciscanus (5.29%). The multiple logistic regression analysis showed a negative association between An. pseudopunctipennis and water turbidity (ß=-1.342; Wald=6.122; p=0.013) and the amount of detritus (ß=-2.206; Wald=3.642; p=0.050). While in An. albimanus, there was a significant positive association with water turbidity (ß=1.344; Wald=4.256; p=0.039), a negative correlation was found with the altitude (ß=-3.445; Wald=5.407; p =0.020). The highest mosquito species diversity index was found in Chiapas (Fisher's α=1.20) and the lowest diversity in Chihuahua (Fisher's α=0.26). The greatest richness was found in streams (n=11).

CONCLUSIONS

The two most abundant species were: An. albimanus and An. pseudopunctipennis. Detailed knowledge of the distribution and characteristics of their larval habitats will be useful for the effective implementation of control strategies in Mexico.

Diversity and potential distribution of culicids of medical importance of the Yucatan Peninsula, Mexico

OBJECTIVE

To determine the species distribution, abundance, and diversity of culicids in the Yucatan Peninsula (YP); their potential distribution, using ecological niche modeling (ENM), and the risk of contact with urban and rural populations.

MATERIALS AND METHODS

A cross-sectional study was carried out through the YP. The diversity of species was determined with the Shannon index. The potential distribution of the culicids was determined through the ENM, as well as the risk of urban and rural populations through contact with vectors.

RESULTS

A total of 10 699 specimens, 15 genera and 52 species were registered. Campeche and the Biosphere Reserve of Calakmul exhibited the highest diversity.

CONCLUSIONS

The ENM predict a high suitability in all the YP of Ae. aegypti, An. albimanus, An. pseudopuntipennis, Cx. coronator, and Cx. quinquefasciatus. The vector species that exhibited the highest risk of contact in the YP were Cx. quinquefasciatus, Ae. aegypti and Ae. albopictus.

Inferring the Potential Distribution of an Emerging Rickettsiosis in America: The Case of Rickettsia parkeri

Tick-borne rickettsioses represent a severe public health problem that has increased in recent decades by several activities that place human populations in contact with a wide range of vectors. In particular, Rickettsia parkeri, an eschar-associated spotted fever agent, represents an emerging pathogen that has been gradually identified throughout America. In the present work, we compiled an occurrence database of these bacteria, as well as its vectors, in order to identify the potential distribution of these bacteria and to detect the risk areas where this emerging pathogen may be circulating. The results show the at-risk areas to be broad regions in Central America, on the coast of Venezuela, Colombia, Ecuador, Peru, and Chile, part of Brazil and Argentina, and the greater part of Bolivia, Paraguay, and Uruguay. Particularly, in Mexico, conditions exist for widespread dissemination. Our results must be considered for the establishment of active acarological surveillance in previously unsampled areas, as well as the establishment of prevention measures for vulnerable populations and risk groups participating in outdoor activities that can place them in contact with this pathogen.

Assessing the Potential Distributions of the Invasive Mosquito Vector Aedes albopictus and Its Natural Wolbachia Infections in México

The Asian tiger mosquito Aedes albopictus is currently the most invasive vector species, with a widespread global distribution. Aedes albopictus is the potential vector of diverse arboviruses, including Zika and dengue. This study updated the ecological niche model of Ae. albopictus and inferred the potential distribution of natural Wolbachia infections in Ae. albopictus in México. The ecological niche models were constructed based on diverse model settings to better estimate the potential distributions and uncertainty indices of both Ae. albopictus and its natural Wolbachia infections in México. The distribution of Ae. albopictus covered the states across Northern México, the Gulf of México, the Pacific Coast of México, Central México, and the southeast of México. The ecological niche model of the natural Wolbachia infections in Ae. albopictus populations anticipated the occurrence of natural Wolbachia infections in the southeast of México, the Chiapas border with Guatemala, and Veracruz. These results can be used to prioritize vector surveillance and control programs in México for strategic and future decision-making; however, it is still necessary to establish active surveillance programs to assess model predictions based on the independent sampling of Ae. albopictus from different invasion zones in México. Finally, vector surveillance should also screen the natural Wolbachia infections in Ae. albopictus to validate Wolbachia predictions across México, particularly in the southeast of México.

Pattern of climate connectivity and equivalent niche of Triatominae species of the Phyllosoma complex

The Phyllosoma complex is a Triatominae (Hemiptera: Reduviidae) group of medical importance involved in Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) transmission. Most of the members of this group are endemic and sympatric species with distribution in Mexico and the southern U.S.A. We employed MaxEnt to construct ecological niche models of nine species of Triatominae to test three hypothesis: (a) whether species with a broad climatic niche breadth occupy a broader geographical range than species with a narrow climatic breadth, (b) whether species with broad distribution present high degree of climatic fragmentation/isolation, which was tested through landscape metrics; and (c) whether the species share the same climatic niche space (niche conservatism) considered through an equivalence test implemented in ENMtools. Overall, our results suggest that the geographical distribution of this complex is influenced mainly by temperature seasonality where all suitable areas are places of current and potential transmission of T. cruzi. Niche breadth in the Phyllosoma complex is associated with the geographical distribution range, and the geographical range affects the climatic connectivity. We found no strong evidence of niche climatic divergence in members of this complex. We discuss the epidemiological implications of these results.

Niche divergence and paleo-distributions of Lutzomyia longipalpis mitochondrial haplogroups (Diptera: Psychodidae)

Lutzomyia longipalpis is a complex of species which has a wide but discontinuous distribution from southeastern Mexico to northern Argentina and Uruguay. To date, eight mitochondrial haplogroups have been identified along its distribution although key environmental tolerances and ecological niche models have been analyzed only at the complex level. The aim of the present study was to analyze whether genetic diversification using three mitochondrial genes of the Lu. longipalpis complex is associated with niche divergence and to explore evolution of distributional projections of all haplogroups between the Last Glacial Maximum (LGM; 21,000 yrs ago) and the present. Current occurrence of all haplogroups was used to develop ecological niche models (ENM) and these were projected in both periods to quantify and identify geographic area shifts. Environmental space was used to estimate niche similarity between major clades and pairwise between individual haplogroups. The two major Lu. longipalpis clades (Mex, CA, Col and Ven vs Arg and Bra) had significantly different environmental space, indicating niche divergence. Environmental space overlap of southern haplogroups was variable, with divergent niche, except between Arg and ArgBra. The most suitable regions for the ArgBra haplogroup were northeastern and southeastern Brazil, and the Gran Chaco region. In contrast, ENM of haplogroups within the northern major clade have significantly similar niche, with highest geographic ENM suitability along both the Caribbean and Pacific coasts. The intensity and coverage of high suitability areas in the LGM decreased for most haplogroups in the present. Integrating ENM and phylogenetic analyses has allowed us to test hypotheses of niche similarity between Lu. longipalpis haplogroups and major clades, and to identify conserved distributional areas of haplogroups since the LGM, with the exception of Arg. Evidence for distributional shifts and overlap of haplogroups is important to analyze Leishmaniasis´ eco-epidemiology and to successfully monitor and control transmission.

Inferring distributional shifts of epidemiologically important North and Central American sandflies from Pleistocene to future scenarios

Nine sandfly species (Diptera: Psychodidae) are suspected or proven vectors of Leishmania spp. in the North and Central America region. The ecological niches for these nine species were modelled in three time periods and the overlaps for all time periods of the geographic predictions (G space), and of ecological dimensions using pairwise comparisons of equivalent niches (E space), were calculated. Two Nearctic, six Neotropical and one species in both bioregions occupied a reduced number of distribution areas. The ecological niche projections for most sandfly species other than Lutzomyia shannoni and Lutzomyia ovallesi have not expanded significantly since the Pleistocene. Only three species increase significantly to 2050, whereas all others remain stable. Lutzomyia longipalpis shared a similar ecological niche with more species than any other, although both L. longipalpis and Lutzomyia olmeca olmeca had conserved distributions over time. Climate change, at both regional and local levels, will play a significant role in the temporal and spatial distributions of sandfly species.

Impact of climate change on vector transmission of Trypanosoma cruzi (Chagas, 1909) in North America

Climate change can influence the geographical range of the ecological niche of pathogens by altering biotic interactions with vectors and reservoirs. The distributions of 20 epidemiologically important triatomine species in North America were modelled, comparing the genetic algorithm for rule-set prediction (GARP) and maximum entropy (MaxEnt), with or without topographical variables. Potential shifts in transmission niche for Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) (Chagas, 1909) were analysed for 2050 and 2070 in Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. There were no significant quantitative range differences between the GARP and MaxEnt models, but GARP models best represented known distributions for most species [partial-receiver operating characteristic (ROC) > 1]; elevation was an important variable contributing to the ecological niche model (ENM). There was little difference between niche breadth projections for RCP 4.5 and RCP 8.5; the majority of species shifted significantly in both periods. Those species with the greatest current distribution range are expected to have the greatest shifts. Positional changes in the centroid, although reduced for most species, were associated with latitude. A significant increase or decrease in mean niche elevation is expected principally for Neotropical 1 species. The impact of climate change will be specific to each species, its biogeographical region and its latitude. North American triatomines with the greatest current distribution ranges (Nearctic 2 and Nearctic/Neotropical) will have the greatest future distribution shifts. Significant shifts (increases or decreases) in mean elevation over time are projected principally for the Neotropical species with the broadest current distributions. Changes in the vector exposure threat to the human population were significant for both future periods, with a 1.48% increase for urban populations and a 1.76% increase for rural populations in 2050.

Ecological Niche Model for Predicting Distribution of Disease-Vector Mosquitoes in Yucatán State, México

The majority of the Yucatán State, México, presents subtropical climate that is suitable for many species of mosquitoes that are known to be vectors of diseases, including those from the genera Aedes and Culex. The objective of this study is to identify the geographic distribution of five species from these two genera and estimate the human population at risk of coming in contact with them. We compiled distributional data for Aedes aegypti (L.), Aedes (Howardina) cozumelensis (Diaz Najera), Culex coronator Dyar and Knab, Culex quinquefasciatus Say, and Culex thriambus Dyar from several entomological studies in Yucatán between March 2010 and September 2014. Based on these data, we constructed ecological niche models to predict the spatial distribution of each species using the MaxEnt algorithm. Our models identified areas with suitable environments for Ae. aegypti in most of Yucatán. A similar percentage of urban (97.1%) and rural (96.5%) populations were contained in areas of highest suitability for Ae. aegypti, and no spatial pattern was found (Moran's I = 0.33, P = 0.38); however, we found an association of abundance of immature forms of this species with annual mean temperature (r = 0.19, P ≤ 0.001) and annual precipitation (r = 0.21, P ≤ 0.001). Aedes cozumelensis is also distributed in most areas of the Yucatán State; Cx. quinquefasciatus, Cx. coronator, and Cx. thriambus are restricted to the northwest. The information generated in this study can inform decision-making to address control measures in priority areas with presence of these vectors.

Influences of climate change on the potential distribution of Lutzomyia longipalpis sensu lato (Psychodidae: Phlebotominae)

This study explores the present day distribution of Lutzomyia longipalpis in relation to climate, and transfers the knowledge gained to likely future climatic conditions to predict changes in the species' potential distribution. We used ecological niche models calibrated based on occurrences of the species complex from across its known geographic range. Anticipated distributional changes varied by region, from stability to expansion or decline. Overall, models indicated no significant north-south expansion beyond present boundaries. However, some areas suitable both at present and in the future (e.g., Pacific coast of Ecuador and Peru) may offer opportunities for distributional expansion. Our models anticipated potential range expansion in southern Brazil and Argentina, but were variably successful in anticipating specific cases. The most significant climate-related change anticipated in the species' range was with regard to range continuity in the Amazon Basin, which is likely to increase in coming decades. Rather than making detailed forecasts of actual locations where Lu. longipalpis will appear in coming years, our models make interesting and potentially important predictions of broader-scale distributional tendencies that can inform heath policy and mitigation efforts.

Shifts in the ecological niche of Lutzomyia peruensis under climate change scenarios in Peru

The Peruvian Andes presents a climate suitable for many species of sandfly that are known vectors of leishmaniasis or bartonellosis, including Lutzomyia peruensis (Diptera: Psychodidae), among others. In the present study, occurrences data for Lu. peruensis were compiled from several items in the scientific literature from Peru published between 1927 and 2015. Based on these data, ecological niche models were constructed to predict spatial distributions using three algorithms [Support vector machine (SVM), the Genetic Algorithm for Rule-set Prediction (GARP) and Maximum Entropy (MaxEnt)]. In addition, the environmental requirements of Lu. peruensis and three niche characteristics were modelled in the context of future climate change scenarios: (a) potential changes in niche breadth; (b) shifts in the direction and magnitude of niche centroids, and (c) shifts in elevation range. The model identified areas that included environments suitable for Lu. peruensis in most regions of Peru (45.77%) and an average altitude of 3289 m a.s.l. Under climate change scenarios, a decrease in the distribution areas of Lu. peruensis was observed for all representative concentration pathways. However, the centroid of the species' ecological niche showed a northwest direction in all climate change scenarios. The information generated in this study may help health authorities responsible for the supervision of strategies to control leishmaniasis to coordinate, plan and implement appropriate strategies for each area of risk, taking into account the geographic distribution and potential dispersal of Lu. peruensis.

Geographical, landscape and host associations of Trypanosoma cruzi DTUs and lineages

Background

The evolutionary history and ecological associations of Trypanosoma cruzi, the need to identify genetic markers that can distinguish parasite subpopulations, and understanding the parasite’s evolutionary and selective processes have been the subject of a significant number of publications since 1998, the year when the first DNA sequence analysis for the species was published.

Methods

The current analysis systematizes and re-analyzes this original research, focusing on critical methodological and analytical variables and results that have given rise to interpretations of putative patterns of genetic diversity and diversification of T. cruzi lineages, discrete typing units (DTUs), and populations, and their associations with hosts, vectors, and geographical distribution that have been interpreted as evidence for parasite subpopulation specificities.

Results

Few studies use hypothesis-driven or quantitative analysis for T. cruzi phylogeny (16/58 studies) or phylogeography (10/13). Among these, only one phylogenetic and five phylogeographic studies analyzed molecular markers directly from tissues (i.e. not from isolates). Analysis of T. cruzi DTU or lineage niche and its geographical projection demonstrate extensive sympatry among all clades across the continent and no significant niche differences among DTUs. DTU beta-diversity was high, indicating diverse host assemblages across regions, while host dissimilarity was principally due to host species turnover and to a much lesser degree to nestedness. DTU-host order specificities appear related to trophic or microenvironmental interactions.

Conclusions

More rigorous study designs and analyses will be required to discern evolutionary processes and the impact of landscape modification on population dynamics and risk for T. cruzi transmission to humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1918-2) contains supplementary material, which is available to authorized users.

Assessing the importance of four sandfly species (Diptera: Psychodidae) as vectors of Leishmania mexicana in Campeche, Mexico

Localized cutaneous leishmaniasis represents a public health problem in many areas of Mexico, especially in the Yucatan Peninsula. An understanding of vector ecology and bionomics is of great importance in evaluations of the transmission dynamics of Leishmania parasites. A field study was conducted in the county of Calakmul, state of Campeche, during the period from November 2006 to March 2007. Phlebotomine sandfly vectors were sampled using Centers for Disease Control light traps, baited Disney traps and Shannon traps. A total of 3374 specimens were captured in the two villages of Once de Mayo (93.8%) and Arroyo Negro (6.1%). In Once de Mayo, the most abundant species were Psathyromyia shannoni, Lutzomyia cruciata, Bichromomyia olmeca olmeca and Psychodopygus panamensis (all: Diptera: Psychodidae). The Shannon trap was by far the most efficient method of collection. The infection rate, as determined by Leishmania mexicana-specific polymerase chain reaction, was 0.3% in Once de Mayo and infected sandflies included Psy. panamensis, B. o. olmeca and Psa. shannoni. There were significant differences in human biting rates across sandfly species and month of sampling. Ecological niche modelling analyses showed an overall overlap of 39.1% for the four species in the whole state of Campeche. In addition, the finding of nine vector-reservoir pairs indicates a potential interaction. The roles of the various sandfly vectors in Calakmul are discussed.

[Current and future ecological niche of Leishmaniasis (Kinetoplastida: Trypanosomatidae) in the Neotropical region]

The leishmaniasis is a complex disease system, caused by the protozoan parasite Leishmania and transmitted to humans by the vector Lutzomyia spp. Since it is listed as a neglected disease according to the World Health Organization, the aim of this study was to determine the current and future niche of cutaneous and visceral leishmaniasis in the Neotropical region. We built the ecological niche model (ENM) of cutaneous (N= 2 910 occurrences) and visceral (N= 851 occurrences) leishmaniasis using MaxEnt algorithm. Nine bioclimatic variables (BIO1, BIO4, BIO5, BIO6, BIO7, BIO12, BIO13, BIO14, BIO15 (downloaded from the Worldclim) and disease occurrences data were used for the construction of ENM for three periods (current, 2050 and 2070) and four climate change scenarios (RCP 2.6, 4.5, 6.0 y 8.5). We analyzed the number of pixels occupied, identity niche, modified niche (stable, loss, and gain) and seasonality. Our analyses indicated the expansion for cutaneous leishmaniasis (CL), a comparison for visceral leishmaniasis (VL). We rejected the null hypothesis of niche identity between CL and VL with Hellinger’s index = 0.91 (0.92-0.98) and Schoener’s Index = 0.67 (0.85-1.00) but with an overlap niche of 56.3 %. The differences between the two leishmaniasis types were detected in relation to RCP scenarios and niche shifts (area gained / loss). Seasonality was more important for CL. We provided a current picture of CL and VL distributions and the predicted distributional changes associated to different climate change scenarios for the Neotropical region. We can anticipate that increasing range is likely although it will depend locally on the future trends in weather seasonality.

Nicho ecológico actual y futuro de la Leishmaniasis (Kinetoplastida: Trypanosomatidae) en la región Neotropical

The leishmaniasis is a complex disease system, caused by the protozoan parasite Leishmania and transmitted to humans by the vector Lutzomyia spp. Since it is listed as a neglected disease according to the World Health Organization, the aim of this study was to determine the current and future niche of cutaneous and visceral leishmaniasis in the Neotropical region. We built the ecological niche model (ENM) of cutaneous (N= 2 910 occurrences) and visceral (N= 851 occurrences) leishmaniasis using MaxEnt algorithm. Nine bioclimatic variables (BIO1, BIO4, BIO5, BIO6, BIO7, BIO12, BIO13, BIO14, BIO15 (downloaded from the Worldclim) and disease occurrences data were used for the construction of ENM for three periods (current, 2050 and 2070) and four climate change scenarios (RCP 2.6, 4.5, 6.0 y 8.5). We analyzed the number of pixels occupied, identity niche, modified niche (stable, loss, and gain) and seasonality. Our analyses indicated the expansion for cutaneous leishmaniasis (CL), a comparison for visceral leishmaniasis (VL). We rejected the null hypothesis of niche identity between CL and VL with Hellinger’s index = 0.91 (0.92-0.98) and Schoener’s Index = 0.67 (0.85-1.00) but with an overlap niche of 56.3 %. The differences between the two leishmaniasis types were detected in relation to RCP scenarios and niche shifts (area gained / loss). Seasonality was more important for CL. We provided a current picture of CL and VL distributions and the predicted distributional changes associated to different climate change scenarios for the Neotropical region. We can anticipate that increasing range is likely although it will depend locally on the future trends in weather seasonality.

Population genetics and ecological niche of invasive Aedes albopictus in Mexico

The Asian tiger mosquito Aedes albopictus (Skuse), is one of the most invasive mosquito species worldwide. In Mexico it is now recorded in 12 states and represents a serious public health problem, given the recent introduction of Chikungunya on the southern border. The aim of this study was to analyze the population genetics of A. albopictus from all major recorded foci, and model its ecological niche. Niche similarity with that from its autochthonous distribution in Asia and other invaded countries were analyzed and its potential future expansion and potential human exposure in climate change scenarios measured. We analyzed 125 sequences of a 317 bp fragment of the cyt b gene from seven A. albopictus populations across Mexico. The samples belong to 25 haplotypes with moderate population structuring (Fst=0.081, p<0.02) and population expansion. The most prevalent haplotype, found in all principal sites, was shared with the USA, Brazil, France, Madagascar, and Reunion Island. The ecological niche model using Mexican occurrence records covers 79.7% of the country, and has an 83% overlap with the Asian niche projected to Mexico. Both Neotropical and Nearctic regions are included in the Mexican niche model. Currently in Mexico, 38.6 million inhabitants are exposed to A. albopictus, which is expected to increase to 45.6 million by 2070. Genetic evidence supports collection information that A. albopictus was introduced to Mexico principally by land from the USA and Central and South America. Prevalent haplotypes from Mexico are shared with most invasive regions across the world, just as there was high niche similarity with both natural and invaded regions. The important overlap with the Asian niche model suggests a high potential for the species to disperse to sylvatic regions in Mexico.

Larval habitat characterization of Anopheles darlingi from its northernmost geographical distribution in Chiapas, Mexico

Background

Anopheles darlingi is considered the most efficient malaria vector in the Neotropical region. In Mexico, its role as an incriminated vector of Plasmodium has not been confirmed in the Lacandon forest. Similarly, knowledge about bionomic and larval ecology is scarce. The study aim was to identify and describe the larval habitats of An. darlingi in Chiapas, México.

Methods

Standard larval collections were performed in the Lacandon forest region and in the Soconusco region of southern Chiapas from January 2010 to April 2014, including dry and rainy seasons. Mean larval density of An. darlingi was estimated according to hydrological types, and associations between the presence of An. darlingi and environmental factors including ecological parameters and geographic positions were statistically analysed.

Results

One hundred and twelve aquatic habitats were analysed, 80 from the Lacandon forest region and 32 from the Soconusco region; 94.64 % of these sites presented anopheline larvae. In total, 10,977 larvae belonging to 11 Anopheles species were collected. The 19 (out of 112) larval habitats positive to An. darlingi were: rain puddles (26.32 %), ground pools (21.05 %), ponds (15.79 %), ditches (15.79 %), river margins (10.53 %) and streams (10.53 %). Overall, the average (±SD) larval density was 6.60 ± 2.41 larvae per dip. Multiple logistic regression analysis showed that temporary habitats, green algae presence and stagnant water were associated with An. darlingi larval presence. The positive habitats were found in the Lacandon forest region during the rainy season (May–September). No specimens were found in the Soconusco region of the coastal plain of Chiapas.

Conclusion

The mosquito An. darlingi larval habitats were found in different hydrological types. The habitat stability, presence of algae and water current were the main factors for An. darlingi larval occurrence. The information on the characteristics of the larval habitats of An. darlingi will be useful in sustainable programmes for malaria control in the Lacandon forest region, Chiapas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-1037-0) contains supplementary material, which is available to authorized users.

Atlas of Mexican Triatominae (Reduviidae: Hemiptera) and vector transmission of Chagas disease

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.