Genetic structure and divergence in populations of Lutzomyia cruciata, a phlebotomine sand fly (Diptera: Psychodidae) vector of Leishmania mexicana in southeastern Mexico

Surveillance of sand flies (Psychodidae, Phlebotominae) from Mexico: Altitudinal and climatic patterns after historical and new geographic records in endemic areas of leishmaniasis

This study updates knowledge on historical geographic distribution of sand fly species through identifying altitudinal and bioclimatic patterns in leishmaniasis endemic areas in Mexico. We analyze and identify sand fly specimens obtained through national efforts by the Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE, Mexico), collected between 1995 and 2001, 2008-2012, and 2017-2023, and add bibliographic information (427 additional records). After a principal components analysis of WorldClim variables and altitudinal ranges, variables that better explain the distribution of sand fly species were chosen (BIO6, BIO12, and BIO16, explaining 72 % of variation). A total of 1,187 specimens of 22 species were retrieved from eight states, providing 29 new municipalities and 48 new localities, being Lutzomyia cruciata, Micropygomyia chiapanensis, and Psathyromyia shannoni the most common species. We presented new historical records of distribution for sand fly species from Morelos (3), Oaxaca (7) and Tabasco (1). The 82.7 % of sand fly species analyzed were distributed in areas with altitudinal ranges below 420 m. The anthropophilic species Psathyromyia shannoni, and Lutzomyia cruciata showed the greatest variability regarding altitudinal range, and climatic preferences, while several wild species showed abiotic preferences. It is likely that the effect of urbanization and climate change generate new beneficial biotopes for the proliferation of the vector sand fly species. Complementary studies that consider seasonality, vegetation types, and change in land use could provide new information to better understand the spread of vector-borne diseases.

Phylogenetic relations among Mexican phlebotomine sand flies (Diptera: Psychodidae) and their divergence time estimation

Phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) have biological relevance as vectors of several pathogens. To ensure periodic entomological monitoring it is necessary to have efficient and accurate tools for an adequate taxonomic identification. There are only few studies on phylogenetic analyses of phlebotomine sand flies from Neotropics, based mostly on morphological and/or molecular data, which makes the delimitation of intra- and interspecific variability of species challenging. Here we generated new molecular information on sand fly species distributed in endemic areas of leishmaniasis in Mexico, using mitochondrial and ribosomal genes, and incorporating morphological information available. Specifically, we established their phylogenetic relationships, and estimated their divergence time. Our study provides molecular information for 15 phlebotomine sand fly species from different areas of Mexico, contributing to the genetic inventory and phylogenetic relations among Neotropical species of the subfamily Phlebotominae. Mitochondrial genes proved to be suitable markers for the molecular identification of phlebotomine sand flies. However, the incorporation of additional nuclear gene information could increase the significance of phylogenetic inferences. We also provided evidence about a possible divergence time of phlebotomine sand fly species, supporting their presumable origin in the Cretaceous period.

Molecular detection of Wolbachia and Bartonella as part of the microbiome of phlebotomine sand flies from Chiapas, Mexico

Phlebotomine sand flies are dipterans of relevance due to their role as vectors of several pathogens worldwide. Bacteria in the gut of sand flies possibly affect their vectorial capacity and competence to transmit parasites. A retrospective study was performed in sand fly specimens that had previously been collected in four localities of the state of Chiapas during the period 2009-2011 to detect Wolbachia and Bartonella and their possible coinfection with Leishmania. For the molecular detection of bacteria, we used primers and conditions that had previously been reported. A total of 531 sand fly specimens of 10 species were analyzed. Four Wolbachia strains were detected in five sand fly species, showing a prevalence of 8.6%. All the Wolbachia strains had previously been reported in other taxa. In one sand fly species, we also detected a new lineage of Bartonella evidenced by a phylogenetic analysis. No sand fly specimens showed coinfections of these bacteria and Leishmania. The bacteria found in the phlebotomine sand flies are possibly transmitted by plant-mediated horizontal transmission and during blood meal feeding.

Genetic variability highlights the invasion route of the Lutzomyia longipalpis complex, the main vector of Visceral Leishmaniasis in Uruguay

In the Americas, the sandfly Lutzomyia longipalpis is the main vector of the parasitic protozoa Leishmania infantum, the etiological agent of visceral leishmaniasis (VL). The Lu. longipalpis species complex is currently discontinuously distributed across the Neotropical region, from Mexico to the north of Argentina and Uruguay. During its continental spreading, it must have adapted to several biomes and temperature amplitudes, when founder events should have contributed to the high genetic divergence and geographical structure currently observed, reinforcing the speciation process. The first report of Lu. longipalpis in Uruguay was in 2010, calling the attention of Public Health authorities. Five years later, the parasite Le. infantum was recorded and in 2015 the first case of VL in canids was reported. Hitherto seven human cases by VL have been reported in Uruguay. Here, we publish the first DNA sequences from the mitochondrial genes ND4 and CYTB of Lu. longipalpis collected in Uruguay, and we used these molecular markers to investigate their genetic variability and population structure. We described four new ND4 haplotypes in a total of 98 (4/98) and one CYTB in a total of 77 (1/77). As expected, we were able to establish that the Lu. longipalpis collected in two localities (i.e. Salto and Bella Unión) from the north of Uruguay are closely related to the populations from neighbouring countries. We also propose that the possible route for the vector arrival to the region may have been through vegetation and forest corridors of the Uruguay River system, as well as it may have benefited from landscape modifications generated by commercial forestation. The ecological-scale processes shaping Lu. longipalpis populations, the identification of genetically homogeneous groups and the gene flow among them must be carefully investigated by using highly sensible molecular markers (i.e. genome wide SNPs) since it will help to the understanding of VL transmission and contribute to the planification of public policies on its control.

Mitochondrial COI and Cytb gene as valid molecular identification marker of sandfly species (Diptera: Psychodidae) in China

The accurate identification of sandfly species is crucial because some species transmit medically significant diseases, including leishmaniasis, bartonellosis and sandfly fever. However, due to the high similarity of the external morphology in sandfly species, identification can only be performed using internal morphological characteristics after dissection, which is time consuming and requires highly experienced staff. Thus, the introduction of suitable molecular markers may solve these identification problems. This study screened suitable DNA barcodes to identify common sandfly species in China. The phlebotomine sandflies were collected from Sichuan, Henan and Hainan Provinces from 2014 to 2016. The species were identified by the morphological characteristics of the pharyngeal armature and spermatheca. The genomic DNA of sandfly was extracted individually, and mitochondrial DNA (mtDNA) cytochrome C oxidase subunit I (COI) and cytochrome B (Cytb) as well as the 18S subunit of ribosomal DNA (rDNA) were amplified using polymerase chain reaction (PCR). Additionally, intraspecific and interspecific differences (p-distance) were calculated to evaluate the feasibility of the three gene fragments as a DNA barcode. The phylogeny trees of all sandfly species in this study were constructed using neighbor joining (NJ) method. Six species were identified by the morphological features, belonging to Phlebotomus and Sergentomyia, as Ph. chinensis s. l., Ph. stantoni, Se. bailyi, Se. iyengari, Se. squamirostris, and Se. squamipleuris. Analysis based on three gene fragments revealed some degree of intraspecific polymorphism among these sandfly species in China. The largest intraspecific variation occurred in Ph. chinensis s. l. (mtDNA COI, p-distance = 0.042; mtDNA Cytb, p-distance = 0.071), but the 18S rDNA fragment showed a small variation (p-distance = 0.005). The ranges of interspecific p-distances for mtDNA COI and mtDNA Cytb were 0.138 - 0.231 and 0.128 - 0.274, respectively. However, the interspecific p-distances of 18S rDNA are relatively low ranging from 0.003 to 0.055. Both mitochondrial COI and Cytb gene fragments are valid molecular identification markers in theses sandfly species. The topological structure of phylogeny trees based on mtDNA COI, mtDNA Cytb and 18S rDNA genes were all consistent with morphological classification. And we also found there were significant intraspecies differences within Ph. chinensis s. l. (0.006-0.071) and Se. bailyi (0.002-0.032) based on mtDNA Cytb gene fragment. Sequence alignment data suggested that Ph. chinensis s. l. from Sichuan should be Ph. sichuanensis, and the sandfly specimen collected from Henan was Ph. chinensis s. s.. There could be cryptic species in Se. bailyi from China.

Molecular taxonomy of phlebotomine sand flies (Diptera, Psychodidae) with emphasis on DNA barcoding: A review

The taxonomy and systematics of sand flies (Diptera, Psychodidae, Phlebotominae) are one of the pillars of research aimed to identifying vector populations and the agents transmitted by these insects. Traditionally, the use of morphological traits has been the main line of evidence for the definition of species, but the use of DNA sequences is useful as an integrative approach for their delimitation. Here, we discuss the current status of the molecular taxonomy of sand flies, including their most sequenced molecular markers and the main results. Only about 37% of all sand fly species have been processed for any molecular marker and are publicly available in the NCBI GenBank or BOLD Systems databases. The genera Phlebotomus, Nyssomyia, Psathyromyia and Psychodopygus are well-sampled, accounting for more than 56% of their sequenced species. However, less than 34% of the species of Sergentomyia, Lutzomyia, Trichopygomyia and Trichophoromyia have been sampled, representing a major gap in the knowledge of these groups. The most sequenced molecular markers are those within mtDNA, especially the DNA barcoding fragment of the cytochrome c oxidase subunit I (coi) gene, which has shown promising results in detecting cryptic diversity within species. Few sequences of conserved genes have been generated, which hampers higher-level phylogenetic inferences. We argue that sand fly species should be sequenced for at least the coi DNA barcoding marker, but multiple markers with different mutation rates should be assessed, whenever possible, to generate multilocus analysis.

Genetic diversity and population structure of Phlebotomus argentipes: Vector of Leishmania donovani in Sri Lanka

Phlebotomus argentipes is the vector of Leishmania donovani which causes the disease leishmaniasis, a neglected tropical disease and a growing health problem in Sri Lanka. A proper understanding of the population genetic structure of sand fly vectors is considered important prior to planning and implementation of a successful vector control program. Thus, the present study was conducted to determine the population genetic structure of sand fly vectors in Sri Lanka. Two mitochondrial genes namely Cytochrome c oxidase subunit 1 (Cox 1) and Cytochrome b (Cytb), and the internal transcribed spacer 2 (ITS2) region from the nuclear ribosomal DNA were used for molecular characterization. Analyses included maximum likelihood method, network analysis and DNA polymorphisms. The outcome revealed unique sequences of all genomic regions studied except the cox 1 gene had a relationship with sand flies isolated previously from Sri Lanka, India and Israel and cytb gene of 4 sand flies that aligned with those isolated earlier from Sri Lanka and 3 from Madagascar. Furthermore, cox 1 gene and ITS 2 region analyses based on F_ST values indicated a possible gene flow between the study sites whereas cytb gene analysis favoured the existence of genetically distinct populations of P. argentipes in each of the study sites. Poor population differentiation of P. argentipes, a possible consequence of a gene flow, is indeed of concern due to the risk imposed by promoting the spread of functionally important phenotypes such as insecticide resistance across the country, making future vector control efforts challenging.

Multiple evolutionary lineages for the main vector of Leishmania guyanensis, Lutzomyia umbratilis (Diptera: Psychodidae), in the Brazilian Amazon

Lutzomyia umbratilis is the main vector of Leishmania guyanensis in the Brazilian Amazon and in neighboring countries. Previous biological and molecular investigations have revealed significant differences between L. umbratilis populations from the central Brazilian Amazon region. Here, a phylogeographic survey of L. umbratilis populations collected from nine localities in the Brazilian Amazon was conducted using two mitochondrial genes. Statistical analyses focused on population genetics, phylogenetic relationships and species delimitations. COI genetic diversity was very high, whereas Cytb diversity was moderate. COI genealogical haplotypes, population structure and phylogenetic analyses identified a deep genetic differentiation and three main genetic groups. Cytb showed a shallower genetic structure, two main haplogroups and poorly resolved phylogenetic trees. These findings, allied to absence of isolation by distance, support the hypothesis that the Amazon and Negro Rivers and interfluves are the main evolutionary forces driving L. umbratilis diversification. The main three genetic groups observed represent three evolutionary lineages, possibly species. The first lineage occurs north of the Amazon River and east of Negro River, where Le. guyanensis transmission is intense, implying that L. umbratilis is an important vector there. The second lineage is in the interfluve between north of Amazon River and west of Negro River, an area reported to be free of Le. guyanensis transmission. The third lineage, first recorded in this study, is in the interfluve between south of Amazonas River and west of Madeira River, and its involvement in the transmission of this parasite remains to be elucidated.

Rickettsial agents detected in the genus Psathyromyia (Diptera:Phlebotominae) from a Biosphere Reserve of Veracruz, Mexico

Phlebotomine sand flies are considered the main vectors of Leishmania, the causal agents of leishmaniasis, which is a serious emerging public health problem worldwide. The use of biological control alternatives, like endosymbiotic bacteria (Wolbachia and Rickettsia), have been proposed to decrease sand fly populations and reduce Leishmania transmissions, yet only few records on the detection of Wolbachia or Rickettsia in sand flies are available worldwide. The aim of this study was to perform the molecular detection of Rickettsial agents associated with sand flies from the last patch of a rainforest in south-eastern Mexico, where a high prevalence of Leishmania infantum has been reported. Sampling effort of sand flies covered 300 trap-nights between 2011 and 2013, and a total of 925 specimens from twelve species were morphologically identified. Using PCR techniques, we identified a new lineage of the endosymbionts Rickettsia in Psathyromyia aclydifera (prevalence of 19.54%), and Wolbachia in Psathyromyia shannoni and Lutzomyia sp. (prevalence of 25%). The detected Wolbachia lineage was similar to the wWhi strain found in Pa. shannoni from Colombia and Nyssomyia whitmani from Brazil; whereas the identified Rickettsia represents a new lineage worldwide. This is the first record of Rickettsial agents associated to sand flies from this region, yet it remains for analysed if these bacteria possibly play a role as vector control agents, capable of reducing the sand fly populations in Mexico.

Molecular detection of Leishmania infantum in sand flies (Diptera: Psychodidae: Phlebotominae) from Veracruz, Mexico

Phlebotomine sand flies are vectors of Leishmania parasites causing different clinical forms of leishmaniases that represent a serious emerging public health problem worldwide. Mexico harbours a large diversity of sand flies, yet only six species have been considered suspected vectors of Leishmania. The disease has been recorded in 25 states, where the State of Veracruz has recorded the highest number of cases with leishmaniases, although no systematic or epidemiological surveillance studies of Leishmania vectors have been carried out in the region. For that reason, the aim of this study was to perform the molecular detection of Leishmania DNA in phlebotomine sand flies collected from a humid tropical region in Veracruz. We confirmed the presence of Leishmania DNA in eight sand fly species. Sand flies with the highest infection were Psathyromyia aclydifera and Pychodopygus panamensis. This is also the first report of Leishmania DNA in Psathyromyia aclydifera, Psathyromyia carpenteri, Dampfomyia beltrani and Brumptomyia mesai. Our findings highlight the importance of entomological surveys and epidemiological studies, since they enable to determine whether sand fly species may be potential Leishmania vectors in a given area of the Mexico, as transmission dynamics can vary in the different regions.

DNA barcoding and fauna of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) from Los Tuxtlas, Veracruz, Mexico

Mexico has great diversity of phlebotomine sand flies related to cases of leishmaniasis, yet few studies have dressed the molecular taxonomy of these sand fly species. The use of the cytochrome oxidase subunit 1 (COI) gene, as a DNA Barcode has facilitated the molecular identification of sand flies species worldwide. We use the DNA barcode as a useful tool for the identification of phlebotomine sand flies of the natural reserve Los Tuxtlas from Veracruz, México. A fragment of 536 bp of the COI gene was obtained from 36 individuals belonging to eight species of five genera (Dampfomyia, Lutzomyia, Psathyromyia, Psychodopygus and Brumptomyia) with coverage between 92-100%, and found similarities ranging from 93-98% with other New World phlebotomine sand flies. The NJ dendogram grouped sand flies into eight clusters according to identified species, supported by bootstrap of 97%-100%. In conclusion, all phlebotomine sand flies were correctly identified and agree with the morphological identification, also could separate genetics the isomorphic females of the genus Brumptomyia.

Traditional and Geometric Morphometry Analyses of Lutzomyia cruciata (Diptera: Psychodidae: Phlebotominae) Populations of Chiapas, Mexico

The presence of Lutzomyia (Tricholateralis) cruciata (Coquillett 1907) species complex has been suggested by morphological analysis of eggs and genetic studies of females. The present work aimed to compare the diversity in morphology of four populations of Lu. cruciata from the Coast of Chiapas, Mexico, using traditional (TM) and geometric (GM) methods. Several morphological characteristics that were analyzed provided consistency to differentiate at least, three populations of Lu. cruciata. Both methods were effective to detect morphological differences associated with the geographical sites of capture. In both sexes, three and four groups were detected by TM and GM, respectively. These results suggest marked morphological differences in both sexes of Lu. cruciata that make these methods potentially useful to identify the geographical origin of any specimen of this species captured in the study region. Although the results produced by both methods are coincident, geometric morphometrics turned out to be most advantageous with respect to traditional morphometry, since the latter requires more time and effort. The consistency of our results shows that the variability of environmental conditions on the coast of Chiapas determines a high degree of phenotypic plasticity in Lu. cruciata, with the possibility of prezygotic isolation and the formation of species complex.

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.

Genetic diversity, phylogeography and molecular clock of the Lutzomyia longipalpis complex (Diptera: Psychodidae)

BACKGROUND

The Lutzomyia longipalpis complex has a wide but discontinuous distribution in Latin America, extending throughout the Neotropical realm between Mexico and northern Argentina and Uruguay. In the Americas, this sandfly is the main vector of Leishmania infantum, the parasite responsible for Visceral Leishmaniasis (VL). The Lu. longipalpis complex consists of at least four sibling species, however, there is no current consensus on the number of haplogroups, or on their divergence. Particularly in Argentina, there have been few genetic analyses of Lu. longipalpis, despite its southern expansion and recent colonization of urban environments. The aim of this study was to analyze the genetic diversity and structure of Lu. longipalpis from Argentina, and to integrate these data to re-evaluate the phylogeography of the Lu. longipalpis complex using mitochondrial markers at a Latin American scale.

METHODOLOGY/PRINCIPAL FINDINGS

Genetic diversity was estimated from six sites in Argentina, using a fragment of the ND4 and the 3´ extreme of the cyt b genes. Greatest genetic diversity was found in Tartagal, Santo Tomé and San Ignacio. There was high genetic differentiation of Lu. longipalpis in Argentina using both markers: ND4 (FST = 0.452, p < 0.0001), cyt b (FST = 0.201, p < 0.0001). Genetic and spatial Geneland analyses reveal the existence of two primary genetic clusters in Argentina, cluster 1: Tartagal, Santo Tomé, and San Ignacio; cluster 2: Puerto Iguazú, Clorinda, and Corrientes city. Phylogeographic analyses using ND4 and cyt b gene sequences available in GenBank from diverse geographic sites suggest greater divergence than previously reported. At least eight haplogroups (three of these identified in Argentina), each separated by multiple mutational steps using the ND4, are differentiated across the Neotropical realm. The divergence of the Lu. longipalpis complex from its most recent common ancestor (MRCA) was estimated to have occurred 0.70 MYA (95% HPD interval = 0.48-0.99 MYA).

CONCLUSIONS/SIGNIFICANCE

This study provides new evidence supporting two Lu. longipalpis genetic clusters and three of the total eight haplogroups circulating in Argentina. There was a high level of phylogeographic divergence among the eight haplogroups of the Lu. longipalpis complex across the Neotropical realm. These findings suggest the need to analyze vector competence, among other parameters intrinsic to a zoonosis, according to vector haplogroup, and to consider these in the design and surveillance of vector and transmission control strategies.

Ecology of phlebotomine sandflies and putative reservoir hosts of leishmaniasis in a border area in Northeastern Mexico: implications for the risk of transmission of Leishmania mexicana in Mexico and the USA

Leishmaniases are a group of important diseases transmitted to humans through the bite of sandfly vectors. Several forms of leishmaniases are endemic in Mexico and especially in the Southeast region. In the Northeastern region, however, there have only been isolated reports of cases and scanty records of sandfly vectors. The main objective of this study was to analyze the diversity of sandflies and potential reservoir hosts of Leishmania spp. in the states of Nuevo León and Tamaulipas. Species richness and abundances of sandflies and rodents were recorded. A fraction of the caught sandflies was analyzed by PCR to detect Leishmania spp. Tissues from captured rodents were also screened for infection. Ecological Niche Models (ENMs) were computed for species of rodent and their association with crop-growing areas. We found 13 species of sandflies, several of which are first records for this region. Medically important species such as Lutzomyia anthophora, Lutzomyia diabolica, Lutzomyia cruciata, and Lutzomyia shannoni were documented. Leishmania spp. infection was not detected in sandflies. Nine species of rodents were recorded, and Leishmania (Leishmania) mexicana infection was found in four species of Peromyscus and Sigmodon. ENMs showed that potential distribution of rodent pest species overlaps with allocated crop areas. This shows that Leishmania (L.) mexicana infection is present in the Northeastern region of Mexico, and that previously unrecorded sandfly species occur in the same areas. These findings suggest a potential risk of transmission of Leishmania (L.) mexicana.

Descriptions of the Immature Stages of Lutzomyia (Tricholateralis) cruciata (Coquillett) (Diptera: Psychodidae, Phlebotominae)

The present study presents morphological and chaetotaxic descriptions of the immature stages of Lutzomyia (Tricholateralis) cruciata (Coquillett), a probable vector of leishmaniasis in Mexico. The egg exochorion is consistent with the species already known as Lu. (Tricholaterialis), but different from the Lu. cruciata egg of Chiapas, Mexico. The fourth instar larva of Lu. (Tricholateralis) cruciata possesses a novel antenna, combining morphological characteristics of categories 2 and 3 for neotropical sandflies. Differences between the chaetotaxy of first and fourth instar larvae of Lu. cruciata with those of Lu. (Lutzomyia) and Lu. (Tricholaterlis) are compared and discussed. This is the first time in which the chaetotaxy and morphology of pupa of a species belonging to Lutzomyia (Tricholateralis) sensu Galati have been described, and we recorded for the first time the anterior prothorax setae, which was previously only considered for Old World species.

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.

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.

Life history of the sand fly vector Lutzomyia cruciata in laboratory conditions

Lutzomyia cruciata Coquillet (Diptera: Psychodidae: Phlebotominae) is a potential vector of Leishmania sp.; its geographical distribution in Mexico is widespread, but its life history is unknown. The present study gives relevant information on the life cycle, morphology, survival and reproduction of Lu. cruciata observed over successive generations under laboratory conditions. Seven successive generations were produced. A total of 975 adults were obtained in a sexual proportion of 1.1 : 1 (female : male). Each Lu. cruciata female produced 20.7 eggs and 1.9 adults, approximately, with a proportion of eggs per female of 2.7% (first generation) and 21.3% (second generation). The life cycle of Lu. cruciata, from egg to adult, occurred in 52.7 ± 0.52 days. The largest percentage of mortality occurred during the egg stage (48.5%) and the first larval instar (26.5%), whereas in the pupal stage mortality was the lowest (9.1%). Lutzomyia cruciata exhibits sexual dimorphism based on size, which is exhibited as of the second larval instar, males being smaller than females. The maximum survival of females and males was 10 and 15 days, respectively. An overview of the immature stages of the species made with an electronic scanning microscope is included. This paper contributes basic information on aspects of Lu. cruciata that were previously unknown related to its life history.

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.

Genetic divergence in populations of Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis, in Ecuador and Peru

Haplotype and gene network analyses were performed on mitochondrial cytochrome oxidase I and cytochrome b gene sequences of Lutzomyia (Lu.) ayacuchensis populations from Andean areas of Ecuador and southern Peru where the sand fly species transmit Leishmania (Leishmania) mexicana and Leishmania (Viannia) peruviana, respectively, and populations from the northern Peruvian Andes, for which transmission of Leishmania by Lu. ayacuchensis has not been reported. The haplotype analyses showed higher intrapopulation genetic divergence in northern Peruvian Andes populations and less divergence in the southern Peru and Ecuador populations, suggesting that a population bottleneck occurred in the latter populations, but not in former ones. Importantly, both haplotype and phylogenetic analyses showed that populations from Ecuador consisted of clearly distinct clusters from southern Peru, and the two populations were separated from those of northern Peru.

Species composition and seasonal abundance of sandflies (Diptera: Psychodidae: Phlebotominae) in coffee agroecosystems

The composition and seasonal occurrence of sandflies were investigated in coffee agroecosystems in the Soconusco region of Chiapas, Mexico. Insect sampling was performed on three plantations located at different altitudes: Finca Guadalupe Zajú [1,000 m above sea level (a.s.l.)], Finca Argovia (613 m a.s.l.) and Teotihuacán del Valle (429 m a.s.l.). Sandflies were sampled monthly from August 2007-July 2008 using three sampling methods: Shannon traps, CDC miniature light traps and Disney traps. Sampling was conducted for 3 h during three consecutive nights, beginning at sunset. A total of 4,387 sandflies were collected during the course of the study: 2,718 individuals in Finca Guadalupe Zajú, 605 in Finca Argovia and 1,064 in Teotihuacán del Valle. The Shannon traps captured 94.3% of the total sandflies, while the CDC light traps and Disney traps captured 4.9% and 0.8%, respectively. More females than males were collected at all sites. While the number of sandflies captured was positively correlated with temperature and relative humidity, a negative correlation was observed between sandfly numbers and rainfall. Five species of sandflies were captured: Lutzomyia cruciata , Lutzomyia texana , Lutzomyia ovallesi , Lutzomyia cratifer / undulata and Brumptomyia sp. Lu. cruciata , constituting 98.8% of the total, was the most abundant species. None of the captured sandflies was infected with Leishmania spp.

Current and future niche of North and Central American sand flies (Diptera: psychodidae) in climate change scenarios

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.