Abstract. Cutaneous leishmaniasis (CL) is endemic to the Yucatan Peninsula ofMexico. The main causative agent is the parasite Leishmania mexicana (Biagi) (Kinetoplastida: Trypanosomatidae) and, based on the classic work of Dr Biagi's research team, it has been generally accepted and frequently reported that the only vector of L. mexicana in the region is the sandfly Lutzomyia olmeca olmeca (Vargas & Diáz-Nájera) (Diptera: Psychodidae). Evidence gathered from recent entomological studies conducted mainly in Calakmul, Campeche, however, suggests that other species may also be vectors of L. mexicana. We conducted a field study in two villages in Calakmul, Campeche in the Yucatan Peninsula, where recent cases of CL have been reported, to document the species composition and relative abundances of the sandfly fauna and to identify which species are likely to be the main vectors by assessing the biting rates and parasite infection rates of the suspected vector species. and Lu. panamensis. The possible role of these four sandfly species in relation to L. mexicana transmission in Calakmul is discussed.

The surveillance of prevalent Leishmania sand fly vectors is an important issue for epidemiological studies in populated areas where leishmaniasis is endemic. In this study, we collected sand flies from a peri-urban area in the southeast of Mexico. Natural infection with Leishmania (L.) mexicana was studied by PCR using a Leishmania internal transcribed spacer of the ribosomal RNA gene for amplification. Infected Lutzomyia olmeca olmeca, Lu. shannoni and Lu. cruciata sand flies were collected mainly during the high transmission season (November to March), coinciding with the highest sand fly densities. Additionally, positive specimens of Lu. olmeca olmeca were also captured during July and August. The infected sand flies were from primary forest (subperennial forest) and secondary forest (18-25 years old and 10-15 years old respectively). Sand flies collected with Disney and Shannon traps were the ones found to be infected with L. (L.) mexicana. We conclude that the high-risk period in which L. (L.) mexicana is transmitted in the peri-urban area of Chetumal City is from July to March and that transmission is associated with both the subperennial forest and the secondary forest.

BackgroundLeptospirosis is widespread in Mexico, yet the potential distribution and risk of the disease remain unknown.Methodology/Principal FindingsWe analysed morbidity and mortality according to age and gender based on three sources of data reported by the Ministry of Health and the National Institute of Geography and Statics of Mexico, for the decade 2000–2010. A total of 1,547 cases were reported in 27 states, the majority of which were registered during the rainy season, and the most affected age group was 25–44 years old. Although leptospirosis has been reported as an occupational disease of males, analysis of morbidity in Mexico showed no male preference. A total number of 198 deaths were registered in 21 states, mainly in urban settings. Mortality was higher in males (61.1%) as compared to females (38.9%), and the case fatality ratio was also increased in males. The overall case fatality ratio in Mexico was elevated (12.8%), as compared to other countries. We additionally determined the potential disease distribution by examining the spatial epidemiology combined with spatial modeling using ecological niche modeling techniques. We identified regions where leptospirosis could be present and created a potential distribution map using bioclimatic variables derived from temperature and precipitation. Our data show that the distribution of the cases was more related to temperature (75%) than to precipitation variables. Ecological niche modeling showed predictive areas that were widely distributed in central and southern Mexico, excluding areas characterized by extreme climates.Conclusions/SignificanceIn conclusion, an epidemiological surveillance of leptospirosis is recommended in Mexico, since 55.7% of the country has environmental conditions fulfilling the criteria that favor the presence of the disease.

Zoonoses are an important class of infectious diseases. An important element determining the impact of a zoonosis on domestic animal and human health is host range. Although for particular zoonoses some host species have been identified, until recently there have been no methods to predict those species most likely to be hosts or their relative importance. Complex inference networks infer potential biotic interactions between species using their degree of geographic co-occurrence, and have been posited as a potential tool for predicting disease hosts. Here we present the results of an interdisciplinary, empirical study to validate a model based on such networks for predicting hosts of Leishmania (L.) mexicana in Mexico. Using systematic sampling to validate the model predictions we identified 22 new species of host (34% of all species collected) with the probability to be a host strongly dependent on the probability of co-occurrence of vector and host. The results confirm that Leishmania (L.) mexicana is a generalist parasite but with a much wider host range than was previously thought. These results substantially change the geographic risk profile for Leishmaniasis and provide insights for the design of more efficient surveillance measures and a better understanding of potential dispersal scenarios.

A kinetic model of trypanothione [T(SH) 2 ] metabolism in Trypanosoma cruzi was constructed based on enzyme kinetic parameters determined under near-physiological conditions (including glutathione synthetase), and the enzyme activities, metabolite concentrations and fluxes determined in the parasite under control and oxidizing conditions. The pathway structure is characterized by a T(SH) 2 synthetic module of low flux and low catalytic capacity, and another more catalytically efficient T(SH) 2 -dependent antioxidant ⁄ regenerating module. The model allowed quantification of the contribution of each enzyme to the control of T(SH) 2 synthesis and concentration (flux control and concentration control coefficients, respectively). The main control of flux was exerted by c-glutamylcysteine synthetase (cECS) and trypanothione synthetase (TryS) (control coefficients of 0.58-0.7 and 0.49-0.58, respectively), followed by spermidine transport (0.24); negligible flux controls by trypantothione reductase (TryR) and the T(SH) 2 -dependent antioxidant machinery were determined. The concentration of reduced T(SH) 2 was controlled by TryR (0.98) and oxidative stress ()0.99); however, cECS and TryS also exerted control on the cellular level of T(SH 2 ) when they were inhibited by more than 70%. The model predicted that in order to diminish the T(SH) 2 synthesis flux by 50%, it is necessary to inhibit cECS or TryS by 58 or 63%, respectively, or both by 50%, whereas more than 98% inhibition was required for TryR. Hence, simultaneous and moderate inhibition of cECS and TryS appears to be a promising multi-target therapeutic strategy. In contrast, use of highly potent and specific inhibitors for TryR and the antioxidant machinery is necessary to affect the antioxidant capabilities of the parasites. DatabaseThe glutathione synthetase gene sequences from the Ninoa and Queretaro strains have been submitted to the GenBank database under accession numbers HQ398240 and HQ398239, respectively Abbreviations

Leishmania (Leishmania) mexicana causes cutaneous leishmaniasis, an endemic zoonosis affecting a growing number of patients in the southeastern states of Mexico. Some foci are found in shade-grown cocoa and coffee plantations, or near perennial forests that provide rich breeding grounds for the sand fly vectors, but also harbor a variety of bat species that live off the abundant fruits provided by these shade-giving trees. The close proximity between sand flies and bats makes their interaction feasible, yet bats infected with Leishmania (L.) mexicana have not been reported. Here we analyzed 420 bats from six states of Mexico that had reported patients with leishmaniasis. Tissues of bats, including skin, heart, liver and/or spleen were screened by PCR for Leishmania (L.) mexicana DNA. We found that 41 bats (9.77%), belonging to 13 species, showed positive PCR results in various tissues. The infected tissues showed no evidence of macroscopic lesions. Of the infected bats, 12 species were frugivorous, insectivorous or nectarivorous, and only one species was sanguivorous (Desmodus rotundus), and most of them belonged to the family Phyllostomidae. The eco-region where most of the infected bats were caught is the Gulf Coastal Plain of Chiapas and Tabasco. Through experimental infections of two Tadarida brasiliensis bats in captivity, we show that this species can harbor viable, infective Leishmania (L.) mexicana parasites that are capable of infecting BALB/c mice. We conclude that various species of bats belonging to the family Phyllostomidae are possible reservoir hosts for Leishmania (L.) mexicana, if it can be shown that such bats are infective for the sand fly vector. Further studies are needed to determine how these bats become infected, how long the parasite remains viable inside these potential hosts and whether they are infective to sand flies to fully evaluate their impact on disease epidemiology.

Leishmania mexicana causes a wide spectrum of clinical diseases. In spite of the variety of clinical forms, no data exist regarding genetic polymorphism of L. mexicana. We analyzed the polymorphism of the internal transcribed spacer (ITS) and the small subunit rRNA genes of 3 reference strains and 24 Mexican isolates of L. mexicana, by means of polymerase chain reaction and subsequent digestion by restriction enzymes. All strains of L. mexicana had invariant patterns for both the ITS and the small subunit of rRNA genes. Leishmania amazonensis and Leishmania venezuelensis displayed polymorphism only in the ITS. The high degree of identity of this region was confirmed by sequencing DNA from three L. mexicana isolates. There was almost complete identity of the sequence for the ITS region of L. venezuelensis and that of strains of Leishmania major, suggesting that these species may be more closely related than previously thought.

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.