Seasonal transmission of Leishmania (Leishmania) mexicana in the state of Campeche, Yucatan Peninsula, Mexico

Phlebotomine sand flies in rural Mayan communities of Southern Mexico: The heterogeneity of the ruralscape increases the entomological risk

In the Yucatan Peninsula, tropical preserved forests harbor a high diversity of phlebotomine sand fly species, potential vectors of Leishmania. As a result, a significant risk of contracting localized cutaneous leishmaniasis (LCL) is associated with entry into these forest ecosystems. However, with the current trajectory of land use in the region, communities now live within modified landscapes which could increase their risk of contact with vectors. In this study, we characterized the sand fly fauna and its relationship with the characteristics of peridomestic habitats in two rural communities in Yucatan characterized by contrasting records of leishmaniasis. Five human dwellings in each community were randomly selected and the peridomestic landscape was characterized (i.e., type and percentage of land use). For the collection of sand flies, CDC traps were deployed in both the intra and peridomicile. Differences in alpha and beta diversity between communities and ecotopes were estimated considering three separate groups, all species together, zoophilic species, and anthropophilic species. In total, 1, 241 sand flies represented by eight species were collected from November 2021-March 2022. Both communities registered the presence of sand flies in the intra and peridomicile, and females were more abundant than males. However, the greatest diversity of species was recorded in the peridomicile of the community with the highest composition of land uses. Our study demonstrates that the transformation of the forest around the communities favors the abundance and richness of sand flies in the peridomestic environment. We discuss the limitations and implications of our findings regarding the potential risk of the emergence of peri‑rural cycles of leishmaniasis in the region.

Biting rhythms and infection rates of anthropophilic sand fly species (Diptera: Phlebotominae) in sites with different land use in southern Mexico

Could tropical forest conversion shape sand fly (Diptera: Phlebotominae) biting rhythms and Leishmania infection rates? Using a Shannon trap, we estimated the bite rate and infection prevalence among anthropophilic sand flies at sites with different land use in southern Mexico. We estimated the expected monthly infection rate of the Leishmania parasite along the gradient and generated information on the biting rhythm of sand flies in a poorly characterized cutaneous leishmaniasis endemic region. We used generalized mixed linear and mixed additives models to evaluate differences in the biting rate, nocturnal activity, and inoculation rate of female sand flies, as well as their relationship with the loss of forest cover and environmental disparities recorded throughout the study area. Our results show that the loss of forest cover influences the biting rhythm of sand fly species and the potential number of infectious bites with Leishmania, but the greatest entomological and potential epidemiological risk continues to be associated with sylvatic areas (amplification events). Despite this, we detected that the effect of forest cover (%) on the entomological exposure seems to be also dependent on the sand fly species, and that, albeit to a lesser extent, Leishmania parasite is circulating in disturbed landscapes through generalist and competent sand fly vector species. We also found that land use change did not affect the nocturnal activity, however we detected that important vector species were active most of the time. Contrary to our expectation, temperature and humidity did not shape the biting rhythm of sand fly species. We discuss the limitations and epidemiological implications of our findings regarding the risk of contracting leishmaniasis in southern Mexico.

Species diversity and detection of pathogens in phlebotomine sand flies collected from forest management areas of Quintana Roo, Mexico

Sand flies have expanded their areas of distribution, thereby increasing the risk of pathogen transmission in non-endemic areas. To establish efficient prevention and control strategies for the transmission of vector-borne pathogens, it is important to understand seasonal dynamics of their vectors. In Mexico, there are several areas where the contact between sand flies, hosts and reservoirs favours the transmission of the pathogen. We compared sand fly communities in a forest management area and a conserved area in Noh-Bec, Quintana Roo, Mexico. The analysis included species diversity, activity peaks and molecular detection of pathogens. Sand flies were collected from November to December 2021 and April to May 2022, during 84 night-traps. The conserved area showed higher numbers and greater species heterogeneity of sand flies as compared with the other sites. The β-diversity analysis revealed that sites disturbed by logging (S1, S2, S3) had greater similarity (90%) in their sand fly species composition than a conserved area (S4) (similarity = 36%). Although none of the specimens were infected with Leishmania, we detected Wolbachia (19.4%) in all four sites, as well as Bartonella (3.25%) only in the disturbed sites. Further studies on the dynamics of sand fly populations and their association with pathogens are necessary.

Cutaneous Leishmaniasis Emergence in Southeastern Mexico: The Case of the State of Yucatan

Environmental changes triggered by deforestation, urban expansion and climate change are present-day drivers of the emergence and reemergence of leishmaniasis. This review describes the current epidemiological scenario and the feasible influence of environmental changes on disease occurrence in the state of Yucatan, Mexico. Relevant literature was accessed through different databases, including PubMed, Scopus, Google, and Mexican official morbidity databases. Recent LCL autochthonous cases, potential vector sandflies and mammal hosts/reservoirs also have been reported in several localities of Yucatan without previous historical records of the disease. The impact of deforestation, urban expansion and projections on climate change have been documented. The current evidence of the relationships between the components of the transmission cycle, the disease occurrence, and the environmental changes on the leishmaniasis emergence in the state shows the need for strength and an update to the intervention and control strategies through a One Health perspective.

Molecular Detection of Leishmania (Leishmania) mexicana in Sandflies from the State of Yucatan, Mexico

Background: Leishmaniases are a group of vector-borne zoonotic diseases of public health relevance within the tropical and subtropical regions of the world. The state of Yucatan is a vulnerable and receptive area to localized cutaneous leishmaniasis (LCL) due to its proximity to the high-transmission endemic states of Campeche and Quintana Roo. Autochthonous cases of LCL caused by Leishmania (Leishmania) mexicana have been documented in the state, showing a geographical expansion of the disease. Materials and Methods: Using CO₂-supplemented Centers for Disease Control and Prevention light traps and Shannon traps, we captured anthropophilic sandflies in the surroundings of a locality with recent records of autochthonous cases of LCL. Sandflies carrying Leishmania DNA were evidenced using PCR. Results: A total of 140 Phlebotominae (Diptera: Psychodidae) females of four species were captured: Lutzomyia (Tricholateralis) cruciata (Coquillett), Psathyromyia (Psathyromyia) shannoni (Dyar), Lutzomyia (Lutzomyia) longipalpis (Lutz and Neiva), and Dampfomyia (Coromyia) deleoni (Fairchild and Hertig). Molecular results showed that 6.1% (95% confidence interval [CI] = 2.3-12.9%) of Lu. cruciata and 43.8% (95% CI = 19.8-70.1%) of Pa. shannoni showed evidence of carrying L. (L.) mexicana DNA. Conclusion: We provide evidence of anthropophilic sandflies carrying L. mexicana DNA in a municipality with recorded autochthonous cases of LCL caused by this parasite species in the state of Yucatan, suggesting the emergence of new focus of LCL in Mexico.

Effect of land use change on the phlebotomine sand fly assemblages in an emergent focus of cutaneous leishmaniasis in Yucatan, Mexico

As land use intensifies in tropical forests, it is expected that species assemblages will be modified and that key functions of these ecosystems will be affected. The latter scenario is important from a public health perspective, because the land use change has been linked the outbreaks of vector-borne diseases. In this study, we evaluated the response of Phlebotominae (Diptera: Psychodidae) assemblages and their pattern of co-occurrence in four sites with different land use in an emerging cutaneous leishmaniasis focus in Yucatan, Mexico. Our hypothesis is that the conservation status (as forest cover) will positively influence the structure and composition of sand flies' assemblages. Using three different traps over a period of five months, a sampling effort of 1, 440 night-traps was performed. A total of 7, 897 sand fly specimens belonging to six genera and 10 species were collected. Our hypothesis was partially achieved since sand fly diversity increased as forest cover increased and vice versa, however random patterns of co-occurrence in assemblages were detected among sites. Even though the high abundance of sand flies in the forest fragment suggests an amplification effect, our results show that different vector species directly dominate in each site. We discuss the potential implications of the nestedness of species dominance. We suggest that in this emerging focus and under the land use gradient, Lutzomyia cruciata and Psathyromyia cratifer could play a pivotal role in maintaining the transmission cycles of Leishmania. The apparent generalist or colonialist profile of Lu. cruciata in disturbed areas deserves attention, due to the potential risk of leishmaniasis "domiciliation". This information is essential to understand the eco-epidemiology of leishmaniasis and the factors associated with its emergence in Yucatan, Mexico.

Leishmania (Leishmania) mexicana Infection in Wild Rodents from an Emergent Focus of Cutaneous Leishmaniasis in Yucatan, Mexico

In 2015, emergent cases of localized cutaneous leishmaniasis (LCL) were reported in Tinum, Yucatan, Mexico. As part of an eco-epidemiological study to characterize the elements that trigger Leishmania infection in that area, we conducted a field study to investigate the occurrence of Leishmania infection in wild rodents. From November 2019 to February 2020, rodents were caught from three sites located in the municipality of Tinum, Yucatan. For each specimen, clinical signs suggestive of Leishmania infection were recorded. Samples from the tail, liver, and spleen were taken for the identification of Leishmania DNA by PCR. Twenty rodents belonging to two species were caught including Heteromys gaumeri (55%, 11/20) and Ototylomys phyllotis (45%, 9/20). Fifty-five percent of the animals presented white spots on the tail, 15% had splenomegaly, and 5% had hepatomegaly. Fifty-five percent (11/20) of the animals were found infected by Leishmania. Heteromys gaumeri was caught in all trapping sites and was the most infected species (63.6%, 7/11). The percentage of infection for O. phyllotis was 44.4% (4/9). Leishmania (Leishmania) mexicana was identified as the infecting species in two H. gaumeri. This study provides, for the first time, evidence of Leishmania infection in wild rodents from the Yucatan state. Heteromys gaumeri and O. phyllotis may be involved in the transmission cycle of L. mexicana in this emergent focus; however, further longitudinal studies are needed to confirm their role as primary reservoirs.

Phlebotomine sand flies (Diptera: Psychodidae) from an emergent focus of localized cutaneous leishmaniasis in Yucatan, Southeast Mexico

Localized cutaneous leishmaniasis (LCL) is endemic in the Yucatan Peninsula, with historical and contemporary records mainly in the states of Campeche and Quintana Roo. Recently, we reported autochthonous LCL cases and 27.6% of asymptomatic infection in the municipality of Tinum, Yucatan, where no studies of Phlebotominae (Diptera: Psychodidae) sand flies have been carried out. In this work, from November, 2019 to February, 2020, we conducted a field study in three areas of Tinum to document, for the first time, the species of Phlebotominae in areas with records of human leishmaniasis transmission. In order of abundance, the species identified were Pifanomyia serrana, Psathyromyia shannoni, Psathyromyia cratifer, Lutzomyia cruciata, Bichromomyia olmeca olmeca, and Dampfomyia deleoni. Most of the sand flies were captured in a Shannon trap where 77.8% of collected specimens were females. The distribution of sand fly species showed some degree of heterogeneity among sites, and the highest species richness was registered in a site located in Xcalakoop. We also discuss the medical importance of Lu. cruciata, Ps. shannoni, and Pi. serrana as potential vectors of causal agents of LCL in this area.

First record of larval microhabitats of sandflies in Mexico with the description of the fourth instar larva of Brumptomyia hamata

Despite the medical importance of sandflies as vectors (Diptera: Phlebotominae) of Leishmania spp., immature stages of phlebotomine sandflies have never been found in the wild in Mexico. In the present investigation, we sought to identify specific microhabitats associated with the presence of sandfly immature stages. Field work was conducted in 11 localities of the Yucatan Peninsula and we collected soil samples from each site during two periods (November 2007 to April 2008, November 2008). Soil samples were transported to our base camp and were processed using the Berlese's funnels. We processed a total 242 soil samples with an average weight of 362 ± (SD) 317 gr. From these samples, we were able to recover 51 phlebotomine larvae in five different microhabitats and largest number was obtained from mammal burrows (88%) and from tree-buttresses of Brosimium alicastrum (Berg) (6%). We identified larval microhabitat for Brumptomyia hamata (Fairchild & Hertig) and those specimens provided the material to describe for the first time the fourth instar larva. We also include information of a larval microhabitat of Lutzomyia cruciata (Coquillett). In addition, we recorded a total of 4872 arthropods from 15 taxa in all those soil samples in which sandfly larvae were found, being Collembola (76%) and Acari (10%) the most abundant.

Historical Spatial Distribution of Zoonotic Diseases in Domestic, Synanthropic, and Wild Animals in the Mexican Territory of the Yucatan Peninsula

The Mexican territory of the Yucatan Peninsula has a tropical climate and harbors a wide variety of domestic, synanthropic, and wild animals, as well as disease vectors. To determine the distribution of recorded zoonotic diseases in the Yucatan Peninsula, scientific publications referring to these diseases in animals and containing geographic coordinates of disease occurrence, were studied. The epidemiological bulletins of the national government were also consulted to obtain information on zoonotic diseases reported in humans in the territory. The territory harbors a wide variety of tropical zoonotic pathogens, including Trypanosoma cruzi, Leptospira interrogans, Toxoplasma gondii, Leishmania mexicana, Dirofilaria immitis, and Rickettsia felis. A variety of domestic, synanthropic, and wild animals act as hosts or reservoirs in the transmission cycle of the zoonotic diseases in the Yucatan Peninsula, and some spillover into human populations has also been recorded. There are still zoonotic diseases that have rarely or never been reported in humans, but it is not clear whether this is because these diseases in humans are not common, there is a lack of viable transmission cycle or there is a lack of appropriate diagnosis. It is necessary to continue monitoring vectors, animal hosts, and humans to identify risk factors for zoonotic diseases in the Yucatan Peninsula.

Environmental and socioeconomic risk factors associated with visceral and cutaneous leishmaniasis: a systematic review

We performed a systematic review of the literature published since 1900 about leishmaniasis a neglected vector-borne disease, focused on environmental and social risk factors for visceral (VL) and cutaneous leishmaniasis (CL) to better understand their impact on the incidence of disease. The search terms were "leishmaniasis" AND "risk factors" using Google Scholar, PudMed, and Scielo. We reviewed 177 articles, 95 studies for VL, 75 for CL, and 7 on both forms. We identified 14 categories of risk factors which were divided into three groups: socioeconomic (7), environmental (5), and climate (2) variables. Socioeconomic factors were also associated with disease incidence in vulnerable human populations of arid and tropical developing regions. Environmental and climate factors showed significant associations with the incidence of VL and CL in all the studies that considered them. Proximity to natural vegetation remnants increased disease risk in both the New and Old World while the climate conditions favorable for disease transmission differed among regions. We propose a common conceptual framework for both clinical forms that highlights networks of interaction among risk factors. In both clinical forms, the interplay of these factors played a major role in disease incidence. Although there are similarities in environmental and socioeconomic conditions that mediate the transmission cycle of tropical, arid, and Mediterranean regions, the behavior of vector and reservoirs in each region is different. Special attention should be given to the possibility of vector adaptation to urban environments in developing countries where populations with low socioeconomic status are particularly vulnerable to the disease.

Preliminary epidemiological findings of Leishmania infection in the municipality of Tinum, Yucatan State, Mexico

Localized cutaneous leishmaniasis (LCL) is endemic in Mexico, mainly in the states of Campeche and Quintana Roo, hyperendemic areas of Leishmania (Leishmania) mexicana transmission. In this report, epidemiological features of Leishmania infections in the municipality of Tinum, Yucatan State, Mexico are presented. Nine cases of LCL were diagnosed in 2015. Patients were men between 30 and 74 years of age, without a history of living or traveling to endemic areas (Quintana Roo or Campeche). Due to asymptomatic infection is the most common outcome after Leishmania inoculation, between November 2017 to June 2018, 47 men working in the forest were tested by Montenegro skin test (MST). Thirteen of them (27.6%) were identified MST positive, in absence of either lesion or typical scar, and evidence of exposure to vector. Findings in Tinum, Yucatan, supported the presence of specific environmental conditions that seem to favor Leishmania transmission in this region. Thus, active surveillance for the detection of new cases in the municipality of Tinum as well as the eco-epidemiological characterization to identify all the transmission components (parasite, vector, and reservoir species) are urgently needed.

Finding a model for the study of Leishmania (Leishmania) mexicana infection: The Yucatan Deer mouse (Peromyscus yucatanicus) as a suitable option

For more than four decades, the murine model has been employed extensively to understand immunological mechanisms associated with Leishmania infection. Although the use of laboratory mice has been very informative, mainly for L. (L.) major infection, the extrapolation to other Leishmania species and more importantly to human disease has been limited. Particularly in the case of L. (L.) mexicana, most infected mouse strains are highly susceptible and never presented asymptomatic infection, which is the main outcome in human. Thus, we postulated the use of Peromyscus yucatanicus, a primary reservoir of L. (L.) mexicana in the Yucatan Peninsula of Mexico, as an experimental model to study Leishmania infection. This rodent species can produce both asymptomatic and clinical infections therefore they seem more appropriate for studying host-pathogen interactions. In this review, we recapitulate the immunological findings observed in the traditional murine model of L. (L.) mexicana highlighting the differences with humans' infection and demonstrate the pertinence of P. yucatanicus as the experimental model for studying L. (L.) mexicana infection.

Leishmaniasis: a review

Leishmaniasis is caused by an intracellular parasite transmitted to humans by the bite of a sand fly. It is endemic in Asia, Africa, the Americas, and the Mediterranean region. Worldwide, 1.5 to 2 million new cases occur each year, 350 million are at risk of acquiring the disease, and leishmaniasis causes 70,000 deaths per year. Clinical features depend on the species of Leishmania involved and the immune response of the host. Manifestations range from the localized cutaneous to the visceral form with potentially fatal outcomes. Many drugs are used in its treatment, but the only effective treatment is achieved with current pentavalent antimonials.

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.

Cloning and sequence analysis of Peromyscus yucatanicus (Rodentia) Th1 (IL-12p35, IFN-γ and TNF) and Th2 (IL-4, IL-10 and TGF-β) cytokines

The Yucatan deer mouse, Peromyscus yucatanicus (order Rodentia), is the principal reservoir of Leishmania (Leishmania) mexicana in the Yucatan peninsula of Mexico. Experimental infection results in clinical and histopathological features similar to those observed in humans with cutaneous leishmaniasis (CL) as well as peritoneal macrophage production of nitric oxide. These results support the possible use of P. yucatanicus as a novel experimental model to study CL caused by L. (L.) mexicana. However, immunological studies in these rodents have been limited by the lack of specific reagents. To address this issue, we cloned and analyzed cytokine sequences of P. yucatanicus as part of an effort to develop this species as a CL model. We cloned P. yucatanicus interleukin 4 (IL-4), IL-10, IL-12p35, gamma interferon, transforming growth factor beta and tumor necrosis factor partial cDNAs. Most of the P. yucatanicus sequences were highly conserved with orthologs of other mammalian species and the identity of all sequences were confirmed by the presence of conserved amino acids with possible biological functions in each putative polypeptide. The availability of these sequences is a first step which will allow us to carry out studies characterizing the immune response during pathogenic and nonpathogenic L. (L.) mexicana infections in P. yucatanicus.

Nitric oxide production by Peromyscus yucatanicus (Rodentia) infected with Leishmania (Leishmania) mexicana

Peromyscus yucatanicus (Rodentia: Cricetidae) is a primary reservoir of Leishmania (Leishmania) mexicana (Kinetoplastida: Trypanosomatidae). Nitric oxide (NO) generally plays a crucial role in the containment and elimination of Leishmania. The aim of this study was to determine the amount of NO produced by P. yucatanicus infected with L. (L.) mexicana. Subclinical and clinical infections were established in P. yucatanicus through inoculation with 1 x 10 2 and 2.5 x 10 6 promastigotes, respectively. Peritoneal macrophages were cultured alone or co-cultured with lymphocytes with or without soluble Leishmania antigen. The level of NO production was determined using the Griess reaction. The amount of NO produced was significantly higher (p ≤ 0.0001) in co-cultured macrophages and lymphocytes than in macrophages cultured alone. No differences in NO production were found between P. yucatanicus with subclinical L. (L.) mexicana infections and animals with clinical infections. These results support the hypothesis that the immunological mechanisms of NO production in P. yucatanicus are similar to those described in mouse models of leishmaniasis and, despite NO production, P. yucatanicus is unable to clear the parasite infection.

The potential economic value of a cutaneous leishmaniasis vaccine in seven endemic countries in the Americas

Cutaneous leishmaniasis (CL) and its associated complications, including mucocutaneous leishmaniasis (MCL) and diffuse CL (DCL) have emerged as important neglected tropical diseases in Latin America, especially in areas associated with human migration, conflict, and recent deforestation. Because of the limitations of current chemotherapeutic approaches to CL, MCL, and DCL, several prototype vaccines are in different states of product and clinical development. We constructed and utilized a Markov decision analytic computer model to evaluate the potential economic value of a preventative CL vaccine in seven countries in Latin America: Bolivia, Brazil, Colombia, Ecuador, Mexico, Peru, and Venezuela. The results indicated that even a vaccine with a relatively short duration of protection and modest efficacy could be recommended for use in targeted locations, as it could prevent a substantial number of cases at low-cost and potentially even result in cost savings. If the population in the seven countries were vaccinated using a vaccine that provides at least 10 years of protection, an estimated 41,000-144,784 CL cases could be averted, each at a cost less than the cost of current recommended treatments. Further, even a vaccine providing as little as five years duration of protection with as little as 50% efficacy remains cost-effective compared with chemotherapy; additional scenarios resembling epidemic settings such as the one that occurred in Chaparral, Colombia in 2004 demonstrate important economic benefits.

Reproductive characteristics of a captive colony of big-eared climbing rats (Ototylomys phyllotis)

The authors analyzed the breeding characteristics of a colony of Ototylomys phyllotis (big-eared climbing rat) from Campeche, México, that was bred in captivity for 6 y. The big-eared climbing rat is a reservoir of Leishmania (Leishmania) mexicana, a causal agent of localized cutaneous leishmaniasis on the Yucatán Peninsula. The colony had been established to facilitate studies analyzing the effectiveness of O. phyllotis as an experimental model for L. (L.) mexicana. The authors describe the housing and husbandry of the colony, the procedures used for mating the animals and the behavior of the animals during mating. They report that the animals showed social behavior and could be bred successfully. Most breeding pairs successfully produced litters; some pairs produced more than one litter. The authors also report data for other parameters, such as the interval between pairing and birth or between births of consecutive litters, litter size, survival to weaning, the timing of sexual maturity and the effects of breeder age on breeding success.

Comparison of small mammal prevalence of Leishmania (Leishmania) mexicana in five foci of cutaneous leishmaniasis in the State of Campeche, Mexico

In the Yucatan Peninsula of Mexico, 95% of the human cases of Cutaneous Leishmaniasis are caused by Leishmania (Leishmania) mexicana with an incidence rate of 5.08 per 100,000 inhabitants. Transmission is limited to the winter months (November to March). One study on wild rodents has incriminated Ototylomys phyllotis and Peromyscus yucatanicus as primary reservoirs of L. (L.) mexicana in the focus of La Libertad, Campeche. In the present study, the prevalence of both infection and disease caused by L. (L.) mexicana in small terrestrial mammals were documented during five transmission seasons (1994-2004) in five foci of Leishmaniasis in the state of Campeche. Foci separated by only 100 km, with similar relative abundances of small mammals, were found to differ significantly in their prevalence of both symptoms and infection. Transmission rates and reservoir species seemed to change in space as well as in time which limited the implementation of effective control measures of the disease even in a small endemic area such as the south of the Yucatan Peninsula.

In vitro activity of Tridax procumbens against promastigotes of Leishmania mexicana

ETHNOPHARMACOLOGICAL RELEVANCE

Tridax procumbens is an active herb against leishmaniasis.

AIM OF THE STUDY

Leishmaniasis is a group of diseases caused by Leishmania protozoa. We investigated the antileishmanial activity of Tridax procumbens extracts and a pure compound against promastigotes of Leishmania mexicana, the causative agent of cutaneous leishmaniasis in the New World.

MATERIALS AND METHODS

Extracts and (3S)-16,17-didehydrofalcarinol (1) were obtained by chromatographic methods from Tridax procumbens, and the latter identified by spectroscopic analysis. The effect of these extracts and 1 on the growth inhibition of promastigotes of Leishmania mexicana was evaluated. In order to test the safety of extracts and 1, mammalian cells were treated with them, and cell viability was assessed using trypan blue and MTT.

RESULTS

We demonstrated that extracts of Tridax procumbens and 1 showed a pronounced activity against Leishmania mexicana. The methanol extract inhibited promastigotes growth of Leishmania mexicana with a 50% inhibitory concentration (IC(50)) of 3 microg/ml, while oxylipin 1 exhibited the highest inhibition at IC(50)=0.478 microg/ml.

CONCLUSIONS

In this study we report the biological activity of extracts and (3S)-16,17-didehydrofalcarinol (1), obtained from Tridax procumbens, on the promastigote form of Leishmania mexicana, with no effect upon mammalian cells.

The histopathology of cutaneous leishmaniasis due to Leishmania (Leishmania) mexicana in the Yucatan peninsula, Mexico

Localized Cutaneous Leishmaniasis (LCL) known as "chiclero's ulcer" in southeast Mexico, was described by SEIDELIN in 1912. Since then the sylvatic region of the Yucatan peninsula has been documented as an endemic focus of LCL. This study of 73 biopsies from parasitological confirmed lesions of LCL cases of Leishmania (Leishmania) mexicana infection was undertaken: 1) to examine host response at tissue level; and 2) to relate manifestations of this response to some characteristics of clinical presentation. Based on Magalhães' classification we found that the most common pattern in our LCL cases caused by L. (L.) mexicana was predominantly characterized by the presence of unorganized granuloma without necrosis, (43.8%). Another important finding to be highlighted is the fact that in 50/73 (68.5%) parasite identification was positive. There was direct relation between the size of the lesion and time of evolution (rs = 0.3079, p = 0.03), and inverse correlation between size of the lesion and abundance of amastigotes (rs = -0.2467, p = 0.03). In view of the complexity of clinical and histopathological findings, cell-mediated immune response of the disease related to clinical and histopathological features, as so genetic background should be studied.