Leishmania chagasi: genotypically similar parasites from Honduras cause both visceral and cutaneous leishmaniasis in humans

A Case of Visceral Leishmaniasis in a 4-Year-Old Child Living in Nonendemic Area Located in Suburbs of Dakar, Senegal

Visceral leishmaniasis (VL) is an infectious disease caused by protozoa of the genus Leishmania. Sporadic cases are observed in nonendemic areas and often associated with limited foci; therefore, the disease is easily overlooked. In addition, other diseases have similar clinical symptoms, which make it difficult for clinicians to make an accurate diagnosis and to provide effective treatment. We identified visceral leishmaniasis in a 4-year-old child in Pikine, Senegal. The patient was admitted to the Pikine National Teaching Hospital for haemorrhagic, tumoral, and infectious syndromes. At admission, the patient presented with epistaxis and gingivorrhagia, a severe anaemic syndrome poorly tolerated, a systemic inflammatory response syndrome with fever at 39.5°C, a tumoral syndrome with 11 cm of hepatomegaly and 12 cm of type IV splenomegaly, and noninflammatory macropoly adenopathies. A spinal cord puncture was performed, and direct microscopy examination of the sample after GIEMSA staining revealed amastigote forms of Leishmania. The PCR amplification of extracted DNA from the bone marrow aspiration using specific primers for VL (forward and reverse) confirmed that VL was responsible for the infection. A treatment with meglumine antimoniate (Glucantime) was given and it gave a successful outcome with remission of clinical symptoms and favourable evolution with 3 months hindsight. Conclusion. This visceral leishmaniasis case diagnosis in Senegal has shown that, apart from haematological malignancies, this disease must be considered in combination with a tumor syndrome, haemorrhagic syndrome, and infectious syndrome.

Genetic Diversity and Population Structure of Leishmania infantum in Morocco as Revealed by Multilocus Sequence Typing (MLST) Approach

Leishmania infantum is endemic in Morocco, and it causes both visceral (VL) and cutaneous leishmaniasis (CL). In this study, the multilocus sequence typing (MLST) approach was used to investigate the phylogeny and population structure of Leishmania infantum strains isolated from CL and VL patients and the canine reservoir in different leishmaniasis endemic foci in Morocco. For this purpose, eight loci (pgm, alat, me, fh, g6pd, pgd, gpi and cytb) were amplified in 40 samples, out of which 31 were successfully sequenced. The genetic diversity analysis detected a high degree of intraspecific genetic variability among the studied strains. The phylogenetic and the haplotype analyses showed that most of the strains from the same geographical areas clustered together. The recombination among Leishmania infantum strains was revealed through a splits tree analysis and the number of recombination events. Moreover, the assessment of the gene flow between Leishmania infantum and Leishmania tropica through phylogenetic analysis and haplotype diversity in two endemic foci where the two species were sympatric showed no genetic exchange between the two species.

Role of antigen-presenting cells in non-ulcerated skin lesions caused by Leishmania (Leishmania) infantum chagasi

In Central America, infection by Leishmania (Leishmania) infantum chagasi causes visceral leishmaniasis and non-ulcerated cutaneous leishmaniasis (NUCL). This work aimed to evaluate the participation of subpopulations of antigen-presenting cells in skin lesions of patients affected by NUCL through double-staining immunohistochemistry using cellular and intracellular markers. Twenty-three skin biopsies from patients affected by NUCL were used. Histological sections stained by HE were used for histopathological study. Immunohistochemical studies were performed using primary antibodies against Langerhans cells, dermal dendritic cells, T lymphocytes, and the cytokines IL-12, IFN-γ, TNF-α, iNOS, and IL-10. The histopathological lesions were characterized by an inflammatory infiltrate, predominantly lymphohistiocytic, of variable intensity, with a diffuse arrangement associated with epithelioid granulomas and discreet parasitism. Double-staining immunohistochemistry showed higher participation of dendritic cells producing the proinflammatory cytokine IL-12 in relation to the other evaluated cytokines. Activation of the cellular immune response was marked by a higher density of CD8 Tc1-lymphocytes followed by CD4 Th1-lymphocytes producing mainly IFN-γ. The data obtained in the present study suggest that antigen-presenting cells play an important role in the in situ immune response through the production of proinflammatory cytokines, directing the cellular immune response preferentially to the Th1 and Tc1 types in NUCL caused by L. (L.) infantum chagasi.

Comparative Genomic Analyses of New and Old World Viscerotropic Leishmanine Parasites: Further Insights into the Origins of Visceral Leishmaniasis Agents

Visceral leishmaniasis (VL), also known as kala-azar, is an anthropozoonotic disease affecting human populations on five continents. Aetiologic agents belong to the Leishmania (L.) donovani complex. Until the 1990s, three leishmanine parasites comprised this complex: L. (L.) donovani Laveran & Mesnil 1903, L. (L.) infantum Nicolle 1908, and L. (L.) chagasi Lainson & Shaw 1987 (=L. chagasi Cunha & Chagas 1937). The VL causal agent in the New World (NW) was previously identified as L. (L.) chagasi. After the development of molecular characterization, however, comparisons between L. (L.) chagasi and L. (L.) infantum showed high similarity, and L. (L.) chagasi was then regarded as synonymous with L. (L.) infantum. It was, therefore, suggested that L. (L.) chagasi was not native to the NW but had been introduced from the Old World by Iberian colonizers. However, in light of ecological evidence from the NW parasite’s enzootic cycle involving a wild phlebotomine vector (Lutzomyia longipalpis) and a wild mammal reservoir (the fox, Cerdocyon thous), we have recently analyzed by molecular clock comparisons of the DNA polymerase alpha subunit gene the whole-genome sequence of L. (L.) infantum chagasi of the most prevalent clinical form, atypical dermal leishmaniasis (ADL), from Honduras (Central America) with that of the same parasite from Brazil (South America), as well as those of L. (L.) donovani (India) and L. (L.) infantum (Europe), which revealed that the Honduran parasite is older ancestry (382,800 ya) than the parasite from Brazil (143,300 ya), L. (L.) donovani (33,776 ya), or L. (L.) infantum (13,000 ya). In the present work, we have now amplified the genomic comparisons among these leishmanine parasites, exploring mainly the variations in the genome for each chromosome, and the number of genomic SNPs for each chromosome. Although the results of this new analysis have confirmed a high genomic similarity (~99%) among these parasites [except L. (L.) donovani], the Honduran parasite revealed a single structural variation on chromosome 17, and the highest frequency of genomic SNPs (more than twice the number seen in the Brazilian one), which together to its extraordinary ancestry (382,800 ya) represent strong evidence that L. (L.) chagasi/L. (L.) infantum chagasi is, in fact, native to the NW, and therefore with valid taxonomic status. Furthermore, the Honduran parasite, the most ancestral viscerotropic leishmanine parasite, showed genomic and clinical taxonomic characteristics compatible with a new Leishmania species causing ADL in Central America.

Evaluation of systemic immunity in atypical cutaneous leishmaniasis caused by Leishmania (L.) infantum chagasi

In some central-American countries, Leishmania (L.) infantum chagasi infection can cause non-ulcerated or atypical cutaneous leishmaniasis (NUCL) in addition to the classic clinical form, visceral leishmaniasis (VL). Little is known about the host-parasite relationship that can contribute to the determination of one or another clinical form. The present study had the objective to evaluate the humoral and cellular immunity in the sera of individuals affected by NUCL to improve the comprehension of this atypical host-parasite interaction. Based on clinical and laboratory diagnosis, serum of 80 individuals was collected to evaluate the cytokines and immunoglobulins profile of NUCL (n = 47), VL patients (n = 5), and negative controls (n = 28). Cytokines were detected using Cytokine Bead Array (CBA) Human Th1/Th2/Th17 kit according to the manufacturer's instructions; class (IgG and IgM), and subclass of (IgG1 and IgG2) immunoglobulins was evaluated by ELISA using specific antigens. The concentration of TNF-α, IFN-γ, IL-2 and IL-4 cytokines in NUCL, VL and control was present below the detection threshold of CBA kit. IL-6, IL-10 and IL-17A cytokines was lower in NUCL compared to LV patients. Regarding to immunoglobulins, NUCL patients produced 4.0 times more IgG than the control, while VL patients produced 6.6 times more; and IgM level was 1.6 times higher in NUCL and 2.6 times in VL patients compared to the control. Concerning the immunoglobulins subclass, only VL patients showed positive reaction for IgG1, and IgG2 did not show positive reaction among the groups. The results showed a weak cellular and humoral systemic immune response in NUCL patients.

DNA barcoding of Lutzomyia longipalpis species complex (Diptera: Psychodidae), suggests the existence of 8 candidate species

The sand fly Lutzomyia (L.) longipalpis has been implicated as the primary vector of Leishmania infantum, the causative agent of visceral leishmaniasis VL. In addition, it has been associated with atypical cutaneous leishmaniasis transmission in the Neotropic and Central America, respectively. The existence of a L. longipalpis complex species has been suggested with important implications for leishmaniasis epidemiology; however, the delimitation of species conforming it remains a topic of controversy. The DNA Barcoding Initiative based on cox1 sequence variation was used to identify the MOTUs in L. longipalpis including previously described L. pseudolongipalpis. The genetic variation was analyzed based on tree and distance methods. Fifty-five haplotypes were obtained from 103 sequences which were assigned to MOTUs, with a clear separation and a high correspondence of individuals to the groups. Maximum likelihood and Bayesian phylogenetic analysis showed eight MOTUs (100% bootstrap) with high genetic divergence (12.6%). Data obtained in the present study suggest that L. longipalpis complex consists of at least 8 lineages that may represent species. It would be desirable perform additional morphological and molecular analysis of L. longipalpis from Colosó (Caribbean ecoregion) considering that specimens from that area were grouped with L. pseudolongipalpis one of the complex species previously described from Venezuela, which has not been registered in Colombia.

Autochthonous and imported tegumentary leishmaniasis in Catalonia (Spain): Aetiological evolution in the last four decades and usefulness of different typing approaches based on biochemical, molecular and proteomic markers

Leishmaniasis is a transmissible disease caused by Leishmania protozoa. Spain is endemic for both visceral and cutaneous leishmaniasis, the autochthonous aetiological agent being Leishmania infantum. Around the world, the L. donovani complex is associated with visceral symptoms, while any species of the Leishmania or Viannia subgenera affecting human can produce tegumentary forms. In a context of growing numbers of imported cases, associated with globalisation, the aim of this study was to analyse the aetiological evolution of human tegumentary leishmaniasis in a region of Spain (Catalonia). Fifty-six Leishmania strains, isolated from 1981 to 2018, were analysed using MLEE, gene sequencing (hsp70, rpoIILS, fh and ITS2) and MALDI-TOF. The utility of these different analytical methods was compared. The results showed an increase in leishmaniasis over the two last decades, particularly imported cases, which represented 39% of all cases studied. Leishmania infantum, L. major, L. tropica, L. braziliensis, L. guyanensis and L. panamensis were identified. The combination of molecular and enzymatic methods allowed the identification of 29 different strain types (A to AC). Strain diversity was higher in L. (Viannia), whilst the different L. major types were relatable with geo-temporal data. Among the autochthonous cases, type C prevailed throughout the studied period (39%). Minor types generally appeared within a short time interval. While all the techniques provided identical identification at the species complex level, MALDI-TOF and rpoIILS or fh sequencing would be the most suitable identification tools for clinical practice, and the tandem hsp70-ITS2 could substitute MLEE in the epidemiological field.

In situ cellular immune response in non-ulcerated skin lesions due to Leishmania (L.) infantum chagasi infection

Background

Skin lesions of patients affected by non-ulcerated cutaneous leishmaniasis (NUCL) caused by L. (L.) infantum chagasi are characterized by lymphohistiocytic inflammatory infiltrate associated with epithelioid granuloma and scarce parasitism. However, the in situ cellular immune response of these patients is unclear. Therefore, the aim of the present study was to characterize the cellular immune response in the skin lesions of patients affected by NUCL.

Methods

Twenty biopsies were processed by immunohistochemistry using primary antibodies to T lymphocytes (CD4, CD8), NK cells, B lymphocytes, macrophages, nitric oxide synthase and interferon-gamma.

Results

Immunohistochemistry revealed higher expression of all cellular types and molecules (IFN-γ, iNOS) in the dermis of diseased skin compared to the skin of healthy individuals (p < 0.05). Morphometric analysis performed in the skin lesions sections showed the predominance of CD8⁺ T lymphocytes in the mononuclear infiltrate, followed by macrophages, mostly iNOS⁺, a response that could be mediated by IFN-γ.

Conclusion

Our study improves knowledge of the cellular immune response in non-ulcerated or atypical cutaneous leishmaniasis caused by L. (L.) infantum chagasi in Central America and pointed to the pivotal participation of CD8⁺ T lymphocytes in the host defense mechanisms against the parasite in patients with NUCL.

First Serological Study Revealing High Humoral Response and Evidence for Antigenic Heterogeneity in Leishmania donovani Induced CL in Sri Lanka

Posing a threat to the ongoing leishmaniasis elimination efforts in the Indian subcontinent, L. donovani-induced cutaneous leishmaniasis (CL) has been recently reported in many countries. Sri Lanka reports a large focus of human cutaneous leishmaniasis (CL) caused by Leishmania donovani, a usually visceralizing parasite. Enhanced case detection, early treatment, and in-depth understanding of sequalae are required to contain the spread of disease. Visceralizing potential of dermotropic strains has not been fully ruled out. Sri Lankan strains have shown a poor response to established serological assays. The present concern was to develop an in-house serological assay and to determine the seroprevalence of CL for identifying visceralizing potential and its usefulness in enhancing case detection. Crude cell lysate of dermotropic L. donovani promastigotes-based indirect enzyme-linked immunosorbent assay (ELISA) was previously optimized. Assay was evaluated using sera from 200 CL patients, 50 endemic and 50 nonendemic healthy controls, 50 patients with other skin diseases, and 50 patients with other systemic diseases. Seroprevalence and clinicoepidemiological associations were analyzed. Assay was compared with light microscopy (LM) and in vitro culturing (IVC). Cost comparison was carried out. Seroprevalence of CL was 82.0%. The assay had 99.5% specificity, and all healthy controls were negative at 0.189 cut-off. Positive and negative predictive values were 99.4% and 84.7%, respectively. Positivity obtained in ELISA was comparable to LM and higher than that of IVC. Cost per patient was 3.0 USD for both ELISA and LM and 6.0 USD for IVC. Infections occurring in all age groups and both genders demonstrated >75.0% of seropositivity. Patients had lesions with different durations/types/sizes showed >70.0% of seropositivity. Study identified a high seroprevalence of L. donovani-induced CL for the first time, indicating potential for visceralization or transient serological response. This can be used as a second line test in LM-negative CL cases to enhance clinical case detection. Further studies are warranted to examine in-depth correlations, antigen profiles, comparison with other established serological tools, and usefulness in the detection of asymptomatic cases. (National patent LK/P/1/19697).

Lipophosphoglycans from dermotropic Leishmania infantum are more pro-inflammatory than those from viscerotropic strains

Although Leishmania infantum is well-known as the aethiological agent of visceral leishmaniasis (VL), in some Central American countries it may cause atypical non-ulcerated cutaneous leishmaniasis (NUCL). However, the mechanisms favoring its establishment in the skin are still unknown. Lipophosphoglycan (LPG) is the major Leishmania multivirulence factor involved in parasite-host interaction. In the case of viscerotropic L. infantum, it causes an immunosuppression during the interaction with macrophages. Here, we investigated the biochemical and functional roles of LPGs from four dermotropic L. infantum strains from Honduras during in vitro interaction with murine macrophages. LPGs were extracted, purified and their repeat units analysed. They did not have side chains consisting of Gal(β1,4)Man(α1)-PO₄ common to all LPGs. Peritoneal macrophages from BALB/c and C57BL/6 were exposed to LPG for nitric oxide (NO) and cytokine (TNF-α and, IL-6) production. LPGs from dermotropic strains from Honduras triggered higher NO and cytokine levels compared to those from viscerotropic strains. In conclusion, LPGs from dermotropic strains are devoid of side-chains and exhibit high pro-inflammatory activity.

Clinical and Immunological Features of Human Leishmania (L.) infantum-Infection, Novel Insights Honduras, Central America

Leishmania (Leishmania) infantum is the etiological agent of both American visceral leishmaniasis (AVL) and non-ulcerated cutaneous leishmaniasis (NUCL) in Honduras. Although AVL is the most severe clinical form of infection, recent studies have shown that human immune response to parasite infection can result in a clinical-immunological spectrum. The overall prevalence rate of infection and clinical-immunological profiles of the L. (L.) infantum infection in Amapala municipality, South Honduras was determined. We examined 576 individuals with diagnosis based on combined ELISA (IgG/IgM) and DTH assays. We also used genus-specific kDNA PCR and Hsp70 PCR-RFLP for NUCL cases. Clinical evaluation found 82% asymptomatic and 18% symptomatic individuals. All symptomatic cases (n = 104) showing NUCL were positive for parasites. We identified L. (L.) infantum species in 100% of the skin lesion scrapings and in 90% of the blood samples from NUCL cases studied. A total of 320 asymptomatic individuals were exposed (ELISA+ and/or DTH+), providing an overall L. (L.) infantum prevalence of 73.6%. Clinical, parasitological, and immunological evaluations suggest seven infection profiles, three asymptomatic and four symptomatic. This represents the first report on clinical and immunological features of human L. (L.) infantum-infection in Amapala municipality, Honduras.

Autochthonous Outbreak of Cutaneous Leishmaniasis due to Leishmania infantum in Corrientes Province, Argentina

Endemic cutaneous leishmaniasis (CL) in northern Argentina has traditionally been caused by Leishmania braziliensis. This study aims to describe an outbreak of Leishmania infantum-caused human CL in the Department Capital of Corrientes Province, Argentina. We retrospectively analyzed the reported cases of CL in this area from May 2015 to December 2016. Eighty cases of CL were clinically and analytically diagnosed, and there was one case of visceral leishmaniasis in a boy who also had CL. Patients' median age was 33.6 years (range 1-89 years), and 18.5% were younger than 15 years; the male:female ratio was 3.5:1. Cases lived mostly in the municipality of Corrientes (72.8%), whereas 27.2% resided in Riachuelo. Although 67.9% had a single lesion, 32.1% had several. Molecular analyses showed that L. infantum was the causative species in all cases. Our results show that for the first time, there was an outbreak of CL by L. infantum in an urban area of Argentina.

Trans-Atlantic Spill Over: Deconstructing the Ecological Adaptation of Leishmania infantum in the Americas

Pathogen fitness landscapes change when transmission cycles establish in non-native environments or spill over into new vectors and hosts. The introduction of Leishmania infantum in the Americas into the Neotropics during European colonization represents a unique case study to investigate the mechanisms of ecological adaptation of this important parasite. Defining the evolutionary trajectories that drive L. infantum fitness in this new environment are of great public health importance as they will allow unique insight into pathways of host/pathogen co-evolution and their consequences for region-specific changes in disease manifestation. This review summarizes current knowledge on L. infantum genetic and phenotypic diversity in the Americas and its possible role in the unique epidemiology of visceral leishmaniasis (VL) in the New World. We highlight the importance of appreciating adaptive molecular mechanisms in L. infantum to understand the parasites' successful establishment on the continent.

Geographical distribution of Leishmania species in Colombia, 1985-2017

INTRODUCTION

Knowledge of the geographical distribution of Leishmania species allows guiding the sampling to little-studied areas and implementing strategies to define risk zones and priority areas for control.

OBJECTIVE

Given that there is no publication that collects this information, the search, review, and compilation of the available scientific literature that has identified species in Colombia is presented in this paper.

MATERIALS AND METHODS

A bibliographic search was performed in PubMed, Web of Knowledge, Google Scholar, SciELO and LILACS with the terms "(Leishmania OR Leishmaniasis) AND species AND Colombia", without restrictions on publication year, language or infected organism; records of national scientific events and repositories of theses from Colombian universities were also included.

RESULTS

Eighty-six scientific documents published between 1985 and 2017 were found in which the species of Leishmania and their geographical origin were indicated. The species reported, in descending order of frequency, were: Leishmania (Viannia) panamensis, L. (V.) braziliensis, L. (V.) guyanensis, L. (Leishmania) infantum, L. (L.) amazonensis, L. (L.) mexicana, L. (V.) colombiensis, L. (V.) lainsoni and L. (V.) equatorensis; the last three were found with the same frequency. Leishmania species were reported from 29 departments.

CONCLUSION

Information on the distribution of Leishmania species in Colombia is limited; therefore, it is necessary to gather existing data and propose studies that consolidate the distribution maps of Leishmania species in Colombia. This would allow the detection of areas where species have not been identified as well as the comparison of existing parasite and vector distributions.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Histopathological features of skin lesions in patients affected by non-ulcerated or atypical cutaneous leishmaniasis in Honduras, Central America

In Honduras visceral leishmaniasis and non-ulcerated or atypical cutaneous leishmaniasis (NUCL) are caused by the species Leishmania (L.) infantum chagasi. NUCL is the most common clinical form in the southern regions of the country, mainly affecting the young. In view of the lack of knowledge about the pathogenesis of the disease pattern caused by L. (L) infantum chagasi in individuals affected by NUCL, the aim of the present study was to describe in detail the histopathological features of the skin lesion caused by the parasite. Biopsies from human NUCL lesions with a positive parasitological diagnosis were collected and processed using standard histological techniques. Paraffin sections stained by haematoxylin and eosin were used to examine the histopathological alterations seen in the skin. The lesions varied between 3 and 5 mm, and the majority of the patients (60%) had a single lesion. Lesions were more frequently seen in females (65%), with an average age of 33.4 years. Microscopically, the skin lesions were characterized by mononuclear inflammatory infiltrate in the dermis composed of lymphocytes, macrophages and a few plasma cells. The intensity of the infiltration varied from discrete to intense. In both cases, the parasitic infection was discrete. Granulomas were present in 60% of cases and were associated with intense inflammation. The data revealed by the histopathological alterations in the skin of individuals affected by NUCL suggest activation of a cellular immune response that potentially controls parasite spreading.

Evaluation of Regulatory Immune Response in Skin Lesions of Patients Affected by Nonulcerated or Atypical Cutaneous Leishmaniasis in Honduras, Central America

In Honduras, Leishmania (L.) infantum chagasi causes both visceral leishmaniasis (LV) and nonulcerated or atypical cutaneous leishmaniasis (NUCL). NUCL is characterized by mononuclear inflammatory infiltration of the dermis, composed mainly of lymphocytes followed by macrophages with discrete parasitism. Considering that little is known about the pathogenesis of NUCL, the aim of this study was to evaluate the regulatory response in situ in skin lesions of patients affected by NUCL. Biopsies (n = 20) from human cutaneous nonulcerative lesions were collected and processed by usual histological techniques. The in situ regulatory immune response was evaluated by immunohistochemistry using antihuman CD4, FoxP3, IL-10, and TGF-β antibodies. CD4⁺, FoxP3⁺, TGF-β⁺, and IL-10⁺ cells were observed in the dermis with inflammatory infiltration in all studied cases and at higher densities compared to the normal skin controls. A positive and strong correlation was observed between CD4⁺ and FoxP3⁺ cells, and a positive and moderate correlation was observed between FoxP3⁺ and TGF-β⁺ but not with IL-10⁺ cells. The data suggest that T regulatory FoxP3⁺ cells and the regulatory cytokines, especially TGF-β, play an important role in the immunopathogenesis of NUCL, modulating a cellular immune response in the skin, avoiding tissue damage, and leading to low tissue parasitic persistence.

Bionomic aspects of Lutzomyia evansi and Lutzomyia longipalpis, proven vectors of Leishmania infantum in an endemic area of non-ulcerative cutaneous leishmaniasis in Honduras

Background

Some Lutzomyia species are the vectors of human leishmaniasis in the Americas. Visceral and cutaneous leishmaniasis are both endemic in the Pacific region of Honduras, but the non-ulcerative form is the more frequent clinical manifestation in this region, where Lutzomyia longipalpis is the most abundant and the only incriminated vector. Taxonomic identification and distribution studies of sand flies are important to understand the epidemiology and to control these neglected tropical diseases.

Results

Here, we identified more than 13,000 Lutzomyia specimens captured in Isla del Tigre, Honduras, through a classical morphological approach. The two most common species were Lutzomyia evansi and Lu. longipalpis, and this is the first report of three Lutzomyia species on this island. The blood meal source was successfully identified for five sand fly species. A barcode analysis using the cox1 mitochondrial marker proved to be effective in discriminating between species and seems to be a valuable tool for future epidemiological studies including a wider geographical area.

Conclusion

This study updates the diversity and blood meal sources of Lutzomyia species in an island endemic for non-ulcerative cutaneous leishmaniasis in the Pacific region of Honduras, and determines the effectiveness of the barcoding approach to discriminate species, as a complementary tool to classical morphology.

Leprosy Associated with Atypical Cutaneous Leishmaniasis in Nicaragua and Honduras

In Central America, few cases of leprosy have been reported, but the disease may be unrecognized. Diagnosis is based on clinical criteria and histology. Preliminary field work in Nicaragua and Honduras found patients, including many children, with skin lesions clinically suggestive of atypical cutaneous leishmaniasis or indeterminate leprosy. Histology could not distinguish these diseases although acid-fast organisms were visible in a few biopsies. Lesions healed after standard antimicrobial therapy for leprosy. In the present study, patients, family members, and other community members were skin-tested and provided nasal swabs and blood samples. Biopsies were taken from a subgroup of patients with clinical signs of infection. Two laboratories analyzed samples, using local in-house techniques. Mycobacterium leprae, Leishmania spp. and Leishmania infantum were detected using polymerase chain reactions. Mycobacterium leprae DNA was detected in blood samples and nasal swabs, including some cases where leprosy was not clinically suspected. Leishmania spp. were also detected in blood and nasal swabs. Most biopsies contained Leishmania DNA and coinfection of Leishmania spp. with M. leprae occurred in 33% of cases. Mycobacterium leprae DNA was also detected and sequenced from Nicaraguan and Honduran environmental samples. In conclusion, leprosy and leishmaniasis are present in both regions, and leprosy appears to be widespread. The nature of any relationship between these two pathogens and the epidemiology of these infections need to be elucidated.

The current status of the Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) species complex

Lutzomyia longipalpis s.l. is a complex of sibling species and is the principal vector of American visceral leishmaniasis. The present review summarises the diversity of efforts that have been undertaken to elucidate the number of unnamed species in this species complex and the phylogenetic relationships among them. A wide variety of evidence, including chemical, behavioral and molecular traits, suggests very recent speciation events and complex population structure in this group. Although significant advances have been achieved to date, differential vector capacity and the correlation between structure of parasite and vector populations have yet to be elucidated. Furthermore, increased knowledge about recent epidemiological changes, such as urbanisation, is essential for pursuing effective strategies for sandfly control in the New World.

Phenotypic diversity and selection maintain Leishmania amazonensis infectivity in BALB/c mouse model

Leishmania are protozoan parasites that show remarkable diversity, as revealed by the various clinical forms of leishmaniasis, which can range from mild skin lesions to severe metastatic cutaneous/mucosal lesions. The exact nature and extent of Leishmania phenotypic diversity in establishing infection is not fully understood. In order to try to understand some aspects of this diversity, we subcutaneously infected BALB/c mice with first and second generation subclones of a L. amazonensis strain isolated from a patient (BA125) and examined in vivo lesion growth rate and antimony susceptibility. In vivo fast-, medium- and slow-growing subclones were obtained; moreover, fast-growing subclones could generate slow-growing subclones and inversely, revealing the continuous generation of diversity after passage into mice. No antimony-resistant subclone appeared, probably a rare occurrence. By tagging subclone cells with a L. amazonensis genomic cosmid library, we found that only a very small number of founding cells could produce lesions. Leishmania clones transfected with in vivo selected individual cosmids were also diverse in terms of lesion growth rate, revealing the cosmid-independent intrinsic characteristics of each clone. Our results suggest that only a few of the infecting parasites are able to grow and produce lesions; later, within the cell mixture of each lesion, there coexist several parasite populations with different potentialities to grow lesions during the next infection round. This may reflect a sort of programmed heterogeneity of individual parasites, favoring the survival of some individuals in various environmental conditions.

FIRST REPORT OF CUTANEOUS LEISHMANIASIS CAUSED BY Leishmania (Leishmania) infantum chagasi IN AN URBAN AREA OF RIO DE JANEIRO, BRAZIL

American tegumentary leishmaniasis (ATL) is an infectious disease caused by protozoa of the genus Leishmania, and transmitted by sandflies. In the state of Rio de Janeiro, almost all of the cases of American tegumentary leishmaniasis (ATL) are caused by Leishmania (Viannia) braziliensis, while cases of visceral leishmaniasis (VL) are caused by Leishmania (Leishmania) infantum chagasi. The resurgence of autochthonous VL cases in Rio de Janeiro is related to the geographic expansion of the vector Lutzomyia longipalpis and its ability to adapt to urban areas. We report the first case of leishmaniasis with exclusively cutaneous manifestations caused by L. (L.) infantum chagasi in an urban area of Rio de Janeiro. An eighty-one-year-old woman presented three pleomorphic skin lesions that were not associated with systemic symptoms or visceromegalies. Multilocus enzyme electrophoresis identified L. (L.) infantum chagasi, but direct smear and PCR of bone narrow were negative for Leishmania sp. (suggesting exclusively cutaneous involvement). We discuss the different dermatological presentations of viscerotropic leishmaniasis of the New and Old World, and the clinical and epidemiological importance of the case. Etiologic diagnosis of ATL based upon exclusive clinical criteria may lead to incorrect conclusions. We should be aware of the constant changes in epidemiological patterns related to leishmaniases.

Leishmania infantum AS A CAUSATIVE AGENT OF CUTANEOUS LEISHMANIASIS IN THE STATE OF MATO GROSSO DO SUL, BRAZIL

Cutaneous leishmaniasis is caused by different species of theLeishmania genus. Leishmania(Leishmania) infantum, causing cutaneous leishmaniasis, has been described in patients living in areas where visceral leishmaniasis is endemic. In this study, it was possible to characterize this species in seven slides from cutaneous tissue imprints from patients with cutaneous leishmaniasis in the State of Mato Grosso do Sul, Brazil.

Lutzomyia migonei is a permissive vector competent for Leishmania infantum

BACKGROUND

Leishmania infantum is the most widespread etiological agent of visceral leishmaniasis (VL) in the world, with significant mortality rates in human cases. In Latin America, this parasite is primarily transmitted by Lutzomyia longipalpis, but the role of Lutzomyia migonei as a potential vector for this protozoan has been discussed. Laboratory and field investigations have contributed to this hypothesis; however, proof of the vector competence of L. migonei has not yet been provided. In this study, we evaluate for the first time the susceptibility of L. migonei to L. infantum.

METHODS

Females of laboratory-reared L. migonei were fed through a chick-skin membrane on rabbit blood containing L. infantum promastigotes, dissected at 1, 5 and 8 days post-infection (PI) and checked microscopically for the presence, intensity and localisation of Leishmania infections. In addition, morphometric analysis of L. infantum promastigotes was performed.

RESULTS

High infection rates of both L. infantum strains tested were observed in L. migonei, with colonisation of the stomodeal valve already on day 5 PI. At the late-stage infection, most L. migonei females had their cardia and stomodeal valve colonised by high numbers of parasites, and no significant differences were found compared to the development in L. longipalpis. Metacyclic forms were found in all parasite-vector combinations since day 5 PI.

CONCLUSIONS

We propose that Lutzomyia migonei belongs to sand fly species permissive to various Leishmania spp. Here we demonstrate that L. migonei is highly susceptible to the development of L. infantum. This, together with its known anthropophily, abundance in VL foci and natural infection by L. infantum, constitute important evidence that L. migonei is another vector of this parasite in Latin America.

Lutzomyia longipalpis urbanisation and control

Since the description of Lutzomyia longipalpis by Lutz and Neiva more than 100 years ago, much has been written in the scientific literature about this phlebotomine species. Soares and Turco (2003) and Lainson and Rangel (2005) have written extensive reviews focused on vector-host-parasite interactions and American visceral leishmaniasis ecology. However, during the last two decades, the success of Lu. longipalpis in colonising urban environments and its simultaneous geographical spreading have led to new theoretical and operational questions. Therefore, this review updates the general information about this species and notes the more challenging topics regarding the new scenario of urbanisation-spreading and its control in America. Here, we summarise the literature on these issues and the remaining unsolved questions, which pose recommendations for operational research.

Comparative microsatellite typing of new world leishmania infantum reveals low heterogeneity among populations and its recent old world origin

Leishmania infantum (syn. L. chagasi) is the causative agent of visceral leishmaniasis (VL) in the New World (NW) with endemic regions extending from southern USA to northern Argentina. The two hypotheses about the origin of VL in the NW suggest (1) recent importation of L. infantum from the Old World (OW), or (2) an indigenous origin and a distinct taxonomic rank for the NW parasite. Multilocus microsatellite typing was applied in a survey of 98 L. infantum isolates from different NW foci. The microsatellite profiles obtained were compared to those of 308 L. infantum and 20 L. donovani strains from OW countries previously assigned to well-defined populations. Two main populations were identified for both NW and OW L. infantum. Most of the NW strains belonged to population 1, which corresponded to the OW MON-1 population. However, the NW population was much more homogeneous. A second, more heterogeneous, population comprised most Caribbean strains and corresponded to the OW non-MON-1 population. All Brazilian L. infantum strains belonged to population 1, although they represented 61% of the sample and originated from 9 states. Population analysis including the OW L. infantum populations indicated that the NW strains were more similar to MON-1 and non-MON-1 sub-populations of L. infantum from southwest Europe, than to any other OW sub-population. Moreover, similarity between NW and Southwest European L. infantum was higher than between OW L. infantum from distinct parts of the Mediterranean region, Middle East and Central Asia. No correlation was found between NW L. infantum genotypes and clinical picture or host background. This study represents the first continent-wide analysis of NW L. infantum population structure. It confirmed that the agent of VL in the NW is L. infantum and that the parasite has been recently imported multiple times to the NW from southwest Europe.

Leishmaniasis is a vector borne disease with a broad spectrum of clinical forms caused by protozoan parasites of the genus Leishmania. Visceral leishmaniasis is the most severe, systemic form of the disease. It is caused by parasites belonging to the Leishmania donovani complex, which includes L. infantum and L. donovani in the Old World (OW) and L. infantum (syn. L. chagasi) in the New World (NW). The identity and origin of the causative agent of VL in the Americas have been the subjects of much debate for decades. Different scientific approaches led to different conclusions, either favouring the hypothesis of indigenous origin of this parasite and its status as distinct species, or a recent importation of L. infantum by European colonists and synonymy of L. infantum and L. chagasi. We performed the first broad population study of these parasites from the NW using highly variable microsatellite markers. The level of heterogeneity and population structure was very low in contrast to the OW. Using a combined data analysis of NW and OW strains we have provided conclusive evidence of recent multiple introductions of L. infantum from Southwest Europe into the New World and for synonymy of L. infantum and L. chagasi.

Genotypic characterization of cutaneous leishmaniasis at Al Baha and Al Qasim Provinces (Saudi Arabia)

Fifty samples of skin ulcers were collected from the western region of Saudi Arabia Kingdom (Al Baha and Al Qasim) to study genotypic characterization of Cutaneous Leishmaniasis in this area. Thirty-six samples were recorded as Leishmania isolates. The same isolates were subsequently tested with fingerprinting with single arbitrary primers. The primers used derived from the core sequence of the phage M13, and the repeat sequences (GTG)5 and (GACA)4. The 36 isolates were all identified as Leishmania major (n = 25 isolates) or Leishmania tropica (n = 11 isolates). All produced polymorphic patterns, which were grouped depending on the species they belonged to, next to the relevant well-characterized strains of the same species. Within the L. major and L. tropica group the subgroupings formed were mainly related to the geographical origin of the strains. A nested polymerase chain reaction-based schizodeme method for identifying Leishmania kinetoplast minicircle classes was used as a diagnostic tool for L. major and L. tropica.

Cutaneous leishmaniasis due to Leishmania chagasi/Le. infantum in an endemic area of Guarico State, Venezuela

This study reports cutaneous leishmaniasis (CL) caused by Leishmania chagasi/Le. infantum in Venezuela, with some atypical characteristics. Out of 63 cases of CL in the suburbs of Altagracia de Orituco, Guarico State, Venezuela, 30 presented clinical, parasitological, immunological and epidemiological features different from those of the classical CL known in the country. The initial lesion was small and nodular, which, if not treated, might progress to a superficial ulcer. No secondary infection was observed. The identification of the isolates was carried out by molecular techniques. Twelve species of phlebotomine sandflies were caught, the most abundant being Lutzomyia evansi and Lu. longipalpis s.l., known vectors of Le. chagasi/Le. infantum. The existence of Le. chagasi/Le. infantum and its vectors in an endemic area of CL has implications and we suggest that epidemiological studies should be carried out to obtain a clearer picture of the extent of this CL form in Venezuela.

Molecular Epidemiology

Molecular epidemiology is now an established discipline in epidemiology.(1) It is the contemporary stage in the evolution of laboratory-based epidemiology that may have begun with the discovery in the late 1800s of ways to differentiate bacterial organisms by pure culture in artificial media.(2) Molecular epidemiology uses new molecular biology tools to address questions difficult or not possible to address by old laboratory tools. Just as statistical tools have become indispensable in epidemiological investigations and interpretations of epidemiologic data, molecular biology tools today have come to elucidate epidemiologic features of diseases that cannot be easily characterized by conventional techniques. Applied to infectious diseases, molecular biology methods have also come to challenge our traditional notions about the epidemiology of these diseases and have engendered novel opportunities for their prevention and control. This chapter will (1) review definitions commonly used in molecular epidemiology, (2) present an overview of molecular biology methods used to study infectious disease epidemiology, and (3) describe examples of the types of epidemiologic problems that can be addressed by molecular biology techniques, highlighting new concepts that emerged in the process of applying this approach to study bacterial infectious diseases.

Aluminium: a natural adjuvant in Leishmania transmission via sand flies?

Genetically identical Leishmania chagasi/infantum parasites cause both atypical cutaneous leishmaniasis and visceral leishmaniasis. In this report we have tested the first part of a hypothesis that states that the form of this disease that is manifested depends upon the adjuvant-like activity of aluminium of dietary origin accumulated in the salivary gland of the sand fly vector. In sand flies fed aluminium-supplemented sucrose we have used histochemistry to qualitatively identify aluminium in their salivary glands and graphite furnace atomic absorption spectrometry to quantify the aluminium content of dissected salivary glands. Aluminium may be acting as a natural adjuvant in some forms of leishmaniasis.

Comparative genomics: from genotype to disease phenotype in the leishmaniases

Recent progress in sequencing the genomes of several Leishmania species, causative agents of cutaneous, mucocutaneous and visceral leishmaniasis, is revealing unusual features of potential relevance to parasite virulence and pathogenesis in the host. While the genomes of Leishmania major, Leishmania braziliensis and Leishmania infantum are highly similar in content and organisation, species-specific genes and mechanisms distinguish one from another. In particular, the presence of retrotransposons and the components of a putative RNA interference machinery in L. braziliensis suggest the potential for both greater diversity and more tractable experimentation in this Leishmania Viannia species.

Cutaneous leishmaniasis

Cutaneous leishmaniasis is a widespread tropical infection caused by numerous different species of Leishmania protozoa that are transmitted by sandflies. Its clinical presentations are extremely diverse and dependent on a variety of parasite and host factors that are poorly understood. Diagnosis should aim to identify the exact species involved, but this requires laboratory investigations that are not widely available. No single ideal treatment has been identified, and those available are limited by variable success rates and toxicity. Clinical guidelines are needed to make better use of the investigations and treatments that do exist. Prevention is currently limited to bite prevention measures.

Single-step duplex kDNA-PCR for detection of Leishmania donovani complex in human peripheral blood samples

A duplex polymerase chain reaction (PCR) assay was performed using a sense Leishmania genus-specific oligonucleotides to amplify the conserved region of 120 bp of minicircle kDNA and an additional antisense Leishmania donovani oligonucleotide that amplifies a complex-specific fragment of 90 bp. All 12 tested reference isolates of the L. donovani complex yielded a complex-specific amplification product of 90 bp concurrently with a genus-specific 120-bp product. All 17 tested reference isolates pertaining to other complexes presented only the genus-specific 120-bp product. Peripheral blood samples of twenty patients with visceral leishmaniasis positive by the genus-specific PCR presented both fragments with the duplex assay. This duplex PCR can be applied as a 1-step diagnostic tool where discrimination of L. donovani complex species is relevant for clinical and epidemiologic purposes.

Leishmania infection impairs beta 1-integrin function and chemokine receptor expression in mononuclear phagocytes

Leishmania spp. are intracellular parasites that cause lesions in the skin, mucosa, and viscera. We have previously shown that Leishmania infection reduces mononuclear phagocyte adhesion to inflamed connective tissue. In this study, we examined the role of adhesion molecules and chemokines in this process. Infection rate (r = -0.826, P = 0.003) and parasite burden (r = -0.917, P = 0.028) negatively correlated to mouse phagocyte adhesion. The decrease (58.7 to 75.0% inhibition, P = 0.005) in phagocyte adhesion to connective tissue, induced by Leishmania, occurred as early as 2 h after infection and was maintained for at least 24 h. Interestingly, impairment of cell adhesion was sustained by phagocyte infection, since it was not observed following phagocytosis of killed parasites (cell adhesion varied from 15.2% below to 24.0% above control levels, P > 0.05). In addition, Leishmania infection diminished cell adhesion to fibronectin (54.1 to 96.2%, P < 0.01), collagen (15.7 to 83.7%, P < 0.05), and laminin (59.1 to 82.2%, P < 0.05). The CD11b(hi) subpopulation was highly infected (49.6 to 97.3%). Calcium and Mg(2+) replacement by Mn(2+), a treatment that is known to induce integrins to a high state of affinity for their receptors, reverted the inhibition in adhesion caused by Leishmania. This reversion was completely blocked by anti-VLA4 antibodies. Furthermore, expression of CCR4 and CCR5, two chemokine receptors implicated in cell adhesion, was found to be downregulated 16 h after infection (2.8 to 4.1 times and 1.9 to 2.8 times, respectively). Together, these results suggest that mechanisms regulating integrin function are implicated in the change of macrophage adhesion in leishmaniasis.

Inorganic particles in the skin of inhabitants of volcanic areas of Central America: their possible immunomodulatory influence in leishmaniasis and leprosy

We have evaluated biopsies from patients with atypical nodular and typical ulcerated lesions of cutaneous leishmaniasis, from leishmanin reactions and skin from normal individuals from Nicaragua, Honduras and Guatemala for the presence of inorganic particles using confocal microscopy with a polarised light source and conventional histopathological techniques. Analysis by semiquantitative confocal microscopy permitted the demonstration of significantly larger numbers of particles in atypical lesions. Silica and aluminium, important components of these particles, were less abundant in particles from normal skin. The histology of these atypical lesions, characterised by 'naked' sarcoidal granulomas with epithelioid differentiation but very few lymphocytes, was very similar to the histological reaction observed after 14 days in persisting inflammation at leishmanin skin test sites. The presence of these unusual lesions in areas of Central American countries characterised by the presence of large amounts of volcanic ash, as well the unexpectedly low prevalence of leprosy in Central America, suggest that environmental factors may contribute significantly to the frequency and clinical manifestations of these infections. Among possible environmental features, the presence of inorganic particles with immunomodulatory properties in the skin may be a significant factor.

Post mortem parasitological evaluation of dogs seroreactive for Leishmania from Rio de Janeiro, Brazil

A parasitological study was conducted on 66 dogs seroreactive for Leishmania captured as a control measure of visceral leishmaniasis in the State of Rio de Janeiro, Brazil. Biological samples from different anatomical sites were collected during autopsy of the animals and cultured on biphasic medium (NNN/Schneider). The Leishmania isolates were characterized by isoenzyme electrophoresis. Leishmania was isolated from 80.3% of the animals: 12 animals with Leishmania (Viannia) braziliensis isolated exclusively from cutaneous lesions, 39 with L. (L.) chagasi isolated from different sites in the same animal, and 2 with simultaneous isolation of L. (V.) braziliensis from cutaneous lesions and L. (L.) chagasi from different sites. Isolation in culture revealed the absence of Leishmania parasites in 13 animals. The results obtained confirm the existence of mixed infections in dogs in Rio de Janeiro and indicate the need to complement the investigation of seroreactive dogs using methods for the parasitological diagnosis and identification of Leishmania species.

Atypical cutaneous leishmaniasis in Central America: possible interaction between infectious and environmental elements

Biopsies of 71 cases of atypical cutaneous leishmaniasis from Costa Rican patients were evaluated by histopathological procedures and attempts were made to culture Leishmania from nine biopsies. Leishmanin skin tests were carried out in 31 patients and 112 healthy individuals. Additional biopsies from 19 patients from Nicaragua were evaluated by routine histopathology. Ten biopsies were studied by confocal and nine by scanning electron microscopy. Inorganic material was analysed using an electron probe for microanalysis. Leishmania parasites were isolated from only two biopsies, but 90.3% of the patients from Costa Rica were leishmanin-positive, as were 27.7% of healthy individuals. Routine histopathological studies revealed naked granulomas formed by differentiated macrophages. Abundant inorganic material was observed in sections examined by confocal microscopy. Electron probe analysis revealed that silica and aluminium were the predominant elements in large particles. We postulate that the presence of this inorganic material, possibly of volcanic origin, in the skin may modulate the immunological response to Leishmania and may inhibit visceralization in the cases caused by Leishmania chagasi.

Leishmania chagasi/infantum: further investigations on Leishmania tropisms in atypical cutaneous and visceral leishmaniasis foci in Central America

In Central America, apparently genetically identical Leishmania chagasi/infantum parasites cause cutaneous (CL) and visceral leishmaniasis (VL), the latter being more frequent in young children. The present study investigated if there were pathology-related differences in virulence between Honduran CL and VL strains using Mediterranean L. infantum strains as a reference. Macrophage infectivity and serum sensitivity, properties thought to be associated with virulence, were similar between CL and VL strains from both regions. Attention focused on the genome organisation of genes for two candidate virulence factors: Leishmania mitogen activated protein kinase (LMPK) and cysteine proteinase b (Cpb). Interestingly, the Mediterranean strains exhibited restriction enzyme polymorphisms associated with tropism for both LMPK and Cpb genes whereas no differences were observed for the Honduran strains. We also report relative genetic homogeneity of the Honduran strains as compared to the Mediterranean strains and discuss it in terms of the probable origin for the Central American L. chagasi/infantum.

Immunopathogenesis of infection with the visceralizing Leishmania species

Human leishmaniasis is a spectral disease that includes asymptomatic self-resolving infection, localized skin lesions, and progressive visceral leishmaniasis. With some overlap, visceral and cutaneous leishmaniasis are usually caused by different species of Leishmania. This review focuses on host responses to infection with the species that cause visceral leishmaniasis, as they contrast with species causing localized cutaneous leishmaniasis. Data from experimental models document significant differences between host responses to organisms causing these diverse syndromes. The visceralizing Leishmania spp. cause localized organ-specific immune responses that are important determinants of disease outcome. Both the Leishmania species causing cutaneous and those causing visceral leishmaniasis require a Type 1 immune response to undergo cure in mouse models. However, during progressive murine infection with the visceralizing Leishmania sp., the Type 1 response is suppressed at least in part by TGF-beta and IL-10 without type 2 cytokine production. This contrasts with the cutaneous species L. major, in which a Type 2 response suppresses type 1 cytokines and leads to murine disease progression. Population and family studies are beginning to elucidate human genetic determinants predisposing to different outcomes of Leishmania infection. These studies should eventually result in a better understanding of the immunopathogenesis and the spectrum of human leishmaniasis.

Does the Leishmania major paradigm of pathogenesis and protection hold for New World cutaneous leishmaniases or the visceral disease?

Parasitic protozoa of the genus Leishmania have provided a useful perspective for immunologists in terms of host defense mechanisms critical for the resolution of infection caused by intracellular pathogens. These organisms, which normally reside in a late endosomal, major histocompatibility complex (MHC) class II(+) compartment within host macrophages cells, require CD4(+) T-cell responses for the control of disease. The paradigm for the CD4(+) T-helper 1 (Th1)/Th2 dichotomy is largely based on the curing/non-curing responses, respectively, to Leishmania major infection. However, this genus of parasitic protozoa is evolutionarily diverse, with the cutaneous disease-causing organisms of the Old World (L. major) and New World (Leishmania mexicana/ Leishmania amazonensis) having diverged 40-80 million years ago. Further adaptations to survive within the visceral organs (for Leishmania donovani, Leishmania chagasi, and Leishmania infantum) must have been required. Consequently, significant differences in host-parasite interactions have evolved. Different virulence factors have been identified for distinct Leishmania species, and there are profound differences in the immune mechanisms that mediate susceptibility/resistance to infection and in the pathology associated with disease. These variations not only point to interesting features of the host-pathogen interaction and immunobiology of this genus of parasitic protozoa, but also have important implications for immunotherapy and vaccine development.

Comparison between splenic and lymph node aspirations as sampling methods for the parasitological detection of Leishmania chagasi infection in dogs

The sensitivities of spleen and lymph node cultures for the diagnosis of canine visceral leishmaniasis were compared in 64 anti-Leishmania antibody positive dogs from an endemic area in Brazil. The sensitivity of spleen cultures for Leishmania detection was 97.9%; in lymph node cultures it was 25%. Positive spleen culture was more frequent (p = 0.048, Fisher's exact probability test) in symptomatic (28 out of 33 animals) than in asymptomatic animals (19 out of 31 animals). These results support the use of spleen instead of lymph node aspiration as the choice method for the parasitological diagnosis of the infection.

Genetic variability within the species Leishmania infantum by RAPD. A lack of correlation with zymodeme structure

The infraspecific variability of the species Leishmania infantum is studied by using genetic markers generated by random amplified polymorphic DNA (RAPD). We have applied this technique, using 18 primers of arbitrary sequence, to 33 strains of the parasite belonging to 18 zymodemes isolated in different clinical forms and hosts. Other strains belonging to the species L. donovani, L. major, L. tropica and L. mexicana were used as a reference. The RAPD technique produced very different genetic profiles between L. infantum and L. major, L. tropica and L. mexicana with all primers used, whereas 11 of the 18 primers distinguished L. infantum strains from the species L. donovani. All primers except 1 (TAF 300), generated polymorphism in the L. infantum strains. The dendrograms constructed with the isoenzyme data and with RAPD are congruent in relation to the separation of the different species but show little agreement within the L. infantum species, reflecting the genetic heterogeneity of the strains belonging to one zymodeme. A geographical structuralisation is observed with two diverging groups that evolve independently whereas there is no relation between the genotype of the parasite and the host or between the former and the clinical form of the disease.

Identification of a differentially expressed mRNA in axenic Leishmania panamensis amastigotes

Differential display technique was applied in order to identify transcripts which are present in axenic amastigotes but not in promastigotes of the Leishmania panamensis parasites. One of them was cloned and the sequence reveals an open reading frame of 364 amino acids (approximately 40 kDa). The deduced protein is homologous to the serine/threonine protein kinases and specially to the mitogen activates protein kinases from eukaryotic species. Southern blot analysis suggest that this transcript, named lpmkh, is present in the genome of the parasite as a single copy gene. These results could imply that lpmkh could be involved in the differentiation process or the preservation of amastigotes in axenic conditions.

Aetiology of visceral leishmaniasis in Mexico

Two children with visceral leishmaniasis (VL), were studied by DNA analysis. DNA from liver biopsy samples from both patients, was amplified by PCR with broad primers specific for the Leishmania subgenus. DNA from the patient from Chiapas was also amplified with primers specific for the Leismania donovani complex and hybridised with a probe specific for L. donovani complex. The second patient, who is the first reported case of visceral leishmaniasis in the Mexican state of Tabasco, where localised cutaneous leishmaniasis and DCL predominate, had a co-infection with Toxoplasma gondii. The DNA from this patient was not amplified with primers specific for the L. donovani complex, did not hybridise with a probe specific for the L. donovani complex, but did hybridise with kDNA from a Mexican Leishmania mexicana strain used as a probe. We therefore, suggest that members of the L. donovani or L. mexicana complexes cause VL in Mexico.

Leishmaniasis at the End of the Millennium

The term leishmaniasis refers to the spectrum of disease caused by Leishmania species. The clinical manifestations of leishmaniasis depend on complex interactions between the virulence characteristics of the infecting Leishmania species and the genetically determined cell-mediated immune responses of its mammalian host. Leishmaniasis comprises three major syndromes: cutaneous, mucosal, and visceral. Variations exist within each syndrome.

A nested-PCR-based schizodeme method for identifying Leishmania kinetoplast minicircle classes directly from clinical samples and its application to the study of the epidemiology of Leishmania tropica in Pakistan

A nested PCR was developed to amplify the variable region of the kinetoplast minicircles of all Leishmania species which infect mammals. Each Leishmania parasite contains approximately 10,000 kinetoplast DNA minicircles, which are unequally distributed among approximately 10 minicircle classes. The PCR primers were designed to bind within the 120-bp conserved region which is common to all minicircle classes; the remaining approximately 600 bp of each minicircle is highly conserved within each minicircle class but highly divergent between classes. The nested PCR generated a strong signal from a minimum of 0.1 fg of Leishmania DNA. Restriction digests of the amplicons from the highest dilutions suggested that minicircles from only a limited number of minicircle classes had acted as template in the reaction. One PCR product was directly sequenced and found to be derived from only one minicircle class. Since the primers amplify all minicircle classes, this indicated that as little as 1/10 of one Leishmania parasite was present in the PCR template. This demonstrated that the nested PCR achieved very nearly the maximum theoretically possible sensitivity and is therefore a potentially useful method for diagnosis. The nested PCR was tested for sensitivity on 20 samples from patients from the Timargara refugee camp, Pakistan. Samples were collected by scraping out a small amount of tissue with a scalpel from an incision at the edge of the lesion; the tissue was smeared on one microscope slide and placed in a tube of 4 M guanidine thiocyanate, in which the sample was stable for at least 1 month. DNA for PCR was prepared by being bound to silica in the presence of 6 M guanidine thiocyanate; washed in guanidine thiocyanate, ethanol, and acetone; and eluted with 10 mM Tris-HCl. PCR products of the size expected for Leishmania tropica were obtained from 15 of the 20 samples in at least one of three replicate reactions. The negative samples were from lesions that had been treated with glucantime or were over 6 months old, in which parasites are frequently scanty. This test is now in routine use for the detection and identification of Leishmania parasites in our clinical laboratory. Fingerprints produced by restriction digests of the PCR products were defined as complex or simple. There were no reproducible differences between the complex restriction patterns of the kinetoplast DNA of any of the parasites from Timargara camp with HaeIII and HpaII. The simple fingerprints were very variable and were interpreted as being the product of PCR on a limited subset of minicircle classes, and consequently, it was thought that the variation was determined by the particular minicircle classes that had been represented in the template. The homogeneity of the complex fingerprints suggests that the present epidemic of cutaneous leishmaniasis in Timargara camp may be due to the spread of a single clone of L. tropica.