Towards a standard battery of microsatellite markers for the analysis of the Leishmania donovani complex

Expanded genome-wide comparisons give novel insights into population structure and genetic heterogeneity of Leishmania tropica complex

Leishmania tropica is one of the main causative agents of cutaneous leishmaniasis (CL). Population structures of L. tropica appear to be genetically highly diverse. However, the relationship between L. tropica strains genomic diversity, protein coding gene evolution and biogeography are still poorly understood. In this study, we sequenced the genomes of three new clinical L. tropica isolates, two derived from a recent outbreak of CL in camps hosting Syrian refugees in Lebanon and one historical isolate from Azerbaijan to further refine comparative genome analyses. In silico multilocus microsatellite typing (MLMT) was performed to integrate the current diversity of genome sequence data in the wider available MLMT genetic population framework. Single nucleotide polymorphism (SNPs), gene copy number variations (CNVs) and chromosome ploidy were investigated across the available 18 L. tropica genomes with a main focus on protein coding genes. MLMT divided the strains in three populations that broadly correlated with their geographical distribution but not populations defined by SNPs. Unique SNPs profiles divided the 18 strains into five populations based on principal component analysis. Gene ontology enrichment analysis of the protein coding genes with population specific SNPs profiles revealed various biological processes, including iron acquisition, sterols synthesis and drug resistance. This study further highlights the complex links between L. tropica important genomic heterogeneity and the parasite broad geographic distribution. Unique sequence features in protein coding genes identified in distinct populations reveal potential novel markers that could be exploited for the development of more accurate typing schemes to further improve our knowledge of the evolution and epidemiology of the parasite as well as highlighting protein variants of potential functional importance underlying L. tropica specific biology.

Dispersion of Leishmania (Leishmania) infantum in central-southern Brazil: Evidence from an integrative approach

Leishmania (Leishmania) infantum is the zoonotic agent of visceral leishmaniasis (VL), a disease with a global distribution. The transmission scenario of VL has been undergoing changes worldwide, with the biologic cycle invading urbanized areas and dispersing the parasites into other previously free areas. The epidemiological cycle in Brazil has dispersed from the Northeast to other regions of the country. In this study, an integrative approach, including genotyping Brazilian strains of L. (L.) infantum for 14 microsatellite markers and reviewing historical records of the disease, was used to assess dispersion routes throughout central-southern Brazil. Our results support three L. (L.) infantum dispersion routes: A) dispersion from Bolivia to the states of Mato Grosso, Mato Grosso do Sul and São Paulo via the Bolivia-Brazil gas pipeline from 1998 to 2005; B) VL dispersion from Paraguay to the Brazilian side of the triple border (Foz do Iguaçu and Santa Terezinha de Itaipu) during after 2012; and C) emergence of a new L. (L.) infantum cluster in western Santa Catarina State and its dispersion to southern Paraná State (municipality of Pato Branco), after 2013. Hypotheses regarding possible entries of Leishmania (L.) infantum into the area of the triple border are presented and discussed. Understanding how VL has dispersed is vital to the development of control measures for this disease and to avoid future dispersion events.

The dispersion of visceral leishmaniasis is an enigma. The State of Paraná, in southern Brazil, borders the states of São Paulo and Mato Grosso, which have experienced LV epidemics over the past 20 years. Therefore, we expected that the disease would enter this state through the contiguity of epidemics from other regions following by "ghost shadows". However, in 2012, the vectors of the parasite were reported in the western region (Foz do Iguaçu) of Paraná state, far from the epidemic regions. In the cross-sectional study, 23.8% of the dogs were infected, which is more than the eyes can see, showing an unexpected scenario where the disease was already widespread in the city. Now the question was: where does the life cycle element came from? In this study, we used genetic markers to understand the dispersion of Leishmania infantum throughout central-southern Brazil. Our results showed two possible agent inputs in the Paraná state, one coming from Paraguay and, another from Santa Catarina state. When we verify our results we perceived the monitoring importance of the distribution of these agents by diverse hypotheses, not only those that the scientific literature presents. Another relevant factor is always to be attentive to the environmental and socioeconomic events that can provide this dispersion.

Multilocus microsatellite typing (MLMT) reveals host-related population structure in Leishmania infantum from northeastern Italy

Background

Visceral leishmaniasis (VL) caused by Leishmania infantum is an ongoing health problem in southern Europe, where dogs are considered the main reservoirs of the disease. Current data point to a northward spread of VL and canine leishmaniasis (CanL) in Italy, with new foci in northern regions previously regarded as non-endemic.

Methodology/Principal findings

Multilocus microsatellite typing (MLMT) was performed to investigate genetic diversity and population structure of L. infantum on 55 samples from infected humans, dogs and sand flies of the E-R region between 2013 and 2017. E-R samples were compared with 10 L. infantum samples from VL cases in other Italian regions (extra E-R) and with 52 strains within the L. donovani complex. Data displayed significant microsatellite polymorphisms with low allelic heterozygosity. Forty-one unique and eight repeated MLMT profiles were recognized among the L. infantum samples from E-R, and ten unique MLMT profiles were assigned to the extra E-R samples. Bayesian analysis assigned E-R samples to two distinct populations, with further sub-structuring within each of them; all CanL samples belonged to one population, genetically related to Mediterranean MON-1 strains, while all but one VL cases as well as the isolate from the sand fly Phlebotomus perfiliewi fell under the second population. Conversely, VL samples from other Italian regions proved to be genetically similar to strains circulating in dogs.

Conclusions/Significance

A peculiar epidemiological situation was observed in northeastern Italy, with the co-circulation of two distinct populations of L. infantum; one population mainly detected in dogs and the other population detected in humans and in a sand fly. While the classical cycle of CanL in Italy fits well into the data obtained for the first population, the population found in infected humans exhibits a different cycle, probably not involving a canine reservoir. This study can contribute to a better understanding of the population structure of L. infantum circulating in northeastern Italy, thus providing useful epidemiologic information for public health authorities.

Visceral leishmaniasis is a sand fly-borne disease caused by protozoan parasites of the genus Leishmania. Leishmania infantum is the only parasitic species circulating in Italy and dogs are considered the main reservoirs of the disease. In this study, 55 L. infantum strains obtained from humans, dogs and sand flies from the Emiliana-Romagna (E-R) region, northeastern Italy, were assessed using multilocus microsatellite typing, a tool applied for population genetic studies. Results were compared with those obtained from 10 samples of visceral leishmaniasis cases occurring in other Italian regions and with 52 strains of the L. donovani complex from other foci of leishmaniasis. Our genetic analysis revealed that canine and human L. infantum strains from the E-R region were separated in two distinct populations; all samples obtained from dogs belonged to one population, while all but one human samples as well as a sand fly sample fell under another population. Samples from patients with visceral leishmaniasis from other Italian regions proved to be genetically similar to strains circulating in dogs. Our findings raise questions on the role of dogs as main reservoirs for human visceral leishmaniasis in the investigated area of northeastern Italy.

Variability of Cutaneous Leishmaniasis Lesions Is Not Associated with Genetic Diversity of Leishmania tropica in Khyber Pakhtunkhwa Province of Pakistan

Leishmania tropica is the causative agent of cutaneous leishmaniasis in Pakistan. Here, intraspecific diversity of L. tropica from northern Pakistan was investigated using multilocus microsatellite typing. Fourteen polymorphic microsatellite markers were typed in 34 recently collected L. tropica isolates from Pakistan along with 158 archival strains of diverse Afro-Eurasian origins. Previously published profiles for 145 strains of L. tropica originating from different regions of Africa, Central Asia, Iran, and Middle East were included for comparison. Six consistently well-supported genetic groups were resolved: 1) Asia, 2) Morroco A, 3) Namibia and Kenya A, 4) Kenya B/Tunisia and Galilee, 5) Morocco B, and 6) Middle East. Strains from northern Pakistan were assigned to Asian cluster except for three that were placed in a geographically distant genetic group; Morocco A. Lesion variability among these Pakistani strains was not associated with specific L. tropica genetic profile. Pakistani strains showed little genetic differentiation from strains of Iraq, Afghanistan, and Syria (F_ST = 0.00-0.06); displayed evidence of modest genetic flow with India (F_ST = 0.14). Furthermore, genetic structuring within these isolates was not geographically defined. Pak-Afghan cluster was in significant linkage disequilibrium (I_A = 1.43), had low genetic diversity, and displayed comparatively higher heterozygosity (F_IS = -0.62). Patterns of genetic diversity observed suggest dominance of a minimally diverse clonal lineage within northern Pakistan. This is surprising as a wide clinical spectrum was observed in patients, suggesting the importance of host and other factors. Further genotyping studies of L. tropica isolates displaying different clinical phenotypes are required to validate this potentially important observation.

Epidemic outbreak of anthroponotic cutaneous leishmaniasis in Kohat District, Khyber Pakhtunkhwa, Pakistan

An epidemiological and molecular study was carried out for the first time in Kohat District of Khyber Pakhtunkhwa (KP) province, Pakistan from April 2015 to May 2016 to determine the prevalence of Cutaneous Leishmaniasis (CL) in local population and Internally Displaced People (IDPs). In 13 different villages, a total of 1359 (out of 26,250 individuals belonging to local population) and 140 (out of 3615 IDPs residing in these villages) cases were recorded and 300 samples were collected. The total prevalence of CL in local population was 5.17% with active lesions and scar prevalence of 3.91% and 1.26% respectively. Similarly a prevalence of 3.86% for CL was recorded in IDPs. Highest number of IDPs having CL active lesions and scars were recorded in villages Sherkot, Surgul, and Jarma and their presence was positively correlated with CL in local population. Age wise prevalence was highest in young children of age group 1-15 years. The microscopic examination showed 64.33% (193/300) positive samples while kinteoplastic PCR showed 84.66% (254/300) positive. For the first time in KP province, 2/784 sandflies trapped from the study villages was found positive for Leishmania by PCR. Restriction Fragment Length Polymorphism of patients and sandflies samples revealed L. tropica as the prevalent Leishmania species in this district. The results of sequencing and RFLP identified L. tropica in Phlebotomus sergenti. This is the first ever report of molecular identification of L. tropica from sandflies of genus P. sergenti in Khyber Pakhtunkhwa province. This data can be helpful for health authorities in finding out new CL foci and to plan effective strategies for the provision of health facilities to poor people of this area.

Leishmania infantum Genetic Diversity and Lutzomyia longipalpis Mitochondrial Haplotypes in Brazil

Leishmania infantum is the etiological agent of visceral leishmaniasis (VL) in the Americas with domestic dogs being its major reservoir hosts. The main VL vector is the sandfly Lutzomyia longipalpis, while other Lutzomyia species may play a role in disease transmission. Although the genetic structure of L. infantum populations has been widely evaluated, only a few studies have addressed this subject coupled to the genetic structure of the respective sandfly vectors. In this study, we analyzed the population structure of L. infantum in three major VL endemic areas in Brazil and associated it with Lutzomyia longipalpis geographic structure.

Genetic Diversity and Population Structure of Leishmania infantum from Southeastern France: Evaluation Using Multi-Locus Microsatellite Typing

In the south of France, Leishmania infantum is responsible for numerous cases of canine leishmaniasis (CanL), sporadic cases of human visceral leishmaniasis (VL) and rare cases of cutaneous and muco-cutaneous leishmaniasis (CL and MCL, respectively). Several endemic areas have been clearly identified in the south of France including the Pyrénées-Orientales, Cévennes (CE), Provence (P), Alpes-Maritimes (AM) and Corsica (CO). Within these endemic areas, the two cities of Nice (AM) and Marseille (P), which are located 150 km apart, and their surroundings, concentrate the greatest number of French autochthonous leishmaniasis cases. In this study, 270 L. infantum isolates from an extended time period (1978–2011) from four endemic areas, AM, P, CE and CO, were assessed using Multi-Locus Microsatellite Typing (MLMT). MLMT revealed a total of 121 different genotypes with 91 unique genotypes and 30 repeated genotypes. Substantial genetic diversity was found with a strong genetic differentiation between the Leishmania populations from AM and P. However, exchanges were observed between these two endemic areas in which it seems that strains spread from AM to P. The genetic differentiations in these areas suggest strong epidemiological structuring. A model-based analysis using STRUCTURE revealed two main populations: population A (consisting of samples primarily from the P and AM endemic areas with MON-1 and non-MON-1 strains) and population B consisting of only MON-1 strains essentially from the AM endemic area. For four patients, we observed several isolates from different biological samples which provided insight into disease relapse and re-infection. These findings shed light on the transmission dynamics of parasites in humans. However, further data are required to confirm this hypothesis based on a limited sample set. This study represents the most extensive population analysis of L. infantum strains using MLMT conducted in France.

In the south of France, the parasite Leishmania infantum is responsible for diseases that primarily affect dogs but can also impact humans. Several endemic areas have been clearly identified in the south of France including the Pyrénées-Orientales, Cévennes (CE), Provence (P), Alpes-Maritimes (AM) and Corsica (CO). In this study, 270 L. infantum isolates from four endemic areas, AM, P, CE and CO, were assessed using Multi-Locus Microsatellite Typing (MLMT), a tool applied for population genetic studies. MLMT revealed a strong genetic differentiation between the Leishmania populations from AM and P with exchanges observed between these two endemic areas. For four patients, the occurrence of disease relapses and re-infections was examined. These findings shed light on the transmission dynamics of parasites in humans. This study represents the most extensive population analysis of L. infantum isolates using MLMT conducted in France.

Comparison of Leishmania killicki (syn. L. tropica) and Leishmania tropica Population Structure in Maghreb by Microsatellite Typing

Leishmania (L.) killicki (syn. L. tropica), which causes cutaneous leishmaniasis in Maghreb, was recently described in this region and identified as a subpopulation of L. tropica. The present genetic analysis was conducted to explore the spatio-temporal distribution of L. killicki (syn. L. tropica) and its transmission dynamics. To better understand the evolution of this parasite, its population structure was then compared with that of L. tropica populations from Morocco. In total 198 samples including 85 L. killicki (syn. L. tropica) (from Tunisia, Algeria and Libya) and 113 L. tropica specimens (all from Morocco) were tested. Theses samples were composed of 168 Leishmania strains isolated from human skin lesions, 27 DNA samples from human skin lesion biopsies, two DNA samples from Ctenodactylus gundi bone marrow and one DNA sample from a Phlebotomus sergenti female. The sample was analyzed by using MultiLocus Enzyme Electrophoresis (MLEE) and MultiLocus Microsatellite Typing (MLMT) approaches. Analysis of the MLMT data support the hypothesis that L. killicki (syn. L. tropica) belongs to the L. tropica complex, despite its strong genetic differentiation, and that it emerged from this taxon by a founder effect. Moreover, it revealed a strong structuring in L. killicki (syn. L. tropica) between Tunisia and Algeria and within the different Tunisian regions, suggesting low dispersion of L. killicki (syn. L. tropica) in space and time. Comparison of the L. tropica (exclusively from Morocco) and L. killicki (syn. L. tropica) population structures revealed distinct genetic organizations, reflecting different epidemiological cycles.

Leishmania killicki (syn. L. tropica) was discovered in 1986. Few studies have been conducted on this parasite exclusively described in Maghreb. Consequently, many elements on its epidemiology, transmission, population structure and dynamics remain unknown.

To better understand the evolution of this parasite, its population structure has been compared with that of L. tropica populations from Morocco using Multilocus Enzyme Electrophoresis (MLEE) and MultiLocus Microsatellite Typing (MLMT) typing. MLMT data support the hypothesis that L. killicki (syn. L. tropica) belongs to the L. tropica complex despite the strong genetic differentiation between them. Despite the probable recent divergence between L. killicki (syn. L. tropica) and L. tropica, they seem to evolve differently. Indeed, L. killicki (syn. L. tropica) appears slightly polymorphic and highly structured in space and time, while L. tropica was genetically heterogeneous, slightly structured geographically and temporally. The different population structures revealed distinct genetic organizations, reflecting different epidemiological cycles. Several parameters could explain these opposite epidemiological and genetic patterns such as ecosystems, vectors and reservoirs.

Multilocus microsatellite typing of Leishmania infantum isolates in monitored Leishmania/HIV coinfected patients

Background

Leishmania infantum is the main etiological agent of both visceral and cutaneous clinical forms of leishmaniasis in the Mediterranean area. Leishmania/HIV coinfection in this area is characterized by a chronic course and frequent recurrences of clinical episodes. The present study using Multilocus Microsatellite Typing (MLMT) analysis, a highly discriminative tool, aimed to genetically characterize L. infantum isolates taken from monitored Leishmania/HIV coinfected patients presenting successive clinical episodes.

Methods

In this study, by the analysis of 20 microsatellite loci, we studied the MLMT profiles of 25 L. infantum isolates from 8 Leishmania/HIV coinfected patients who had experienced several clinical episodes. Two to seven isolates per patient were taken before and after treatment, during clinical and non-clinical episodes, with time intervals of 6 days to 29 months. Genetic diversity, clustering and phenetic analyses were performed.

Results

MLMT enabled us to study the genetic characteristics of the 25 L. infantum isolates, differentiating 18 genotypes, corresponding to a genotypic diversity of 0.72. Fifteen genotypes were unique in the total sample set and only 3 were repeated, 2 of which were detected in different patients. Both clustering and phylogenetic analyses provided insights into the genetic links between the isolates; in five patients isolates showed clear genetic links: either the genotype was exactly the same or only slightly different. In contrast, the isolates of the other three patients were dispersed in different clusters and some could be the result of mixing between populations.

Conclusions

Our data indicated a great MLMT variability between isolates from coinfected patients and no predominant genotype was observed. Despite this, almost all clinical episodes could be interpreted as a relapse rather than a reinfection. The results showed that diverse factors like an intrapatient evolution over time or culture bias could influence the parasite population detected in the patient, making it difficult to differentiate between relapse and reinfection.

The Genetic Relationship between Leishmania aethiopica and Leishmania tropica Revealed by Comparing Microsatellite Profiles

BACKGROUND

Leishmania (Leishmania) aethiopica and L. (L.) tropica cause cutaneous leishmaniases and appear to be related. L. aethiopica is geographically restricted to Ethiopia and Kenya; L. tropica is widely dispersed from the Eastern Mediterranean, through the Middle East into eastern India and in north, east and south Africa. Their phylogenetic inter-relationship is only partially revealed. Some studies indicate a close relationship. Here, eight strains of L. aethiopica were characterized genetically and compared with 156 strains of L. tropica from most of the latter species' geographical range to discern the closeness.

METHODOLOGY/PRINCIPAL FINDINGS

Twelve unlinked microsatellite markers previously used to genotype strains of L. tropica were successfully applied to the eight strains of L. aethiopica and their microsatellite profiles were compared to those of 156 strains of L. tropica from various geographical locations that were isolated from human cases of cutaneous and visceral leishmaniasis, hyraxes and sand fly vectors. All the microsatellite profiles were subjected to various analytical algorithms: Bayesian statistics, distance-based and factorial correspondence analysis, revealing: (i) the species L. aethiopica, though geographically restricted, is genetically very heterogeneous; (ii) the strains of L. aethiopica formed a distinct genetic cluster; and (iii) strains of L. aethiopica are closely related to strains of L. tropica and more so to the African ones, although, by factorial correspondence analysis, clearly separate from them.

CONCLUSIONS/SIGNIFICANCE

The successful application of the 12 microsatellite markers, originally considered species-specific for the species L. tropica, to strains of L. aethiopica confirmed the close relationship between these two species. The Bayesian and distance-based methods clustered the strains of L. aethiopica among African strains of L. tropica, while the factorial correspondence analysis indicated a clear separation between the two species. There was no correlation between microsatellite profiles of the eight strains of L. aethiopica and the type of leishmaniasis, localized (LCL) versus diffuse cutaneous leishmaniasis (DCL), displayed by the human cases.

Multilocus microsatellite typing of Leishmania and clinical applications: a review

Microsatellite markers have been used for Leishmania genetic studies worldwide, giving useful insight into leishmaniasis epidemiology. Understanding the geographic distribution, dynamics of Leishmania populations, and disease epidemiology improved markedly with this tool. In endemic foci, the origins of antimony-resistant strains and multidrug treatment failures were explored with multilocus microsatellite typing (MLMT). High genetic variability was detected but no association between parasite genotypes and drug resistance was established. An association between MLMT profiles and clinical disease manifestations was highlighted in only three studies and this data needs further confirmation. At the individual level, MLMT provided information on relapse and reinfection when multiple leishmaniasis episodes occurred. This information could improve knowledge of epidemiology and guide therapeutic choices for active chronic visceral leishmaniasis, the disease form in some HIV-positive patients.

Screening and characterization of RAPD markers in viscerotropic Leishmania parasites

Visceral leishmaniasis (VL) is mainly due to the Leishmania donovani complex. VL is endemic in many countries worldwide including East Africa and the Mediterranean region where the epidemiology is complex. Taxonomy of these pathogens is under controversy but there is a correlation between their genetic diversity and geographical origin. With steady increase in genome knowledge, RAPD is still a useful approach to identify and characterize novel DNA markers. Our aim was to identify and characterize polymorphic DNA markers in VL Leishmania parasites in diverse geographic regions using RAPD in order to constitute a pool of PCR targets having the potential to differentiate among the VL parasites. 100 different oligonucleotide decamers having arbitrary DNA sequences were screened for reproducible amplification and a selection of 28 was used to amplify DNA from 12 L. donovani, L. archibaldi and L. infantum strains having diverse origins. A total of 155 bands were amplified of which 60.65% appeared polymorphic. 7 out of 28 primers provided monomorphic patterns. Phenetic analysis allowed clustering the parasites according to their geographical origin. Differentially amplified bands were selected, among them 22 RAPD products were successfully cloned and sequenced. Bioinformatic analysis allowed mapping of the markers and sequences and priming sites analysis. This study was complemented with Southern-blot to confirm assignment of markers to the kDNA. The bioinformatic analysis identified 16 nuclear and 3 minicircle markers. Analysis of these markers highlighted polymorphisms at RAPD priming sites with mainly 5′ end transversions, and presence of inter– and intra– taxonomic complex sequence and microsatellites variations; a bias in transitions over transversions and indels between the different sequences compared is observed, which is however less marked between L. infantum and L. donovani. The study delivers a pool of well-documented polymorphic DNA markers, to develop molecular diagnostics assays to characterize and differentiate VL causing agents.

The associations of Leishmania major and Leishmania tropica aspects by focusing their morphological and molecular features on clinical appearances in Khuzestan Province, Iran

Cutaneous leishmaniasis has various phenotypic aspects consisting of polymorphic amastigotes with different genetic ranges. Samples were collected from suspected patients of Khuzestan province. Prepared smears were stained, scaled, and measured using ocular micrometer. The Cyt b, ITS-rDNA, and microsatellite genes of Leishmania were amplified and Leishmania species were identified by molecular analyses. Of 150 examined suspected patients, 102 were identified to Leishmania species (90 L. major, nine L. tropica, and three unidentified). The amastigotes of 90 L. major had regular and different irregular shapes within three clinical lesions with no and/or low genetic diversity. Three haplotypes of Cyt b of L. major were found but no variation was observed using ITS-rDNA gene. Interesting findings were that all nine L. tropica had regular amastigote shapes with more genetic variations, also a patient which had coinfection of L. major, L. tropica, and Crithidia. At least two L. major and L. tropica were identified in suspected patients of the regions. Different irregular amastigotes' shapes of L. major can be explained by various reservoir hosts and vectors. In contrast, more molecular variations in L. tropica could be justified by genetic characters. Unidentified Leishmania could be mixed pathogens or nonpathogens with mammals' Leishmania or Crithidia.

LeishMicrosatDB: open source database of repeat sequences detected in six fully sequenced Leishmania genomes

A Leishmania Microsatellite Database (LeishMicrosatDB) is reported for genome wise mining of microsatellites in six Leishmania species, using in silico techniques. This was created to provide parasitologists a platform to understand the genome characterization, mapping, phylogeny and evolutionary analysis. The present version of the database contains 1,738,669 simple sequence repeats of which 181 s756 repeats are present in compound form. The repeats can be sought in a chromosome using input parameters such as repeat type (mono- hexa), coding status, repeat unit length and repeat sequence motif. The genic repeats have been further hyperlinked with their corresponding locus id, and the database is appended with primer3 plus for primer designing of selected repeats with left and right flanking sequences up to 250 bp. Information on clustering and polymorphic repeats can also be retrieved. This database may also be adopted as a tool to study the relative occurrence and distribution of microsatellites across the parasitic genome. The database can enable a biologist to select markers at desired intervals over the chromosomes, and can be accessed as an open source repository at http://biomedinformri.com/leishmicrosat.

DATABASE URL

http://biomedinformri.com/leishmicrosat.

Non-healing old world cutaneous leishmaniasis caused by L. infantum in a patient from Spain

BACKGROUND

The prevalence of Old World Cutaneous Leishmaniasis in the Mediterranean region is increasing and in Southern Europe often caused by Leishmania infantum. Spontaneous healing of cutaneous leishmaniasis is commonly observed, especially if caused by L. major, whereas L. infantum associated lesions have been reported with longer disease duration and decreased tendency for self-limitation, however, available information is sparse.

CASE PRESENTATION

We report the case of an otherwise healthy woman from Southern Spain who presented with a seven years persistent, non-healing, painless, central ulcerated, nodular cutaneous lesion with a diameter of 2 cm of the forearm. Cutaneous leishmaniasis was diagnosed by smear and histology, showing large amounts of leishmania amastigotes in subepidermal histiocytes and extensive lymphocyte and plasma cell inflammation. L. infantum as the causative pathogen was confirmed by restriction fragment length polymorphism and microsatellite-PCR. Systemic or visceral involvement was excluded by negative leishmania serology and clinical presentation, relevant concomitant diseases or immunosuppression were excluded including quantification of immunoglobulin levels and lymphocyte phenotyping. Topical and systemic anti-infectious treatment options, often limited in terms of efficacy, tolerability and long lasting treatment duration, were considered. Treatment was successfully performed by surgical extraction in local anaesthesia only.

CONCLUSION

To our knowledge this is the longest reported duration of a L. infantum associated cutaneous leishmaniasis indicating a potential long lasting natural evolution of the disease in an otherwise healthy and immunocompetent patient, however, high parasite density may have reflected a lack of a L. infantum specific immune response. Complete surgical extraction can be successfully performed as treatment.

Multilocus microsatellite typing reveals a genetic relationship but, also, genetic differences between Indian strains of Leishmania tropica causing cutaneous leishmaniasis and those causing visceral leishmaniasis

BACKGROUND

Leishmaniases are divided into cutaneous (CL) and visceral leishmaniasis (VL). In the Old World, CL is caused by Leishmania (L.) major, L. tropica and L. aethiopica. L. tropica can also visceralize and cause VL. In India, the large epidemics of VL are caused by L. donovani and cases of CL are caused by L. major and L. tropica. However, strains of L. tropica have also been isolated from Indian cases of VL.This study was done to see if Indian strains of L. tropica isolated from human cases of CL are genetically identical to or different from Indian strains of L. tropica isolated from human cases of VL and to see if any genetic differences found correlated with clinical outcome presenting as either CL or VL.

METHODS

Multilocus microsatellite typing (MLMT), employing 12 independent genetic markers specific to L. tropica, was used to characterize and identify eight strains of L. tropica isolated from human cases of CL examined in clinics in Bikaner City, Rajasthan State, north-west India. Their microsatellite profiles were compared to those of 156 previously typed strains of L. tropica from various geographical locations that were isolated from human cases of CL and VL, hyraxes and sand fly vectors.

RESULTS

Bayesian, distance-based and factorial correspondence analyses revealed two confirmed populations: India/Asia and Israel/Palestine that subdivided, respectively, into two and three subpopulations. A third population, Africa/Galilee, as proposed by Bayesian analysis was not supported by the other applied methods. The strains of L. tropica from Bikaner isolated from human cases of CL fell into one of the subpopulations in the population India/Asia together with strains from other Asian foci. Indian strains isolated from human cases of VL fell into the same sub-population but were not genetically identical to the Bikaner strains of L. tropica.

CONCLUSIONS

It seems that the genetic diversity encountered between the two groups of Indian strains is mainly owing to their geographical origins rather than their different times of isolation. Also, the genetic differences seen between the dermatotropic and viscerotropic strains might be connected with the difference in pathogenicity.

Multilocus microsatellite signature and identification of specific molecular markers for Leishmania aethiopica

BACKGROUND

Leishmaniasis is a clinically and epidemiologically diverse zoonotic disease caused by obligatory, intracellular protozoan parasites of the genus Leishmania. Cutaneous leishmaniasis is the most widely distributed form of the disease characterized by skin lesions. Leishmania aethiopica is considered the predominant etiological agent in Ethiopia. The current study was aimed at developing multilocus microsatellite markers for L. aethiopica isolated from human cutaneous leishmaniasis patients in Ethiopia.

RESULTS

L. aethiopica parasites for the study were obtained from Ethiopia and laboratory analysis was conducted at The Ohio State University. DNA was extracted from cultured parasites and an internal transcribed spacer located at the ribosomal region of L. aethiopica genomic DNA was PCR amplified for species identification. Microsatellite markers were identified using multilocus microsatellite typing. We generated an enriched genomic library, and using Primer3 software, designed PCR primers to amplify sequences flanking the detected microsatellites. Subsequent screening of the amplified markers for length variations was performed by gel electrophoresis.Using a variety of molecular methods, 22 different microsatellite markers were identified and tested for typing L. aethiopica strains using a number of clinical isolates. Of the 22 markers tested, 5 were polymorphic and showed distinctive multilocus genotypes, classifying them into four clusters. One marker was found to be specific for L. aethiopica, discriminating it from other species of Leishmania.

CONCLUSION

Multilocus microsatellite typing using the markers developed in this study could be useful for epidemiological and population genetic studies of strains of L. aethiopica in order to investigate the structure and dynamics of the corresponding natural foci. It could also help to answer specific clinical questions, such as the occurrence of local and diffuse lesions, strain correlates of parasite persistence after subclinical infection and lesion comparisons from patients suffering from L. aethiopica infections.

Spatial distribution and population genetics of Leishmania infantum genotypes in São Paulo State, Brazil, employing multilocus microsatellite typing directly in dog infected tissues

This study investigated the genetic characteristics of Leishmania infantum samples from São Paulo (SP) State, Brazil in order to collaborate with information about the possible origins of the parasites, as well as, the introduction and spread of visceral leishmaniasis in this Brazilian State. Multilocus microsatellite typing (MLMT) was performed using a set of 17 microsatellite markers. DNA was extracted from 250 samples collected from dogs diagnosed with visceral leishmaniasis and 112 (45%) were genotyped: 67 from the northwest region (NWSP), and 29 from the southeast region (SESP) of SP. The results were correlated with other 16 samples from Mato Grosso do Sul State (MS) (which borders NWSP). Although, a small portion of samples was genotyped, it was possible to genotype multiple loci using small amounts of Leishmania DNA extracted directly from dog tissues. Despite the fact that MLMT analysis defined 33 different genotypes, a low polymorphism was detected within the parasites studied with 10 polymorphic loci. There are two main genetic clusters circulating in SP with strong genetic differentiation, one (POP-A) is composed by samples from SESP and NWSP and presented a weak signal of geographical substructure. The other, belongs to the same cluster found in the state of MS (POP-B), which was the main one. The majority (93.75%) of MS parasite genotypes belonged to POP-B, with just one sample (6.25%) grouped in POP-A. POP-B also comprised 10.34% of SESP and 26.87% of NWSP samples. Besides one sample from MS, POP-A is composed by 73.13% of NWSP and 89.66% of SESP samples. The MLMT analysis supported the idea of canine visceral leishmaniasis being introduced in the Northwest region of SP State by the traffic of humans and dogs from MS. In the southeast region of SP occurred an introduction of a new L. infantum genetic cluster. Probably the transmission was spread by traffic of infected dogs from other Brazilian regions, or by introduction of imported dogs from other countries. All these data together contributed to the detection of the genetic profile of L. infantum population in SP State.

Parasitic genotypes appear to differ in leishmaniasis patients compared with asymptomatic related carriers

For numerous infectious diseases affecting humans, clinical manifestations range from asymptomatic forms to severe pathologies. The originality of this study was its focus on asymptomatic carriers of Leishmania infantum in southern France. The fundamental interest in these asymptomatic carriers is that they can be a reservoir of potentially pathogenic microorganisms. It remains to be established whether the parasitic genomes from asymptomatic carriers differ from those of patients. Multilocus microsatellite typing was used to investigate the genetic variation among 36 French strains of L. infantum. Nine Leishmania strains isolated from blood donors (asymptomatic carriers) were compared with 27 strains of L. infantum belonging to zymodemes, MON-1, -33 and -183. These strains were isolated from HIV positive or negative patients with visceral leishmaniasis, cutaneous leishmaniasis, from canine leishmaniasis or from phlebotomine sandflies. Multilocus microsatellite typing data generated using 33 loci were analyzed by a Bayesian model-based clustering algorithm and construction of a phylogenetic tree based on genetic distances. Both analyses structured the MON-1 sample into two main clusters. Furthermore, genetic analysis demonstrated that these nine asymptomatic carrier strains are divided into two clusters grouped with the MON-1 strains. One cluster with seven strains is related to, but different from, human symptomatic strains from the Alpes-Maritimes region whereas the other cluster has the two remaining strains together with canine leishmaniasis strains as well as one strain from a visceral leishmaniasis patient. Genetic diversity among asymptomatic carrier was very weak since the nine Leishmania strains belong to only two genotypes. Genetic differentiations were evidenced between asymptomatic carrier strains and non-asymptomatic carrier strains and especially between asymptomatic carrier and HIV+ populations, although these findings require confirmation with a larger sample size. We believe that our data explore for the first time, the genetic diversity among L. infantum from asymptomatic human carriers and reveal a weak polymorphism compared with Leishmania parasites isolated from human patients.

Multifaceted population structure and reproductive strategy in Leishmania donovani complex in one Sudanese village

Leishmania species of the subgenus Leishmania and especially L. donovani are responsible for a large proportion of visceral leishmaniasis cases. The debate on the mode of reproduction and population structure of Leishmania parasites remains opened. It has been suggested that Leishmania parasites could alternate different modes of reproduction, more particularly clonality and frequent recombinations either between related individuals (endogamy) or between unrelated individuals (outcrossing) within strongly isolated subpopulations. To determine whether this assumption is generalized to other species, a population genetics analysis within Leishmania donovani complex strains was conducted within a single village. The results suggest that a mixed-mating reproduction system exists, an important heterogeneity of subsamples and the coexistence of several genetic entities in Sudanese L. donovani. Indeed, results showed significant genetic differentiation between the three taxa (L. donovani, L. infantum and L. archibaldi) and between the human or canine strains of such taxa, suggesting that there may be different imbricated transmission cycles involving either dogs or humans. Results also are in agreement with an almost strict specificity of L. donovani stricto sensu to human hosts. This empirical study demonstrates the complexity of population structure in the genus Leishmania and the need to pursue such kind of analyses at the smallest possible spatio-temporal and ecological scales.

Leishmaniases are a serious public health problem, especially in developing countries, caused by Leishmania parasites and transmitted by sandfly bites. More information is needed on the population biology of these pathogens for diagnostic and epidemiological inquiries and for drug and vaccine elaboration. For studies dealing with the population genetics, exploring the genetic patterns of such organisms at microgeographic scales is fundamental. In this context, we made a population genetic study, based on 20 microsatellite loci, on 61 strains of Leishmania donovani complex collected in a Sudanese village, Babar El Fugara, during the epidemic of 1996–2000. Results showed that considering the whole sample as a single population was not adequate because of the coexistence of several genetic entities and a genetic differentiation between the human or canine strains. In addition, our findings suggested that clonality may have a strong impact on the L. donovani complex, unlike other Leishmania species. This study demonstrates the need to pursue population genetics studies in Leishmania species from sampling designs that control maximum possible confounding factors and to elaborate such kinds of analyses at the smallest possible spatio-temporal and ecological scales.

Multilocus genotyping reveals a polyphyletic pattern among naturally antimony-resistant Leishmania braziliensis isolates from Peru

In order to understand the epidemiological dynamics of antimonial (Sb(V)) resistance in zoonotic tegumentary leishmaniasis and its link with treatment outcome, we analyzed the population structure of 24 Peruvian Leishmania braziliensis clinical isolates with known in vitro antimony susceptibility and clinical phenotype by multilocus microsatellite typing (14 microsatellite loci). The genetic variability in the Peruvian isolates was high and the multilocus genotypes were strongly differentiated from each other. No correlation was found between the genotypes and in vitro drug susceptibility or clinical treatment outcome. The finding of a polyphyletic pattern among the Sb(V)-resistant L. braziliensis might be explained by (i) independent events of drug resistance emergence, (ii) sexual recombination and/or (iii) other phenomena mimicking recombination signals. Interestingly, the polyphyletic pattern observed here is very similar to the one we observed in the anthroponotic Leishmania donovani (Laurent et al., 2007), hereby questioning the role of transmission and/or chemotherapeutic drug pressure in the observed population structure.

Multilocus microsatellite typing shows three different genetic clusters of Leishmania major in Iran

Ten polymorphic microsatellite markers were used to analyse 25 strains of Leishmania major collected from cutaneous leishmaniasis cases in different endemic areas in Iran. Nine of the markers were polymorphic, revealing 21 different genotypes. The data displayed significant microsatellite polymorphism with rare allelic heterozygosity. Bayesian statistic and distance based analyses identified three genetic clusters among the 25 strains analysed. Cluster I represented mainly strains isolated in the west and south-west of Iran, with the exception of four strains originating from central Iran. Cluster II comprised strains from the central part of Iran, and cluster III included only strains from north Iran. The geographical distribution of L. major in Iran was supported by comparing the microsatellite profiles of the 25 Iranian strains to those of 105 strains collected in 19 Asian and African countries. The Iranian clusters I and II were separated from three previously described populations comprising strains from Africa, the Middle East and Central Asia whereas cluster III grouped together with the Central Asian population. The considerable genetic variability of L. major might be related to the existence of different populations of Phlebotomus papatasi and/or to differences in reservoir host abundance in different parts of Iran.

Molecular approaches for a better understanding of the epidemiology and population genetics ofLeishmania

Molecular approaches are being used increasingly for epidemiological studies of visceral and cutaneous leishmaniases. Several molecular markers resolving genetic differences betweenLeishmaniaparasites at species and strain levels have been developed to address key epidemiological and population genetic questions. The current gold standard, multilocus enzyme typing (MLEE), needs cultured parasites and lacks discriminatory power. PCR assays identifying species directly with clinical samples have proven useful in numerous field studies. Multilocus sequence typing (MLST) is potentially the most powerful phylogenetic approach and will, most probably, replace MLEE in the future. Multilocus microsatellite typing (MLMT) is able to discriminate below the zymodeme level and seems to be the best candidate for becoming the gold standard for distinction of strains. Population genetic studies by MLMT revealed geographical and hierarchic population structure inL. tropica, L. majorand theL. donovanicomplex. The existence of hybrids and gene flow betweenLeishmaniapopulations suggests that sexual recombination is more frequent than previously thought. However, typing and analytical tools need to be further improved. Accessible databases should be created and sustained for integrating data obtained by different researchers. This would allow for global analyses and help to avoid biases in analyses due to small sample sizes.

Development and evaluation of different PCR-based typing methods for discrimination ofLeishmania donovaniisolates from Nepal

Introduction.Leishmania donovani, the causative agent of visceral leishmaniasis in the Indian subcontinent, has been reported to be genetically homogeneous. In order to support ongoing initiatives to eliminate the disease, highly discriminative tools are required for documenting the parasite population and dynamics.Methods.Thirty-four clinical isolates ofL.donovanifrom Nepal were analysed on the basis of size and restriction endonuclease polymorphisms of PCR amplicons from kinetoplast minicircle DNA, 5 nuclear microsatellites, and nuclear loci encoding glycoprotein 63, cysteine proteinase B, and hydrophilic acylated surface protein B. We present and validate a procedure allowing standardized analysis of kDNA fingerprint patterns.Results.Our results show that parasites are best discriminated on the basis of kinetoplast minicircle DNA (14 genotypes) and 1 microsatellite defining 7 genotypes, while the remaining markers discriminated 2 groups or were monomorphic. Combination of all nuclear markers revealed 8 genotypes, while extension with kDNA data yielded 18 genotypes.Conclusion.We present tools that allow discrimination of closely relatedL.donovanistrains circulating in the Terai region of Nepal. These can be used to study the micro-epidemiology of parasite populations, determine the geographical origin of infections, distinguish relapses from re-infection, and monitor the spread of particular variants.

Development of a multilocus microsatellite typing approach for discriminating strains of Leishmania (Viannia) species

A multilocus microsatellite typing (MLMT) approach based on the analysis of 15 independent loci has been developed for the discrimination of strains belonging to different Viannia species. Thirteen microsatellite loci were isolated de novo from microsatellite-enriched libraries for both Leishmania braziliensis and L. guyanensis. Two previously identified markers, AC01 and AC16, were modified and added to our marker set. Markers were designed to contain simple dinucleotide repeats flanked by the minimal possible number of nucleotides in order to allow variations in repeat numbers to be scored as size variations of the PCR products. The 15 markers in total were amplified for almost all of the strains of Viannia tested; one marker did not amplify from the two L. peruviana strains included in the study. When 30 strains of L. braziliensis, 21 strains of L. guyanensis, and 2 strains of L. peruviana were tested for polymorphisms, all strains except two strains of L. guyanensis had individual MLMT types. Distance-based analysis identified three main clusters. All strains except one strain of L. guyanensis grouped together. Two clusters consisted of strains of L. braziliensis according to their geographical origins. The two strains of L. peruviana grouped together with strains of L. braziliensis from Peru and the adjacent Brazilian state of Acre. MLMT has proven capable of individualizing strains even from the same areas of endemicity and of detecting genetic structures at different levels. MLMT is thus applicable for epidemiological and population genetic studies of strains within the subgenus Viannia.

Multilocus microsatellite typing (MLMT) reveals genetic homogeneity of Leishmania donovani strains in the Indian subcontinent

In this population genetic study of Leishmania donovani parasites in the Indian subcontinent, 132 isolates obtained from patients in Bangladesh, India, Nepal and Sri Lanka suffering from Kala-azar (100), post-Kala-azar dermal leishmaniasis (PKDL) (25) and cutaneous leishmaniasis (CL) (2), and from 5 patients whose clinical patterns were not defined, were analysed by using 15 hyper-variable microsatellite loci. Multilocus microsatellite typing (MLMT) data were analysed by using a Bayesian model-based clustering algorithm and constructing phylogenic tree based on genetic distances. In total, 125 strains from Bangladesh, Bihar (India) and Nepal formed a very homogeneous population regardless of geographical origin, clinical manifestation, and whether they presented in vitro or in vivo susceptibility to antimonial drugs. Identical multilocus microsatellite profiles were found for 108 strains, other strains differed in only one marker. Considerably different microsatellite profiles were identified for three Indian strains most closely related to L. donovani from Kenya, and for four strains from Indian and Sri Lankan CL cases. The circulation of a single homogeneous population of L. donovani in Bihar (India), Bangladesh and Nepal is, most probably, related to the epidemic spread of visceral leishmaniasis in this area.

An integrated pipeline for the development of novel panels of mapped microsatellite markers for Leishmania donovani complex, Leishmania braziliensis and Leishmania major

A panel of microsatellites mapped to the Leishmania genome might make it possible to find associations between specific loci and phenotypic traits. To identify such loci, a Perl programme was written that scans the sequence of a genome and writes all loci containing microsatellites to a MySQL database. The programme was applied to the sequences of the L. braziliensis, L. infantum and L. major genomes. The database is publicly available over the internet: http://www.genomics.liv.ac.uk/tryps/resources.html 'Microsatellite Locus Extractor', and allows the selection of mapped microsatellites that meet user-defined criteria from a specified region of the selected genome. The website also incorporates a primer design pipeline that will design primers to amplify the selected loci. Using this pipeline 12 out of 17 primer sets designed against the L. infantum genome generated polymorphic PCR products. A tailed primer protocol was used to label all microsatellite primers with a single set of labelled primers. To avoid the culture of parasites prior to genotyping, sets of nested PCR primers were developed to amplify parasite DNA eluted from microscope slides. The limit of detection was approximately 1.6 parasite equivalents. However, only 6/56 DNA from slides stored at ambient temperature for over 6 months gave positive PCR results.

Leishmania and the leishmaniases: a parasite genetic update and advances in taxonomy, epidemiology and pathogenicity in humans

Leishmaniases remain a major public health problem today despite the vast amount of research conducted on Leishmania pathogens. The biological model is genetically and ecologically complex. This paper explores the advances in Leishmania genetics and reviews population structure, taxonomy, epidemiology and pathogenicity. Current knowledge of Leishmania genetics is placed in the context of natural populations. Various studies have described a clonal structure for Leishmania but recombination, pseudo-recombination and other genetic processes have also been reported. The impact of these different models on epidemiology and the medical aspects of leishmaniases is considered from an evolutionary point of view. The role of these parasites in the expression of pathogenicity in humans is also explored. It is important to ascertain whether genetic variability of the parasites is related to the different clinical expressions of leishmaniasis. The review aims to put current knowledge of Leishmania and the leishmaniases in perspective and to underline priority questions which 'leishmaniacs' must answer in various domains: epidemiology, population genetics, taxonomy and pathogenicity. It concludes by presenting a number of feasible ways of responding to these questions.

The Leishmania donovani complex: Genotypes of five metabolic enzymes (ICD, ME, MPI, G6PDH, and FH), new targets for multilocus sequence typing

Flagellates of the Leishmania donovani complex are causative agents of human cutaneous and visceral leishmaniasis. The complex is comprised of L. donovani, Leishmania infantum and Leishmania archibaldi, although the latter is not now considered to be a valid species. Morphological distinction of Leishmania species is impractical, so biochemical, immunological and DNA-based criteria were introduced. Multilocus enzyme electrophoresis (MLEE) is the present gold standard. We have sequenced the genes encoding five metabolic enzymes used for MLEE, both to resolve the DNA diversity underlying isoenzyme mobility differences and to explore the potential of these targets for higher resolution PCR-based multilocus sequence typing. The genes sequenced were isocitrate dehydrogenase, malic enzyme, mannose phosphate isomerase, glucose-6-phosphate dehydrogenase, and fumarate hydratase, for 17 strains of L. infantum, seven strains of L. donovani, and three strains of L. archibaldi. Protein mobilities predicted from amino acid sequences did not always accord precisely with reported MLEE profiles. A high number of heterozygous sites was detected. Heterozygosity was particularly frequent in some strains and indirectly supported the presence of genetic exchange in Leishmania. Phylogenetic analysis of a concatenated alignment based on a total of 263 kb protein-coding sequences showed strong correlation of genotype with geographical origin. Europe and Africa appear to represent independent evolutionary centres.

Transmembrane molecules for phylogenetic analyses of pathogenic protists: Leishmania-specific informative sites in hydrophilic loops of trans- endoplasmic reticulum N-acetylglucosamine-1-phosphate transferase

A sequence database was created for the Leishmania N-acetylglucosamine-1-phosphate transferase (nagt) gene from 193 independent isolates. PCR products of this single-copy gene were analyzed for restriction fragment length polymorphism based on seven nagt sequences initially available. We subsequently sequenced 77 samples and found 19 new variants (genotypes). Alignment of all 26 nagt sequences is gap free, except for a single codon addition or deletion. Phylogenetic analyses of the sequences allow grouping the isolates into three subgenera, each consisting of recognized species complexes, i.e., subgenus Leishmania (L. amazonensis-L. mexicana, L. donovani-L. infantum, L. tropica, L. major, and L. turanica-L. gerbilli), subgenus Viannia (L. braziliensis, L. panamensis), and one unclassified (L. enriettii) species. This hierarchy of grouping is also supported by sequence analyses of selected samples for additional single-copy genes present on different chromosomes. Intraspecies divergence of nagt varies considerably with different species complexes. Interestingly, species complexes with less subspecies divergence are more widely distributed than those that are more divergent. The relevance of this to Leishmania evolutionary adaptation is discussed. Heterozygosity of subspecies variants contributes to intraspecies diversity, which is prominent in L. tropica but not in L. donovani-L. infantum. This disparity is thought to result from the genetic recombination of the respective species at different times as a rare event during their predominantly clonal evolution. Phylogenetically useful sites of nagt are restricted largely to several extended hydrophilic loops predicted from hypothetical models of Leishmania NAGT as an endoplasmic reticulum transmembrane protein. In silico analyses of nagt from fungi and other protozoa further illustrate the potential value of this and, perhaps, other similar transmembrane molecules for phylogenetic analyses of single-cell eukaryotes.

Multilocus microsatellite typing as a new tool for discrimination of Leishmania infantum MON-1 strains

The Leishmania donovani complex, which consists of L. donovani, L. infantum-L. chagasi, and L. archibaldi, is responsible for visceral manifestations of leishmaniasis. Multilocus enzyme electrophoresis is the standard method for the characterization and identification of strains of Leishmania. For L. infantum, the predominance of zymodeme MON-1 significantly reduces the discriminative power of this approach. In the present study, we developed 17 independent polymorphic microsatellite markers for the typing of strains of L. infantum, with the main emphasis on zymodeme MON-1. The discriminative powers of 11 markers selected from among these markers were tested by using a panel of 63 isolates of the L. donovani complex. Unique multilocus genotypes were observed for the strains analyzed, with only three exceptions. Model-based and distance-based analyses of the data set showed comparable results. It was possible to discriminate between L. donovani sensu stricto, a non-MON-1 group of L. infantum isolates, and a MON-1 group of L. infantum isolates. Within MON-1, three clusters with geographical correlations became apparent. The frequency of heterozygosity in the alleles analyzed varied extremely between the different groups of isolates. The main clusters described are not consistent with species definitions based on isoenzyme analysis but confirm the results of former PCR-based investigations.

An Integrated Morphological and Molecular Approach to a New Species Description in the Trypanosomatidae: the Case of Leptomonas podlipaevi n. sp., a Parasite of Boisea rubrolineata (Hemiptera: Rhopalidae)

Leptomonas podlipaevi n. sp., a new trypanosomatid species, is described herein based on light microscopic, ultrastructural, and molecular phylogenetic data. The organism is pleomorphic both in host and culture, with two predominant forms-a typical promastigote with a long flagellum and a shorter promastigote with a small or barely extending flagellum. Several spliced leader RNA repeat sequences obtained from the original cultures and the clonal lines representing two types of cells were all nearly identical. These sequences formed a tight cluster in the neighbor-joining tree well separated from other trypanosomatid species. Glyceraldehyde phosphate dehydrogenase gene sequences were determined for L. podlipaevi and 10 previously described trypanosomatid species. Molecular phylogenetic analysis has demonstrated that the new species is most closely related to Leptomonas seymouri and Leptomonas pyrrhocoris. The analysis has also highlighted the polyphyly of the genus Leptomonas.

Microsatellite analysis reveals genetic structure of Leishmania tropica

The current rapid spread of leishmaniases caused by Leishmania tropica and the complexity of its clinical spectrum call for this parasite's epidemiological and evolutionary investigation. Evaluation of its population structure by isoenzyme electrophoresis and previous molecular biological analysis has proved difficult. In this study, we used 21 microsatellite loci to type 117 strains from different African and Asian locations. Eighty-one different genotypes were found. A genetic bottleneck supported by a gradient in the number of alleles and consistent with the geographical structure of the Middle East suggests an African origin of this species. A Bayesian approach identified 10 genetic clusters that correlated predominantly with geographical origin. The strains in the 'Asia' cluster form a very heterogeneous sub-population, with a varied but inter-related genotype that is geographically very widely dispersed and consistent with anthroponotic transmission of the parasite. The other nine clusters were more homogenous. The propagation of L. tropica appears to be predominantly clonal. In Africa and the Middle East, anthroponotic and zoonotic systems of distribution may contribute to the development of overlapping, genetically distinct populations of L. tropica.

Leishmania tropica (Kinetoplastida: Trypanosomatidae)--a perplexing parasite

Leishmania tropica is one of the causative agents of cutaneous leishmaniasis (CL), a disfiguring parasitic disease that recently was found to be viscerotropic. In urban areas it is transmitted from infected individuals by the bite of phlebotomine sand flies to naïve persons (anthroponotic CL). In rural areas animals are thought to be the reservoir, but the full life cycle is still under investigation (zoonotic CL). For many years L. tropica was either confused or merely grouped with L. major while Phlebotomus sergenti was the only proven vector. In recent years new foci have erupted, but few have been investigated. This review describes some of the history, recent findings, epidemiology, potential vectors, and the search for possible reservoir hosts besides man.