Characterization of Leishmania (Leishmania) waltoni n.sp. (Kinetoplastida: Trypanosomatidae), the Parasite Responsible for Diffuse Cutaneous Leishmaniasis in the Dominican Republic

A review on potential therapeutic targets for the treatment of leishmaniasis

Leishmania, a protozoan parasite, is responsible for the occurrence of leishmaniasis, a disease that is prevalent in tropical regions. Visceral Leishmaniasis (VL), also known as kala-azar in Asian countries, is one of the most significant forms of VL, along with Cutaneous Leishmaniasis (CL) and Mucocutaneous Leishmaniasis (ML). Management of this condition typically entails the use of chemotherapy as the sole therapeutic option. The current treatments for leishmaniasis present several drawbacks, including a multitude of side effects, prolonged treatment duration, disparate efficacy across different regions, and the emergence of resistance. To address this urgent need, it is imperative to identify alternative treatments that are both safer and more effective. The identification of appropriate pharmacological targets in conjunction with biological pathways constitutes the initial stage of drug discovery. In this review, we have addressed the key metabolic pathways that represent potential pharmacological targets as well as prominent treatment options for leishmaniasis.

Laboratory diagnostics for human Leishmania infections: a polymerase chain reaction-focussed review of detection and identification methods

Leishmania infections span a range of clinical syndromes and impact humans from many geographic foci, but primarily the world's poorest regions. Transmitted by the bite of a female sand fly, Leishmania infections are increasing with human movement (due to international travel and war) as well as with shifts in vector habitat (due to climate change). Accurate diagnosis of the 20 or so species of Leishmania that infect humans can lead to the successful treatment of infections and, importantly, their prevention through modelling and intervention programs. A multitude of laboratory techniques for the detection of Leishmania have been developed over the past few decades, and although many have drawbacks, several of them show promise, particularly molecular methods like polymerase chain reaction. This review provides an overview of the methods available to diagnostic laboratories, from traditional techniques to the now-preferred molecular techniques, with an emphasis on polymerase chain reaction-based detection and typing methods.

Species Diversity, Habitat Distribution, and Blood Meal Analysis of Haematophagous Dipterans Collected by CDC-UV Light Traps in the Dominican Republic

Haematophagous insects cause major economic losses by both direct damage and the transmission of pathogens. However, the biting Diptera species in the Caribbean region have been poorly documented. During 2021, CDC downdraft suction traps with UV light were employed to assess both the species occurrence and blood meal sources across three different habitats in the Dominican Republic. Eighteen species of mosquitoes (n = 274), six species of Culicoides (n = 803), two black fly species (n = 2), and one species of muscid fly (n = 25) were identified at species-level by morphology and/or molecular phylogenetic approaches based on the mitochondrial cytochrome c oxidase subunit 1 (COI). Engorged mosquito (n = 5) and Culicoides (n = 28) females showed host preferences derived exclusively from mammals (cows and pigs), except Culex species containing the blood of chickens. Our study provides new records of the Diptera Dominican catalogue (Culex salinarius for the Greater Antilles, Culicoides jamaicensis for Hispaniola, and Culicoides haitiensis and Culicoides borinqueni for the Dominican Republic), the first available COI DNA sequences of different Diptera in the GenBank, some pictures of diagnostic features of closely related specimens, spatial distribution across the habitats studied, and new insights on their feeding preferences in the Caribbean region.

Surveillance of leishmaniasis cases from 15 European centres, 2014 to 2019: a retrospective analysis

Background

Surveillance of human leishmaniasis in Europe is mostly limited to country-specific information from autochthonous infections in the southern part. As at the end of 2021, no integrated analysis has been performed for cases seen across centres in different European countries.

Aim

To provide a broad perspective on autochthonous and imported leishmaniasis cases in endemic and non-endemic countries in Europe.

Methods

We retrospectively collected records from cutaneous, mucosal and visceral leishmaniasis cases diagnosed in 15 centres between 2014 and 2019. Centres were located in 11 countries: Belgium, France, Germany, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Data on country of infection, reason for travelling, infecting species, age and sex were analysed.

Results

We obtained diagnostic files from 1,142 cases, of which 76%, 21% and 3% had cutaneous, visceral, and mucosal disease, respectively. Of these, 68% were men, and 32% women, with the median age of 37 years (range: 0–90) at diagnosis. Visceral leishmaniasis was mainly acquired in Europe (88%; 167/190), while cutaneous leishmaniasis was primarily imported from outside Europe (77%; 575/749). Sixty-two percent of cutaneous leishmaniasis cases from outside Europe were from the Old World, and 38% from the New World. Geographic species distribution largely confirmed known epidemiology, with notable exceptions.

Conclusions

Our study confirms previous reports regarding geographic origin, species, and traveller subgroups importing leishmaniasis into Europe. We demonstrate the importance of pooling species typing data from many centres, even from areas where the aetiology is presumably known, to monitor changing epidemiology.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Leishmania spp. and leishmaniasis on the Caribbean islands

The kinetoplastid protozoan Leishmania spp. cause leishmaniasis, which clinically exhibit mainly as a cutaneous, mucocutanous or visceral form depending upon the parasite species in humans. The disease is widespread geographically, leading to 20 000 annual deaths. Here, leishmaniases in both humans and animals, reservoirs and sand fly vectors on the Caribbean islands are reviewed. Autochthonous human infections by Leishmania spp. were found in the Dominican Republic, Guadeloupe and Martinique as well as Trinidad and Tobago; canine infections were found in St. Kitts and Grenada; and equine infections were found in Puerto Rico. Imported human cases have been reported in Cuba. The parasites included Leishmania amazonensis, Le. martiniquensis and Le. waltoni. Possible sand fly vectors included Lutzomyia christophei, Lu. atroclavatus, Lu. cayennensis and Lu. flaviscutellata as well as Phlebotomus guadeloupensis. Reservoirs included rats, rice rats and mouse opossum. An updated study is warranted for the control and elimination of leishmaniasis in the region because some of the data are four decades old.

What makes mucosal and anergic diffuse cutaneous leishmaniases so clinically and immunopathogically different? A review in Brazil

American cutaneous leishmaniasis (ACL) is a parasitic protozoan disease caused by different Leishmania species widely distributed throughout Latin America. Fifteen Leishmania species belonging to the subgenera Viannia, Leishmania and Mundinia are known to cause ACL. Seven of these species are found in Brazil, of which Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis have the highest potential to cause mucosal (ML) and anergic diffuse cutaneous leishmaniasis (DCL), respectively, the most severe forms of ACL. The clinical and immunopathological differences between these two clinical forms are reviewed here, taking into account their different physiopathogenic mechanisms of dissemination from cutaneous lesions to mucosal tissues in the case of ML and to almost all body surfaces in the case of anergic DCL. We also discuss some immunopathogenic mechanisms of species-specific Leishmania antigens (from the subgenera Viannia and Leishmania) that are most likely associated with the clinical and immunopathological differences between ML and anergic DCL. Those discussions emphasize the pivotal importance of some surface antigens of L. (V.) braziliensis and L. (L.) amazonensis, such as lipophosphoglycan, phosphatidylserine and CD200 (an immunoregulatory molecule that inhibits macrophage activation), that have been shown to exert strong influences on the clinical and immunopathological differences between ML and anergic DCL.

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.

Autochthonous cutaneous leishmaniasis in urban domestic animals (Felis catus / Canis lupus familiaris) from central-western Venezuela

Leishmaniasis is a zoonotic disease caused by intracellular protozoa of the Leishmania genus that are spread and transmitted by sandflies. Natural infection and clinical disease in domestic cats and dogs appear to be rare or perhaps largely under-reported in endemic areas. However, previous reports on infected domestic animals usually implicate the same Leishmania species that affect humans in tropical and subtropical areas of the world suggesting a potential role for zoonotic transmission. In the present study we assessed a representative sample of cats and dogs from endemic urban / suburban areas of Lara state in central western Venezuela. In both dogs and cats, cutaneous disease exhibits a spectrum of manifestations that range from single papules or nodules, which may evolve into ulcerative, plaque-like or scaly lesions. Cytochrome b (cyt b) PCR gene sequence analysis revealed L. mexicana as the causative agent in all cases, including two human cases proceeding from the same study area at the same time the study was carried out. In order to improve our understanding on feline/canine infection with Leishmania mexicana, and address potential zoonotic concerns it is necessary to characterize its enzootic reservoirs and vectors as well as the possible anthropophilic players linking to the peridomestic and domestic cycles.

Phylogenetic Studies

Phylogenetics is an important component of the systems biology approach. Knowledge about evolution of the genus Leishmania is essential to understand various aspects of basic biology of these parasites, such as parasite-host or parasite-vector relationships, biogeography, or epidemiology. Here, we present a comprehensive guideline for performing phylogenetic studies based on DNA sequence data, but with principles that can be adapted to protein sequences or other molecular markers. It is presented as a compilation of the most commonly used genetic targets for phylogenetic studies of Leishmania, including their respective primers for amplification and references, as well as details of PCR assays. Guidelines are, then, presented to choose the best targets in relation to the types of samples under study. Finally, and importantly, instructions are given to obtain optimal sequences, alignments, and datasets for the subsequent data analysis and phylogenetic inference. Different bioinformatics methods and software for phylogenetic inference are presented and explained. This chapter aims to provide a compilation of methods and generic guidelines to conduct phylogenetics of Leishmania for nonspecialists.

Comparison of Leishmania typing results obtained from 16 European clinical laboratories in 2014

Leishmaniasis is endemic in southern Europe, and in other European countries cases are diagnosed in travellers who have visited affected areas both within the continent and beyond. Prompt and accurate diagnosis poses a challenge in clinical practice in Europe. Different methods exist for identification of the infecting Leishmania species. Sixteen clinical laboratories in 10 European countries, plus Israel and Turkey, conducted a study to assess their genotyping performance. DNA from 21 promastigote cultures of 13 species was analysed blindly by the routinely used typing method. Five different molecular targets were used, which were analysed with PCR-based methods. Different levels of identification were achieved, and either the Leishmania subgenus, species complex, or actual species were reported. The overall error rate of strains placed in the wrong complex or species was 8.5%. Various reasons for incorrect typing were identified. The study shows there is considerable room for improvement and standardisation of Leishmania typing. The use of well validated standard operating procedures is recommended, covering testing, interpretation, and reporting guidelines. Application of the internal transcribed spacer 1 of the rDNA array should be restricted to Old World samples, while the heat-shock protein 70 gene and the mini-exon can be applied globally.

The Expanding World of Human Leishmaniasis

New Leishmania isolates form a novel group of human parasites related to Leishmania enrietti, with cases in Ghana, Thailand, and Martinique; other relatives infect Australian and South American wildlife. These parasites apparently cause both cutaneous and visceral disease, and may have evolved a novel transmission mechanism exploiting blood-feeding midges.

The history of leishmaniasis

In this review article the history of leishmaniasis is discussed regarding the origin of the genus Leishmania in the Mesozoic era and its subsequent geographical distribution, initial evidence of the disease in ancient times, first accounts of the infection in the Middle Ages, and the discovery of Leishmania parasites as causative agents of leishmaniasis in modern times. With respect to the origin and dispersal of Leishmania parasites, the three currently debated hypotheses (Palaearctic, Neotropical and supercontinental origin, respectively) are presented. Ancient documents and paleoparasitological data indicate that leishmaniasis was already widespread in antiquity. Identification of Leishmania parasites as etiological agents and sand flies as the transmission vectors of leishmaniasis started at the beginning of the 20^th century and the discovery of new Leishmania and sand fly species continued well into the 21^st century. Lately, the Syrian civil war and refugee crises have shown that leishmaniasis epidemics can happen any time in conflict areas and neighbouring regions where the disease was previously endemic.

Leishmaniases in Ecuador: Comprehensive review and current status

This article reviews current knowledge about leishmaniases in Ecuador, proceeding from 1920, when the first human case was described, to the present, mainly focusing on the recent research events published. Regarding basic situations, it appears that 23 of Ecuador's 24 provinces have leishmaniasis-case reports. The disease is one of the mandatory notification infectious diseases in the country since 2005. All the 21,305 cases notified to the Ministry of Public Health, during the period from 2001 through 2014, were said to involve different clinical features of cutaneous leishmaniasis (CL) but not visceral (VL). Eight Leishmania species, L. (Viannia) guyanensis, L. (V.) panamensis, L. (V.) braziliensis, L. (Leishmania) mexicana, L. (L.) amazonensis, L. (L.) major-like, L. (V.) naiffiand L. (V.) lainsoni were characterized. The last two species were most recently reported from the Ecuadorian Amazon regions. Of the 73 Ecuadorian Lutzomyia species (43 man-biting species) recorded, only four, Lu. trapidoi, Lu. gomezi, Lu. ayacuchensis, and Lu. tortura were incriminated as vectors of the Leishmania parasites. Current knowledge on the reservoir hosts of Leishmania in Ecuador is extremely poor. Recently, in Ecuador different kinds of molecular techniques were developed for diagnosis and mass screening of the disease, employing various materials derived from patients and sand fly vectors. These are PCR-RFLP, colorimetric FTA-LAMP etc. Brief comments and recommendations were also given, for future research and control of leishmaniases in Ecuador.

Leishmania infections: Molecular targets and diagnosis

Progress in the diagnosis of leishmaniases depends on the development of effective methods and the discovery of suitable biomarkers. We propose firstly an update classification of Leishmania species and their synonymies. We demonstrate a global map highlighting the geography of known endemic Leishmania species pathogenic to humans. We summarize a complete list of techniques currently in use and discuss their advantages and limitations. The available data highlights the benefits of molecular markers in terms of their sensitivity and specificity to quantify variation from the subgeneric level to species complexes, (sub) species within complexes, and individual populations and infection foci. Each DNA-based detection method is supplied with a comprehensive description of markers and primers and proposal for a classification based on the role of each target and primer in the detection, identification and quantification of leishmaniasis infection. We outline a genome-wide map of genes informative for diagnosis that have been used for Leishmania genotyping. Furthermore, we propose a classification method based on the suitability of well-studied molecular markers for typing the 21 known Leishmania species pathogenic to humans. This can be applied to newly discovered species and to hybrid strains originating from inter-species crosses. Developing more effective and sensitive diagnostic methods and biomarkers is vital for enhancing Leishmania infection control programs.

Medical Parasitology Taxonomy Update: January 2012 to December 2015

Parasites of medical importance have long been classified taxonomically by morphological characteristics. However, molecular-based techniques have been increasingly used and relied on to determine evolutionary distances for the basis of rational hierarchal classifications. This has resulted in several different classification schemes for parasites and changes in parasite taxonomy. The purpose of this Minireview is to provide a single reference for diagnostic laboratories that summarizes new and revised clinically relevant parasite taxonomy from January 2012 through December 2015.

The Montpellier Leishmania Collection, from a Laboratory Collection to a Biological Resource Center: A 39-Year-Long Story

We report the development of a laboratory collection of Leishmania that was initiated in 1975 and, after 39 years, has become an international Biological Resource Center (BRC-Leish, Montpellier, France, BioBank No. BB-0033-00052), which includes 6353 strains belonging to 36 Leishmania taxa. This is a retrospective analysis of the technical and organizational changes that have been adopted over time to take into account the technological advances and related modifications in the collection management and quality system. The technical improvements concerned the culture and cryopreservation techniques, strain identification by isoenzymatic and molecular techniques, data computerization and quality management to meet the changes in international standards, and in the cryogenic and microbiological safety procedures. The BRC is working toward obtaining the NF-S 96-900 certification in the coming years. Our long-term expertise in Leishmania storage and typing and collection maintenance should encourage field epidemiologists and clinical practitioners in endemic countries to secure their own strain collection with the help of the French BRC-Leish.