Multi-locus characterization and phylogenetic inference of Leishmania spp. in snakes from Northwest China

hsp70 PCR-RFLP as an alternative tool to identify Sauroleishmania species

Sauroleishmania spp. comprises one of the four Leishmania subgenera, which has been historically considered a non-pathogenic protozoan of reptiles. However, some strains appear to be transiently infective to mammals, and recent findings have detected these parasites in dogs and humans in areas where leishmaniasis is endemic. Herein, the digestion pattern of PCR-RFLP of the 234 bp-hsp70 fragment was evaluated as a simpler and cheaper tool to distinguish the Sauroleishmania species from the other Leishmania subgenera. As a result, the digestion of the 234 bp-hsp70 fragments with HaeIII produced a banding pattern specific to the four Sauroleishmania strains assessed. This technique could contribute to the identification of Leishmania parasites isolated from sandflies, reptiles, or even mammals in fieldworks as an alternative to the use of laborious and expensive methodologies.

From roads to biobanks: Roadkill animals as a valuable source of genetic data

To protect biodiversity we must understand its structure and composition including the bacteria and microparasites associated with wildlife, which may pose risks to human health. However, acquiring this knowledge often presents challenges, particularly in areas of high biodiversity where there are many undescribed and poorly studied species and funding resources can be limited. A solution to fill this knowledge gap is sampling roadkill (animals that die on roads as a result of collisions with circulating vehicles). These specimens can help characterize local wildlife and their associated parasites with fewer ethical and logistical challenges compared to traditional specimen collection. Here we test this approach by analyzing 817 tissue samples obtained from 590 roadkill vertebrate specimens (Amphibia, Reptilia, Aves and Mammalia) collected in roads within the Tropical Andes of Ecuador. First, we tested if the quantity and quality of recovered DNA varied across roadkill specimens collected at different times since death, exploring if decomposition affected the potential to identify vertebrate species and associated microorganisms. Second, we compared DNA stability across taxa and tissues to identify potential limitations and offer recommendations for future work. Finally, we illustrate how these samples can aid in taxonomic identification and parasite detection. Our study shows that sampling roadkill can help study biodiversity. DNA was recovered and amplified (allowing species identification and parasite detection) from roadkill even 120 hours after death, although risk of degradation increased overtime. DNA was extracted from all vertebrate classes but in smaller quantities and with lower quality from amphibians. We recommend sampling liver if possible as it produced the highest amounts of DNA (muscle produced the lowest). Additional testing of this approach in areas with different environmental and traffic conditions is needed, but our results show that sampling roadkill specimens can help detect and potentially monitor biodiversity and could be a valuable approach to create biobanks and preserve genetic data.

Leishmania tarentolae: A new frontier in the epidemiology and control of the leishmaniases

Leishmaniasis (or the leishmaniases), classified as a neglected tropical parasitic disease, is found in parts of the tropics, subtropics and southern Europe. Leishmania parasites are transmitted by the bite of phlebotomine sand flies and million cases of human infection occur annually. Leishmania tarentolae has been historically considered a non-pathogenic protozoan of reptiles, which has been studied mainly for its potential biotechnological applications. However, some strains of L. tarentolae appear to be transiently infective to mammals. In areas where leishmaniasis is endemic, recent molecular diagnostics and serological positivity to L. tarentolae in humans and dogs have spurred interest in the interactions between these mammalian hosts, reptiles and Leishmania infantum, the main aetiologic agent of human and canine leishmaniasis. In this review, we discuss the systematics and biology of L. tarentolae in the insect vectors and the vertebrate hosts and address questions about evolution of reptilian leishmaniae. Furthermore, we discuss the possible usefulness of L. tarentolae for new vaccination strategies.

Leishmania (Sauroleishmania) tarentolae isolation and sympatric occurrence with Leishmania (Leishmania) infantum in geckoes, dogs and sand flies

The trypanosomatid protist Leishmania tarentolae is a saurian-associated parasite vectored by the Sergentomyia minuta sand fly. This study aimed to confirm the circulation of L. infantum and L. tarentolae in sand flies, reptiles and dogs and to isolate new strains of these protists. Reptilian and sheltered dog blood samples were collected, and sand flies were captured. Samples were tested for Leishmania spp. using duplex real-time PCR (dqPCR) and real-time PCR (qPCR); the origin of blood meal was identified in engorged sand flies by conventional PCR. The reptilian blood and intestinal content of sand fly females were cultured. Dog sera were tested by IFAT using both Leishmania species. Four Tarentola mauritanica geckoes were molecularly positive for L. infantum or L. tarentolae, with no co-infections; moreover, amastigote-like forms of L. infantum were observed in the bone marrow. 24/294 sand flies scored positive for Leishmania spp. by dqPCR, 21 S. minuta and two Phlebotomus perniciosus were positive for L. tarentolae, while only a single Ph. perniciosus was positive for L. infantum. Blood meal analysis confirmed reptile and dog in S. minuta, dog and human in Ph. perniciosus and dog in Phlebotomus neglectus. Two axenic strains of L. tarentolae were obtained. Twelve of 19 dogs scored positive for L. infantum and L. tarentolae by IFAT and three of them also for L. infantum by dqPCR, and six by qPCR. These data confirm the sympatric circulation of L. infantum and L. tarentolae in geckoes, sand flies, and dogs, and suggest that geckoes may be infected with L. infantum.

Leishmania tarentolae is a saurian-associated parasite recently reported in geographical areas where Leishmania infantum is endemic. To confirm the circulation of both protists in sand flies, reptiles and dogs and to isolate new Leishmania spp. strains, reptilian and sheltered dog blood samples were collected and sand flies captured. Samples were molecularly tested for Leishmania spp. and sandflies for origin of blood meal. Dog sera were tested by IFAT for both Leishmania species and reptilian blood and intestine of sand flies were cultured. Four Tarentola mauritanica geckoes were positive for L. infantum or L. tarentolae; moreover, amastigote-like forms of L. infantum were observed in the bone marrow. 24/294 sand flies scored PCR positive for Leishmania spp. Reptile and dog blood were found in S. minuta, dog and human in Ph. perniciosus and dog in Phlebotomus neglectus. Two axenic strains of L. tarentolae were obtained. Twelve of 19 dogs scored positive for L. infantum and L. tarentolae by IFAT and three of them also for L. infantum by PCR, and six by qPCR. Data confirm the sympatric circulation of L. infantum and L. tarentolae in geckoes, sand flies, and dogs, and suggest that geckoes may be infected with L. infantum.

First Report of Anuran Trypanosoma DNA in Flat-Tailed House Geckos (Reptilia: Gekkonidae) Collected from Southern Thailand: No Evidence as a Reservoir for Human Trypanosomatids

Over the years, cases of autochthonous leishmaniasis have been dramatically increasing in Thailand. Recently, several publications have claimed certain species of the phlebotomine sand flies and biting midges potentially serve as natural vectors of Leishmania and Trypanosoma species in this country. However, more information regarding the vector–parasite relationships, as well as their natural reservoirs in the country, still needs to be explored. Herein, we hypothesized that synanthropic reptiles in the leishmaniasis-affected area might be a natural reservoir for these parasites. In this present study, a total of nineteen flat-tailed house geckos were collected from the house of a leishmaniasis patient in Songkhla province, southern Thailand, and then dissected for their visceral organs for parasite detection. Small subunit ribosomal RNA (SSU rRNA) gene and internal transcribed spacer 1 (ITS-1)-specific amplifications were conducted to verify the presence of Trypanosoma and Leishmania parasites, respectively. Only Trypanosoma DNA was screened positive in eight gecko individuals by SSU rRNA-PCR in at least one visceral organ (4, 4, and 6 of the heart, liver, and spleen, respectively) and phylogenetically related to the anuran Trypanosoma spp. (An04/Frog1 clade) previously detected in three Asian sand fly species (Phlebotomus kazeruni, Sergentomyia indica, and Se. khawi). Hence, our data indicate the first detection of anuran Trypanosoma sp. in the flat-tailed house geckos from southern Thailand. Essentially, it can be inferred that there is no evidence for the flat-tailed house gecko (Hemidactylus platyurus) as a natural reservoir of human pathogenic trypanosomatids in the leishmaniasis-affected area of southern Thailand.

Leishmania spp. in Squamata reptiles from the Mediterranean basin

Leishmania tarentolae is a non-pathogenic trypanosomatid species isolated from geckoes in the Mediterranean basin. In Italy, L. tarentolae and Leishmania infantum occur in sympatry in areas where canine leishmaniosis (CanL) is endemic. Here, we investigated the prevalence and distribution of L. tarentolae in reptilian hosts, and the presence of L. infantum in these hosts in southern Italy. From April 2020 to April 2021, lizards and snakes were captured in urban, peri-urban sites, natural parks and dog shelters. Blood was individually sampled and assessed for the presence of Leishmania spp. by cytology and/or molecular biology. Captured lizards were euthanized and their tissues/organs were tested by duplex real-time-PCR for the detection of L. infantum and L. tarentolae and the positive ones were amplified by conventional PCR to confirm the species identification by sequencing. Samples were also screened by real-time-PCR for L. infantum kDNA minicircle. Of the 259 collected Squamata reptiles, 34 (13.1%) specimens scored positive for Leishmania spp., with a prevalence of 10% for L. tarentolae (n = 26) and of 3.1% for L. infantum (n = 8). Positive lizards were mostly Podarcis siculus (n = 26) from dog shelters, with six specimens positive for L. infantum. In addition, L. tarentolae was detected in one Podarcis filfolensis lizard, and in five T. mauritanica geckos (with one gecko and P. filfolensis lizard showing amastigote-like forms in thrombocytes), whereas L. infantum was detected in one T. mauritanica, and one Hemidactylus turcicus. Saurian reptiles living in CanL endemic areas of the Mediterranean basin may be exposed to both L. tarentolae and L. infantum indicating a sympatric circulation of these species in different vertebrate hosts. Moreover, this study represents the first molecular evidence of L. infantum infection in European reptiles. This article is protected by copyright. All rights reserved.

From infection to vaccination: reviewing the global burden, history of vaccine development, and recurring challenges in global leishmaniasis protection

INTRODUCTION

Leishmaniasis is a major public health problem and the second most lethal parasitic disease in the world due to the lack of effective treatments and vaccines. Even when not lethal, leishmaniasis significantly affects individuals and communities through life-long disabilities, psycho-sociological trauma, poverty, and gender disparity in treatment.

AREAS COVERED

This review discusses the most relevant and recent research available on Pubmed and GoogleScholar highlighting leishmaniasis' global impact, pathogenesis, treatment options, and lack of effective control strategies. An effective vaccine is necessary to prevent morbidity and mortality, lower health care costs, and reduce the economic burden of leishmaniasis for endemic low- and middle-income countries. Since there are several forms of leishmaniasis, a pan-Leishmania vaccine without geographical restrictions is needed. This review also focuses on recent advances and common challenges in developing prophylactic strategies against leishmaniasis.

EXPERT OPINION

Despite advances in pre-clinical vaccine research, approval of a human leishmaniasis vaccine still faces major challenges - including manufacturing of candidate vaccines under Good Manufacturing Practices, developing well-designed clinical trials suitable in endemic countries, and defined correlates of protection. In addition, there is a need to explore Challenge Human Infection Model to avoid large trials because of fluctuating incidence and prevalence of leishmanasis.

Detection of Leishmania tarentolae in lizards, sand flies and dogs in southern Italy, where Leishmania infantum is endemic: hindrances and opportunities

Background

Leishmania tarentolae is a protozoan isolated from geckoes (Tarentola annularis, Tarentola mauritanica), which is considered non-pathogenic and is transmitted by herpetophilic Sergentomyia spp. sand flies. This species occurs in sympatry with Leishmania infantum in areas where canine leishmaniasis is endemic. In the present study, we investigated the circulation of L. tarentolae and L. infantum in sand flies, dogs and lizards in a dog shelter in southern Italy, where canine leishmaniasis by L. infantum is endemic.

Methods

Sheltered dogs (n = 100) negative for Leishmania spp. (March 2020) were screened by immunofluorescence antibody test (IFAT) using promastigotes of both species at two time points (June 2020 and March 2021). Whole blood from dogs, tissues of Podarcis siculus lizards (n = 28) and sand flies (n = 2306) were also sampled and tested by a duplex real-time PCR (dqPCR). Host blood meal was assessed in sand flies by PCR.

Results

Overall, 16 dogs became positive for L. infantum and/or L. tarentolae by IFAT at one or both sampling periods. One canine blood sample was positive for L. infantum, whilst two for L. tarentolae by dqPCR. At the cytology of lizard blood, Leishmania spp. amastigote-like forms were detected in erythrocytes. Twenty-two tissue samples, mostly lung (21.4%), scored molecularly positive for L. tarentolae, corresponding to 10 lizards (i.e., 35.7%). Of the female Sergentomyia minuta sampled (n = 1252), 158 scored positive for L. tarentolae, four for L. infantum, and one co-infected. Two Phlebotomus perniciosus (out of 29 females) were positive for L. tarentolae. Engorged S. minuta (n = 10) fed on humans, and one P. perniciosus, positive for L. tarentolae, on lagomorphs.

Conclusions

Dogs and lacertid lizards (Podarcis siculus) were herein found for the first time infected by L. tarentolae. The detection of both L. tarentolae and L. infantum in S. minuta and P. perniciosus suggests their sympatric circulation, with a potential overlap in vertebrate hosts. The interactions between L. tarentolae and L. infantum should be further investigated in both vectors and vertebrate hosts to understand the potential implications for the diagnosis and control of canine leishmaniasis in endemic areas.

Graphical abstract

Reptile vector-borne diseases of zoonotic concern

Reptile vector-borne diseases (RVBDs) of zoonotic concern are caused by bacteria, protozoa and viruses transmitted by arthropod vectors, which belong to the subclass Acarina (mites and ticks) and the order Diptera (mosquitoes, sand flies and tsetse flies). The phyletic age of reptiles since their origin in the late Carboniferous, has favored vectors and pathogens to co-evolve through millions of years, bridging to the present host-vector-pathogen interactions. The origin of vector-borne diseases is dated to the early cretaceous with Trypanosomatidae species in extinct sand flies, ancestral of modern protozoan hemoparasites of zoonotic concern (e.g., Leishmania and Trypanosoma) associated to reptiles. Bacterial RVBDs are represented by microorganisms also affecting mammals of the genera Aeromonas, Anaplasma, Borrelia, Coxiella, Ehrlichia and Rickettsia, most of them having reptilian clades. Finally, reptiles may play an important role as reservoirs of arborivuses, given the low host specificity of anthropophilic mosquitoes and sand flies. In this review, vector-borne pathogens of zoonotic concern from reptiles are discussed, as well as the interactions between reptiles, arthropod vectors and the zoonotic pathogens they may transmit.