Detection of Leishmania infantum in Lutzomyia longipalpis captured in Campo Grande, MS

Multiplex qPCR assay to determine Leishmania infantum load in Lutzomyia longipalpis sandfly samples

The study aimed to develop a multiplex qPCR to detect Leishmania infantum load in different sandfly sample settings using Leishmania kDNA and sandfly vacuolar ATPase (VATP) subunit C as internal control gene. The amplification of Lutzomyia longipalpis VATP gene was evaluated together with Leishmania infantum kDNA in a multiplex reaction. The concentration of VATP gene oligonucleotides was adjusted until no statistically significant difference was observed between all multiplex standard curves and singleplex curves, that is, only kDNA amplification. Limit of detection (LoD) was measured using a probit model and a cut-off defined by receiver operating characteristic analysis. Limit of quantification (LoQ) was assessed by a linear model using the coefficient of variation threshold of 25%. After assuring VATP gene amplification, its primer-probe concentrations were best at 100 nM/10 nM, respectively. The cut-off C_q value for L. infantum kDNA was defined as 35.46 with 100% of sensitivity and specificity. A total of 95% LoD was determined to be of 0.162 parasites while LoQ was 5.858. Our VATP/kDNA multiplex qPCR assay shows that it can be used to evaluate both DNA integrity and determine L. infantum load in L. longipalpis even for low yielded samples, that is, individual midguts.

Investigation of Leishmania (Viannia) braziliensis Infection in Wild Mammals in Brazil

PURPOSE

Leishmaniasis are infectious and zoonotic diseases and present in cutaneous and visceral forms. Cutaneous leishmaniasis is endemic and widely distributed throughout the state of Espírito Santo, Brazil. Several cases of cutaneous leishmaniasis in humans and dogs associated with Leishmania (Viannia) braziliensis have been reported in the state. This study aimed to investigate the occurrence of natural infection by Leishmania(Viannia) braziliensis in wild mammals found dead (by trampling or natural death) in the Sooretama Biological Reserve, Espírito Santo State.

METHODS

From January 2018 to December 2019, 60 animals were collected. Of these, 47 animals from 12 different species were analyzed. The results were demonstrated using descriptive analysis of the observations to calculate the absolute and relative frequencies of the data.

RESULTS

In the PCR, using specific primers for the genus Leishmania (D1, D2, and D3) and the species Leishmania (Viannia) braziliensis (ISVB/ISVC), 4 positive animals (8.5%) were detected: 1 Cuniculus paca (paca) (25%) and 3 Callithrix geoffroyi (white-faced marmoset) (25%). In the histopathological analysis, the parasitic amastigote form was not observed.

CONCLUSIONS

The natural infection, detected by PCR, by Leishmania (Viannia) braziliensis in Cuniculus paca (paca) and Callithrix geoffroyi (white-faced marmoset) constitutes the first report of infection of this rodent and primate species in the literature. Despite the confirmation of Leishmania (Viannia) braziliensis infection in rodents and primates, the role of these species in the transmission of this zoonosis still needs further observational studies to identify their seasonal variation, transmissibility, infection stability, and the effects of a given parasite on the population and/or individual.

Leishmania infantum infecting the carnivore Nasua nasua from urban forest fragments in an endemic area of visceral leishmaniasis in Brazilian Midwest

Introduction

The aim of the present study was to investigate the occurrence of Leishmania infantum in South American coatis inhabiting two forest fragments in Campo Grande, Mato Grosso do Sul, Midwest region of Brazil, an endemic area of human and canine visceral leishmaniasis (VL).

Material and methods

A total of 110 South American coatis were sampled in the conservation unit "Parque Estadual do Prosa" (PEP) and in the residential area "Vila da Base Aérea" (VBA) from March 2018 to April 2019. As a longitudinal study that include up to six recaptures of the same individual, a total of 190 capture events were obtained. Blood, bone marrow and skin samples were obtained for parasitological (axenic culture), serological (Enzyme Linked Immunosorbent Assay - ELISA and Dual-path Platform immunoassay - DPP^® CVL) and molecular diagnostic assays (targeting kDNA for Leishmania spp. and L. infantum; and HSP70 followed by sequence analysis).

Results

Seropositivity for L. infantum was found in 33 individuals, six in PEP and 27 in VBA. Furthermore, L. infantum was detected by molecular analysis in 16 individuals, seven from PEP and nine from VBA. We also isolated L. infantum from bone marrow of one individual and detected a single positive skin sample in molecular assay from other individual, both from VBA.

Discussion

An overall infection rate of 36.4% (40/110) was observed, significantly higher in the VBA (49.1%) than in the PEP (21.6%), probably because VBA presents: (i) a large number of resident dogs and chickens that would be attracting sandflies; (ii) a denser population of this wild mammal species; and (iii) physical barriers and a lack of functional connectivity in the surroundings, preventing these animals to disperse out. We conclude that South American coati populations living in urban forest fragments of Campo Grande are affected by the epidemiological scenario of VL, known to involve dogs, vectors and humans. We highlight the importance of investigate the parasitism by L. infantum in this and other potential L. infantum reservoirs that inhabit urbanized regions endemic to VL.

Phlebotominae (Diptera: Psychodidae) and Biomes in the State of Mato Grosso do Sul, Brazil

The state of Mato Grosso do Sul, Brazil is an important region of South America regarding leishmaniasis, with the great diversity of sandflies reported since 1938 and wide biodiversity represented by its biomes (Atlantic Forest, Cerrado, and Pantanal). A checklist of sandflies is presented here for the state and respective biomes. The data base was compiled from primary and secondary data. The primary data collection involved automatic light traps at Miranda-Abobral Pantanal subregion and in subregion Baixa Nhecolância of Pantanal. The secondary data were obtained from entomology scientific collections and a literature review of articles from 1938 to 2019, including entomological museum collections. A total of 71 species were reported, belonging to 14 genera and 13 subgenera, in 61 municipalities of the state, including the type locality of 9 species, and the first report of Lutzomyia cruzi (Mangabeira 1938), vector of Leishmania infantum (Nicolle 1937), in the Pantanal region of Miranda-Abobral. Other vector species, Bichromomyia flaviscutellata (Mangabeira 1942), Lutzomyia longipalpis (Lutz & Neiva 1912), Nyssomyia antunesi (Coutinho 1939), Nyssomyia intermedia (Lutz & Neiva 1912), Nyssomyia neivai (Pinto 1926), and Nyssomyia whitmani (Antunes & Coutinho 1939), are reported in the entire area of the state. Maps containing the distribution of sandflies on Mato Grosso do Sul biomes were produced. The eclecticism of the species in relation to their ecotypes was observed, with several species using the three biome types as habitats and breeding sites.

Fast multiplex real-time PCR assay for simultaneous detection of dog and human blood and Leishmania parasites in sand flies

Background

The blood-feeding behaviour of female sand flies may increase their likelihood of acquiring and transmitting Leishmania parasites. Studies on the host usage by these insects may thus improve our understanding of the Leishmania transmission risk in leishmaniasis-endemic areas. Here, we developed a fast multiplex real-time PCR assay for simultaneous detection of dog, human and Leishmania DNA in sand flies.

Methods

Primers and TaqMan probes targeting the mitochondrial cytochrome c oxidase subunit 1 and cytochrome b genes of dog and human, respectively, were combined in a multiplex assay, which also includes primers and a TaqMan probe targeting the Leishmania minicircle kinetoplast DNA.

Results

The multiplex assay was 100% specific, with analytical sensitivities of 10³ fg/reaction for dog and human and 1 fg for Leishmania. By testing field-collected engorged female sand flies (95 Migonemyia migonei and two Nyssomyia intermedia), 50 M. migonei were positive for one or two targets (positivity rates: 45.4% for human, 4.1% for dog and 12.4% for Leishmania DNA).

Conclusions

This multiplex real-time PCR assay represents a novel fast assay for detecting dog, human and Leishmania DNA in female sand flies and therefore a tool for assessing the risk of Leishmania transmission to these hosts in areas of active transmission.

Leishmania presence in bats in areas endemic for leishmaniasis in central-west Brazil

Leishmaniasis involves the participation of several species of both wild and domestic mammal hosts and sandfly vectors, which demonstrates the eco-epidemiological complexity observed in this disease. Bats are among the most abundant types of mammals and the scarcity of research on Leishmania infection in these animals gives evidence of the importance of new studies that aim to clarify this relationship. This study aimed to detect the Leishmania spp. in bats. 146 bats, representing 16 different species belonging to the Molossidae, Vespertilionidae, and Phyllostomidae families, were received and processed for collection of tissues. Skin samples were collected from 100% of the bats, and liver samples were collected from 87% (n = 127). After evaluating the quality of the DNA extracted by means of PCR directed to the IRBP gene, the samples considered suitable for the Leishmania detection test were submitted for PCR directed to Leishmania kDNA, and to confirm positivity, were tested to the SSUrRNA gene-directed Nested-PCR. The Leishmania presence in the species Molossus pretiosus, Nyctinomops macrotis, and Lasiurus cinereus are the first reports this encounter in these species of bats in Brazil. Furthermore, new species of bats as possible hosts for L. infantum are reported, such as Molossus pretiosus, Myotis nigricans, Nyctinomops laticaudatus, Nyctinomops macrotis, and, for L. braziliensis, Lasiurus cinereus and Cynomops planirostris. These findings in bats in an area endemic for leishmaniasis indicate that these animals may be involved in sustaining the disease cycle in this location.

Molecular detection and identification of Leishmania DNA and blood meal analysis in Phlebotomus (Larroussius) species

BACKGROUND

Phlebotomus (Larroussius) perniciosus and Canis familiaris are respectively the only confirmed vector and reservoir for the transmission of Leishmania (L.) infantum MON-1 in Tunisia. However, the vector and reservoir hosts of the two other zymodemes, MON-24 and MON-80, are still unknown. The aim of this study was to analyze the L. infantum life cycle in a Tunisian leishmaniasis focus. For this purpose, we have focused on: i) the detection, quantification and identification of Leishmania among this sand fly population, and ii) the analysis of the blood meal preferences of Larroussius (Lar.) subgenus sand flies to identify the potential reservoirs.

METHODOLOGY AND FINDINGS

A total of 3,831 sand flies were collected in seven locations from the center of Tunisia affected by human visceral leishmaniasis. The collected sand flies belonged to two genus Phlebotomus (Ph.) (five species) and Sergentomyia (four species). From the collected 1,029 Lar. subgenus female sand flies, 8.26% was positive to Leishmania by ITS1 nested PCR. Three Leishmania spp. were identified: L. infantum 28% (24/85), L. killicki 13% (11/85), and L. major 22% (19/85). To identify the blood meal sources in Ph. Lar. subgenus sand flies, engorged females were analyzed by PCR-sequencing targeting the vertebrate cytochrome b gene. Among the 177 analyzed blood-fed females, 169 samples were positive. Sequencing results showed seven blood sources: cattle, human, sheep, chicken, goat, donkey, and turkey. In addition, mixed blood meals were detected in twelve cases. Leishmania DNA was found in 21 engorged females, with a wide range of blood meal sources: cattle, chicken, goat, chicken/cattle, chicken/sheep, chicken/turkey and human/cattle. The parasite load was quantified in fed and unfed infected sand flies using a real time PCR targeting kinetoplast DNA. The average parasite load was 1,174 parasites/reaction and 90 parasites/reaction in unfed and fed flies, respectively.

CONCLUSION

Our results support the role of Ph. longicuspis, Ph. perfiliewi, and Ph. perniciosus in L. infantum transmission. Furthermore, these species could be involved in L. major and L. killicki life cycles. The combination of the parasite detection and the blood meal analysis in this study highlights the incrimination of the identified vertebrate in Leishmania transmission. In addition, we quantify for the first time the parasite load in naturally infected sand flies caught in Tunisia. These findings are relevant for a better understanding of L. infantum transmission cycle in the country. Further investigations and control measures are needed to manage L. infantum transmission and its spreading.

Isolation and Molecular Typing of Leishmania infantum from Phlebotomus perfiliewi in a Re-Emerging Focus of Leishmaniasis, Northeastern Italy

Visceral leishmaniasis (VL) caused by Leishmania (L.) infantum is a public health threat in the Emilia-Romagna region, northeastern Italy, but its epidemiology has not been fully elucidated in this area. The objective of this study was to characterize Leishmania infection in sand flies collected in a re-emerging focus of VL in the Bologna province. During the summer of 2016, 6114 sand flies were collected, identified, and tested for Leishmania detection. Of the identified sand flies, 96.5% were Phlebotomus (P.) perfiliewi and 3.5% were P. perniciosus. Detected parasites were characterized by biomolecular methods (multilocus microsatellite typing and characterization of repetitive region on chromosome 31), and quantified by real-time PCR. The prevalence of Leishmania infection in individually-tested P. perfiliewi sand flies varied from 6% to 10% with an increasing trend during the season. Promastigotes of L. infantum were isolated by dissection in one P. perfiliewi female; the isolated strain (Lein-pw) were closely related to Leishmania parasites from VL cases in northeastern Italy, but differed from strains isolated in dogs from the same area. Our findings strongly support the vector status of P. perfiliewi for human VL in the study area.

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.

Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longipalpis population and to elucidate the influence of bioclimatic factors on the monthly fluctuations of this vector. HP light traps were monthly set in the intradomicile and peridomicile of residences located in the central and beachfront areas of Camaçari, a VL endemic area. The sand fly collection was conducted in two periods: i) period 1-between December 2011 and November 2012 and ii) period 2-August 2014 and July 2015. Sand fly species were identified and detection of L. infantum infection by qPCR was performed in pools of female Lu. longipalpis. For the first time, the parasite load of positive pools was correlated with the number of Lu. longipalpis captured per month in both periods. Correlation analyses between the monthly fluctuation of the sand fly population and bioclimatic indices of the municipality in both collection periods were also performed. In both evaluated periods, more than 98% of the collected sand flies were Lu. longipalpis, confirming the predominance of this species in the region. It was captured mostly in the beachfront area in all months evaluated (99%). For the period 1, Leishmania DNA was detected in 81% of tested pools representing a minimal infection rate of 9.6%. In the period 2, 40% of the pools were positive with a minimal infection rate of 10.2%. Infected sand flies were only detected in the beachfront area in both periods. The parasite load was low and did not vary in the evaluated months despite the number of collected sand flies. No correlation was observed for climatic factors in both areas of Camaçari. These findings emphasize the high risk of Leishmania transmission in Camaçari regardless of the season and that other factors, aside from bioclimatic elements, are influencing the sand fly population monthly fluctuation.

First autochthonous case of canine visceral leishmaniasis in Rondônia, Brazil, a region with no history of visceral leishmaniasis

This report describes the first autochthonous case of canine visceral leishmaniasis in Rondônia, northern Brazil. A canine resident of the municipality of Cacoal, with clinical signs and symptoms of visceral leishmaniasis, was treated by a veterinarian. Samples were analyzed by a reference laboratory. Dual-path platform (DPP) assay, indirect immunofluorescence technique (IIT), enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), isolation in a culture medium, and direct parasitological analysis were performed. DPP assay, IIT, and ELISA revealed positive results for Leishmania; PCR identified the species as Leishmania infantum. Based on the clinical presentation and test results, canine visceral leishmaniasis was diagnosed.

High molecular prevalence of Leishmania in phlebotomine sand flies fed on chicken blood in Brazil

Leishmaniases are endemic in Brazil, where Leishmania infantum has been detected in humans, dogs, cats, and phlebotomine vectors. Monitoring synanthropic vector populations is critical for leishmaniasis control-surveillance in such transmission-prone areas. Here, a suite of molecular approaches were used to assess Leishmania infection prevalence and to identify blood-meal sources in a large sample of sand flies collected in anthropic environments of a Leishmania-transmission area in Mato Grosso do Sul State (Rio Verde de Mato Grosso municipality), Central-West Brazil. We sampled sand flies monthly (January-June 2014 and 2016) in one peri-domestic site within each of six neighborhoods with recent records of human visceral and/or tegumentary leishmaniasis. kDNA-qPCR plus rDNA ITS-sequencing were used to detect and identify Leishmania in pooled female sand flies. Individual engorged females (n = 58) were used for blood-meal analyses through High-Resolution Melting (HRM) targeting the mtDNA cytb gene. Overall, 90.5% of 420 CDC trap-nights yielded vectors, for a total catch of 24,989 sand flies. We sub-sampled and identified 3088 sand flies of 12 species, including 2775 Lutzomyia longipalpis (the most abundant species at all sampling sites) and 297 Nyssomyia whitmani. Female sand flies (n = 1261) were grouped in 159 pools, of which 92 Lu. longipalpis (minimum infection rate [MIR] 8%) and 7 Ny. whitmani pools (MIR 7%) were Leishmania kDNA-positive. Most positive Lu. longipalpis were collected in the 2016 rainy season. Sequencing confirmed L. infantum in Lu. longipalpis samples. HRM analyses identified chicken DNA in 57 sand flies (98.3%), 37 of which were Leishmania DNA-positive (64.9%); human blood was found in just one (Leishmania-negative) female. Our data show ongoing risk of L. infantum transmission to humans in the study area, where Leishmania-infected sandfly vectors are common and heavily rely on chicken blood in the peri-domestic environment.

Real-time PCR applications for diagnosis of leishmaniasis

Leishmaniasis is a vector-borne disease caused by many Leishmania species, which can infect both humans and other mammals. Leishmaniasis is a complex disease, with heterogeneous clinical manifestations ranging from asymptomatic infections to lesions at cutaneous sites (cutaneous leishmaniasis), mucosal sites (mucocutaneous leishmaniasis) or in visceral organs (visceral leishmaniasis), depending on the species and host characteristics. Often, symptoms are inconclusive and leishmaniasis can be confused with other co-endemic diseases. Moreover, co-infections (mainly with HIV in humans) can produce atypical clinical presentations. A correct diagnosis is crucial to apply the appropriate treatment and the use of molecular techniques in diagnosis of leishmaniasis has become increasingly relevant due to their remarkable sensitivity, specificity and possible application to a variety of clinical samples. Among them, real-time PCR (qPCR)-based approaches have become increasingly popular in the last years not only for detection and quantification of Leishmania species but also for species identification. However, despite qPCR-based methods having proven to be very effective in the diagnosis of leishmaniasis, a standardized method does not exist. This review summarizes the qPCR-based methods in the diagnosis of leishmaniasis focusing on the recent developments and applications in this field.

Detection of high Leishmania infantum loads in Phlebotomus perniciosus captured in the leishmaniasis focus of southwestern Madrid region (Spain) by real time PCR

Since 2010 a human leishmaniasis outbreak has been notified in southwestern Madrid region that still remains active. Entomological surveys have been carried out in the affected area in order to obtain information about species diversity, distribution, and density of sand flies. Moreover, molecular identification of blood meal preferences of sand flies and molecular detection of Leishmania infantum has been performed. In this work, we optimized a real time PCR assay in order to determine parasite loads in unfed and blood-fed Phlebotomus perniciosus female sand flies caught in the focus area. Results showed elevated parasite loads in nearly 70% of the studied positive sand flies. Furthermore, significantly higher parasite loads were observed in females without blood in their guts. In conclusion, high L. infantum loads found in P. perniciosus sand flies from the Madrid focus support the exceptional characteristics of this outbreak.

Detection of Leishmania spp. in Bats from an Area of Brazil Endemic for Visceral Leishmaniasis

The multihost parasites Leishmania spp. infect a broad range of wild mammalian species including bats. Several species of bats have adapted to a variety of food resources and shelters in urban areas. This study aimed to detect Leishmania spp. DNA in bats present in forest fragments located in metropolitan areas endemic for leishmaniasis in Campo Grande, Mato Grosso do Sul (MS), Brazil. Blood samples were obtained from 80 individuals, including eight species of Phyllostomidae and one species of Vespertilionidae. Thirty of the 80 bats were positive for Leishmania spp. using conventional PCR, all belonging to the family Phyllostomidae. Eighteen samples tested by real-time PCR (qPCR) using specific primers for the kDNA of Leishmania infantum were positive. To the best of our knowledge, this is the first report detecting Leishmania spp. in Platyrrhinus incarum in addition to being the first reported detection of L. infantum in the bat species Phyllostomus discolor, Platyrrhinus lineatus, Artibeus planirostris and Artibeus lituratus. Our results show that bats can host Leishmania spp. in areas endemic for leishmaniasis, which must be taken into account in disease control operations by public health authorities.