Rapid identification of Leishmania species from formalin-fixed biopsy samples by polymorphism-specific polymerase chain reaction

Effective immuno-therapeutic treatment of Canine Leishmaniasis

BACKGROUND

Canine Leishmaniasis (CanL) caused by the L. infantum species is one of the biggest threats to the health of the South American canine population. Chemotherapeutics currently used for the treatment of CanL fail to induce a total parasite clearance while inducing numerous side effects. As CanL is an immunomodulated disease, the use of immuno-treatments should strengthen the deficient immune response of infected dogs. In this study, we evaluated a nasally administered immunotherapy in dogs naturally infected with L. infantum (stage 2), with both visceral and cutaneous manifestations. Noteworthy, some of them were also infected by other parasites (E. canis, D. immitis, A. platys), what worsen their chance of survival.

METHODOLOGY/PRINCIPAL FINDINGS

The treatment was based on 2 intranasal (IN.) administrations of a killed L. infantum parasite loaded into maltodextrin nanoparticles, which treatment was compared with the classical oral administration of Miltefosine (2 mg/kg) for 28 days, as well as a combination of these 2 treatments. The results showed that two IN administrations significantly reduced the serology, and were at least as efficient as the chemotherapy to reduce the skin and bone marrow parasite burden, as well as clinical scores, and that unlike Miltefosine treatments, this nasally administered nanoparticle vaccine was without side effects.

CONCLUSIONS

These results confirm the feasibility of a simple therapeutic immuno-treatment against L. infantum infected dogs, which is a promising tool for future developments.

In silico and in vitro evaluation of primers for molecular differentiation of Leishmania species

Leishmaniasis is a zoonotic disease caused by over 20 species of protozoan parasites of the genus Leishmania. Infection is commonly spread by sandflies and produces a wide spectrum of clinical signs and symptoms. Therefore, from an epidemiological and therapeutic standpoint, it is important to detect and differentiate Leishmania spp. The objective of this study was to combinate in silico and in vitro strategies to evaluate the analytical specificity of primers previously described in the literature. According to electronic PCR (e-PCR) analysis, 23 out of 141 pairs of primers selected through literature search matched their previously reported analytical specificity. In vitro evaluation of nine of these primer pairs by quantitative PCR (qPCR) confirmed the analytical specificity of five of them at the level of Leishmania spp., L. mexicana complex or Leishmania and Viannia subgenera. Based on these findings, the combination of e-PCR and qPCR is suggested to be a valuable approach to maximize the specificity of new primer pairs for the laboratory diagnosis of infections with Leishmania spp.

Cost-effectiveness analysis of Mucosal Leishmaniasis diagnosis with PCR-based vs parasitological tests in Colombia

To estimate the cost-effectiveness of available diagnosis alternatives for Mucosal Leishmaniasis (ML) in Colombian suspected patients. A simulation model of the disease's natural history was built with a decision tree and Markov models. The model´s parameters were identified by systematic review and validated by expert consensus. A bottom-up cost analysis to estimate the costs of diagnostic strategies and treatment per case was performed by reviewing 48 clinical records of patients diagnosed with ML. The diagnostic strategies compared were as follows: 1) no diagnosis; 2) parasite culture, biopsy, indirect immunofluorescence assay (IFA), and Montenegro skin test (MST) combined ; 3) parasite culture, biopsy, and IFA combined; 4) PCR-miniexon; and 5) PCR-kDNA. Three scenarios were modeled in patients with ML clinical suspicion, according to ML prevalence scenarios: high, medium and low. Adjusted sensitivity and specificity parameters of a combination of diagnostic tests were estimated with a discrete event simulation (DES) model. For each alternative, the costs and health outcomes were estimated. The time horizon was life expectancy, considering the average age at diagnosis of 31 years. Incremental cost-effectiveness ratios (ICERs) were calculated per Disability Life Year (DALY) avoided, and deterministic and probabilistic sensitivity analyses were performed. A threshold of willingness to pay (WTP) of three-time gross domestic product per capita (GDPpc) (US$ 15,795) and a discount rate of 3% was considered. The analysis perspective was the third payer (Health System). All costs were reported in American dollars as of 2015. PCR- kDNA was the cost-effective alternative in clinical suspicion levels: low, medium and high with ICERs of US$ 7,909.39, US$ 5,559.33 and US$ 4,458.92 per DALY avoided, respectively. ML diagnostic tests based on PCR are cost-effective strategies, regardless of the level of clinical suspicion. PCR-kDNA was the most cost-effective strategy in the competitive scenario with the parameters included in the present model.

PCR primers designed for new world Leishmania: A systematic review

Studies of the primers that were designed to detect New World Leishmania were systematically reviewed to report the characteristics of each target, detection limit, specificity of the primers designed and diagnostic sensibility. The papers identified in the databases PubMed and Web of Science involved 50 studies. Minicircle is the most applied target in molecular research for diagnosis, due to its high sensitivity in detecting Leishmania in different clinical samples, a characteristic that can be partially attributed to the higher number of copies of the minicircle per cell. The other molecular targets shown in this review were less sensitive to diagnostic use because of the lower number of copies of the target gene per cell, but more specific for identification of the subgenus and/or species. The choice of the best target is an important step towards the result of the research. The target allows the design of primers that are specific to the genus, subgenus or a particular species and also imparts sensitivity to the method for diagnosis. The findings of this systematic review provide the advantages and disadvantages of the main molecular targets and primers designed for New World Leishmania, offering information so that the researcher can choose the PCR system best suited to their research need. This is a timely and extremely thorough review of the primers designed for New World Leishmania.

Leishmania in synanthropic rodents (Rattus rattus): new evidence for the urbanization of Leishmania (Leishmania) amazonensis

This study aimed to detect parasites from Leishmania genus, to determine the prevalence of anti-Leishmania spp. antibodies, to identify circulating species of the parasite, and to determine epidemiological variables associated with infection in rats caught in urban area of Londrina, Paraná, Brazil. Animal capture was carried out from May to December 2006, serological and molecular methods were performed. DNA was extracted from total blood, and nested-PCR, targeting SSu rRNA from Leishmania genus, was performed in triplicate. The positive samples were sequenced twice by Sanger method to species determination. In total, 181 rodents were captured, all were identified as Rattus rattus and none showed clinical alterations. Forty-one of the 176 (23.3%) animals were positive for Leishmania by ELISA and 6/181 (3.3%) were positive by IFAT. Nine of 127 tested animals (7.1%) were positive by PCR; seven were identified as L. (L.) amazonensis, one as L. (L.) infantum. Four rats were positive using more than one test. This was the first description of synanthropic rodents naturally infected by L. (L.) amazonensis (in the world) and by L. (L.) infantum (in South Brazil). Regarding L. (L.) amazonensis, this finding provides new evidence of the urbanization of this etiological agent.

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.

Polymerase chain reaction-based method for the identification of Leishmania (Viannia) braziliensis and Leishmania (Viannia) guyanensis in mucosal tissues conserved in paraffin

INTRODUCTION

In the Americas, mucosal leishmaniasis is primarily associated with infection by Leishmania (Viannia) braziliensis. However, Leishmania (Viannia) guyanensis is another important cause of this disease in the Brazilian Amazon. In this study, we aimed at detecting Leishmaniadeoxyribonucleic acid (DNA) within paraffin-embedded fragments of mucosal tissues, and characterizing the infecting parasite species.

METHODS

We evaluated samples collected from 114 patients treated at a reference center in the Brazilian Amazon by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses.

RESULTS

Direct examination of biopsy imprints detected parasites in 10 of the 114 samples, while evaluation of hematoxylin and eosin-stained slides detected amastigotes in an additional 17 samples. Meanwhile, 31/114 samples (27.2%) were positive for Leishmania spp. kinetoplast deoxyribonucleic acid (kDNA) by PCR analysis. Of these, 17 (54.8%) yielded amplification of the mini-exon PCR target, thereby allowing for PCR-RFLP-based identification. Six of the samples were identified as L. (V.) braziliensis, while the remaining 11 were identified as L. (V.) guyanensis.

CONCLUSIONS

The results of this study demonstrate the feasibility of applying molecular techniques for the diagnosis of human parasites within paraffin-embedded tissues. Moreover, our findings confirm that L. (V.) guyanensisis a relevant causative agent of mucosal leishmaniasis in the Brazilian Amazon.

Species typing in dermal leishmaniasis

Leishmania is an infectious protozoan parasite related to African and American trypanosomes. All Leishmania species that are pathogenic to humans can cause dermal disease. When one is confronted with cutaneous leishmaniasis, identification of the causative species is relevant in both clinical and epidemiological studies, case management, and control. This review gives an overview of the currently existing and most used assays for species discrimination, with a critical appraisal of the limitations of each technique. The consensus taxonomy for the genus is outlined, including debatable species designations. Finally, a numerical literature analysis is presented that describes which methods are most used in various countries and regions in the world, and for which purposes.

Leishmaniases in Maghreb: an endemic neglected disease

Maghreb is known to be one of the most endemic areas of leishmaniases where both visceral and cutaneous forms are reported. Cutaneous leishmaniasis (CL) is older and has a higher prevalence than visceral one (VL). It is caused by four taxa (Leishmania (L.) major, L. infantum, L. tropica and L. killicki) which are responsible for a large clinical spectrum of lesions. Most transmission cycles of these taxa are known and many phlebotomine sandflies vectors and reservoir hosts are identified. The zoonotic transmission is well established for L. major. However, for L. infantum and L. killicki it needs more investigations to be proven. Regarding L. tropica, studies suggest it to be of both zoonotic and anthroponotic types. The isoenzymatic characterization of these four taxa showed a large enzymatic polymorphism varying from two zymodemes for L. major to 10 zymodemes for L. tropica. Cutaneous leishmaniasis is widely distributed and covers all bioclimatic stages with the coexistence of more than one taxon in the same foci. Visceral leishmaniasis is the second form of leishmaniases in Maghreb. Only L. infantum is known to cause this disease. The transmission cycle of this parasite is zoonotic but still not well known. The isoenzymatic identification of L. infantum causing VL showed the presence of six zymodemes. Geographically, VL is distributed in all bioclimatic stages of Maghreb countries. Despite all the previous studies realized on leishmaniases in Maghreb, they are still considered as neglected diseases because of the rarity or the absence of efficient control strategies.

Ixodid fauna and zoonotic agents in ticks from dogs: first report of Rickettsia rickettsii in Rhipicephalus sanguineus in the state of Mato Grosso do Sul, mid-western Brazil

Ticks from 148 dogs from the urban area of the municipality of Campo Grande, state of Mato Grosso do Sul, Brazil, were collected, classified and analyzed using polymerase chain reaction (PCR) for the identification of Rickettsia spp., Trypanosoma cruzi and Leishmania spp. A total of 2015 ticks were collected. The species Rhipicephalus sanguineus (98.9 %) and Amblyomma cajennense (1.1 %) were identified. Molecular analysis revealed that no tick samples were infected by T. cruzi. Regarding Leishmania spp., tick samples from 36 dogs spread across all regions of the municipality were positive for L. chagasi. One tick sample was positive for Rickettsia spp. (gltA gene) in the PCR reaction. This sample was submitted to further PCR based on the ompA gene and the amplicon was sequenced. Identity of 100 % was found with homologous sequences of R. rickettsii available in GenBank. This paper is the first to report the natural infection of R. sanguineus by R. rickettsii in the municipality of Campo Grande, state of Mato Grosso do Sul, mid-western Brazil.

The use of polymerase chain reaction to confirm diagnosis in skin biopsies consistent with American tegumentary leishmaniasis at histopathology: a study of 90 cases

BACKGROUND

Cutaneous leishmaniasis is a chronic, infectious disease caused by protozoa of the genus leishmania. The incidence of this disease is high in Brazil, with 19,746 new cases having been detected in 2008. The presence of amastigotes in the cytoplasm of histiocytes constitutes diagnosis of the disease; however, their presence is rarely found in late lesions, making histological diagnosis difficult. Polymerase chain reaction has been shown to represent a highly sensitive and specific technique for the diagnosis of cutaneous leishmaniasis.

OBJECTIVES

To use polymerase chain reaction to evaluate paraffin-embedded skin biopsies with histopathological features consistent with cutaneous leishmaniasis.

MATERIAL AND METHODS

Polymerase chain reaction amplification of a 120-base-pair fragment of Leishmania kinetoplast DNA (kDNA) minicircles was performed on 90 skin biopsies. The male/female ratio was 75/15. Mean age was 32.36 years, with a median of 31 years, range 4-72 years. Samples were histologically compatible with cutaneous leishmaniasis but a definitive diagnosis could not be made since amastigotes were not found. All cases were histologically classified according to the patterns described by de Magalhães.

RESULTS

According to the de Magalhães classification, the most common histological pattern was type IV (exudative granulomatous reaction), which was found in 65.6% of cases (56/90), followed by type I (exudative cellular reaction) in 21.1% of cases (19/90) and type III (exudative and necrotic granulomatous reaction) in 12.2% of cases (11/90). Leishmania DNA was found in 96.7% of the biopsies (87/90).

CONCLUSION

Polymerase chain reaction performed by amplifying kDNA is able to confirm a diagnosis of cutaneous leishmaniasis with a high degree of sensitivity in cases in which histopathology is consistent with a diagnosis of cutaneous leishmaniasis but not definitive.

Consecutive cutaneous and visceral leishmaniasis manifestations involving a novel Leishmania species in two HIV patients in Thailand

Leishmaniasis is an emerging disease in Thailand. Herein, we report on two human immunodeficiency virus (HIV)-infected patients with leishmaniasis who presented with overlapping manifestations between cutaneous and visceral leishmaniasis. Sequencing analysis of the internal transcribed spacer 1 (ITS1) of the ribosomal RNA gene showed that the species was identical to a new species recently described in Thailand. The detection of DNA of this Leishmania species in saliva may have important implications for transmission and epidemiological studies.

Polymorphism-specific PCR enhances the diagnostic performance of American tegumentary leishmaniasis and allows the rapid identification of Leishmania species from Argentina

Background

The diagnosis of the leishmaniases poses enormous challenges in Argentina. The Polymorphism-Specific PCR (PS-PCR) designed and validated in our laboratories has been proven effective for typifying the Leishmania genus from cultured material. Here we evaluated the performance of this method in the diagnosis of American tegumentary leishmaniasis (ATL) and the rapid identification of Leishmania spp. directly from clinical specimens.

Methods

A total of 63 patients from northwestern Argentina, with cutaneous or mucocutaneous lesions, underwent an ATL diagnosis protocol which included clinical examination, Leishmanin skin test, and microscopic examination of dermal smears. In addition, we performed PS-PCR on DNA directly extracted from the specimens scraped from the lesions.

Results

Out of the 63 patients, 44 were classified as ATL cases and 19 as non-ATL cases. The diagnostic sensitivity of the microscopic analysis of dermal smears and PS-PCR individually were 70.5% and 81%, respectively. When performing both tests in parallel, this parameter increased significantly to 97.6% (p = 0.0018). The specificities, on the other hand, were 100%, 84.2%, and 83.3% for the combination, respectively (p > 0.05). Using the PS-PCR analysis we successfully identified the Leishmania spp. in 31 out of the 44 ATL cases. Twenty-eight (90.3%) cases were caused by L. (V.) braziliensis, two (6.5%) by L. (V.) guyanensis, and one (3.2%) by L. (V.) panamensis.

Conclusions

The efficacy of the ATL diagnosis was significantly improved by combining the dermal smear examination with a PS-PCR analysis. Our strategy allowed us to reach the diagnosis of ATL with high accuracy regarding the species of the etiological agent in 70.5% of the cases. Moreover, we diagnosed two cases of the disseminated cutaneous form caused by L. (V.) braziliensis and a cutaneous case due to L. (V.) panamensis infection, both findings reported for the first time in Argentina.

Evaluation of 4 polymerase chain reaction protocols for cultured Leishmania spp. typing

Leishmaniasis is a disease caused by the protozoan Leishmania resulting in a variety of clinical manifestations, from self-healing skin lesions to fatal visceral disease. The development of polymerase chain reaction (PCR)-based techniques has made species identification easier, faster, and less labor intensive. The main targets for PCR amplification include kinetoplastid DNA (kDNA), miniexon, and conserved regions such as the internal transcribed spacer. The objective of this work was to evaluate 4 different PCR techniques designed to type Leishmania using laboratory strains. Parasites were subjected to 4 PCR procedures using specific Leishmania primers for miniexon (designated A1 and A2) and kDNA (designated B1 and B2, C1 and C2, and D1, D2 and D3). Discrimination between some species and the 2 main subgenera Leishmania and Viannia was achieved. Unweighted pair group method analysis resulted in the expected clustering of the 2 species from the subgenus Leishmania. However, some species in the subgenus Viannia could not be distinguished, representing a continued challenge for PCR-based protocols. Results are discussed in terms of advantages, limitations, and reproducibility of these 4 PCR-based techniques in the taxonomy of Leishmania.

Mucosal Leishmaniasis caused by Leishmania (Viannia) braziliensis and Leishmania (Viannia) guyanensis in the Brazilian Amazon

Background

Leishmania (Viannia) braziliensis is a parasite recognized as the most important etiologic agent of mucosal leishmaniasis (ML) in the New World. In Amazonia, seven different species of Leishmania, etiologic agents of human Cutaneous Leishmaniasis, have been described. Isolated cases of ML have been described for several different species of Leishmania: L. (V.) panamensis, L. (V.) guyanensis and L. (L.) amazonensis.

Methodology

Leishmania species were characterized by polymerase chain reaction (PCR) of tissues taken from mucosal biopsies of Amazonian patients who were diagnosed with ML and treated at the Tropical Medicine Foundation of Amazonas (FMTAM) in Manaus, Amazonas state, Brazil. Samples were obtained retrospectively from the pathology laboratory and prospectively from patients attending the aforementioned tertiary care unit.

Results

This study reports 46 cases of ML along with their geographical origin, 30 cases caused by L. (V.) braziliensis and 16 cases by L. (V.) guyanensis. This is the first record of ML cases in 16 different municipalities in the state of Amazonas and of simultaneous detection of both species in 4 municipalities of this state. It is also the first record of ML caused by L. (V.) guyanensis in the states of Pará, Acre, and Rondônia and cases of ML caused by L. (V.) braziliensis in the state of Rondônia.

Conclusions/Significance

L. (V.) braziliensis is the predominant species that causes ML in the Amazon region. However, contrary to previous studies, L. (V.) guyanensis is also a significant causative agent of ML within the region. The clinical and epidemiological expression of ML in the Manaus region is similar to the rest of the country, although the majority of ML cases are found south of the Amazon River.

[Identification of Leishmania species isolated in human cases in Mato Grosso do Sul, by means of the polymerase chain reaction]

Leishmaniases are endemic zoonoses in the State of Mato Grosso do Sul. Their etiological agents in this region of Brazil are Leishmania (Leishmania) chagasi, Leishmania (Leishmania) amazonensis and Leishmania (Viannia) braziliensis. The polymerase chain reaction (PCR) is a tool with high specificity and sensitivity for identifying Leishmania species. This study examined 39 cryopreserved isolates of Leishmania that had been collected by bone marrow aspiration and/or lesion biopsy, depending on the clinical suspicion. The isolates were subjected to DNA extraction and PCR using the following primers: RV1/RV2 for identifying Leishmania (Leishmania) chagasi, a1/a2 for Leishmania (Leishmania) amazonensis and b1/b2 for Leishmania (Viannia) braziliensis.Leishmania (Leishmania) chagasi was the only species identified in the 37 cases of visceral leishmaniasis.Leishmania (Leishmania) amazonensis was identified in two isolates from patients with a diagnosis of cutaneous leishmaniasis. The results obtained confirm that it is possible to use these three pairs of primers as a tool for characterizing Leishmania isolates.

Leishmania (Viannia) braziliensis: New primers for identification using polymerase chain reaction

The objective of this study was to develop specific primers for Leishmania (Viannia) braziliensis species identification using PCR. The designed primers (LBF1 and LBR1) were evaluated for sensitivity and specificity using various L. (V.) braziliensis serodemes and various Leishmania species and also using Trypanosoma cruzi. A specific fragment of 536bp was detected from 50ng of DNA in a crude extract derived from L. (V.) braziliensis. The DNA fragment was not detected when DNA from other Leishmania species or from T. cruzi was used as template in the PCR. Furthermore, when tested with DNA from cutaneous leishmaniasis the designed primers and reaction gave positive results. Taking into consideration that the primers LBF1 and LBR1 could specifically identify L. (V.) braziliensis, they could be considered for use in L. (V.) braziliensis diagnosis and epidemiological studies.

Molecular diagnosis of leishmaniosis in the Paraná state of southern Brazil

The objective of the present study was to establish a polymerase chain reaction (PCR) technique for the diagnosis of cutaneous and mucocutaneous leishmaniosis from autochthonous cases in the state of Paraná in southern Brazil as well as imported cases. We sought to determine its utility and accuracy compared with smears and present culture methods. To standardize PCR samples, skin and mucosal punch biopsies from human lesions were performed on patients living in different regions of the Paraná state (76 cases) and other endemic areas of Brazil and Argentina (7 cases). For PCR standardization, two pairs of primers (MP1L/MP3H and B1/B2) were utilized for amplification of the conserved sequences in the minicircle of kinetoplast DNA (kDNA) for the Leishmania braziliensis complex. Two other primer pairs (b1/b2 and a1/a2) were species-specific for L. (V.) braziliensis and L. (V.) amazonensis, respectively. After differential diagnosis, eight patients had clinical diagnosis of the cutaneous ulcer changed to others pathologies such as syphilis, baso-cellular carcinoma, varicose ulcer, ecthyma and paracoccidioidomycosis. Of the 75 patients with cutaneous (CL) and mucocutaneous (MCL) lesions who provided samples, 47 (46 CL + 1 MCL) were diagnosed with leishmaniosis by smear and 57 (52 LC + 5 MCL) were diagnosed by culture methods. In contrast, our PCR technique presented higher accuracy when compared to the direct examination and culture of parasites. PCR is applicable both for CL where all 61 lesions were diagnosed, and MCL where 12 of 14 lesions were diagnosed. This molecular biology technique is also a faster and more specific diagnostic method compared with present parasitological procedures.

Epidemiology of leishmaniasis in Ecuador: current status of knowledge -- a review

Although leishmaniasis is regarded as a significant health problem in Ecuador by the Ministry of Health, and the incidence has increased over the last years, an official map on the geographic distribution of disease and sand fly vectors or a control strategy do not exist yet. This article reviews the current situation based on published information to improve our knowledge and understand the epidemiological situation of leishmaniasis in Ecuador in order to help future research and to develop a national control strategy. The disease is endemic in most provinces throughout Pacific coastal region, Amazonian lowlands, and some inter-Andean valleys with a total 21,805 cases reported during 1990-2003. Whereas cutaneous leishmaniasis (CL) is found throughout Ecuador, mucocutaneous leishmaniasis (MCL) appears to be restricted to the Amazon region; one, parasitologically unconfirmed case of visceral form was reported in 1949. Most human infections are caused by Leishmania (Viannia) spp., which is distributed in the subtropical and tropical lowlands; infections due to L. (Leishmania) spp. are found in the Andean highlands and in the Pacific lowlands as well. The proven vectors are Lutzomyia trapidoi and Lu. ayacuchensis. Canis familiaris, Sciurus vulgaris, Potos flavus, and Tamandua tetradactyla have been found infected with Leishmania spp. It is estimated that around 3000-4500 people may be infected every year, and that 3.1 to 4.5 millions people are estimated to be at risk of contracting leishmaniasis.

New PCR assay using glucose-6-phosphate dehydrogenase for identification of Leishmania species

Glucose-6-phosphate dehydrogenase (G6PD) is one of the multilocus enzymes used to identify Leishmania by zymodeme analysis. The polymorphic pattern revealed by partial characterization of the gene encoding G6PD generated molecular markers useful in the identification of different Leishmania species by PCR. Initially degenerate oligonucleotides were designed on the basis of data on the conserved active center described for other organisms. Primers for reverse transcription-PCR experiments, designed from the nucleotide sequence of the PCR product, enabled us to characterize the 5' and 3' untranslated regions and the G6PD open reading frame of reference strains of Leishmania (Viannia) braziliensis, Leishmania (Viannia) guyanensis, Leishmania (Leishmania) mexicana, and Leishmania (Leishmania) amazonensis. Sets of paired primers were designed and used in PCR assays to discriminate between the parasites responsible for tegumentar leishmaniasis of the subgenera Leishmania (Leishmania) and Leishmania (Viannia) and to distinguish L. (Viannia) braziliensis from others organisms of the subgenus Leishmania (Viannia). No amplification products were detected for the DNA of Crithidia fasciculata, Trypanosoma cruzi, or Leishmania (Sauroleishmania) tarentolae or DNA from a healthy human control. The tests proved to be specific and were sensitive enough to detect parasites in human biopsy specimens. The successful discrimination of L. (Viannia) braziliensis from other parasites of the subgenus Leishmania (Viannia) opens the way to epidemiological studies in areas where more than one species of the subgenus Leishmania (Viannia) exist, such as Amazonia, as well as follow-up studies after chemotherapy and assessment of clinical prognoses.

Usefulness of sampling with cotton swab for PCR-diagnosis of cutaneous leishmaniasis in the New World

In this study, we tested the polymerase chain reaction (PCR)-method to diagnose cutaneous leishmaniasis (CL) by taking exudate materials from lesions with cotton swabs, using our previously tested (PCR) panel comprised of Leishmania (Viannia) panamensis, L. (V.) braziliensis, L. (V.) guyanensis, L. (Leishmania) mexicana and L. (L.) amazonensis. The objectives of the present study were to improve the sampling method convenient for the patients and to test the usefulness of samples taken with cotton swabs. Sixteen patients were clinically diagnosed to have CL including one case of diffuse cutaneous leishmaniasis (DCL) in Ecuador and the causative Leishmania parasites were identified by PCR. All the 12 samples from CL patients of La Mana, positive for Leishmania DNA, were identified as L. (V.) panamensis, while two from CL of Huigra and one from DCL of San Ignacio were L. (L.) mexicana. In the field condition, taking biopsy material is not only painful but sometimes causes iatrogenic bacterial infections. Considering the sensitivity of the test, and convenient sampling procedure, it may be suggested that collection of exudates using cotton swabs may be a better alternative to biopsy sample for PCR-diagnosis of CL.

PCR-based diagnosis of acute and chronic cutaneous leishmaniasis caused by Leishmania (Viannia)

We evaluated PCR methods for diagnosis of acute and chronic cutaneous leishmaniasis (CL) in an area of Colombia where Leishmania (Viannia) is endemic. The PCR method specifically amplified whole linearized minicircle kinetoplast DNA (kDNA) of the Leishmania subgenus Viannia from biopsy lysates. PCR products were detected in agarose gels. For 255 acute cases, this PCR method had greater sensitivity (75.7%) than each conventional method, i.e., microscopic examination of Giemsa-stained lesion scraping (46.7%), biopsy culture (55.3%), aspirate culture (46.3%), and the conventional methods combined (70.2%). Among 44 cases of chronic CL, amplification of biopsy DNA was more sensitive (45.5%) than the individual (4.5 to 27.7%) and combined (27.3%) conventional methods. The detection of kDNA in biopsies from chronic lesions was enhanced by a chemiluminescent dot blot hybridization, which produced a sensitivity of 65.8% when alone and 90.9% when in combination with DNA extraction of biopsy lysates (P < 0.001). Three biopsies from 84 skin lesions of other etiologies were falsely positive by PCR (specificity, 96.4%). PCR detected kDNA more frequently in biopsies (detection level, 83.9%) than in aspirates (74.7%) from 103 cases of acute CL. Among aspirates from 53 chronic cases of CL, the alternative methods, DNA extraction and hybridization, increased sensitivity from 41.5 to 56.6% (P > 0.05). This enhanced PCR method in chronic biopsies was so much more sensitive than conventional methods that it should be considered the preferred diagnostic method for chronic CL. These findings support the appropriate incorporation of PCR into diagnostic strategies for cutaneous leishmaniasis.

New data from old Trypanosomatid preparations

Assessing the diversity of the Trypanosomatidae is difficult because of the relatively small number of species that can be cultured. This same problem thwarts efforts to identify the hosts and insect vectors of Phytomonas, a genus of parasites of plants that includes species responsible for devastating epiphytotics of economically important plantations. Here, Myrna Serrano, Marta Teixeira and Erney Camargo review the studies that have led to the development of a PCR-based technique for processing insect and plant juices fixed on glass slides. The method overcomes the need for cultivation, facilitates field collections and also permits the molecular examination of archival smears of Phytomonas. In principle, the method can be adapted to any trypanosomatid as well as to any fastidious parasitic or free-living organism.

PCR amplification of the spliced leader gene for the diagnosis of trypanosomatid parasites of plants and insects in methanol-fixed smears

A PCR-based method was adapted for the amplification of DNA from methanol-fixed smears of insects and plants parasitized by trypanosomatids. The PCR target was the multicopy spliced leader (SL) gene. Amplicons were hybridized with an oligonucleotide probe (SL3') specific for Phytomonas. The method has the advantage of dispensing with the cultivation of parasites, many of which are very fastidious or non-cultivable. The technique was applied to archival glass slides and to newly collected material. It proved to specific for Phytomonas spp., enabling their detection in plants and insects. Sequence comparison of the amplicons obtained revealed the existence of different strains/species of Phytomonas circulating among diseased palsms and fruit.