Leishmaniasis in Brazil: XV. Biochemical distinction of Leishmania mexicana amazonensis, L. braziliensis braziliensis and L. braziliensis guyanensis--aetiological agents of cutaneous leishmaniasis in the Amazon Basin of Brazil

Further insights into the eco-epidemiology of American cutaneous leishmaniasis in the Belem metropolitan region, Pará State, Brazil

INTRODUCTION:

In the Belém Metropolitan Region (BMR), Pará State, Brazil, American cutaneous leishmaniasis (ACL) is endemic; however, very little is known regarding its causative agents. Therefore, we used our standard diagnostic approach combined with an RNA polymerase II largest subunit (RNAPOIILS)-polymerase chain reaction (PCR) followed by analysis of restriction fragment length polymorphism (PCR-RFLP) to identify Leishmania spp. ACL agents in this region.

METHODS:

Thirty-two Leishmania spp. isolates from patients with ACL in the BMR during 1995-2018 were analyzed. Leishmania spp. DNA samples were amplified using the primers RPOR2/RPOF2, and the 615-bp PCR products were subjected to enzymatic digestion using TspRI and HgaI endonucleases.

RESULTS:

ACL etiological agents in the BMR comprised Leishmania (Viannia) lindenbergi (43.7%) followed by Leishmania (Viannia) lainsoni (34.4%), Leishmania (Leishmania) amazonensis (12.5%), and Leishmania (Viannia) braziliensis (9.4%).

CONCLUSIONS:

To our knowledge, the results of the study revealed for the first time that L. (V.) lindenbergi and L. (V.) lainsoni are the main ACL agents in BMR.

Phenotypic characterization of Leishmania spp. causing cutaneous leishmaniasis in the lower Amazon region, western Pará state, Brazil, reveals a putative hybrid parasite, Leishmania (Viannia) guyanensis × Leishmania (Viannia) shawi shawi

We phenotypically characterized 43 leishmanial parasites from cutaneous leishmaniasis by isoenzyme electrophoresis and the indirect immunofluorescence antibody test (23 McAbs). Identifications revealed 11 (25.6%) strains of Leishmania (V.) braziliensis, 4 (9.3%) of L. (V.) shawi shawi, 7 (16.3%) of L. (V.) shawi santarensis, 6 (13.9%) of L. (V.) guyanensis and L. (V.) lainsoni, 2 (4.7%) of L. (L.) amazonensis, and 7 (16.3%) of a putative hybrid parasite, L. (V.) guyanensis/L. (V.) shawi shawi. McAbs detected three different serodemes of L. (V.) braziliensis: I-7, II-1, and III-3 strains. Among the strains of L. (V.) shawi we identified two populations: one (7 strains) expressing the B19 epitope that was previously considered to be species-specific for L. (V.) guyanensis. We have given this population sub-specific rank, naming it L. (V.) s. santarensis. The other one (4 strains) did not express the B19 epitope like the L. (V.) shawi reference strain, which we now designate as L. (V.) s. shawi. For the first time in the eastern Brazilian Amazon we register a putative hybrid parasite (7 strains), L. (V.) guyanensis/L. (V.) s. shawi, characterized by a new 6PGDH three-band profile at the level of L. (V.) guyanensis. Its PGM profile, however, was very similar to that of L. (V.) s. shawi. These results suggest that the lower Amazon region - western Pará state, Brazil, represents a biome where L. (V.) guyanensis and L. (V.) s. shawi exchange genetic information.

Developments in diagnosis and antileishmanial drugs

Leishmaniasis ranks the third in disease burden in disability-adjusted life years caused by neglected tropical diseases and is the second cause of parasite-related deaths after malaria; but for a variety of reasons, it is not receiving the attention that would be justified seeing its importance. Leishmaniasis is a diverse group of clinical syndromes caused by protozoan parasites of the genus Leishmania. It is estimated that 350 million people are at risk in 88 countries, with a global incidence of 1–1.5 million cases of cutaneous and 500,000 cases of visceral leishmaniasis. Improvements in diagnostic methods for early case detection and latest combitorial chemotherapeutic methods have given a new hope for combating this deadly disease. The cell biology of Leishmania and mammalian cells differs considerably and this distinctness extends to the biochemical level. This provides the promise that many of the parasite's proteins should be sufficiently different from hosts and can be successfully exploited as drug targets. This paper gives a brief overview of recent developments in the diagnosis and approaches in antileishmanial drug discovery and development.

Sand fly captures with Disney traps in area of occurrence of Leishmania (Leishmania) amazonensis in the state of Mato Grosso do Sul, mid-western Brazil

INTRODUCTION: The work was conducted to study phlebotomine fauna (Diptera: Psychodidae) and aspects of American cutaneous leishmaniasis transmission in a forested area where Leishmania (Leishmania) amazonensis occurs, situated in the municipality of Bela Vista, State of Mato Grosso do Sul, Brazil. METHODS: The captures were conducted with modified Disney traps, using hamster (Mesocricetus auratus) as bait, from May 2004 to January 2006. RESULTS: Ten species of phlebotomine sandflies were captured: Brumptomyia avellari, Brumptomyia brumpti, Bichromomyia flaviscutellata, Evandromyia bourrouli, Evandromyia lenti, Lutzomyia longipalpis, Psathyromyia campograndensis, Psathyromyia punctigeniculata, Psathyromyia shannoni and Sciopemyia sordellii. The two predominant species were Ev bourrouli (57.3%) and Bi flaviscutellata (41.4%), present at all sampling sites. Two of the 36 hamsters used as bait presented natural infection with Leishmania. The parasite was identified as Leishmania (Leishmania) amazonensis. CONCLUSIONS: Analysis of the results revealed the efficiency of Disney traps for capturing Bichromomyia flaviscutellata and the simultaneous presence of both vector and the Leishmania species transmitted by the same can be considered a predictive factor of the occurrence of leishmaniasis outbreaks for the human population that occupies the location.

The molecular epidemiology and phylogeography of Trypanosoma cruzi and parallel research on Leishmania: looking back and to the future

Trypanosoma cruzi is the protozoan agent of Chagas disease, and the most important parasitic disease in Latin America. Protozoa of the genus Leishmania are global agents of visceral and cutaneous leishmaniasis, fatal and disfiguring diseases. In the 1970s multilocus enzyme electrophoresis demonstrated that T. cruzi is a heterogeneous complex. Six zymodemes were described, corresponding with currently recognized lineages, TcI and TcIIa-e – now defined by multiple genetic markers. Molecular epidemiology has substantially resolved the phylogeography and ecological niches of the T. cruzi lineages. Genetic hybridization has fundamentally influenced T. cruzi evolution and epidemiology of Chagas disease. Genetic exchange of T. cruzi in vitro involves fusion of diploids and genome erosion, producing aneuploid hybrids. Transgenic fluorescent clones are new tools to elucidate molecular genetics and phenotypic variation. We speculate that pericardial sequestration plays a role in pathogenesis. Multilocus sequence typing, microsatellites and, ultimately, comparative genomics are improving understanding of T. cruzi population genetics. Similarly, in Leishmania, genetic groups have been defined, including epidemiologically important hybrids; genetic exchange can occur in the sand fly vector. We describe the profound impact of this parallel research on genetic diversity of T. cruzi and Leishmania, in the context of epidemiology, taxonomy and disease control.

Multilocus enzyme electrophoresis for parasites and other pathogens

In this chapter, I expose the main properties and theoretical background of a somewhat out-of-fashion technique, multilocus enzyme electrophoresis (MLEE). I show that the remarkable properties of this marker-clear Mendelian inheritance, codominance, strong phylogenetic signal-are still valid, although of course more modern markers now are able to yield far more refined results. MLEE can still be used in many circumstances when a cheap and reliable marker is required. I summarize what have been the main contributions of MLEE to the study of parasites and other pathogens.

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

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

Species diversity causing human cutaneous leishmaniasis in Rio Branco, state of Acre, Brazil

OBJECTIVE

Information on Leishmania species diversity in western Brazilian Amazon and the clinical picture of human cutaneous leishmaniasis it causes is scarce. We describe clinical findings, diagnostic procedures and identification of Leishmania species in patients from that region.

METHODS

The sample consisted of 50 patients, prospectively evaluated for epidemiological and clinical characteristics by means of a structured questionnaire. Conventional and molecular tools were applied to confirm the parasitological diagnosis and identify the species responsible for the disease.

RESULTS

Patients were predominantly male (76.5%) and living in rural areas. Median average age was 18 years and median average disease evolution was 8 weeks. For the diagnostic procedures of leishmanin skin test, direct visualization of amastigotes in dermal scrapings and parasite culture of aspirates of the ulcer border were positive for 98%, 52% and 34%, respectively. Molecular methods applied to DNA extracted from skin biopsies of the 50 patients yielded 100%, 82% and 44% positivity by PCR minicircle kDNA, PCR-RFLP ITS1rDNA and PCR-glucose-6-phosphate (G6P), respectively. Fourteen samples from 13 patients were successfully isolated and identified. Multilocus enzyme electrophoresis, PCR-RFLP ITS1rDNA and PCR-G6P permitted identification of the Leishmania species responsible for the aetiology of American tegumentary leishmaniasis in 60% of the examined patients: 16 Leishmania (Viannia) braziliensis, 12 Leishmania (Viannia) lainsoni, 1 Leishmania (Viannia) guyanensis and 1 putative hybrid of Leishmania (Viannia) naiffi and L. (V.) lainsoni.

CONCLUSION

The clinical and epidemiological behaviour of cutaneous leishmaniasis in Acre, Brazil, is similar to other Amazon scenarios previously described; however Acre's complex parasite diversity may be contributed to the concomitant circulation of at least three distinct Leishmania species. The implementation of control interventions in the studied area must take into consideration the possibility of various expected phlebotomine vectors and reservoirs.

Microsatellite DNA: a tool for population genetic analysis

Microsatellite deoxyribonucleic acid repeats provide a source of high variability that makes them ideal for use in studies requiring such molecular markers, including large population studies and genetic typing of individuals for kinship investigations. This paper provides reviews of the use of such markers in parasitology. Most studies to date have been carried out using protozoan and vector species. Recent investigations have, however, demonstrated their usefulness in the study of helminths, illustrating their ability to distinguish between individuals within hosts as well as from different hosts. The detection of microsatellites within parasites has provided a tool that will prove invaluable in parasitology and should lead to significant advances in our understanding of the processes that affect the organisms' population genetic structure.

[Cutaneous leishmaniasis in Amazonia: isolation of Leishmania (Viannia) lainsoni from the rodent Agouti paca (Rodentia: Dasyproctidae), in the state of Pará, Brazil]

The isolation of Leishmania (V.) lainsoni is recorded for the first time from a wild animal, the rodent Agouti paca (Rodentia: Dasyproctidae), from Pará State, north Brazil. Isolates of the parasite were made from apparently normal skin of 3 specimens of this rodent captured on the Island of Tocantins, in the municipality of Tucuruí, an area subsequently flooded in the formation of the lake associated with the Tucuruí hydroelectric dam. No isolations were made from the viscera. Identification of the parasite was in each case based on morphology of the amastigotes and promastigotes, behavior of the organism in hamsters, isoenzymes profiles and the use of monoclonal antibodies. The inapparent nature of the infection leads us to suggest that the "paca", Agouti paca, represents a primitive host of L. (V.) lainsoni in the Amazon Region.

Biochemical characterization of Leishmania spp. isolated from man and wild animals in Kenya

Isoelectrofocusing in agarose was used to characterize Leishmania spp. isolated from a kala-azar patient, a lizard, genet cat and elephant shrew. Isoenzyme profiles of 12 enzymes and general protein patterns were examined. Both methods were found to be useful for distinguishing between the isolates. The wild animal Leishmania spp. were shown to be indistinguishable from a reference strain of L. major, but the isolate from man was distinctly different from L. donovani sensu stricto. The unique finding that the lizard isolate was similar to L. major and its significance are discussed in some detail. The use of the isoelectrofocusing technique for separation of enzymes and general proteins for characterization purposes is emphasized.

Cell-mediated immunity in localized cutaneous leishmaniasis patients before and after treatment with immunotherapy or chemotherapy

In previous studies of the treatment of localized cutaneous leishmaniasis (LCL) we demonstrated that the therapeutic efficiency of immunotherapy (BCG plus promastigotes of Leishmania mexicana) is equal to that of chemotherapy (Glucantime), without causing the serious side-effects of the drug treatment. In the present study, various aspects of cell-mediated immunity, including the lymphoproliferative response, and leucocyte subpopulations were evaluated both before treatment and after cure in 39 LCL patients who had received immunotherapy (IT), in 34 submitted to chemotherapy (CT), and in 14 patients cured by the administration of BCG alone. We demonstrated evident signs of T-cell activation in cured patients who had received either CT or IT. For example, an increased expression of IL-2 receptors was observed in such patients, compared to their pretreatment values. Also, a significant percentage of patients showed augmented in-vitro responses to mitogen, and both in-vitro and in-vivo reactivity to leishmanial antigen. No evidence was found for the development of an exaggerated immune response to Leishmania parasites in the IT group, because the final level of immunological reactivity was comparable to the CT group. Neither was there any difference in terms of the final immune response between the patients cured by BCG treatment alone and the other groups. However, the therapeutic efficiency of BCG was lower and the mean cure time was longer. We conclude that IT is very useful in the treatment of LCL patients because of its high efficiency, low propensity to produce side-effects, and the fact that it does not induce a state of hyper-reactivity.

Acid phosphatase isoenzyme mapping in Leishmania

The profiles of acid phosphatase isoenzymes of several well defined species of the genus Leishmania were compared. The profiles were generated after isoelectric focusing of parasite extracts in polyacrylamide and incubation of the gels with an appropriate substrate coupled to an azo dye. Analysis of the zymograms showed that there is species-specificity of the acid phosphatase isoenzyme maps in Leishmania. It was also demonstrated that different strains of the same species present identical pattern of enzyme activity. The method even enabled the differentiation of closely related species which were previously difficult to identify. Some technical aspects of the isoelectric focusing procedure are discussed. The method described here can be used as an aid for species identification of Leishmania.

T-cell subpopulations, expression of interleukin-2 receptor, and production of interleukin-2 and gamma interferon in human American cutaneous leishmaniasis

Leukocyte subpopulations, the expression of the interleukin-2 (IL-2) receptor, and the production of IL-2 and gamma interferon (IFN-gamma) were studied in the peripheral blood mononuclear cells of American cutaneous leishmaniasis patients that had been stimulated in vitro with either leishmanial antigen or mitogen (phytohemagglutinin M). The 75 patients examined were classified as having either the localized (LCL; 66 patients), mucocutaneous (MCL; 5 patients), or the rare diffuse (DCL; 4 patients) form of the disease. Patients with DCL, who are characterized by their defective cell-mediated immune response to leishmanial antigen, failed to express the IL-2 receptor and did not produce IFN-gamma when exposed to the antigen but did so when stimulated by phytohemagglutinin M. Both LCL and MCL patients showed strong proliferative responses to leishmanial antigen; these were by far the greatest in MCL patients. Both groups had significantly increased IL-2 receptor expression and IFN-gamma production after exposure to either antigen or mitogen, and these were highest in the MCL patients. Concerning the leukocyte subpopulations evaluated (CD2, CD4, CD8, CD20, MO2), the most significant findings were a decrease of both CD4+ cells and the CD4/CD8 ratio in MCL patients compared with the other groups. Considering IL-2 production, in response to phytohemagglutinin M both MCL and LCL patients showed amounts of IL-2 comparable to those of the controls. Our results help explain the anergy of T cells from DCL patients to leishmanial antigen, which could lead to a defective production of IFN-gamma and possibly contribute to their incapacity to kill the Leishmania parasite. Concerning MCL patients, the significantly increased expression of IL-2 receptor, decreased expression of the CD4 (helper-inducer of suppression) phenotype, and elevated IFV-gamma production might partially explains the state of hypersensitivity and mucosal damage exhibited by these patients.

Epidemiology of a natural focus of Leishmania braziliensis in the Pacific lowlands of Colombia. III. Natural infections in wild mammals

A natural infection of Leishmania braziliensis panamensis in the edentate, Choloepus hoffmanni is recorded from the Pacific Coast of Columbia.

Responsiveness in diffuse versus local cutaneous leishmaniasis is due to parasite differences

Leishmania aethiopica infection results in two main clinical entities, diffuse disease (DCL) and localized ulcers (LCL). The lack of reactivity to leishmanial antigens has been attributed, among other things, to some inherent immunological defect of the host or considered as a consequence of the initial site of infection. Properties unique to the infecting parasite have been said to contribute little if anything to the differences between DCL and LCL found in the same areas of Ethiopia. Data are given to show that infected individuals respond by higher production of IL-2 to antigens from LCL isolates (lcl antigen), than to antigens derived from DCL isolates (dcl antigen). Furthermore, dcl antigen induced less gamma interferon from lymphocytes of all individuals tested than did lcl antigen. Lymphocytic proliferation of cells from control individuals working in the endemic area was higher in response to lcl isolates than to dcl isolates. These findings suggest that some differences in the parasites may contribute to the clinical outcome of infection with L. aethiopica.

Evolution of the genus Leishmania as revealed by comparisons of nuclear DNA restriction fragment patterns

Restriction endonuclease DNA fragment patterns have been used to examine the relationships among 28 isolates of Leishmania as well as Crithidia, Endotrypanum, and Trypanosoma cruzi. Fragments of nuclear DNA were generated with six restriction enzymes, and blots were hybridized with probes from three loci. Among the major lineages the fragment patterns are essentially completely different, while within the major lineages various degrees of divergence are found. Molecular evolutionary trees were constructed using the method of Nei and Li to estimate the percent nucleotide sequence divergence among strains from the fraction of fragments shared. Defined groups, such as species or subspecies within the major lineages, are also grouped by nuclear DNA comparisons. Within the donovani complex, we find Leishmania donovani chagasi and Leishmania donovani infantum to be as similar as strains within Leishmania donovani donovani, consistent with the proposal by other workers that New World visceral leishmaniasis originated quite recently.

A focus of mucocutaneous leishmaniasis in Três Braços, Bahia, Brazil: characterization and identification of Leishmania stocks isolated from man and dogs

The characterization and identification to species and subspecies of 20 stocks of Leishmania isolated from the region of Três Braços, Bahia, Brazil, are described: 17 stocks were from patients and three from dogs. The following techniques were used (i) biological (growth in culture, hamster tissues and phlebotomine gut), (ii) biochemical (isoenzyme and kinetoplast DNA analysis) and (iii) immunological (using monoclonal antibodies). All except two stocks belong to the L. braziliensis complex. One of these two corresponded to L. mexicana amazonensis but the other, while clearly in the mexicana complex, showed slight differences from the L. mexicana amazonensis reference strain on isoenzyme analysis. Two stocks from different lesions in the same patient and with different growth characteristics in hamster tissues were both identified as L. braziliensis braziliensis. All the fully characterized stocks of the L. braziliensis complex were identified as L. braziliensis braziliensis. L. braziliensis guyanensis was not identified. Dog and human stocks of L. braziliensis braziliensis were indistinguishable. From these findings and other evidence, L. braziliensis braziliensis seems to be the predominant species transmitted in Três Braços.

[Cutaneous leishmaniasis in Amazonia. Report of the 1st human case of mixed infection, determined by 2 different Leishmania species: Leishmania brasiliensis and Leishmania mexicana amazonensis]

Fez-se o registro, na Amazônia, do primeiro caso humano de infecção cutânea mista determinada por duas espécies distintas de Leishmania: a Leishmania braziliensis braziliensis e a Leishmania mexicana amazonensis. As duas amostras, em questão, foram isoladas de lesões distintas de um mesmo paciente, e a caracterização das espécies foi feita com base em observações de infecção experimental em hamsters, comportamento em meios artificiais de cultura, desenvolvimento de infecção experimental em Lutzomyia longipalpis, e eletroforese de isoenzimas em gel de amido. Conclui-se ser de interesse o achado que, combinado com o fato já conhecido de ausência de imunidade cruzada entre a maioria das leishmânias, sugere a necessidade do emprego de uma vacina polivalente para a região.

Características epidemiológicas da leishmaniose tegumentar americana em uma região endêmica do Estado da Bahia: II leishmaniose canina

Um inquérito em cães realizado na região de Três Braços, Bahia, mostrou que 3,0% de 98 animais tinham amastigotas em lesões de pele. Parasitos não foram encontrados em pele normal da orelha. De uma amostra selecionada de 13 cães, portadores de lesão cutânea ativa, nove (69,2%) deles estavam comprovadamente infectados. Sete amostras de lesão produziram infecção em hamsters. O estudo biológico (crescimento em meio de cultura, evolução da lesão em hamster e desenvolvimento no tubo digestivo de Lutzomyia longipalpis) identificou o parasito como pertencente ao complexo L. braziliensis. A caracterização bioquímica (mobilidade eletroforética de enzimas em placas de acetato de celulose) e o estudo imunotaxonômico (anticorpos monoclonais) definiram as amostras como L. braziliensis braziliensis. O papel do cão como um possível reservatório de L. b. braziliensis na região de Três Braços é discutido.

Identification of cross-reactive promastigote cell surface antigens of some leishmanial stocks by 125I labeling and immunoprecipitation

Externally oriented surface membrane constituents of promastigotes from several Leishmania species were radiolabeled with 125I. Autoradiographs of cell surface-labeled and sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated proteins of the stocks revealed distinctive patterns of bands in the molecular weight range of 6,000 to 240,000. Immunoprecipitation of detergent extracts of the labeled promastigote stocks with anti-Leishmania donovani membrane serum demonstrated that each of the stocks contained some antigenically cross-reactive determinants. The electrophoretic patterns of these determinants serve both to distinguish the parasite stocks (by unique, species-specific patterns) and to indicate antigenic similarities in stocks thought to be different by other biochemical criteria. At least 12 cross-reactive cell surface antigens in two New World leishmanias are recognized by polyvalent anti-L. donovani serum, suggesting that these common leishmanial antigens may account for the documented serological cross-reactivities among various Leishmania species. In all stocks tested, an iodinated protein was identified which had a relative molecular weight of 65,000 under reducing conditions but which demonstrated an increase in relative mobility in sodium dodecyl sulfate-polyacrylamide gels under nonreducing conditions. Distinctive patterns of the antigens common to the several stocks were also demonstrated with the use of monoclonal antibodies.

The isolation and isoenzyme characterization of Leishmania braziliensis subsp. from patients with cutaneous leishmaniasis acquired in Belize

Leishmanial organisms were cultivated from cutaneous lesions of British military personnel returning from Belize. Isoenzyme profiles of the freshly isolated organisms and 'marker' strains of New World Leishmania spp. were compared using 10 enzymes (ALAT, ASAT, ME, GPI, MPI, PGM, SOD, 6-PGDH, G-6-PDH and MDH), by starch gel electrophoresis. 19 of the 22 new isolates from Belize were isoenzymically indistinguishable from Leishmania braziliensis braziliensis (10 out of 10 enzymes) and clearly differentiated from L. b. guyanensis and L. b. panamensis (different in 6 out of 10 enzymes) and from L. mexicana mexicana and L. m. amazonensis (9 out of 10 enzymes). Two isolates closely resembled L. m. mexicana and one could not be positively identified. This is the first report of autochthonous human leishmaniasis caused by L. braziliensis group organisms as far north as latitude 16 degrees N.

Sexual processes in the kinetoplastida

The commonly held view that the kinetoplastida, and in particular trypanosomes, are asexual is largely derived from the principle that an organism is asexual until proved sexual. If the basis for this view is examined in detail, it largely arises from the lack of morphologically distinguishable gametes, the difficulties encountered in visualizing chromosomes and a few experiments, using drug-resistant stocks, in which no recombination between stocks could be demonstrated. While it is clear that these organisms are able to reproduce asexually, the existence of a sexual cycle was, until recently, an entirely open question. The early work strongly suggests that any sexual process (in the species examined extensively at the morphological level) does not involve classical well-differentiated gametes and so must involve fusion of morphologically very similar cells. These findings taken together with the inability to visualize chromosomes and thereby identify meiosis, mean that classical methods are unable to detect any sexual process even if it did occur. This review examines the evidence provided by the experimental approaches which have been applied recently to the question of kinetoplastid sexuality. These approaches include isoenzyme studies and the analysis of possible genetic exchange by the use of selective markers (e.g. drug resistance). The results which these techniques have produced make it clear that the kinetoplastid protozoans cannot be regarded as a totally asexual group of organisms.

The use of DNA probes in the identification of leishmanias: discrimination between isolates of the Leishmania mexicana and L. braziliensis complexes

Kinetoplast DNA (kDNA), initially characterized by buoyant density, from ten reference isolates of the Leishmania braziliensis and L. mexicana complexes has been radio-actively labelled and used as hybridization probes. Filters containing endonuclease digested, electrophoresed, Southern transferred fragments of kDNA from reference and other isolates sent to us for DNA typing have been tested for kDNA sequence homology. We record a complete lack of sequence homology between kDNA of any isolate of the L. braziliensis complex and kDNA of any isolate of the L. mexicana complex. L. b. braziliensis, L. b. guyanensis and L. b. panamensis have kDNA sequences in common with each other and with a number of test isolates from Brazil, Panama, Venezuela and Peru. L. b. panamensis (1.695 g/ml) can be separated from L. b. braziliensis or L. b. guyanensis (1.691-1.693 g/ml) by differences in buoyant density of kDNA. L. m. mexicana and L. m. pifanoi have kDNA sequences in common with each other but kDNA of L. m. amazonensis has insignificant homology with kDNA of other reference isolates of the L. mexicana complex. We conclude that the kDNAs of species of the L. mexicana complex are sufficiently different from kDNA of species of the L. braziliensis complex to make kDNA sequence homology identification a feasible proposition.

A genetic comparison between Brazilian and Bolivian zymodemes of Trypanosoma cruzi

The enzyme profiles of three major Brazilian Trypanosoma cruzi zymodemes (Brazilian Z1, Brazilian Z2, Brazilian Z3) and of two principal Bolivian zymodemes were compared. Relationships were assessed both intuitively and by calculating genetic distances. One of the Bolivian zymodemes, Bolivian Z1, was closely related to the Brazilian Z1. The second Bolivian zymodeme, Bolivian Z2, was related to brazilian Z2 but differed from all the Brazilian zymodemes in the occurrence of typical heterozygous isozyme patterns in five out of 12 enzyme loci. Parental stocks and clones of Bolivian Z2 had the same putative heterozygous patterns. The evidence from enzyme profiles on the ploidy of T. cruzi and the possibility of recombination was considered. The presence of putative heterozygous patterns in Bolivian Z2 supported the hypothesis that T. cruzi is diploid. The definition of T. cruzi as a single polytypic species or as a species complex was considered to be dependent on the presence or absence of genetic recombination between or within the zymodemes, which has not been demonstrated in the ecotopes so far examined.

The American leishmaniases: some observations on their ecology and epidemiology

As the first species of Leishmania encountered were the agents of human visceral and cutaneous leishmaniasis, it is understandable that studies on these parasites for a long time concentrated on those organisms commonly causing disease in man. Epidemiological studies over the past 20 years or so, however, have led to the inescapable conclusion that the genus Leishmania is comprised of numerous species of well adapted parasites, in a wide range of mammals, throughout most of those tropical and subtropical regions of the world where phlebotomine sandflies exist (Diptera: Psychodidae). Many of the leishmanias probably never gain entrance into man: due either to an incapacity to survive in his tissues, or (more likely) because the natural sandfly vectors do not feed on him. The leishmanias that do infect man are, nevertheless, among the greatest protozoological scourges of mankind, and a better understanding of their life-cycles may well help in future prevention or control of the diseases they cause. With few exceptions the leishmaniases are zoonoses, with a major source of infection in wild or domestic animals. In the Americas, the disease is essentially a rural one, and most commonly acquired by those penetrating forested or wooded regions. The following paper deals with the better known human leishmaniases of the New World, and some new ones, and discusses the major historical events in the laborious task of elucidating their ecology and epidemiology.

Monoclonal antibodies to Leishmania tropica major: specificities and antigen location

Six murine monoclonal antibodies to Leishmania tropica major have been prepared and the properties of these antibodies studied. Two (WIC 79.3 and 79.7) were L. tropica major species-specific and bound to promastigote cell surfaces, to parasitized macrophages, but not isolated amastigotes. No evidence was found for the production of antibody to the antigenic determinants recognized by WIC 79.3 or 79.7 during L. tropica major infections in mice and hamsters. One antibody (WIC 79.1) bound to sub-cellular organelles of Leishmania species but to a different sub-cellular organelle of Trypanosoma cruzi. Two others bound to the flagellum, one (WIC 79.2) to all Leishmania species, T. cruzi and Trypanosoma brucei, the other (WIC 79.4) only of L. tropica major and L. donovani species. One antibody (WIC 79.5) was directed against an unknown internal antigen found in all Leishmania species and T. cruzi.

Leishmaniasis in Brazil: XVII. Enzymic characterization of a Leishmania from the armadillo, Dasypus novemcinctus (Edentata), from Pará State

A comparison of enzyme profiles, by starch-gel electrophoresis, has distinguished a Leishmania of armadillos (Dasypus novemcinctus), from Pará State, north Brazil, from Leishmania braziliensis braziliensis, L. braziliensis guyanensis, L. mexicana amazonensis, L. donovani sensu lato (from Bahia, Brazil), and L. hertigi deanei. The parasite was separated from L. b. braziliensis and L. b. guyanensis by 8 of the 14 enzymes used (ASAT, ALAT, PGM, GPI, G6PD, PEP, MPI and GD), although differences in the mobility of some of the enzymes were small. At least 9 of the enzymes separated the organism from L. m. amazonensis, L. donovani s.l., and L. h. deanei.

Leishmaniasis in Brazil: XVI. Isolation and identification of Leishmania species from sandflies, wild mammals and man in north Para State, with particular reference to L. braziliensis guyanensis causative agent of "pian-bois"

A total of 125 wild mammals (14 different species) were examined for evidence of infection with Leishmania in an area of primary forest highly endemic for "pian-bois", due to Leishmania braziliensis guyanensis, in north Pará State, Brazil. Parasites isolated were characterized biologically, and biochemically on enzymic profiles. L. b. guyanensis was isolated from the viscera of one lesser anteater (Tamandua tetradactyla) and one opossum (Didelphis marsupialis), and the skin of one rodent (Proechimys guyannensis). The isolates were indistinguishable from 10 others previously made from the sandfly vectors Lutzomyia umbratilis (five) and Lu. whitmani (five), and nine isolates from field-workers who became infected during these studies. Leishmania mexicana amazonensis was obtained from the skin of 21 animals, including three species of opossums (D. marsupialis, Philander opossum and Metachirus nudicaudatus) and two species of rodents (proechimys guyannensis and Dasyprocta sp.). A peripylarian Leishmania isolated from the viscera of two armadillos (Dasypus novemcinctus) was shown to be different, biologically and biochemically, from L. b. guyanensis and L. m. amazonensis. Four other isolates of Leishmania, from the rodents Rhipidomys leucodactylus (one) and P. guyannensis (three) have yet to be characterized owing to their very poor growth in both hamster skin and in vitro culture: they appear closest, however, to L. braziliensis braziliensis. The complexity of Amazonian leishmaniasis is discussed, and attention drawn to the importance of edentates as reservoir hosts of some leishmanias in the New World. Whereas L. mexicana subspecies appear largely restricted to the skin of their natural hosts, subspecies of L. braziliensis are commonly found in the viscera.

The opossum, Didelphis marsupialis (Marsupialia: Didelphidae), as a reservoir host of Leishmania braziliensis guyanensis in the Amazon Basin of Brazil

A total of 52 opossums (six species) were examined for evidence of infection with Leishmania in three different areas of forest near Manaus, Amazonas State, Brazil. No infections were detected in 27 opossums from a region of relatively undisturbed forest, including specimens of Didelphis marsupialis (18); Metachirus nudicaudatus (four); Monodelphis brevicaudata (one); Marmosa cinerea (two); M. murina (one) and M. parvidens (one). Of 15 D. marsupialis captured from a biological reserve, much disturbed by man, three were infected with L. braziliensis guyanensis: isolations were made from the skin of two of the animals, and from the viscera of the third. The isolates were biologically and biochemically indistinguishable from one isolate of L. b. guyanensis made from man and two from the sandfly vector Lutzomyia umbratilis from the same area. Two of eight D. marsupialis and both of two M. cinerea from another area of virgin forest used for army manoeuvres were infected with Leishmania mexicana amazonensis: the parasite was in all four cases isolated from normal skin. Five of nine specimens of Proechimys guyannensis, from the vicinity of Manaus, were also infected with L. m. amazonensis. A further 13 mammals (eight species) were negative for Leishmania. The importance of opossums as a reservoir of L. b. guyanensis is discussed. Although they may play only a minor role in virgin forest which is undisturbed by man, opossums (D. marsupialis) may become a significant reservoir of infection where man's activities have eliminated the major reservoir--which has yet to be incriminated.