[Sensitivity of the culture of circulating leukocytes in the detection of Leishmania in the peripheral blood of patients with tegumentary leishmaniasis]

Anthropogenic Dispersal of Leishmania (Viannia) braziliensis in the Americas: A Plausible Hypothesis

There are several gaps in our knowledge on the origin and spread of Leishmania (Viannia) braziliensis, an etiological agent of cutaneous and mucocutaneous or American tegumentary leishmaniasis, to different biomes, hosts, and vectors, with important epidemiological implications, including the possible existence of an anthroponotic component. Historical, biological, and epidemiological evidence suggests that Leishmania (V.) braziliensis and its variants were preexistent in Amazonia with great genetic variability, where they dispersed with less variability to other regions (clonal expansion). During pre-Columbian times the parasite may have been transported by migrating humans and probably also their dogs, from western Amazonia to the high inter-Andean valleys and from there to other regions of South America. The same thing could have happened later, in the same way, when it spread to non-Amazonian regions of Brazil and other countries of South and Central America, between the late 19th and early 20th centuries, during the so-called Rubber Boom and construction of the Madeira-Mamoré Railway in the Brazilian Amazon, by migrant workers who later returned to their places of origin, transporting the agent. The parasite’s dispersal in genetic correlated clusters, involving unexpectedly distinct ecosystems in Brazil (Amazonian, Cerrado, Caatinga and Atlantic Forest biomes), has continued until the present through human displacement. The infection of certain species of domestic, synanthropic and even wild animals, could be secondary to anthropogenic introduction of L. (V.) braziliensis in new environments. We admit the same phenomena happening in the probable transference of Leishmania infantum (visceral leishmaniasis), and of Yersinia pestis (plague) from the Old world to the New world, generating domestic and wild enzotic cycles from these agents. These assumptions associated with human infections, chronicity and parasite persistence with possibility of recovery of Leishmania in peripheral blood, skin and scars of cured or asymptomatic patients, (that may provide an alternative blood meal), along with the sand flies’ adaptation to the peri-domicile and the high susceptibility of domestic dogs, horses, mules and cats to the parasite, can reinforce the evidence of anthropogenic spread of L. (V.) braziliensis.

PCR associated with molecular hybridization detects Leishmania (Viannia) braziliensis in healthy skin in canine tegumentary leishmaniasis

Tegumentary leishmaniasis (TL) is a zoonotic disease that affects humans and domestic dogs. In Brazil, TL is considered endemic, and Leishmania (Viannia) braziliensis is the prevalent species causing this disease. There is debate about the role of dogs (Canis familiaris) as domestic reservoirs in the transmission cycle of TL. To date, classical parasitological techniques, including parasite isolation in culture media, have been able to detect parasites only from cutaneous lesions. In this study, we detected L. (V.) braziliensis DNA in intact skin fragments collected from 3 naturally infected dogs from the state of Rio de Janeiro, Brazil, with the use of PCR techniques associated with molecular hybridization. The detection of parasitic DNA in this anatomical site is an important finding vis-à-vis the importance of the domestic dogs in endemic areas of TL.

Detection of Leishmania (Viannia) DNA in blood from patients with American cutaneous leishmaniasis

The aim of the present study was to investigate the presence of Leishmania (Viannia) subgenus DNA in peripheral blood from patients with cutaneous lesions due to American cutaneous leishmaniasis. The buffy coats from 68 blood samples were analyzed by polymerase chain reaction using the MP1L/MP3H primers. The parasite DNA was detected in 2 (3.4%) out of 59 patients who had amastigotes present in samples taken from lesions. The presence of Leishmania (Viannia) DNA in the blood of these patients indicates hematogeneous parasite dissemination.

Haematogenous dissemination of Leishmania (Viannia) braziliensis in human American tegumentary leishmaniasis

One of the potential dangers of American tegumentary leishmaniasis (ATL) caused by Leishmania (Viannia) braziliensis is the development of mucosal lesions. Haematogenous dissemination of the parasite is the most likely mechanism to explain this occurrence, but most attempts to isolate the parasite from blood have so far been unsuccessful. The presence of Leishmania in peripheral blood was therefore evaluated by PCR using DNA samples isolated from patients presenting active cutaneous or mucosal disease, and from individuals cured by antimonial treatment as well as individuals without a past history of leishmaniasis but with a positive Montenegro skin test, all living in L. (V.) braziliensis-endemic areas. Leishmania DNA was found not only in those patients presenting active cutaneous (24.8%) or mucosal (35%) lesions, but also in samples isolated from healed individuals (27.3%) as well as in asymptomatic skin-test-positive residents of endemic areas (37.5%). Overall, PCR showed the presence of parasite DNA in the blood of 26.2% of the 225 examined samples. These data suggest that persistence of parasites within the host may last for many years and, rather than being a risk factor, might be important in maintaining the protective response in those living in endemic areas.

Is Leishmania (Viannia) braziliensis preferentially restricted to the cutaneous lesions of naturally infected dogs?

Nineteen dogs naturally infected with Leishmania (Viannia) braziliensis were studied in order to determine the presence of the parasite outside cutaneous lesions. Eleven (57.9%) animals showed single cutaneous or mucosal lesions and eight (42.1%) presented two or three lesions. Twenty-eight active lesions were biopsied. Isolation in culture and characterization by enzyme electrophoresis were possible in 100% of cases and amastigote forms were visualized upon histopathological examination in three samples (n=25, 12%). Isolation of the parasite in culture from peripheral blood and intact skin fragments obtained from the scapular region was negative in all animals, as was the histopathological analysis of skin from this region. Serological reactivity determined by an immunofluorescent antibody test and/or enzyme-linked immunosorbent assay was demonstrated in 15 animals. The results obtained suggest that L. braziliensis preferentially remains at the site of lesion, in contrast to the systemic distribution of parasites observed in dogs infected with L. (Leishmania) chagasi. A better understanding of this aspect may help direct diagnostic and control strategies applicable to areas characterized by the simultaneous occurrence of the cutaneous and visceral forms of leishmaniasis, as is the case for the Municipality of Rio de Janeiro, Brazil.

Parasitological and immunological follow-up of American tegumentary leishmaniasis patients

A long-term evaluation of human American tegumentary leishmaniasis patients was conducted to detect immunological and/or parasitological indicators associated with cure or protection against leishmaniasis. Cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML) patients from endemic areas of Leishmania braziliensis infection in Brazil were studied during the active disease, at the end of therapy, and up to 10 years after the end of therapy. For immunological studies, lymphocyte proliferative responses, phenotypic characterization of CD4+ and CD8+ T cells reactive to L. braziliensis and cytokine production in vitro were assayed. In CL, with its tendency for healing lesions, at or shortly after the completion of therapy the ratio of CD4+ to CD8+ T cells was approximately one and production of interferon gamma (IFN gamma) remained roughly constant. In ML, these apparently beneficial CD4+/CD8+ ratios and cytokine patterns appeared later. The long-term memory T cell responses were associated with preferential induction of CD4+ subpopulations and IFN gamma production that probably led to protection against relapses or reinfection. Deoxyribonucleic acid (DNA) was isolated from peripheral blood and oligonucleotides that amplify the conserved region of the minicircle molecules of Leishmania were used in a 'hot-start' polymerase chain reaction (PCR). Leishmania DNA was found in about one-quarter of the patients with active disease as well as in individuals who had received chemotherapy. The PCR was also positive in one-third of the individuals with a positive skin test but no past or present history of leishmaniasis. The well-modulated T cell response leading to long-term protection observed in CL patients could result from a favourable host genetic background and/or a particular parasite genotype, leading to a beneficial T cell immune response even in the presence of parasite antigens. The possibility of parasite persistence after clinical cure suggests that the immune response can control, but not fully eliminate, the infection. It could prevent the parasite from causing disease, maintaining a leishmanial antigen-specific response and hampering reinfection.

Dissemination of Leishmania (Viannia) braziliensis

Destructive human mucocutaneous leishmaniasis may appear many years after the primary cutaneous infection with Leishmania (Viannia) braziliensis. Hamsters (Mesocricetus auratus) were infected with metacyclic L. braziliensis promastigotes. It was found that secondary metastatic visceral lesions could arise from a primary cutaneous lesion, or secondary cutaneous lesions from a primary visceral lesion. Parasites in the viscera were shown to be viable, multiplying and capable of metastasis to either secondary visceral or cutaneous sites. The finding of an early metastasis in the wall of a small cutaneous vessel indicates that dissemination can occur by the haematogenous route. Slow growing organisms in viscera may thus be a source for late metastasis to mucocutaneous sites or for systemic relapse after immunosuppression.

[Lymphadenopathies in American cutaneous leishmaniasis: comments on 2 cases]

Two patients, with cervical lymphadenopathies and a presumptive diagnosis of lymphoma or scrofula, were submitted to biopsies of the affected lymph nodes. Unexpectedly, the histological picture revealed a necrotic-granulomatous reaction and the presence of leishmania (amastigotes) in some vacuolated macrophages. The patients were from different endemic areas of leishmaniasis in Brazil, and had no perceptible cutaneous or mucosal lesions. Later, however, one of them developed such lesions, probably as an effect of a treatment for toxoplasmosis. These findings support the idea that the agents of the disease, once in the host organism, would invade the organs of the phagocytic-mononuclear system, there remaining for a long time, maybe for the rest of the host life. Eventually, under the action of several factors, that could modify the host resistance, the parasites migrate to the skin or the mucosal membranes, causing secondary or reactivating lesions.

[Disseminated cutaneous leishmaniasis due to Leishmania viannia braziliensis in the state of Maranhão, Brazil]

The authors describe a case of a patient from Barreirinhas, MA with disseminated cutaneous leishmaniasis, who presented 58 lesions spread all over his body, with many different aspects, but ulcerative lesions were predominant. They discuss the difficulty of laboratory diagnosis in the beginning of the investigation and its therapeutics implications. The parasite isolated was identified as Leishmania viannia braziliensis using monoclonal antibodies in the fluorescent antibody test. This form of the disease is different from the diffuse cutaneous leishmaniasis found in Maranhão, due to Leishmania (Leishmania) amazonensis which is responsible for most of the cases of cutaneous leishmaniasis in our state. The possible mechanisms of lesions dissemination are discussed.