P.A. Magalhães

Epidemiology of dermal leishmaniasis in the Rio Doce Valley, State of Minas Gerais, Brazil.

Dermal leishmaniasis is prevalent in the predominantly settled agricultural areas in the Rio Doce Valley in the eastern part of the State of Minas Gerais, Brazil. The disease has been recorded almost equally in both sexes. Cases have been confirmed in all age groups but youths aged ten to 14 years form the population segment at greatest risk to infection. Cases of single cutaneous lesions, multiple cutaneous lesions and muco-cutaneous lesions have been recorded in the area. Isolates of parasites include representatives of the Leishmania mexicana and L. braziliensis complexes and at least one parasite that does not fit into either category. Infections have not been detected in small mammals (mainly rodents) but about 3% of dogs are infected. The phlebotomine fauna includes no species (or close relatives of species) previously incriminated as vectors of mexicana and braziliensis infections in Brazil. In the complex and confusing epidemiological situation in the Rio Doce Valley it seems unwise to apply traditional specific names to Leishmania of the area.

A field trial of a vaccine against American dermal leishmaniasis

A field trial was carried out in the eastern part of the State of Minas Gerais (Brazil) of a vaccine containing killed promastigotes of five stocks of Leishmania. Tests with Montenegro antigen showed that a high proportion of the vaccinated persons became positive within three months, but circulating antibodies were not detected. A proportion of those vaccinated continued to give positive Montenegro reactions for up to three years. Lymphocyte sensitivity tests carried out, on a small sample, three years after vaccination were positive and gave no evidence of immunological depression. No cases of cutaneous or mucocutaneous leishmaniasis occurred in the trial area during the three years of observations.

An experimental vaccine against American dermal leishmaniasis: experience in the State of Espírito Santo, Brazil

A vaccine prepared from killed and sonicated promastigotes of five Brazilian strains of Leishmania was used during an epidemic of American dermal leishmaniasis that occurred in Viana county, State of Espírito Santo, Brazil. Initially, all of the participants in the vaccination programme had negative reactions to Montenegro antigen. Forty days after the last dose of vaccine had been given, 87.6% of the 216 vaccinated individuals had become Montenegro-positive whereas the 266 unvaccinated persons remained Montenegro-negative. The study area had an unstable population and details are given about the human population changes that occurred during the two-year study period. Taking into account population movements, 1.5% of those vaccinated and 6.4% of the unvaccinated group developed dermal leishmanial lesions by the end of the first year. At the end of the second year, 1.7% of those vaccinated and 8.9% of the unvaccinated group had become infected. The difference in infection rates of the two groups is statistically significant at both the end of the first and second years of observation. Diagnosis of the disease(s) was based on the clinical appearance of lesions combined with parasitological and/or immunological evidence and subsequent responses to treatment. The experience gained in Viana also provided information about the storage and administration of the experimental vaccine which have been used in mounting a randomized clinical trial.

Immunotherapy, immunochemotherapy and chemotherapy for American cutaneous leishmaniasis treatment

The first choice of treatment for American cutaneous leishmaniasis is the pentavalent antimonial drug. Although it has been shown that this treatment is mostly effective and indicated, some disadvantages should be taken into account such as side effects, long term treatment inconveniences and counter-indication for patients suffering from cardiopathy, nephropathy; yet, aging, pregnancy and other conditions. With the advent of the vaccine anti-American cutaneous leishmaniasis as a prophylactic measure, studies on therapy using the vaccine associated or not with other drugs have been performed by many investigators and it is currently among the alternative treatments and prevention measures for American cutaneous leishmaniasis. In conclusion, the association between antimony and vaccine (immunochemotherapy) showed the same cure rate when compared with the standard treatment (100%) and it was also able to reduce the salt volume in 17.9% and treatment length from 87 to 62 days, decreasing side effects.

Histological observations on Montenegro's reaction in man

The Montenegro skin test is widely used as a diagnostic method for American cutaneous leishmaniasis (ACL) but little is known about the histological changes that occur in the skin after administration of the antigen. This report is based on histological studies of biopsied material obtained, from inoculation sites, 48 hours after individuals had been given intradermal injections with a standardized Montenegro antigen. The material examined was obtained from four distinctly different test groups: naturally infected patients with parasitologically proved ACL and with positive Montenegros reaction; individuals without previous history of ACL and not previously tested with Montenegro antigen; participants in anti-ACL vaccine trials who developed positive reactions to Montenegro antigen after vaccination; other participants in vaccine trials who had negative Montenegro responses after vaccination or had served as controls in the trials. The histological pictures of each group are described and discussed. Histologically, the reactions of vaccinated individuals were indistinguishable from those with naturally acquired infections.

The change of behavior of two strains of Leishmania after cultivation in a defined medium

Attempts have been made to characterize two strains of Leishmania that became infective to golden hamsters only after they had been maintained for several years in a chemically defined culture medium. Observations were made on the growth rates of promastigotes in vitro, course of infection in hamsters, morphology of amastigotes, and electrophoretic mobility patterns of eight isoenzymes. Information was obtained about the buoyant densities of n-DNA and k-DNA, and one strain was tested against monoclonal antibodies. The identity of both strains remains obscure.

Mastomys natalensis as an experimental host for Leishmania mexicana mexicana

Young multimammate rats (Mastomys natalensis) can be readily infected when inoculated intradermally with the amastigotes of Leishmania mexicana mexicana. Lesions appear at the site of inoculation in the second week of infection and continue to increase in size for the first month; amastigotes can be detected during this period. In the second month, lesions begin to decrease in size and it is more difficult to detect amastigotes. Three months after inoculation, the rats show no sign of infection. The results suggest that M. natalensis could be a useful laboratory host for immunological studies on dermatotropic Leishmania and for chemotherapeutic assays.