Melo Mn

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.

Dengue Virus Type 4, Manaus, Brazil

We report dengue virus type 4 (DENV-4) in Amazonas, Brazil. This virus was isolated from serum samples of 3 patients treated at a tropical medicine reference center in Manaus. All 3 cases were confirmed by serologic and molecular tests; 1 patient was co-infected with DENV-3 and DENV-4.

Co-infection of Dengue virus by serotypes 3 and 4 in patients from Amazonas, Brazil

The natural co-infection with dengue virus can occur in highly endemic areas where different serotypes have been observed for many years. We report here four cases of DENV-3/DENV-4 co-infection detected by serological and molecular tests among 674 patients with acute undifferentiated fever from the tropical medicine reference center of Manaus City, Brazil, between 2005 and 2010. Analysis of the sequences obtained indicated the presence of genotype 3 and 1 for DENV-3 and DENV-4 respectively.

Influence of lysates of the salivary glands of Lutzomyia longipalpis on the development of a Leishmania-major-like parasite in the skin of the golden hamster.

Twelve years ago, some mice inoculated with Leishmania major were found to develop larger lesions, containing more amastigotes, if the inoculum used to infect them contained a lysate of salivary glands from Lutzomyia longipalpis than if no lysate was included. In the present study, outbred golden hamsters (Mesocricetus auratus) were each inoculated in a footpad with 104, 105, 106 or 107 stationary-phase promastigotes of a Leishmania-major-like parasite (MHOM/BR/71/BH49). Some of the inocula used each contained a lysate of the salivary glands from a laboratory-reared, female Lu. longipalpis. Only the hamsters inoculated with 107 promastigotes each developed macroscopic cutaneous lesions (all 10 co-inoculated with lysate but only two of the 10 co-inoculated with diluent). Each of the lesions developed into cutaneous nodule affecting the dermis and underlying subcutaneous tissue of the inoculated footpad, with, histologically, an intensive, diffuse and productive, inflammatory reaction. There were no apparent differences between the lesions of hamsters infected with inocula containing salivary-gland lysate and those seen in the animals infected with lysate-free inocula. Future studies will follow the histological changes at the sites of Lu. longipalpis bites.

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.