Alba Valéria Machado da Silva

Canine visceral leishmaniasis in Barra de Guaratiba, Rio de Janeiro, Brazil: assessment of risk factors

Barra de Guaratiba is a coastal area of the city of Rio de Janeiro where American visceral leishmaniasis (AVL) is endemic. Although control measures including killing of dogs and use of insecticides have been applied at this locality, the canine seroprevalence remains at 25% and during 1995 and 1997 eight autochthonous human cases were notified. In order to evaluate factors related to the increase of the risk for Leishmania (Leishmania) chagasi infection in dogs we have screened 365 dogs by anti-Leishmania immunofluorescent antibody test (IFAT) and captured sandflies in the domestic and peridomestic environment. Some variables related to the infection were assessed by uni- and multivariate analysis. The distance of the residence from the forest border, its altitude and the presence of the opossum Didelphis marsupialis in the backyard, were found predictor factors for L. (L.) chagasi infection in dogs in Barra de Guaratiba. The presence of Lutzomyia longipalpis in the peridomestic environment indicates the possibility of appearence of new human cases. Our data also suggest the presence of a sylvatic enzootic cycle at this locality.

Leishmaniose em cães domésticos: aspectos epidemiológicos

In Barra de Guaratiba, an endemic area for American visceral leishmaniasis (AVL) in Rio de Janeiro, Brazil, control campaigns were unable to reduce canine infection rates. This difficulty prompted an in-depth study of dogs as a reservoir for Leishmania chagasi in the peri-urban environment through clinical and serological follow-up using the immunofluorescence and Western blot techniques. Recognition of 29 kDa and 32 kDa peptides by sera from dogs with proven L. chagasi infection was observed. Furthermore, only sera from symptomatic dogs recognized the 68.5 kDa antigen, so the latter should be considered a parameter for culling dogs from endemic areas. The WB technique proved to be more sensitive than IFA, since the 29 and 32 kDa peptide fractions were even recognized by sera from AVL seronegative dogs up to 8 months before IFA seroconversion. Proximity to wooded areas was an important risk factor for L. chagasi infection in dogs, possibly due to the presence of wild reservoirs.

Natural infection of Didelphis aurita (Mammalia: Marsupialia) with Leishmania infantum in Brazil

BackgroundThe opossum Didelphis have been considered as natural hosts of Leishmania parasites in the New World, suggesting an important role in the epidemiology of Visceral Leishmaniasis (VL). Among six extant species that belong to the genus Didelphis, only two (D. marsupialis and D. albiventris), have been mentioned as natural hosts of Leishmania infantum in Brazil and Colombia. In the present paper, it is reported for the first time, the observation of intracellular parasites (amastigotes) in tissues of Didelphis aurita naturally infected with Leishmania infantum in Brazil. We also discuss some aspects associated to the relationship between L. infantum and the geographical distribution of some species of the genus Didelphis.MethodsThe opossums studied were caught by wire traps (Tomahawk) in Barra de Guaratiba, a peri-urban area in Rio de Janeiro. The opossums were killed with an overdose of Thiopental sodium.At necropsy, macroscopic alterations were examined and samples from liver, spleen, lymph nodes, ear, abdominal skin, scent glands and bone marrow were collected for parasitological and molecular diagnoses.ResultsForty-eight opossums were captured in an AVL endemic region, 30 being caught in a mangrove area and eighteen animals in a forest area near to some residential-yards. Among the thirty opossums trapped in the mangrove area, all of them were negative by both imprint and sera samples assayed on Dipstick Tests, that is a test based on a combination of protein-A colloidal gold conjugate and rk39 Leishmania antigen to detect anti-Leishmania antibody in serum or plasma. At the macroscopic examination one out of eighteen opossums, caught close to the forest, presented alterations compatible with spleen hypertrophy and three were positive by Dipstick Tests (16.6%) and presented amastigotes in the spleen and in one of them, the parasites were also observed in a submandibular lymph node. Leishmania infantum infections were confirmed through dot blot hybridization using a L. infantum-specific biotinylated probe.ConclusionsIn the present paper we present the first report of amastigotes in the tissues of Didelphis aurita (Mammalia: Marsupialia) naturally infected with Leishmania infantum. We also attempt to claim the particular role of some opossum species as hosts of Leishmania infantum, contributing at least in part on the description of potential sylvatic reservoirs.

Canine Leishmaniasis in Brazil: Serological Follow-Up of a Dog Population in an Endemic Area of American Visceral Leishmaniasis

We performed a serological, clinical, and parasitological follow-up of a dog population in an endemic area of American Visceral Leishmaniasis estimated by indirect immunofluorescent assay (IFA) and western blot (WB). After twelve months, the results obtained from IFA demonstrated that 50% were seropositive and two serological profiles were observed: the first one ranging from 1/40 to 1/80 and the second ≥1/160. By WB, it was observed that the same percentage and sera from positive dogs presented the recognition of the peptides of 29 and 32 kDa up to 8 months before IFA serum conversion. Among the positive dogs, all the sera from symptomatic ones with tissue parasitism recognized the peptide of 68.5 kDa. Our results suggest the need of modifications in the control measures regarding the elimination of the dogs. They also corroborate the high sensitivity and specificity of western blot in the diagnosis of canine leishmaniasis, suggesting the possibility of its association with IFA.

Haementeria lutzi Pinto, 1920 (Hirudinea: Glossiphoniidae) as a putative Vector of Trypanosoma evansi (Kinetoplastida: Trypanosomatidae) in the Pantanal Matogrossense (MS, Brazil)

In the present study, it was shown under experimental conditions that Trypanosoma evansi could be mechanically transmitted to Rattus norvegicus by leeches (Haementeria lutzi). Additionally, we also described some aspects related to the behavior of the Trypanosoma evansi in the leeches after an infective blood feeding, as follows: a) 10 minutes after the parasites were ingested; they promptly progressed to the coelomic cavity. b) Approximately, from 10 to 30 minutes inside the gut, rounded and dividing forms together with stumpy and slender trypomastigotes showed a random dispersion. c) 24 hours after, the trypanosomes also invaded both, the salivary glands as well as the proboscis cells. Our results suggest that leeches of the species Haementeria lutzi could have some role as a probable alternative vector of Trypanosoma evansi at wetlands in Brazil.