Importance of Lutzomyia longipalpis in the dynamics of transmission of canine visceral leishmaniasis in the endemic area of Porteirinha Municipality, Minas Gerais, Brazil.

A study of Lutzomyia longipalpis (Lutz and Neiva, 1912) (Diptera: Psychodidae), the primary vector of American visceral leishmaniasis (AVL), and the canine form of the disease, was carried out in Porteirinha. The city is situated in the northern part of the Brazilian State of Minas Gerais and is an endemic area of AVL. Systematic phlebotomine captures were performed in seven districts with previously reported cases of canine visceral leishmaniasis, during 2 years (January 2000--December 2001). A total of 2328 specimens of L. longipalpis were captured. The association between the local climate variables and the population density of L. longipalpis was evaluated and rainfall was determined to be a major factor, with increased populations during the rainy season (October--March). At the same time period, blood samples from every dog domiciled in the same seven districts, in total 14,077 animals, were analyzed for infection by viscerotropic Leishmania using indirect immunofluorescence assay (IFA). Accumulated incidence rates of canine VL per district varied from 3.40 to 14.34 for the 2-year period. A positive correlation between the population density of L. longipalpis and the canine cases of visceral leishmaniasis in Porteirinha was observed.

Evaluation of enzyme-linked immunosorbent assay using crude Leishmania and recombinant antigens as a diagnostic marker for canine visceral leishmaniasis

The performances of ELISA assays with different antigen preparations, such as Leishmania amazonensis or L. chagasi lysates and the recombinant antigens rK-39 and rK-26, were compared using sera or eluates from dried blood collected on filter paper to detect anti-Leishmania antibodies in dogs from a visceral leishmaniasis-endemic area in Brazil. Of 115 IFAT-reactive dogs at 1:40 titre, 106 (92.2 percent) were positive in parasitological exams (skin and/or spleen). These animals were compared to healthy animals (n = 25), negative for IFAT at a titre of 1:40 and parasitological exams. The sensitivities of crude and recombinant antigens were similar and remarkably high for both sera and eluates (97-100 percent). Specificity was higher than 96 percent for sera and eluates for different antigens, except for L. chagasi antigen using eluates (88 percent). Concordance values among the tests were higher either for sera or eluates (J = 0.95-1.00). High concordances were observed between sera and eluates tested with different antigens (kappa = 0.93-0.97). Crude and recombinant antigens identified different clinical phases of canine leishmaniasis. These results show that eluates could be used in canine surveys to identify L. chagasi infection. Recombinant antigens added little when compared to crude antigen in identifying positive dogs. Cross-reactivity with other diseases whose distribution often overlaps VL-endemic areas is a limitation of crude antigen use however.

Leishmaniose visceral canina: avaliaçäo da metodologia sorológica utilizada em inquéritos epidemiológicos / Canine visceral leishmaniasis: evaluation of the serologic method used in epidemiologic studies

Foi realizado um estudo comparativo da reaçäo de imunofulorescência em eluatos de sangue de cäes infectados experimentalmente com diferentes tripanosomatídeos. Utilizaram-se como antígeno promastigotas de L. mexicana, L. braziliensis e L chagasi. Os resultados mostraram que a sensibilidade do método foi de 87,5%para o diagnóstico do calazr canino, independentemente do antígeno empregado; e que ocorre reaçäo cruzada com Leishmaniose tegumentar em 75%dos casos e com doença de Chagas em 83,3%. Levantamento epidemiológico em área de leishmaniose confirma que a reaçäo de imunofluorescência em eluatos de sangue canino fornece reaçöes cruzadas em cäes infectados com Leishmania brasiliensis e L. chagasi. Näo se verificou reaçäo cruzada pela RFC. Sugere-se a utilizaçäo da reaçäo de imunofluorescência nas campanhas de saúde pública mas é de se chamar a atençäo para o fato de que as taxas de positividade näo devem ser utilizadas como indicadores da prevalência do calazar canino