Navegando por Autor "Silva, Shara Regina"
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Item Epidemiological aspects of vector, parasite, and domestic reservoir in areas of recent transmission and no reported human cases of visceral leishmaniasis in Brazil.(2015) Silva, Fabiana de Oliveira Lara; Michalsky, Érika Monteiro; Dias, Consuelo Latorre Fortes; Fiuza, Vanessa de Oliveira Pires; Pessanha, José Eduardo Marques; Silva, Shara Regina; Avelar, Daniel Moreira de; Silva, Maiara Alves; Lima, Ana Cristina Vianna Mariano da Rocha; Costa, Ailton Junior Antunes da; Coelho, George Luiz Lins Machado; Dias, Edelberto SantosAbout 97% of the human cases of the American visceral leishmaniasis (VL) occur in Brazil. In the last fewyears, the disease expanded to medium- and large-sized cities, in which surveillance and control actionshave been intensified, in an effort to control VL spreading. Our two-year study was conducted in BeloHorizonte, the sixth most populous city in Brazil, which is endemic for VL. We focused in two particulardistricts of recent transmission of the disease, with no reported human cases and submitted to minorsurveillance and control actions. Our aim was to draw an epidemiological profile of the local situationconcerning Lutzomyia vector, Leishmania parasites, and the main domestic reservoirs (dogs). Lutzomyialongipalpis comprised 96.5% of the total phlebotomine sand flies captured and displayed an expressiveminimal infection rate by Leishmania infantum (16.7%). Positive correlations were found between the pop-ulation densities of L. longipalpis, rainfall and temperature. L. infantum was also detected in the cortelezziicomplex and, for the first time, in Lutzomyia lloydi. Leishmania braziliensis, an etiological agent of theAmerican cutaneous leishmaniasis, was also identified in L. longipalpis. Among the 1408 dogs serologi-cally tested by standard enzyme-linked and fluorescence immune assays (ELISA/IFA) 3.6% were positivefor VL. L. infantum DNA and Leishmania parasites were identified in 100% and 72.5% of the seropositivedogs, respectively. The co-positivity of other diagnostic tests for VL—Leishmania-nested PCR, imprintand myeloculture—was compared to the standard serology. Both symptomatic or asymptomatic dogsdisplayed an equal average number of positive diagnostic tests for VL. The districts studied display favor-able conditions for the rapid spreading of human infection, in terms of L. longipalpis population density,and presence of L. infantum in both vector and main reservoir.Item Field randomized trial to evaluate the efficacy of the Leish - Tec vaccine against canine visceral leishmaniasis in anendemic area of Brazil.(2016) Silva, Shara Regina; Feres, Ana Maria Leonardi Tibúrcio; Silva, João Carlos França da; Dias, Edelberto Santos; Michalsky, Érika Monteiro; Andrade, Hélida Monteiro de; Coelho, Eduardo Antônio Ferraz; Ribeiro, Gustavo Meirelles; Fernandes, Ana Paula Salles Moura; Coelho, George Luiz Lins MachadoBackground: A canine vaccine remains a promising approach for effective control of visceral leishmaniasis(VL), given its complex epidemiology in areas where zoonotic VL is prevalent. Leish-Tec®is a recombi-nant vaccine, based on the Leishmania A2 antigen, against canine VL (CVL). It is, since 2014, the singlecommercial vaccine licensed in Brazil. Here, Leish-Tec®efficacy was estimated through a randomizedfield trial (RFT), in a highly VL endemic area.Methods: The RFT was conducted from 2008 to 2010 in an endemic area of southeastern Brazil, presentinga CVL seroprevalence of 41.9%. Eight hundred forty-seven seronegative dogs were randomly selected toreceive Leish-Tec®(n = 429) or placebo (n = 418). Animals were followed up by clinical, serological, andparasitological exams for 18 months. The CVL incidence in both groups was compared through proportionanalysis.Results: A significant reduction in the number of cases of CVL was observed in the vaccine group, ascompared with the placebo group, whether efficacy was estimated according to parasitological results(71.4%; 95% CI: 34.9–87.3%; p = 0.001; risk ratio = 0.287), by adding results of xenodiagnosis and parasito-logical exams (58.1%; 95% CI: 26.0–76.3%; p = 0.002; risk ratio = 0.419). Among the animals that convertedto a positive anti-A2 serology, efficacy reached 80.8% (95% CI: 37.6–94.1%, p = 0.001; risk ratio = 0.192).Xenodiagnosis has detected a reduction of 46.6% (p = 0.05) in transmission to sand flies from vaccinatedanimals presenting anti-A2 positive serology.Conclusion: The Leish-Tec®vaccine proved significantly effective for prophylaxis of CVL, after naturalchallenge assured by transmission of Leishmania parasites, in a highly endemic area. Noteworthy, thisreport has unveiled the complexity of performing a RFT for anti-CVL vaccines in Brazil, which may behelpful for designing of future studies.