RESUMEN

Although a national programme for control of visceral leishmaniosis (VL) is being run in Brazil, the disease continues to spread. This programme is essentially based on culling infected dogs from endemic regions. Thus, there is an urgent need to develop other control measures against VL to deter its advance. Here, a subunit vaccine, a recombinant vaccine, an insecticide-impregnated collar and the associations between these measures were evaluated for reducing the incidence of Leishmania infection in dogs. This was through a cohort study conducted in an endemic region of Brazil, considering the incidence and time of total exposure over a period of 1 year. The incidence of VL was estimated by means of serological and molecular diagnostic tests, 180 and 360 days after the application of the control measures. The estimates of the effectiveness (EF) were not significant in any cohort. The EF of the subunit vaccine, the recombinant vaccine and the collar were 26.4%, 32.8% and 57.7% and the upper limit of the 95% confidence interval for EF were 63.7%, 67.9% and 82.5%, respectively. In conclusion, under the conditions of this study, none of the immunogens for VL control was sufficiently effective to protect dogs against infection. On the other hand, use of collars impregnated with insecticide seems to constitute a method with better prognosis, corroborating other studies in this field.

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Euthanasia of infected dogs is one of the measures adopted in Brazil to control visceral leishmaniasis (VL) in endemic areas. To detect infected dogs, animals are screened with the rapid test DPP® Visceral Canine Leishmaniasis for detection of antibodies against K26/K39 fusion antigens of amastigotes (DPP). DPP-positives are confirmed with an immunoenzymatic assay probing soluble antigens of promastigotes (ELISA), while DPP-negatives are considered free of infection. Here, 975 dogs from an endemic region were surveyed by using DPP, ELISA and real-time PCR (qPCR) for the diagnosis of VL. When DPP-negative dogs were tested by qPCR applied in blood and lymph node aspirates, 174/887 (19·6%) were positive in at least one sample. In a second sampling using 115 cases, the DPP-negative dogs were tested by qPCR in blood, lymph node and conjunctival swab samples, and 36/79 (45·6%) were positive in at least one sample. Low-to-moderate pairwise agreement was observed between all possible pair of tests. In conclusion, the official diagnosis of VL in dogs in Brazilian endemic areas failed to accuse an expressive number of infected animals and the impact of the low accuracy of serological tests in the success of euthanasia-based measure for VL control need to be assessed.

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Visceral leishmaniasis (VL) has spread rapidly across cities in the metropolitan region of Belo Horizonte. The aim of this study was to investigate VL dynamics in a prospective cohort study of dogs in Juatuba, between 2010 and 2011, to confirm the incidence of Leishmania infantum, and to assess possible risk factors associated with infection. An observational and prospective closed cohort study was performed using serology testing in dogs, randomly selected from the whole municipality. All seronegative dogs, or dogs with inconclusive results were monitored using indirect immunofluorescence (IIF) at 6-month intervals. The dog's owners completed a semi-structured questionnaire to assess possible causal factors of seroconversion, and the responses were assessed using logistic regression. The canine incidence coefficient was 206/1,000 dogs per year (CI: 178-238), and a cluster was identified in an area with a high concentration of seropositive dogs, but a low overall canine population. Large dogs were identified as a risk factor and the following variables were identified as protection factors: dogs aged over 4 years, daily peridomicile cleaning, and better socioeconomic conditions. VL is spreading over a large area in Juatuba in a short period of time.(AU)

A leishmaniose visceral (LV) expandiu-se de forma rápida e extensa pelos municípios da Região Metropolitana de Belo Horizonte. Objetivou-se estudar a dinâmica da LV em uma coorte prospectiva de cães em Juatuba, entre 2010 e 2011, para verificar a incidência e fatores de risco associados à infecção por Leishmania infantum. Foi feito um estudo observacional e prospectivo de coorte fechada por meio de análise sorológica em cães selecionados aleatoriamente em todo o município, com acompanhamento semestral dos resultados soronegativos e indeterminados na imunofluorescência indireta (IFI). Usou-se questionário semiestruturado junto aos proprietários de cães para avaliação da soroconversão e dos fatores determinantes a essa, por meio da regressão logística. O coeficiente de incidência canina foi de 206/1000 cães.ano (IC: 178 - 238), e foi identificado cluster em área com elevada concentração de cães soropositivos, mas com baixa densidade populacional canina. A variável cão de porte grande foi identificada como fator de risco, e as variáveis idade do cão superior a quatro anos, limpeza diária do peridomicílio e melhores condições socioeconômicas como fatores de proteção. A infecção por LV está ocorrendo em curto período de tempo e com ampla distribuição em Juatuba.(AU)

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RESUMEN

Visceral leishmaniasis (VL) has spread rapidly across cities in the metropolitan region of Belo Horizonte. The aim of this study was to investigate VL dynamics in a prospective cohort study of dogs in Juatuba, between 2010 and 2011, to confirm the incidence of Leishmania infantum, and to assess possible risk factors associated with infection. An observational and prospective closed cohort study was performed using serology testing in dogs, randomly selected from the whole municipality. All seronegative dogs, or dogs with inconclusive results were monitored using indirect immunofluorescence (IIF) at 6-month intervals. The dog's owners completed a semi-structured questionnaire to assess possible causal factors of seroconversion, and the responses were assessed using logistic regression. The canine incidence coefficient was 206/1,000 dogs per year (CI: 178-238), and a cluster was identified in an area with a high concentration of seropositive dogs, but a low overall canine population. Large dogs were identified as a risk factor and the following variables were identified as protection factors: dogs aged over 4 years, daily peridomicile cleaning, and better socioeconomic conditions. VL is spreading over a large area in Juatuba in a short period of time.(AU)

A leishmaniose visceral (LV) expandiu-se de forma rápida e extensa pelos municípios da Região Metropolitana de Belo Horizonte. Objetivou-se estudar a dinâmica da LV em uma coorte prospectiva de cães em Juatuba, entre 2010 e 2011, para verificar a incidência e fatores de risco associados à infecção por Leishmania infantum. Foi feito um estudo observacional e prospectivo de coorte fechada por meio de análise sorológica em cães selecionados aleatoriamente em todo o município, com acompanhamento semestral dos resultados soronegativos e indeterminados na imunofluorescência indireta (IFI). Usou-se questionário semiestruturado junto aos proprietários de cães para avaliação da soroconversão e dos fatores determinantes a essa, por meio da regressão logística. O coeficiente de incidência canina foi de 206/1000 cães.ano (IC: 178 - 238), e foi identificado cluster em área com elevada concentração de cães soropositivos, mas com baixa densidade populacional canina. A variável cão de porte grande foi identificada como fator de risco, e as variáveis idade do cão superior a quatro anos, limpeza diária do peridomicílio e melhores condições socioeconômicas como fatores de proteção. A infecção por LV está ocorrendo em curto período de tempo e com ampla distribuição em Juatuba.(AU)

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O objetivo desta pesquisa foi descrever as análises da série cronológica e determinar a tendência da leishmaniose visceral em humanos e cães para o município de Belo Horizonte, de 1993 a 2007. De 1994, quando surgiram os primeiros casos da doença, até 2007, foram registrados 994 casos humanos autóctones com 116 óbitos. De 1993 a 2007, foram analisadas 1.492.401 amostras de sangue canino com percentual de positividade de 5,9 por cento, utilizando-se os testes de enzyme-linked immunosorbent assay (ELISA) como triagem e de imunofluorescência indireta (IFI) como confirmatório. As análises indicaram que a leishmaniose visceral apresentou tendência crescente dos coeficientes de incidência em humanos e de prevalência em cães, e observaram-se arquétipos distintos dessa tendência, retratando o momento histórico de transição endêmica. A leishmaniose visceral em cães não apresentou características de distribuição sazonal, e não foi possível concluir a existência ou não de ciclicidade do fenômeno. A leishmaniose visceral em humanos e cães tem ampla distribuição espacial nas nove regionais administrativas com risco diferenciado de acometimento da doença, apesar da presença das fontes de infecção e dos susceptíveis em todo o município.

The chronological series analysis and the tendencies of both human and canine visceral leishmaniasis were determined in Belo Horizonte city, from 1993 to 2007. From 1994, when the first cases of the disease were reported, until 2007, 994 human cases were recorded, which led to 116 deaths. From 1993 to 2007, 1,492,401 samples of canine blood were analyzed by the enzyme-linked immunosorbent assay (ELISA) as screening test and by the Indirect Immunofluorescence (IFI) as confirmatory test. The rate of positive results was 5.9 percent. The analyses indicated that the visceral leishmaniasis presents a tendency of increasing the coefficient of incidence in humans and prevalence in dogs and different archetypes of this tendency were observed portraying historical moment of endemic transition. Canine visceral leishmaniasis did not show a seasonal distribution, and it was not possible to determine whether the phenomenon was cyclic or not. Human and canine visceral leishmaniasis showed a broad spatial distribution in the nine administrative sectors with a differentiated risk of illness, in spite of the presence either of the sources of infection or the susceptible individuals in the whole county.

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RESUMEN

O objetivo desta pesquisa foi descrever as análises da série cronológica e determinar a tendência da leishmaniose visceral em humanos e cães para o município de Belo Horizonte, de 1993 a 2007. De 1994, quando surgiram os primeiros casos da doença, até 2007, foram registrados 994 casos humanos autóctones com 116 óbitos. De 1993 a 2007, foram analisadas 1.492.401 amostras de sangue canino com percentual de positividade de 5,9 por cento, utilizando-se os testes de enzyme-linked immunosorbent assay (ELISA) como triagem e de imunofluorescência indireta (IFI) como confirmatório. As análises indicaram que a leishmaniose visceral apresentou tendência crescente dos coeficientes de incidência em humanos e de prevalência em cães, e observaram-se arquétipos distintos dessa tendência, retratando o momento histórico de transição endêmica. A leishmaniose visceral em cães não apresentou características de distribuição sazonal, e não foi possível concluir a existência ou não de ciclicidade do fenômeno. A leishmaniose visceral em humanos e cães tem ampla distribuição espacial nas nove regionais administrativas com risco diferenciado de acometimento da doença, apesar da presença das fontes de infecção e dos susceptíveis em todo o município.(AU)

The chronological series analysis and the tendencies of both human and canine visceral leishmaniasis were determined in Belo Horizonte city, from 1993 to 2007. From 1994, when the first cases of the disease were reported, until 2007, 994 human cases were recorded, which led to 116 deaths. From 1993 to 2007, 1,492,401 samples of canine blood were analyzed by the enzyme-linked immunosorbent assay (ELISA) as screening test and by the Indirect Immunofluorescence (IFI) as confirmatory test. The rate of positive results was 5.9 percent. The analyses indicated that the visceral leishmaniasis presents a tendency of increasing the coefficient of incidence in humans and prevalence in dogs and different archetypes of this tendency were observed portraying historical moment of endemic transition. Canine visceral leishmaniasis did not show a seasonal distribution, and it was not possible to determine whether the phenomenon was cyclic or not. Human and canine visceral leishmaniasis showed a broad spatial distribution in the nine administrative sectors with a differentiated risk of illness, in spite of the presence either of the sources of infection or the susceptible individuals in the whole county.(AU)

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