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Anti-Leishmania antibodies survey in dogs from Portugal
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Portugal é um país endémico para a leishmaniose canina (CanL), zoonose
causada pelo parasita Leishmania infantum, em que o cão é o principal hospedeiro
reservatório doméstico. Sendo uma zoonose, o controlo e monitorização da CanL é de
grande relevância para a Saúde Pública humana e animal. Nas últimas décadas, têm sido
realizados diversos estudos de prevalências da CanL, incidindo em diferentes regiões de
Portugal. O último estudo de prevalência a nível nacional conta com mais de uma
década, e com a introdução no mercado de novas medidas profiláticas, nomeadamente
vacinas contra a CanL. O presente estudo teve como objectivos fazer uma atualização da
seroprevalência de CanL em Portugal Continental face ao estudo anterior de 2009, bem
como a determinação de fatores de risco associados à infecção por L. infantum.
Para o presente estudo, 98 Centros de Atendimento Medico-Veterinário
(CAMV) de todo o país efetuaram colheitas de amostras de sangue em papel de filtro
num total de 1860 amostras e de questionários sobre características dos cães e hábitos
de vida. Foi efetuada a técnica serológica de Aglutinação Direta (DAT) para a pesquisa
de anticorpos anti-Leishmania e efetuada a análise estatística das variáveis qualitativas e
quantitativas face aos resultados da técnica serológica utilizando o programa IBM®
SPSS® Statistics.
Observou-se uma seroprevalência global de 12.5% (CI 10.3 – 13.2%), que se
traduz num aumento comparativamente ao estudo de 2009, no qual foi determinada uma
seroprevalência de 6.31%. Os distritos com maior seroprevalência são Portalegre
(30.5%, CI 19.9 – 43.8), Castelo Branco (29.9%, CI 20.1 – 42.0) e Guarda (19.3%, CI
9.6 – 35.1). A menor seroprevalência registou-se em Viana do Castelo (0.0%, CI 0.0 –
7.5).
Os fatores de risco identificados associados à infecção por L. infantum em cães
foram estes terem idade superior a 2 anos (aOR = 2.14, CI 1.45 - 3.14) e residirem no
interior de Portugal (aOR = 1.63, CI 0.91 – 1.72). Para cães que não tinham sido
vacinados, o não uso de repelentes ou insecticidas foi também identificado como factor
de risco (aOR = 1.74, CI 1.20 – 2.53). Uma vez que a técnica serológica utilizada –
DAT - não permite a discriminação entre anticorpos vacinais e anticorpos resultantes de
exposição ou infecção ao parasita Leishmania, uma especial atenção foi prestada à vacinação, pois esta aparentava ser um fator de risco.
Quando comparados cães vacinados e não vacinados com resultado positivo e
com sinais clínicos compatíveis com CanL, verificou-se que apenas 7% de cães
vacinados positivos apresentavam sinais clínicos, comparativamente com 26% de cães
não vacinados positivos, demonstrando a eficácia da vacinação na prevenção da
progressão da doença.
O desenvolvimento de testes serológicos capazes de diferenciar entre anticorpos
vacinais e de infeção será determinante para o melhoramento de estudos
seroepidemiológicos de CanL. Igualmente o uso adequado de repelentes/inseticidas e
vacinação devem ser privilegiados para reduzir a CanL. Globalmente, o presente estudo
proporcionou informação atualizada referente à seroprevalência da infeção por L.
infantum em Portugal.
Portugal is endemic for canine leishmaniosis (CanL), a zoonosis caused by the Leishmania infantum parasite, for which dog is the main domestic host. The control and monitoring of CanL, as a zoonosis, is of great relevance for public and animal health. In the last few decades, several studies have been performed to determine CanL seroprevalence in various regions in Portugal. The last nationwide seroprevalence study was conducted over a decade ago (2009), and since then new prophylactic measures have been introduced, namely vaccines against CanL. The present study aimed to update seroprevalence of CanL in Mainland Portugal, compared to the 2009 study, as well as determine risk factors associated with L. infantum infection. For the present study, 98 veterinary clinics throughout the country collected blood samples on filter paper, in a total of 1860 samples, and questionnaires regarding dog’s characteristics and living habits. Direct Agglutination Test (DAT) was the chosen method for the anti-Leishmania antibody survey and a statistical analysis of quantitative and qualitative variables and serological results was performed using IBM® SPSS® Statistics. A national seroprevalence of 12.5% (CI 10.3 – 13.2%) was determined, which translates into an increase in comparison with the 2009 study, in which a seroprevalence of 6.31% was determined. The districts with higher seroprevalence were Portalegre (30.5%, CI 19.9 – 43.8), Castelo Branco (29.9%, CI 20.1 – 42.0) and Guarda (19.3%, CI 9.6 – 35.1). The lowest seroprevalence was recorded in Viana do Castelo (0.0%, CI 0.0 – 7.5). The risk factors associated with L. infantum infection in dogs were being 2 years old or older (aOR = 2.14, CI 1.45 - 3.14) and residing in the interior of Portugal (aOR = 1.63, CI 0.91 – 1.72). When vaccinated dogs were excluded from the analysis, the nonuse of repellents/insecticides was also identified as a risk factor (aOR = 1.74, CI 1.20 – 2.53). Since the serological technique used – DAT – does not discriminate between vaccinal antibodies and antibodies resulting from infection or exposure to Leishmania parasite, this variable was further analyzed, as it was an apparent risk factor. When comparing vaccinated and unvaccinated dogs that had a positive result and presented with compatible clinical signs for the disease, only 7% of vaccinated positive dogs presented clinical signs, compared to 26% of unvaccinated positive dogs, demonstrating the efficiency of vaccination in disease progression prevention. The development of serological tests capable of differentiating between vaccinal and infection antibodies is determinant for the improvement of CanL seroepidemiological studies. Moreover, the correct use of effective repellents/insecticides and vaccination should be a strategy to reduce CanL. Overall, the present study provided updated information regarding the seroprevalence of L. infantum infection in Portugal.
Portugal is endemic for canine leishmaniosis (CanL), a zoonosis caused by the Leishmania infantum parasite, for which dog is the main domestic host. The control and monitoring of CanL, as a zoonosis, is of great relevance for public and animal health. In the last few decades, several studies have been performed to determine CanL seroprevalence in various regions in Portugal. The last nationwide seroprevalence study was conducted over a decade ago (2009), and since then new prophylactic measures have been introduced, namely vaccines against CanL. The present study aimed to update seroprevalence of CanL in Mainland Portugal, compared to the 2009 study, as well as determine risk factors associated with L. infantum infection. For the present study, 98 veterinary clinics throughout the country collected blood samples on filter paper, in a total of 1860 samples, and questionnaires regarding dog’s characteristics and living habits. Direct Agglutination Test (DAT) was the chosen method for the anti-Leishmania antibody survey and a statistical analysis of quantitative and qualitative variables and serological results was performed using IBM® SPSS® Statistics. A national seroprevalence of 12.5% (CI 10.3 – 13.2%) was determined, which translates into an increase in comparison with the 2009 study, in which a seroprevalence of 6.31% was determined. The districts with higher seroprevalence were Portalegre (30.5%, CI 19.9 – 43.8), Castelo Branco (29.9%, CI 20.1 – 42.0) and Guarda (19.3%, CI 9.6 – 35.1). The lowest seroprevalence was recorded in Viana do Castelo (0.0%, CI 0.0 – 7.5). The risk factors associated with L. infantum infection in dogs were being 2 years old or older (aOR = 2.14, CI 1.45 - 3.14) and residing in the interior of Portugal (aOR = 1.63, CI 0.91 – 1.72). When vaccinated dogs were excluded from the analysis, the nonuse of repellents/insecticides was also identified as a risk factor (aOR = 1.74, CI 1.20 – 2.53). Since the serological technique used – DAT – does not discriminate between vaccinal antibodies and antibodies resulting from infection or exposure to Leishmania parasite, this variable was further analyzed, as it was an apparent risk factor. When comparing vaccinated and unvaccinated dogs that had a positive result and presented with compatible clinical signs for the disease, only 7% of vaccinated positive dogs presented clinical signs, compared to 26% of unvaccinated positive dogs, demonstrating the efficiency of vaccination in disease progression prevention. The development of serological tests capable of differentiating between vaccinal and infection antibodies is determinant for the improvement of CanL seroepidemiological studies. Moreover, the correct use of effective repellents/insecticides and vaccination should be a strategy to reduce CanL. Overall, the present study provided updated information regarding the seroprevalence of L. infantum infection in Portugal.
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Palavras-chave
Ciências biomédicas Biologia molecular Leishmaniose Canina Seroprevalência Fatores de risco Portugal