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Estudo da seroprevalência referente à infeção por dengue da população da Ilha da Madeira.
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A febre da dengue é causada por um Flavivirus e é transmitida por mosquitos do género Aedes. Estima-se que haja cerca de 50 a 100 milhões de infeções por ano, das quais 80% são assintomáticas. Após a introdução de Aedes aegypti (Linnaeus, 1762) na Ilha da Madeira, um surto de dengue foi declarado em Outubro de 2012 com um total de 2.168 de casos prováveis, dos quais 1.080 foram confirmados laboratorialmente. Baseada na percentagem de 80% de casos assintomáticos, o impacto da doença pode ser estimado em cerca de 5.400 infeções humanas. Assim, os objetivos do nosso trabalho foram: (i) realizar o primeiro estudo da seroprevalência na Ilha da Madeira após o surto, (ii) determinar a viabilidade da saliva para a deteção de imunoglobulinas G (IgG) anti-dengue com o “kit” Panbio®; e; (iii) testar um novo teste de ELISA “in-house” criado pelo “Institut Pasteur” para a deteção de IgG em soro e saliva. Soro e saliva foram colhidos de 355 participantes com idades superiores a dez anos. Durante a colheita, realizou-se um inquérito referente a indicadores pessoais, como a idade, género, peso, se viajou para países endémicos, se possui a vacina da febre-amarela e concelho de residência. Realizou-se o teste de ELISA indireto para IgG Panbio® e as infeções secundárias foram determinadas com o ELISA Capture para IgG Panbio®. Das amostras de soro testadas, observaram-se 32 resultados positivos. Estas foram também testadas com o “kit” de ELISA Capture para IgG, obtendo-se um resultado de cinco amostras positivas para infeções secundárias recentes. O “kit” de ELISA indireto para IgG não demonstrou resultados promissores para a deteção de IgG anti-dengue nas amostras de saliva. Nenhum dos indicadores pessoais demonstrou diferenças estatisticamente significativas no que se refere à percentagem de participantes seropositivos. O “kit” de ELISA “in-house” obteve uma sensibilidade e especificidade para soro de 72% (IC 95%: 53%-86%) e 89% (IC 95%: 74%-97%) respetivamente, e uma sensibilidade e especificidade para saliva de 19% (IC 95%: 7%-36%) e 92% (IC 95%: 78-99%), respetivamente. Com estes resultados é possível estimar que cerca de 19.000 pessoas foram afetadas pelo surto de dengue na Ilha da Madeira, uma proporção quase quatro vezes mais alta do que a estimada com base numa proporção de 80% de casos assintomáticos. A presença de amostras com resultados positivos para prováveis infeções secundárias em indivíduos que não viajaram para países endémicos de dengue sublinha a importância da vigilância epidemiológica de dengue e a necessidade de estratégias de controlo do mosquito como fatores chave para a prevenção de futuros surtos.
Dengue fever is a vector-borne disease that has spread rapidly throughout the world. It is caused by a Flavivirus and transmitted by mosquitoes of the genus Aedes. There are an estimated 50 to 100 million infections per year, in more than 100 endemic countries, of which 80% are asymptomatic. Seven years after the introduction of Aedes aegypti (Linnaeus, 1762) in Madeira, a dengue outbreak was declared in October 2012 with a total of 2,168 probable cases of which 1,080 were confirmed. Thus, based on the threshold of 80% asymptomatic cases, the overall impact of the outbreak can be estimated in circa 5,400 human infections. Our study aims to: (i) perform the first seroprevalence survey in Madeira Island after the outbreak: (ii) assess the usefulness of saliva for dengue immunoglobulin G (IgG) detection with Panbio® “kit” and: (iii) to test a new ELISA “in-house” for IgG detection in serum and saliva samples created by “Institut Pasteur”. Serum and saliva samples were collected from 355 participants with ages over 10 years old. During the sample collection, an inquiry was conducted about personal indicators such as age, gender, weight, if the participant travelled abroad, if the participant has yellow-fever vaccine and residency county. Anti-dengue IgG detection was carried-out with a commercial “kit” -IgG indirect ELISA, Panbio® and secondary infections determined by IgG Capture ELISA “kit” (Panbio®). Regarding serum samples, we observed 32 positive results. Positive samples were also tested with IgG Capture ELISA “kit” showing that five samples are positive for recent secondary infections. Immunoglobulin G indirect ELISA showed no promising results for dengue antibody detection in saliva samples. None of the personal indicators showed statistical significant differences regarding participants seropositivity. The “in-house” ELISA “kit” obtained a sensitivity and specificity for serum samples of 72% (IC 95%: 53%-86%) and 89% (IC 95%: 74%-97%) respectively and a sensitivity and specificity for saliva samples of 19% (IC 95%: 7%-36%) e 92% (IC 95%: 78-99%) respectively. These results suggest that circa 19,000 people were affected by 2012’s dengue outbreak in Madeira Island, an estimate almost four times higher than the initial expected based on the threshold of 80% asymptomatic cases. The presence of probable secondary infections in individuals that have not travelled for dengue endemic countries highlights the importance of dengue surveillance and mosquito control strategies as a key factor to prevent future outbreaks.
Dengue fever is a vector-borne disease that has spread rapidly throughout the world. It is caused by a Flavivirus and transmitted by mosquitoes of the genus Aedes. There are an estimated 50 to 100 million infections per year, in more than 100 endemic countries, of which 80% are asymptomatic. Seven years after the introduction of Aedes aegypti (Linnaeus, 1762) in Madeira, a dengue outbreak was declared in October 2012 with a total of 2,168 probable cases of which 1,080 were confirmed. Thus, based on the threshold of 80% asymptomatic cases, the overall impact of the outbreak can be estimated in circa 5,400 human infections. Our study aims to: (i) perform the first seroprevalence survey in Madeira Island after the outbreak: (ii) assess the usefulness of saliva for dengue immunoglobulin G (IgG) detection with Panbio® “kit” and: (iii) to test a new ELISA “in-house” for IgG detection in serum and saliva samples created by “Institut Pasteur”. Serum and saliva samples were collected from 355 participants with ages over 10 years old. During the sample collection, an inquiry was conducted about personal indicators such as age, gender, weight, if the participant travelled abroad, if the participant has yellow-fever vaccine and residency county. Anti-dengue IgG detection was carried-out with a commercial “kit” -IgG indirect ELISA, Panbio® and secondary infections determined by IgG Capture ELISA “kit” (Panbio®). Regarding serum samples, we observed 32 positive results. Positive samples were also tested with IgG Capture ELISA “kit” showing that five samples are positive for recent secondary infections. Immunoglobulin G indirect ELISA showed no promising results for dengue antibody detection in saliva samples. None of the personal indicators showed statistical significant differences regarding participants seropositivity. The “in-house” ELISA “kit” obtained a sensitivity and specificity for serum samples of 72% (IC 95%: 53%-86%) and 89% (IC 95%: 74%-97%) respectively and a sensitivity and specificity for saliva samples of 19% (IC 95%: 7%-36%) e 92% (IC 95%: 78-99%) respectively. These results suggest that circa 19,000 people were affected by 2012’s dengue outbreak in Madeira Island, an estimate almost four times higher than the initial expected based on the threshold of 80% asymptomatic cases. The presence of probable secondary infections in individuals that have not travelled for dengue endemic countries highlights the importance of dengue surveillance and mosquito control strategies as a key factor to prevent future outbreaks.
Descrição
Palavras-chave
Parasitologia médica Saúde pública Dengue Seroprevalência Ilha da Madeira
Contexto Educativo
Citação
Editora
Instituto de Higiene e Medicina Tropical