Porcine Reproductive and Respiratory Syndrome (PRRS): perfil sorológico da descendência numa exploração intensiva de suínos
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2016-02-25
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A PRRS (Porcine Reproductive and Respiratory Syndrome) é uma doença de suínos que surgiu quase simultaneamente no Norte da América (no final dos anos 80) e na Europa (no início dos anos 90), sendo uma das principais enfermidades atuais que afetam a indústria suinícola globalmente, responsável pela perda anual de 664 milhões de dólares nos E.U.A. A PRRS é causada pelo vírus PRRSV, o qual é dividido em dois genótipos principais: o Tipo 1 (Europeu) e tipo 2 (Norte Americano), diferindo a nível antigénico, genético ou sintomatológico. Carateriza-se por manifestações a nível respiratório, como tosse e dispneia nos animais em crescimento, e a nível reprodutor em porcas, com abortos tardios, partos prematuros ou elevada mortalidade dos leitões nas maternidades. O diagnóstico é obtido por isolamento do vírus ou através da identificação de anticorpos, antigénios ou ácido nucleico. As serologias para o PRRSV normalmente detetam os anticorpos 14-21 dias pós-infeção mas não permitem a distinção entre o vírus de campo e o vacinal. Os principais objetivos deste trabalho foram a avaliação dos perfis serológicos da descendência relativamente aos anticorpos contra o PRRSV numa exploração intensiva e a determinação da melhor idade para obter as amostras usando os porcos como sentinelas, usando um total de 66 amostras provenientes de suínos de diferentes idades. A proporção de animais seropositivos foi 75,0% na maternidade, 33,3% no desmame e 95,8% na engorda, sendo 46 vezes mais provável de encontrar-se animais seropositivos na engorda comparativamente com o desmame (P < 0,01). Estimou-se (P < 0,001) uma rápida diminuição dos anticorpos de origem materna até à sexta semana de idade, seguindo um aumento progressivo da imunidade humoral até 21 semanas de idade. O PRRSV foi detetado, por PCR, no soro de animais com 6, 9 e 15 semanas de idade. Os resultados indicam que os leitões podem apresentar-se virémicos no desmame, e as 18-21 semanas são a melhor idade para recolha de amostras dos animais em crescimento, como sentinelas, em explorações infetadas.
PRRS (Porcine reproductive and respiratory syndrome) is a swine disease which appeared simultaneously in Europe (early 1990s) and North America (late 1980s) and is one of the major diseases nowadays that affect the swine industry worldwide, being responsible for losses of $664 million annually in U.S.A. PRRS is caused by the virus PRRSV, which is divided into two major genotypes, the type I (European) and type II (North American), which are antigenically, genetically and clinically different. PRRS is characterized by respiratory problems, like cough and dyspnea, in growing pigs and reproductive failure in sows, with late term abortion, stillbirth and increased preweaning mortality. The diagnosis is obtained by virus isolation or by the identification of antibodies, antigens or nucleic acid. Serological tests for PRRSV normally detect serum antibody response after 14-21 days post-infection, but do not allow the distinction between infected and vaccinated animals. The main objectives of the present study were to evaluate the offspring serum profile of antibodies against PRRSV in an affected intensive herd and determine the better sample time using pigs as sentinels, using a total of 66 samples of swine of different ages. The proportion of seropositive animals was 75.0% at farrowing, 33.3% at nursery and 95.8% and growing/finishing phases, being 46 times more likely to meet seropositive animals in fattening compared with weaning (P <0.01). It was estimated (P < 0.001) a rapid decrease of antibodies of maternal origin until the sixth week of age, followed by a progressive increase of humoral immunity until 21 weeks of age. PRRSV was detected by PCR in the serum of animals with 6, 9 and 15 weeks. The results indicate that the piglets may present viremic weaning and the 18th – 21st weeks are the best time to collect samples from offspring pigs, as sentinel, from PRRSV contaminated intensive herds.
PRRS (Porcine reproductive and respiratory syndrome) is a swine disease which appeared simultaneously in Europe (early 1990s) and North America (late 1980s) and is one of the major diseases nowadays that affect the swine industry worldwide, being responsible for losses of $664 million annually in U.S.A. PRRS is caused by the virus PRRSV, which is divided into two major genotypes, the type I (European) and type II (North American), which are antigenically, genetically and clinically different. PRRS is characterized by respiratory problems, like cough and dyspnea, in growing pigs and reproductive failure in sows, with late term abortion, stillbirth and increased preweaning mortality. The diagnosis is obtained by virus isolation or by the identification of antibodies, antigens or nucleic acid. Serological tests for PRRSV normally detect serum antibody response after 14-21 days post-infection, but do not allow the distinction between infected and vaccinated animals. The main objectives of the present study were to evaluate the offspring serum profile of antibodies against PRRSV in an affected intensive herd and determine the better sample time using pigs as sentinels, using a total of 66 samples of swine of different ages. The proportion of seropositive animals was 75.0% at farrowing, 33.3% at nursery and 95.8% and growing/finishing phases, being 46 times more likely to meet seropositive animals in fattening compared with weaning (P <0.01). It was estimated (P < 0.001) a rapid decrease of antibodies of maternal origin until the sixth week of age, followed by a progressive increase of humoral immunity until 21 weeks of age. PRRSV was detected by PCR in the serum of animals with 6, 9 and 15 weeks. The results indicate that the piglets may present viremic weaning and the 18th – 21st weeks are the best time to collect samples from offspring pigs, as sentinel, from PRRSV contaminated intensive herds.
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Dissertação de Mestrado Integrado em Medicina Veterinária
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Síndrome respiratória e reprodutiva suína , Técnica imunológica , Teste elisa , Reação em cadeia por polimerase , Epidemiologia , Animais sentinela