Detection of swine proliferative enteropathy (Lawsonia intracellularis) in slaughtered pigs by histochemical and immunohistochemical techniques

Estudou-se a eficácia do diagnóstico macroscópico de lesões da enteropatia proliferativa suína (EPS) usando-se fragmentos de íleo de 663 suínos, coletados em abatedouros localizados em três municípios do Rio Grande do Sul. As amostras foram processadas por métodos histológicos rotineiros e coradas por uma técnica desenvolvida pela combinação das colorações Warthin-Starry, alcian blue e hematoxilina-eosina para detecção simultânea de Lawsonia intracellularis e lesões associadas com EPS. Lâminas suspeitas de EPS foram submetidas à técnica de imunoistoquímica, utilizando anticorpo policlonal anti-Lawsonia intracellularis na diluição de 1:15.000 pelo método avidina-biotina. A coloração combinada detectou 11 casos positivos, e a imunoistoquímica, nove casos adicionais. Entre as 643 amostras consideradas negativas, 12 apresentaram desaparecimento de células caliciformes e proliferação adenomatosa características de EPS, mas ausência de bactérias intracelulares. A eficiência do exame macroscópico para diagnóstico de EPS foi medida pela associação entre os resultados das avaliações macroscópicas e histológicas realizadas em 219 amostras. Embora 51 delas tenham sido consideradas macroscopicamente positivas, apenas quatro foram confirmadas pela presença de bactérias intracelulares associadas com lesões características de EPS. Não se observou associação entre as alterações macroscópicas e histológicas de EPS.Fragments of terminal ileum were collected from 663 pigs at slaughter from three municipalities of the Rio Grande do Sul state, southern Brazil, to study the efficacy of the macroscopic diagnosis of porcine proliferative enteropathy (PPE). All samples were processed by standard histological methods and stained with a technique that combined Warthin-Starry, alcian blue and hematoxylin-eosin. Sections were simultaneously evaluated for the detection of Lawsonia intracellularis and lesions associated with PPE. Sections in which the occurrence of PPE was suspected were stained by the avidin-biotin immunoperoxidase technique using a polyclonal antiserum to Lawsonia intracellularis, at the dilution of 1:15,000. The histochemical method detected 11 positive sections and immunohistochemical staining detected additional nine positive cases. Twelve out of 643 negative samples had reduced number of goblet cells and adenomatous proliferation without any detectable bacteria. The efficiency of gross evaluation for detecting PPE was measured through the comparison between the results from gross and histological evaluations performed on samples from 219 animals. Although 51 of these samples were considered positive by gross evaluations, only four of them were confirmed as positive by detection of intracellular bacteria associated with characteristic lesions of PPE. The association between gross and histological changes often reported in PPE was not observed in this study