COMPARISON OF TECHNIQUES FOR DIAGNOSIS OF PROLIFERATIVE ENTERITIS OF SWINE

In an abattoir-based case-control study, histologic, and macroscopic e xamination of porcine intestines at slaughter and 2 molecular assays w ere compared for use as diagnostic tests of proliferative enteritis (P E). Fecal samples and intestinal specimens were collected from pigs wi th grossly thick ileum and from clinically normal pigs at slaughter. T issue specimens were fixed in neutral buffered 10% formalin, and secti oned. Sections stained with H&E were examined for proliferative lesion s by a pathologist unaware of the group to which the pig had been assi gned on the basis of results of gross examination. Adjacent tissue sec tions, stained with Warthin-Starry (silver) stain, were examined for p resence of the intracellular bacterium of PE, ileal symbiont (IS)-intr acellularis, in the enterocytes of the intestinal crypts by the senior author, who was unaware either of the group to which the pig had been assigned or diagnosis by the pathologist. Bacterial DNA was extracted from the fecal samples and assayed by dot-blot hybridization and poly merase chain reaction (PCR) for presence of IS-intracellularis DNA, wi thout knowledge of results of the other examinations. The PCR assay fo r IS-intracellularis was a specific and sensitive diagnostic test for PE, and dot-blot hybridization was sensitive, but was less specific. M acroscopic examination of intestines at slaughter was a sensitive, but not specific, test. Association between IS-intracellularis and prolif erative lesions was statistically examined in the same study. There wa s a highly significant (P = 0.0078) association between presence of na turally acquired proliferative lesions and intracellular infection by IS-intracellularis, The odds ratio of greater than or equal to 14 and estimated attributable fraction of greater than or equal to 32% indica te that IS-intracellularis may be a necessary cause of PE.