DIAGNOSIS OF PORCINE PROLIFERATIVE ENTERITIS

Porcine proliferative enteritis (PPE), caused by Lawsonia intracellula ris, is a major disease of swine worldwide. L. intracellularis is an o bligate intracellular bacterium and cannot yet be cultivated in conven tional cell-free media. Consequently, isolation of the infective organ ism in culture is not a practical means of diagnosis. This column comp ares various methods of diagnosis of PPE. Serologic testing has thus f ar been limited because of low titers and short duration of antibody. Polymerase chain reaction (PCR) is the most specific test and appears to have high sensitivity. Fecal PCR can be used to detect the infectio n in live pigs but can yield false-negative results if the animal is n ot shedding the infective organism. At necropsy, PCR of ileal mucosa i s the most specific test and had the highest sensitivity for pigs give n a high dose of inoculum. Fluorescent antibody staining is also speci fic and had a higher sensitivity than PCR for pigs given a low dose of inoculum. The H&E stain and Warthin-Starry silver strain are currentl y used by most diagnostic laboratories for detection of PPE. They are less expensive than PCR but may not provide a definitive diagnosis.