Porcine proliferative enteropathy: a case-control study in swine herds in the United States

To describe epidemiologic characteristics of outbreaks of porcine proliferative enteropathy (PPE) and evaluate associations between herd production and management factors, and disease occurrence. A questionnaire about management factors was administered by telephone to the owners or managers of 30 PPE-affected herds (cases) and 18 unaffected herds (controls). Morbidity, mortality, and demographics of animals in affected herds were recorded. Faecal samples from approximately six pigs in each herd were tested by polymerase chain reaction (PCR) for Lawsonia intracellularis. Porcine hemorrhagic enteropathy (PHE) occurred in 11 herds, and porcine intestinal adenomatosis (PIA) in 19 herds. In multivariable logistic regression analysis, use of a new building and recent mixing of pigs were associated (P<0.05) with PPE. Management stressors such as overheating, chilling, number of times mixed, number of feeders per pen, and group size were not significantly associated with PPE. Faecal samples were more likely (P<0.05) to be positive by PCR in case than control herds. Herds with PHE were more likely (P=0.05) than herds with PIA to have at least one PCR-positive faecal sample. Implications: Placement of pigs into new facilities and commingling of groups of pigs significantly increase the risk of PPE. Production and management practices linked with high health status may not be associated with reduced risks of PPE outbreaks. Analysis of faecal samples by PCR is useful to detect L. intracellularis in the population, but faecal samples are more likely to be PCR positive in herds with PHE than in herds with PIA.