Postweaning multisystemic wasting syndrome: Epidemiology and clinical presentation

Objective: To describe the characteristics of postweaning multisystemic wasting syndrome (PMWS). Methods: A retrospective analysis of the production records of a 600-sow herd with clincial signs consistent with endemic PMWS was conducted. Also, data elicited by a descriptive epidemiologic survey that was completed by 15 producers with herds that had confirmed PMWS was analyzed. Results: In the case herd, postweaning mortality rate peaked at 7.67% on month 9 of the epidemic, then returned within 16 months to pre-outbreak levels of 2.1%-2.5%. The most common causes of death reported by the farm were unthriftiness (weight loss, emaciation),jaundice (liver disease), and dyspnea (respiratory disease). In the surveyed herds, PMWS was found to be a slow and progressive disease with a high case fatality rate (81.4% +/- 23.4%). Clinical disease was observed most commonly in pregrower barns (90%), followed by nursery (62%) and grower barns (39%). The syndrome was first noted in pigs 42 +/- 13.5 days of age. The most frequent clinical signs of PMWS included unthriftiness, dyspnea, pallor, rough hair coat, diarrhea, and jaundice. Postweaning mortality averaged 6.7% +/- 5.1% (SD) in affected herds, and was reported as 18.3% in the most severely affected herd. Poor response to various modes of antimicrobial therapy was reported. Implications: Control of PMWS is difficult and may depend largely on pig flow, improved sanitation, and early recognition and segregation of sick pigs.