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3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915

12-5-00

Contacts:
Pat Halbur, Department of Veterinary Diagnostic and Production Animal Medicine, (515) 294-1950, pghalbur@iastate.edu
Sherry Hoyer, Iowa Pork Industry Center, (515) 294-4496, shoyer@iastate.edu

Postweaning Multisystemic Wasting Syndrome Is Emerging Disease of Pigs in the U.S.

AMES, Iowa -- Scientists at Iowa State University's Department of Veterinary Diagnostic and Production Animal Medicine (VDPAM) are seeing a dramatic increase in the number of cases of a recently identified swine disease in Iowa. Pathology section leader Pat Halbur said the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL) first diagnosed postweaning multisystemic wasting syndrome (PMWS) in late 1996, and the number of PMWS cases has grown markedly each year since that time. More than 500 cases were diagnosed by the ISU-VDL in the first nine months of 2000.

"PMWS tends to be a grow-finish disease with the onset of most cases occurring between 10-14 weeks of age," Halbur said. "However, the duration of the disease within a system varies. It's often just a single batch problem in smaller herds that use internal gilt replacement and all-in-all-out pig flow, but there are an increasing number of cases where PMWS has become endemic in multiple building finishing sites run on a continuous flow basis."

Halbur and his colleagues are finding that PMWS often is accompanied by concurrent infections like PRRS (porcine reproductive and respiratory syndrome) and mycoplasmal pneumonia, and that's why PMWS symptoms can mimic other diseases. External symptoms of PMWS include respiratory difficulties, weight loss, failure to thrive and occasional paleness and yellow discoloration. Microscopic examination of tissues reveals unique lung and lymphoid lesions (lymph nodes, spleen, tonsil). Diagnostic tools such as immunohistochemistry allow the diagnosticians to demonstrate the presence of porcine circovirus type 2 (PCV2) infection within lesions and further confirm the diagnosis of PMWS.

"Field and experimental evidence to date supports the contention that PCV2 infection plays a major role in PMWS," Halbur said. "Because there currently is no vaccine for PMWS, producers should focus on biosecurity, proper sanitation, and prevention and treatment of coinfection with other known pathogens."

A large and diverse team of virologists and pathologists at the ISU College of Veterinary Medicine is conducting research to better understand the cause(s) of PMWS and to investigate and test control measures for this emerging disease.

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ml: isufarm


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