SHIC Creates Guidelines for CNS Disease Case and Identification and Reporting

September 28, 2016 — Paul Sundberg

The Swine Health Information Center (SHIC) convened a cross-section of experts involved in swine disease diagnostics at the veterinary diagnostic laboratories of Iowa State University, University of Minnesota and South Dakota State University to create specific guidelines to follow for improved accuracy and efficiency in reporting diseases of unknown etiology affecting the central nervous system (CNS).

Among the many possible infectious causes of CNS syndromes are various members of the virus family Picornaviridae, e.g. porcine teschovirus (PTV), porcine enteroviruses (PEV) and porcine sapelovirus (PSV), as well as atypical porcine pestivirus (APPV). Communications continue to suggest a wide range of neurologic signs possibly related to the presence of these viruses in growing pigs. These viruses are not new to the United States. Historically, cases have been reported only sporadically.

There are significant knowledge gaps about the pathogenicity and epidemiology of these viruses. The diagnostic criteria and tests used by veterinary diagnostic labs should strive to be consistent to effectively monitor infection status and disease occurrence with these or other diseases.

The overarching objective of SHIC is to monitor domestic diseases affecting swine health and provide reliable data to practitioners and producers that will support on-farm, prospective producer decision-making. Cases which meet two of the three of the following criteria will qualify as a case definition for the veterinary diagnostic labs to report to SHIC.

Clinical history includes any of:

• CNS signs implicating brain stem, spinal cord, cerebellum or cerebrum functional compromise
  • Ataxia
  • Muscle tremors
  • Muscle weakness

• PCR-positive for sapelovirus, teschovirus, enterovirus or atypical pestivirus
  • Positive test results must be from brain or spinal cord samples.
  • The diagnostician of the case will define when the test is “PCR-positive.”

• Histologic lesions
  • The histologic examination must be consistent with viral encephalitis.

The veterinary diagnostic labs have agreed to report the number of cases that are positive according to this set of case-defining criteria to SHIC every two weeks via email unless the incident rate indicates that more frequent reporting is needed. There will be no individual producer or veterinarian identifiers included in the reporting.

More information about these viruses and information about SHIC’s financial support for additional diagnostic testing in cases where the initial diagnostic workup is unsatisfactory are posted under the Emerging Diseases tab of SHIC website, www.swinehealth.org.

The mission of the Swine Health Information Center is to protect and enhance the health of the United States swine herd through coordinated global disease monitoring, targeted research investments that minimize the impact of future disease threats, and analysis of swine health data. For more information, visit www.swinehealth.org or contact Dr. Sundberg at [email protected].