Diagnosing viral myelitis cases in pigs

Webinar provides resources on viruses associated with central nervous system diseases.

December 9, 2019

3 Min Read
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On Dec. 4, the Swine Health Information Center (SHIC) and American Association of Swine Veterinarians sponsored a webinar titled, “Disease Management of Viral Myelitis.”

Designed for veterinary practitioners and pork producers, information presented by diagnosticians as well as case studies provided insight into symptoms of these central nervous system (CNS) diseases, appropriate steps for diagnosis, as well as on-farm management experience with porcine astrovirus 3 (PoAstV3), porcine sapelovirus (PSV), and porcine teschovirus (PTV). A video of the webinar presentations is available here.

Dr. Matthew Sturos, University of Minnesota department of veterinary population medicine, noted symptoms of CNS disease include incoordination/ataxia, weakness, head tilt, inappropriate mentation, circling, blindness, knuckling, tremors, paddling, paresis and convulsions. Each of these symptoms has a root cause from differing segments of the CNS: brain, vestibular or cervical, he said.

An appropriate diagnosis is important because other causes of similar symptoms can be the result of non-spinal diseases, Sturos said. Diagnostic assays for viral myelitides require fresh tissues for testing and analysis. During the webinar, Sturos detailed the appropriate sampling options for accurate diagnoses. In addition to the processes for sample collection, he also said it is helpful to the pathologist when information included with the submission includes the observed CNS signs. He also recommended submission of non-CNS tissues for the best testing protocol and results.

Dr. Bailey Arruda with the Iowa State University Veterinary Diagnostic Laboratory further emphasized the necessity of aseptic collection. She described the necessity of choosing the right pigs for tissue collection, noting disease progression will impact the accuracy of analysis.

With PSV and PTV, Arruda noted that affected herds have pigs aged 4 to 16 weeks impacted, with a case fatality rate of 90-100%. The typical disease duration is less than four days in individual pigs, weeks to months in a group of pigs and months to years in intergroup settings, she said.

PoAstV3 has been diagnosed around the world with five lineages identified. Pigs from 20 days of age through sows are affected when infection is present. There is a case fatality rate of 90-100%. Treatment has been unrewarding, she said.

Arruda said fecal shedding of all three viruses is common. She also said development of CNS disease is relatively uncommon, pointing to risk factors for infection of co-infections, genetics, immune response and maternal immunity as well as diet and microbiota.

In addition to the technical information provided by Sturos and Arruda, three swine practitioners shared their experience with CNS diseases: Dr. Grant Allison with the Walcott (Iowa) Veterinary Clinic described a client’s PoAstV3 infection; Dr. Pete Thomas with Iowa Select Farms explained how they managed a PTV diagnosis, and Dr. Aaron Lower with Carthage (Illinois) Veterinary Service detailed a client’s PSV experience. These case studies demonstrated the realities on the farm including diagnosis, recovery, treatments and learning.

Arruda concluded the webinar by exploring scientific design to test management options. She said an evidence-based approach is necessary. “We need more information to make decisions for defensing versus reacting,” she said. The goal is better understanding of the viruses, hosts and environment.

With her proposed design for exploring CNS, the important of maternal immunity, herd and individual impact, co-infection and/or prior infection role in severity, along with determining other risk factors could help predict infections.

Funded by America’s pork producers to protect and enhance the health of the U.S. swine herd, SHIC focuses its efforts on prevention, preparedness and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health.

Source: SHIC, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

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