It’s often easy to spot a sick pig, but diagnosing the disease or ailment is often not. In a recent webinar, “Disease Management of Viral Myelitis,” veterinarians and veterinary pathologists detailed the clinical signs producers need to consider to accurately diagnose—and potentially address—three diseases of the central nervous system (CNS) in pigs: porcine astrovirus 3 (PoAstV3), porcine sapelovirus (PSV), and porcine teschovirus (PTV).
Incoordination/ataxia, weakness, head tilt, inappropriate mentation, circling, blindness, knuckling, tremors, paddling, paresis and convulsions, are all signs of CNS disease, according to Matthew Sturos, a veterinary pathologist at the University of Minnesota Veterinary Diagnostic Laboratory. Each of these clinical signs may have a root cause from differing segments of the CNS: brain, vestibular system or spinal cord.
In addition, some of the signs can be caused by diseases or health issues outside of the CNS. For instance, a pig that goes down in the front end might have a CNS disease, or that could also be a sign of arthritis, he said.
“Don’t assume the issue you’re seeing now is the same disease or health issue you saw six months ago and automatically treat just for that,” he added.
Instead, involve your veterinarian in the diagnostic process. If you need diagnostic tests done, ask your veterinarian which animals or samples/tissues you need to submit so the most accurate diagnosis of the problem can be made. Brain and spinal cord are likely to be needed in CNS cases. In some cases, Sturos said you may even need to sample skeletal muscles, joints, or section some bones to submit for analysis.
In addition to the processes for sample collection, Sturos said it will help the pathologist when information included with the submission includes the specific CNS signs seen. He also recommends submission of non-CNS tissues, such as liver, muscle, and joint tissue for the best testing protocol and results.
A video of the webinar presentations is available here. It details how to collect the appropriate tissues to submit to your diagnostic laboratory.
Along with that, Sturos recommends taking pictures or videos of what you’ve observed in the animal. Those can be submitted with the tissue samples or provided to the pathologist, if there are questions. You can often use your phone camera to document what you’re observing in the pig, both close-up and from different angles. Blurry, dark or otherwise poor-quality photos or videos are of little to no help, so make sure the quality is good.
Bailey Arruda, veterinary pathologist at the Iowa State University Veterinary Diagnostic Lab, further emphasized the necessity of aseptic collection. She also described the necessity of choosing the right pigs for tissue collection, noting disease progression will impact the accuracy of analysis, according to a news release prepared by the Swine Health Information Center (SHIC).
With PSV and PTV, Arruda noted affected herds have pigs from 4 to 16 weeks old impacted with a case fatality rate of 90% to 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. PoAstV3 has been diagnosed around the world with five lineages identified. Pigs from 20 days of age through sows are impacted when infection is present. There is a case fatality rate of 90% to 100%. Treatment has been unsuccessful.
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.
Arruda said an evidence-based approach is necessary to address CNS. “We need more information to make decisions for defensing versus reacting,” she remarked. The goal is better understanding of the viruses, hosts and environment. With her proposed design for exploring CNS, the importance 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.
The webinar was sponsored by the Swine Health Information Center and American Association of Swine Veterinarians.