SHIC-Funded Study First to Confirm Porcine Astrovirus 4 as a Primary Cause of Tracheitis and Bronchitis in Piglets

With the goal of determining if porcine astrovirus 4 alone can cause respiratory disease, a collaborative team of investigators from North Carolina State University, USDA Agricultural Research Service, Iowa State University, and University of California Santa Cruz investigated if piglets infected with PoAstV4 exhibited reproducible lesions in the respiratory tract. Funded by the Swine Health Information Center, the study design included infecting PoAstV4 naïve piglets with the virus and characterizing the resulting infection and pathological lesions. Infected piglets shed the virus in nasal secretions, exhibited tracheitis and bronchitis with virus detected in tissues, and developed a productive immune response to infection.  Results from this study are the first to confirm that PoAstV4 can be a primary cause of epitheliotropic viral infection in the respiratory tract of piglets.

`Find the industry summary for study #23-077 here.

PoAstV4 has frequently been detected in nasal swabs from young pigs exhibiting respiratory disease. Retrospective studies, including an evaluation of 117 IAV negative cases of tracheitis and bronchitis, demonstrated a strong association between PoAstV4 detection in respiratory epitheliotropic viral infection lesions. However, observational associations do not establish causation. Understanding the pathogenesis of PoAstV4 as an emerging virus is crucial for accurate diagnosis, differential considerations, and effective management strategies for respiratory disease in swine.

The study described the use of caesarean-derived colostrum-deprived (CDCD) piglets challenged intratracheally (17 – challenged and 11 negative controls) with PoAstV4 PCR positive tissue homogenate that had been screened by next generation sequencing for the presence of other primary swine pathogens. Nasal swabs were collected to monitor viral shedding, and piglets were necropsied at five- and eight-days post-challenge (DPC) to evaluate gross and microscopic lesions. Viral localization within tissues was confirmed using PoAstV4 in situ hybridization. The immune response was characterized by detecting anti-PoAstV4 IgM and IgG antibodies in serum and quantifying infiltrating lymphocytes (T and B cells) within lesioned airways using immunohistochemistry and digital image analysis software.