Long considered strictly gut pathogens that cause diarrhea, rotaviruses (RVA, RVB and RVC) have now been detected in the lungs of young pigs, according to recent study led by Nathan Lourenco Dias de Oliveira, a student at the Federal University of Minas Gerais in Brazil.
“Rotaviruses are major causes of diarrhea in young pigs worldwide, persisting in herds despite vaccination and other control strategies,” de Oliveira says. “We pursued this study because of growing evidence that RVA spreads to extraintestinal organs, especially the lungs. We wanted to expand that knowledge to include RVB and RVC using field samples.”
Funded by the Swine Disease Eradication Center (SDEC) and conducted at the University of Minnesota Veterinary Diagnostic Laboratory under the supervision of Dr. Talita Resende, the study is the first to combine multiplex RT-PCR with RNAscope in situ hybridization (ISH). This approach will support the investigation into whether rotaviruses are transcriptionally active within swine lung architecture, rather than merely passive bystander particles circulating in the bloodstream.
High Prevalence in Nursery Lungs
Using RNAscope targeting VP6 mRNA, researchers observed active viral transcription directly inside bronchial, bronchiolar and alveolar septal tissues.
Out of 111 lung samples taken from pigs under 50 days old (mostly nursery pigs), de Oliveira discovered:
- 87.39% (97/111) tested positive for at least one rotavirus via RT-PCR
- RVA was most prevalent (87.39%), followed by RVC (67.57%) and RVB (45.95%)
- RVA was detected by ISH in lungs from several pigs
- ISH signals for RVB and RVC are currently under evaluation
An Overlooked Player in PRDC?
The study also revealed high coinfection rates between rotaviruses and major endemic respiratory pathogens:
- Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Present in 39% to 45% of rotavirus-positive cases
- Influenza A Virus (IAV): Present in 23% to 28% of rotavirus-positive cases
Porcine Cirovirus Type 2 (PCV2): Present in 10% to 12% of rotavirus-positive cases
These findings suggest rotaviruses may be an overlooked contributor to Porcine Respiratory Disease Complex (PRDC), complicating diagnostic interpretations and herd health management.
Rethinking Transmission Routes
The presence of replicating virus in respiratory pathways opens new questions regarding disease transmission and herd management.
“For producers, this research could help expand the knowledge about the presence of rotaviruses in the respiratory tract and shed light on whether they can be transmitted nasally or causing respiratory disease,” de Oliveira says.
Understanding when pigs transition from maternal antibody protection to active exposure will be key to optimizing gilt acclimation, herd closures and vaccination timing.
For his work on this project, de Oliveira was selected as one of seven finalists for the Morrison Swine Innovator Prize at the Allen D. Leman Swine Conference, where he presented these findings to industry leaders and veterinarians.
