Pleasant early-autumn weather can create a false sense of security, but fall farming activities and temperature swings often signal disease challenges ahead. September diagnostic data showed the typical seasonal rise in viral respiratory and enteric diseases, including increased detections of porcine epidemic diarrhea virus (PEDV), active porcine reproductive and respiratory syndrome virus (PRRSV) variants, and seasonal influenza.
“People are harvesting, moving site to site and pumping manure,” says Dr. Lisa Becton, executive director of the Swine Health Information Center (SHIC). “We observe a lot of fluctuations in temperature, so seeing more activity in viral disease detections is something to definitely watch. Fall can be a signal of what we may see in the winter. “
Grow-finish and wean-to-harvest facilities continue to be the most vulnerable sector for pathogen transmission and persistence, Becton says.
Pathogen-by-Pathogen Breakdown
Porcine Epidemic Diarrhea Virus (PEDV)
“PEDV has really increased in September, especially in our wean-to-harvest sites,” Becton says.
The report shows a significant, expected upward spike in September from an overall 4.87% positivity in August to 6.76% in September. The biggest spike and heaviest concentration are in the wean-to-market category at 11.92% compared to 8.68% last month.
Porcine Reproductive and Respiratory Syndrome (PRRSV)
“PRRSV 1C.5.32 has been very active, too,” Becton says. “If you’re around an area that has the virus and you don’t have it, always ask what can you do to prevent it from coming in? And if you do have it on your farm, what can you do to prevent it from exiting?”
Vaccines can be a tool for management but vaccine efficacy varies widely depending on the homology/match to circulating field strains; vaccination alone cannot replace strict biosecurity, she says. In addition to following biosecurity protocols, she reminds producers to support animals through an infection.
“If they are ill, take steps such as management of a fever,” she adds. “Treat any secondary bacterial infections.”
Mycoplasma hyopneumoniae (M. hyo)
The September report notes a moderate increase in M. hyo diagnostic detections. Grow-finish barns still maintain relatively high positivity rates, indicating ongoing active circulation that warrants continued surveillance.
Because the pork industry is currently engaged in farm and regional M. hyo elimination programs, Becton says this naturally involves heightened routine monitoring and diagnostic testing. A rise in laboratory submissions can reflect increases in testing but also could indicate natural infection and those increasing trends should be closely monitored.
Swine Influenza A (IAV-S)
Multiple mixed viral strains are circulating concurrently, including H3N1, H3N2 and H1N1. Becton notes highly variable patterns rather than just a clean seasonal spike.
“We do see influenza activity across all seasons, and it’s an interesting change with this virus because fall had traditionally been a time where we saw a lot of activity due to changing weather and seasons,” Becton says.
She encourages producers to be mindful of influenza and notes that increased activity is occurring in grow-finish and sow sectors.
“This viral activity serves as another reminder about the increased risk for disease transmission and the need for improving biosecurity in that growing pig population,” Becton adds.
Influenza moves bidirectionally (pig-to-human and human-to-pig). In addition to herd protocols, producers should actively encourage seasonal flu vaccinations for farm personnel to protect worker health and prevent introducing human influenza strains into swine barns.
These September diagnostic trends offer both a timely warning and an opportunity for proactive intervention. Because fall pathogen circulation frequently forecasts the severity of winter herd health challenges, producers cannot rely on vaccination alone to safeguard vulnerable grow-finish and wean-to-harvest facilities. Tightening day-to-day biosecurity remains the most effective strategy to break transmission cycles, protect herd productivity and shield farm personnel in the months ahead.
