Porcine reproductive and respiratory syndrome virus (PRRSV) case detection had a moderate decrease in June, but overall case positivity continues to be relatively high, especially in grow-finish populations, according to the July Domestic Swine Disease Monitoring Report.
“Unfortunately, diseases, like PRRS, are quite active right now,” says Lisa Becton, DVM and associate director of the Swine Health Information Center.
The July report details splits of the L1C.2 PRRS variant into a different variant – L1C.2.45, Becton explains. This is now the most detected variant in North Carolina.
“This highlights the variability and mutability of that virus,” she says. “Why does that matter? Some of these variants are quite virulent and they may or may not correlate with current vaccine strategies. A lot of times they don’t cross-protect against each other. So, if you had exposure to one strain, you may not have protection against another new strain.”
New PRRS Variant Makes An Appearance
An additional PRRS variant – 1A.13.49 – is increasing in identification and case detections. Reports highlight this variant needs to be closely monitored as it can be “quite virulent and can cause significant harmful impact on the farm,” Becton says.
She encourages producers to check out the monthly report to determine what variants are present in their region so they can understand the risks, especially around animal movement into a different region.
“The Midwest does appear to have the lion’s share of cases, especially with the L1C,” Becton notes. “However, North Carolina has seen more now of the variant that split from L1C. There are definitely some regional differences. State-by-state information of disease status is also available in the report.”
Key PRRS Findings in June
- 25.65% of 6,826 cases tested PRRSV-positive in June, a moderate decrease from 29.08% of 7,231 in May.
- L1C.5.32 (276) was the PRRSV variant most detected in the U.S., followed by L1A.13.49 (70), and L1C.5 (59).
- States with higher number of PRRSV L1C.5.32 detections were detected IA, MN, IL, MO, IN, NC, NE, KS, OH and OK.
- The split of L1C.2 moved variant L1A.13.49 into the top three most frequently detected variants, with five first-state detections reported in the SDRS database in 2026.
“These variants are important to monitor because the number of detections is well above expected levels and certain segments have increasing case detections,” Becton says. “We really need to be vigilant on biosecurity. Understand the potential impact for animal movements if you’re shipping pigs into an area with those increased risks. Be informed and be aware.”
It’s Not Just PRRS
In addition to PRRS, other diseases of note include porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV) and Mycoplasma hyopneumoniae (MHP).
PEDV activity in June was above expected levels.
- 8.09% of 4,279 cases tested PEDV-positive in June, a moderate decrease from 10.39% of 4,388 in May.
- PDCoV activity declined slightly in June.
- 2.75% of 4,179 cases tested PDCoV-positive in June, similar to 4.16% of 4,301 in May.
- MHP case positivity showed an uptick in June in both adult/sow farms and wean-to-market categories, following the expected seasonal trend.
- 14.53% of 716 cases tested MHP-positive in June, a moderate increase from 10.06% of 686 in May.
