PRRS-2 Lineage 1C.5 Clonally Expanded Clade Now Most Dominant PRRS Lineage in the U.S.

The Swine Health Information Center reports a newly emerged PRRS lineage has spread to eight states and become the dominant lineage circulating in the United States. Since its emergence in 2020, the PRRS-2 Lineage 1C.5 Clonally Expanded Clade has become the dominant lineage in circulation in the United States.

Swine Health Information Center Executive Director Dr. Megan Niederwerder says the detection frequency of cases related to this clade of Lineage has increased steadily and, after a modest but noticeable rise in cases during November and December of 2023, a significant surge occurred in early 2024.

Quote-Dr. Megan Niederwerder-Swine Health Information Center:

From July 2023 to December 2024 there have been 945 cases of PRRS virus with sequences that have belonged to this clade of viruses.When we think about this high genetic similarity of this group of viruses increasing, it's really indicative that the virus that's similar to this L 1C.5 virus clade has increased with regards to distribution.

There was an index case that was first identified on a grow finish farm in Iowa in the summer of 2023 and subsequently the majority of cases were detected in swine farms in Iowa.
However, we've seen over the last year, starting in march of 2024 the virus had expanded to other states including Minnesota, Illinois, Missouri, Indiana, Nebraska, South Dakota and Wisconsin indicating its ability to transmit and spread across the swine population.

Dr. Niederwerder suggest this is something pork producers should be considering when they think about PRRS management strategies such as herd closure, depopulation, vaccination, surveillance to ensure they know what strains are circulating in their herds and the regional risks for introduction and spread.Details on this emerging infection can be found through the SHIC's January eNewsletter which can be accessed at swinehhealth.org.