Protect Sheep Against OPP
February 14, 2014

Sheep producers should develop a plan to keep ovine progressive pneumonia (OPP) out of their flock, North Dakota State University (NDSU) Extension Service sheep specialist Reid Redden, Ph.D., said. 
 OPP is a slowly progressive viral disease of adult sheep. Often, the first sign is a general loss of body condition referred to as "thin-ewe syndrome," according to Neil Dyer, director of the NDSU Veterinary Diagnostic Laboratory. 
Once infected, animals remain infected for life, although many will never show clinical signs of the disease. Flocks infected with OPP can have lowered production efficiency because of early culling, decreased milk production and lower weaning weights, Redden says. 
Researchers at the U.S. Meat Animal Research Center in Clay Center, Neb., recently discovered a genetic marker to identify animals that are less susceptible to OPP. This new genetic test, TMEM154, determines the risk level for infection with OPP. 
Sheep that have two copies of the desirable gene (haplotype 1) are three to five times less likely to contract the disease than sheep with one or two copies of haplotypes 2 or 3 during their lifetime, Dyer says. 
Although previous research indicated that most disease transmission occurs from ewe to lamb, Clay Center researchers reported that only 10 to 30 percent of lambs born to infected ewes contracted the disease from their mothers. Most sheep were infected from their flock mates during subsequent lambing seasons. The researchers say this means that the transmission of this disease within a flock will vary depending on how sheep are managed during the winter and/or lambing season. 
As a result of that research, Redden and Dyer suggest that an OPP prevention plan include testing to identify the infection rate, sourcing genetically tested replacements and/or testing replacement ewe lambs for serotype or haplotype. Reprinted in part from Prairie Star