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Published February 17, 2014, 10:32 AM

Plans devloping to protect sheep against OPP

Sheep producers should develop a plan to keep ovine progressive pneumonia (OPP) out of their flock, says North Dakota State University Extension Service sheep specialist Reid Redden.

By: NDSU Agriculture Communications,

Sheep producers should develop a plan to keep ovine progressive pneumonia (OPP) out of their flock, says North Dakota State University Extension Service sheep specialist Reid Redden.

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. Another common sign of OPP is a sheep increasing its effort to breathe while at rest.

OPP infection also can cause “hard bag,” an enlarged, firm udder with reduced or no milk flow.

Once infected, animals remain infected for life, although many 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, the U.S. Meat Animal Research 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 lambing season.

To further investigate the disease, researchers at NDSU collected blood samples from 735 sheep representing 12 flocks and eight breeds in North Dakota. The researchers determined that 66 percent of flocks had infected animals. The overall infection rate of the sheep tested was 28 percent.

“We demonstrated that OPP is a prevalent disease in North Dakota,” Redden says. “However, the infection rate varies considerably from flock to flock. The overall infection rate in flocks that we tested was similar to that estimated for the U.S. sheep industry. Although the genetic test does not guarantee that sheep will be resistant to OPP, it does appear to provide some protection from infection.”

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 or testing replacement ewe lambs for serotype or haplotype.

“Work with your local veterinarian, or extension agent or state specialist to develop a plan that works best for your farm,” Redden advises.

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