Sheep producers are busy this time of year with lambing going full swing for most producers and according to South Dakota Cooperative Extension (SDCE) Sheep Specialist Jeff Held, in an extension press release, producers should be aware of the potential for Cache Valley virus (CVV), to affect their lambing crop.
Held reports that many flock owners have reported an unusual number of lambs born with skeletal and other development deformities. Diagnostic laboratories including the South Dakota State University Animal and Disease Research and Diagnostic Laboratory (ADRDL) at Brookings have confirmed CVV-affected newborn lambs.
Producers in South Dakota aren’t the only ones seeing evidence of CVV. The virus is also having some effect on sheep producers in Minnesota, according to Mike Caskey, instructor in the Pipestone Lamb and Wool Program at Minnesota West Community and Technical College in Pipestone.
CVV infects pregnant ewes and mosquitoes are the sole carrier of the virus.
Conditions this fall during the early breeding season (August through September) were particularly right because there remained a high population of mosquitoes following the warm, wet summer.
SDCE Veterinarian Russ Daly said, in the news release, “although CVV is found throughout the United States, the reported cases affecting sheep in South Dakota and the upper Midwest region historically have been minimal.”
CVV has been around for years, Caskey explained, but most often you see it in the south and westareas that have a wetter climate. CVV gets its name from the Cache Valley in Idaho.
Daly explained that CVV is a potential cause of the birth of abnormal lambs, and that the most dramatic effects of the virus lead to birth defects in lambs, mostly affecting the brain and central nervous system. The virus also affects the skeletal tissue and muscles that show up as fused joints, curved or twisted spines, unusually thin and underdeveloped muscles, and enlarged skulls.
“We have seen some flocks having a problem this year,” said Caskey. “CVV usually doesn’t cause big losses. One flock had 10 out of 400 ewes that had problems.”
These were ewes that gave birth in January.
Problems are less likely to be seen in ewes that give birth in February. When those ewes were bred, he said, there are generally less mosquitoes.
“From an economic standpoint these losses aren’t big,” said Caskey. “But you do end up with ewes that don’t have lambs.”
Ewes having problems most likely were infected during the most critical period of between days 28 and 45 of gestation. Infections up to 28 days generally result in fetal reabsorption. After day 45 of gestation, a CVV infection is not expected to cause abnormalities in lambs.
The virus is not spread from ewe to ewe, Daly said, even during the lambing season. There is no vaccine for CVV and since the cause is a virus, there are no treatments available either.
