by: Dr. G.F. Kennedy
Every year, questions arise about aborted and malformed lambs. Cache Valley virus is defined as a mosquito-transmitted cause of infertility, abortions, still births and multiple congenital abnormalities in sheep. It is endemic in North America and often there are outbreaks over a wide area. Sheep grazing in swampy areas during breeding season are most susceptible. Attempts to control mosquitoes are indicated but difficult. At time of abortion or birth the virus is usually no longer viable. Generally, the incidence within a flock is low and I suspect once there has been exposure the ewe is resistant going forward. Occasionally lambs are so malformed that a cesarean is the only way than can be removed from the ewe.