Cache Valley Fever (CVF) causes abortions, malformed fetuses, infertility, and congenital abnormalities in sheep and goats. The CVF virus is transmitted by mosquitoes and is endemic in many parts of the United States (US). The Animal Health Diagnostic Center (AHDC) receives samples from throughout the country, with the majority of samples coming from the northeastern US. In the past two years, the AHDC tested 73 small ruminant fetuses for CVF, of which 33 (45%) were positive, with 19 of 45 positives in sheep (42%) and 14 of 28 positives in goats (50%).

Classic fetal deformities from CVF include malformations in the musculoskeletal system and central nervous system (CNS), resulting in scoliosis, hydrocephalus and arthrogryposis. However, it is important to note that this disease does not always cause clinical signs; if two or more offspring are born, one may be alive and healthy while the other is stillborn. Malformations are common but not always present in an aborted fetus or stillborn. Typically, if the dam is infected with CVF prior to day 32 of pregnancy, the fetus will be aborted. If infection occurs between day 32-37, then the fetus is likely to have musculoskeletal and CNS lesions. If infection occurs after day 37, the fetus clears the virus and has no congenital defects.

Diagnosis of CVF is complicated by the fact that the virus is cleared prior to the abortion or birth of affected offspring. Diagnosis therefore relies on fetal antibody detection and the AHDC offers a CVF serum neutralization test. Acceptable samples from a fetus include free abdominal (peritoneal) fluid, free fluid around the heart in the pericardial sac, fluid around the lungs (pleural effusion), or heart blood. Pre-colostral serum is the sample of choice from live newborns suspected of CVF infection.