Cache Valley virus serologically identified in sheep with congenitally malformed lambs in Alabama.

Objective: To report serological identification of Cache Valley virus (CVV) in ewes from Auburn, Alabama.

Animals: 6 ewes and 1 ram from the teaching flock at Auburn University College of Veterinary Medicine were tested for CVV via virus neutralization. From October through November 2024, 3 ewes underwent Cesarean sections, with 2 lambs delivered from each ewe. Severe musculoskeletal deformities in 3 of the 6 lambs, delivered from 2 of the ewes that underwent Cesarean sections, prompted investigation into a causative agent.

Clinical presentation: 3 of the 6 lambs were clinically normal, but 3 of the lambs demonstrated severe arthrogryposis, kyphosis, and scoliosis and were humanely euthanized. Upon necropsy, affected lambs had severe internal hydrocephalus with severe cerebellar hypoplasia and marked atrophy of the spinal cord.

Results: Of the 7 sheep in the teaching flock, all 6 ewes tested positive for CVV titers via virus neutralization, whereas the ram tested negative. Two ewes had deformed lambs, 1 had normal lambs, and the other 3 were open following a controlled breeding period with the ram. All ewes and the ram remained healthy throughout breeding and lambing, and the 3 unaffected lambs were raised to weaning normally.

Clinical relevance: This case series documents the spread of CVV in the US and highlights the validity of testing for CVV in flocks experiencing characteristic congenital malformations. Veterinarians must consider CVV as a differential even in previously nonendemic regions.