Attention small ruminant practitioners! Suspected Cache Valley virus abortions in southern Ontario  

Emily Brouwer, Courtney Schott

Since the outbreak in 2015-2016, small ruminant producers, practitioners, and pathologists have been vigilant in monitoring small ruminant abortions for fetal deformities associated with Cache Valley virus (CVV). An update published in the March 2017 issue of this newsletter identified 2 ovine fetuses with craniofacial and spinal deformities that were submitted for examination between December 2016 and February 2017. Both of these lambs subsequently tested negative for CVV via serology.

Recently, a set of quadruplet lambs were submitted for postmortem examination. The history provided indicated that the lambs had multiple skeletal deformities, and were either born dead or immediately euthanized at lambing. The external lesions in these lambs varied in severity and included combinations of pronounced lordosis/kyphosis (2 lambs), sternal malformation (2 lambs), subjectively long limbs (4 lambs), and arthrogryposis (3 lambs). Internally, lesions were limited to the brain, calvaria, and skeletal muscle. Brain lesions included hydranencephaly, microencephaly, cerebellar hypoplasia, mild lissencephaly, and suspected holoprosencephaly (Fig. 1). The skeletal muscle in all lambs was markedly pale, firm, and shrunken.

The top differential diagnosis is in utero neurotropic virus infection, of which Cache Valley Virus is the most likely etiology. Serologic tests for fetal antibody to CVV and PCR for viral antigen are pending. This update is to serve as a reminder to practitioners and producers to consider CVV in cases of ovine abortion where there are skeletal (Fig. 2) and neurologic deformities. Lambs are commonly born at term and may be alive, but they may also be aborted and lesions vary in severity between lambs.   AHL

Brains from quadruplet lambs.

Figure 1. Brains from quadruplet lambs. Brain lesions included hydranencephaly, microencephaly, cerebellar hypoplasia, and mild lissencephaly.

Aborted lamb with kyphosis and arthrogryposis.

Figure 2. Aborted lamb with kyphosis and arthrogryposis. Photo courtesy of Dr. M. Spinato.