Swollen, sore muzzles with mucous membrane erosions, high fevers, and lameness suggests infection with bluetongue virus. Signs are worse in young lambs (up to 30% mortality). Remember infection of pregnant dams produces fetuses with hydrancephaly or porencephaly causing ataxic and blind lambs.
Bluetongue is almost exclusively seen in sheep, though white-tailed deer, pronghorn antelope, and desert bighorn sheep in North America can be severely affected. Rare in cows. REPORTABLE.
There are at least 24 serotypes of the bluetongue virus (genus Orbivirus in the family Reoviridae). Worldwide distribution mimics its vector’s (Culicoides biting midges) distribution. Dx: serology (ELISA or AGID), virus isolation from blood of febrile animals, and PCR to identify the specific isolate.
Treatment is supportive care. Prevention relies on controlling vectors and vaccination, the latter of which is used in endemic regions (but no cross-protection between different serotypes) or during outbreaks in non-endemic regions.
Bluetongue is clinically indistinguishable from foot and mouth disease (FMD), so that is a good second choice. But FMD is unlikely in the scenario above because FMD mainly affects pigs and cattle.
Ovine progressive pneumonia (OPP) is a chronic disease of wasting and dyspnea in sheep and goats, caused by a lentivirus (retrovirus family). OPP is most common in animals older than four years and rarely occurs in sheep and goats under two years of age.
Image courtesy of Fourrure.
