Archive Case #236: Ovine Bluetongue

Clinical Clues

1. Several sheep in a region with documented midge-borne disease become febrile and stop eating.
2. Affected animals drool and develop swelling of the lips and face.
3. Painful coronary bands cause lameness alongside inflamed oral mucosa.
4. Some sheep have oral erosions, but this clinical pattern overlaps with other infectious and photosensitising diseases.
5. An RT-PCR assay on blood from a symptomatic sheep detects the suspected midge-borne orbivirus during the outbreak investigation.
6. The compatible syndrome and virus-specific result support ovine bluetongue, a Culicoides-borne orbiviral disease.

Diagnosis

Ovine Bluetongue

Fever, facial swelling, oral erosions and coronitis make bluetongue plausible, and a virus-specific result in a symptomatic sheep supports the exact answer. Orf commonly causes proliferative crusts around the mouth; foot-and-mouth disease and photosensitisation can also overlap, so clinical appearance or midge exposure alone is insufficient. Remember: In sheep with mouth lesions and sore coronary bands, consider bluetongue but use appropriate virus-specific testing to separate major mimics.

Educational Use

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