We must watch for signs of bluetongue

During March, we investigated a case where housed sheep had been found dull, going off their legs and developing swollen lips.

A sheep submitted for postmortem was thin and had pale mucous membranes. Its top and bottom lips were swollen and its liver was abnormal.

The sheep had been treated for liver fluke 10 days previously, but liver damage was extensive and fasciolisis was diagnosed.

"Bottle jaw" is a common manifestation of liver fluke in sheep, it is due to subcutaneous oedema (fluid accumulating under the skin). In this case the oedema was in the lips, which was very unusual.

However, swelling of the face and muzzle is one of the clinical signs of bluetongue.

Many other diseases also have similar clinical signs to bluetongue, but it is important we remain vigilant for the symptoms of this notifiable disease.

Bluetongue is caused by a virus and is spread from animal to animal only by infected midges.

The virus attacks cells lining blood vessels causing the vessels to leak. This leads to redness (hyperaemia) and swelling (oedema), especially in areas subject to abrasion such as the muzzle, mouth, head and the lower legs.

In sheep, this can take the form of swelling of the lips and muzzle, and the nose can become crusty if there is a secondary bacterial infection. Ulcers may be present on the lips or inside the mouth. The sheep may also have watery eyes and noses.

Some of these signs could be confused with orf, photosensitisation or conjunctivitis.