We must watch for signs of bluetongue
Last updated 22:08, Tuesday, 13 May 2008
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.
Sheep may salivate and develop difficulty breathing and this might be confused with pneumonia.
In severe cases, the tongue can swell. Swelling under the jaw could be confused with fluke.
Inflammation of the coronary band of the hoof causes severe pain. The feet are hot and swollen. This lameness could be confused with foot rot, CODD or laminitis.
In cattle, there is redness and crusting of the muzzle, which could be confused with malignant catarrhal fever or IBR.
Ulcers are visible in the mouth, a symptom shared with BVD or foot and mouth disease.
Cattle may have inflammation around the teat base or sore teats, which could be confused with photosensitisation or local teat conditions.
A Dutch farmer who has experienced bluetongue in his sheep gave this description:
“You have to be aware that the first signs are sudden. One day the flock is healthy and the next day you spot an animal that is stiff, has a very careful gait, separated from the flock, having difficulty in standing up, foaming at the mouth, with swollen and warm legs.
“The level in the water bucket is suddenly dropping and the sheep’s voices are changing; they get softer and higher.”
If you suspect a bluetongue outbreak, you are required to phone your local Defra divisional veterinary manager immediately. Contact John Kelsey at Animal Health on 01228 591999.
