The onset of spring and the imminent promise of vaccination have drawn bluetongue into focus again, Jonathan Long reviews the UK disease situation.
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Warmer days may be just the boon flagging grassland needs this spring, but they are also the one thing that will encourage the spread of bluetongue disease across the UK as midge activity and virus replication step up a gear.
Bluetongue is the quiet killer, arriving unannounced on the wind with the midges and striking quickly to affect ruminants of all shapes and sizes. Sheep, cattle, goats, llamas and deer are all at risk, although sheep are most affected by the disease and most likely to die as a consequence.
When vaccinating cattle a large fold of skin should be taken hold off and the vaccination given under this skin. Farmers should vaccinate wherever they normally do, but the neck and over the ribs are usual places
And while some farmers believe the threat is not that large, Jules Dare of Westpoint Vet Group points to the experience of the Netherlands last year as an example of just what the disease can do. “More than 30% of the Dutch national flock had the disease last year and 6% of the country’s sheep died because of bluetongue. In the cattle population 10-20% were affected, with total mortality of 1%.
“Businesses suffered losses, largely because of lost production, secondary infection, infertility, lameness, weight loss, dead animals and vet and medical costs. More than 1.35m sheep, 3.8m cattle and 280,000 goats were affected and the total economic impact is estimated to have been E81m.”
Bluetongue can be difficult to spot in some species, but that is no excuse for letting your guard down and failing to keep an eye on susceptible stock. In sheep, the most common symptoms are a nasal discharge, facial swelling, including oedema under the jaw, oral ulceration and lameness or a reluctance to stand, says Mr Dare. “It can present similarly to other conditions, including pneumonia, foot-and-mouth, claw abscess polyarthritis and extreme orf. So accurate diagnosis is essential. When you suspect bluetongue or, more importantly, can’t rule out bluetongue infection, contact your vet.”
Bluetongue can also cause chronic arthritis, wool loss and result in increased incidence of other diseases, including pneumonia, mastitis, weight loss and lameness, explains Mr Dare. “While in cattle it can cause a long-lasting milk drop, reduced fertility, long-lasting herd lameness, increased mastitis incidence, foetal losses, calf losses and weight loss. Conjunctivitis is also a classic symptom in cattle.”
But in many cases it will cause only mild symptoms in cattle and may be as little as linear erosion around the base of teats, says Dutch vet Daan Derksen. “In suckler cows, the first thing you notice may be cows not allowing calves to suckle properly. This is a sign that teats may be sore and cows are uncomfortable with calves suckling.
Treatment options
As bluetongue is a virus there is no specific therapy against the disease itself, says Mr Dare. “The animal has to cure itself supported by treatment and nursing. Supportive treatment should include long-acting non-steroidal anti-inflammatory drugs, diuretics, antibiotics and cortico steroids.
