Bluetongue threat

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Use the pre-midge season wisely to minimise the bluetongue threat.

The threat of Bluetongue and all that goes with that – from movement restrictions to vaccination strategy and from contingency plans for dealing with sick animals to how midges spread the virus – is at the forefront of everyone’s mind as we head towards spring.
Currently, producers throughout the UK are dealing with the implications of the tight controls associated with Protection and Surveillance Zones (PZ and SZ). At the same time, everyone is carefully monitoring reports concerning the rise in midge numbers that goes with warmer temperatures. In the period before the vaccine becomes available, testing and bio-security are essential. Farmers should also discuss disease prevention with the practice; and that means both vaccination and management to minimise the midge threat.
Livestock farmers across the country are being advised to get their fly treatments on early this season to help control biting and nuisance flies, and in particular any midges that could be infected with the bluetongue virus. It is advisable to monitor daytime temperatures, and when these reach 12º-15ºC (the temperature at which the bluetongue virus replicates inside midges), get on with a treatment that controls midges. In some parts of the country, this might be as early as late April
While fly treatments with midge activity cannot guarantee protection against bluetongue, what they can do is kill the female midges that are responsible for transmitting the disease, and in doing so limit the replication of these much-worried-about insects. Fewer midges mean fewer animals are bitten and the chance of limiting the spread of the disease is improved. Currently there’s only one fly treatment in the UK that has trial data to show its effectiveness against midges, and that is Intervet’s Butox SWISH.
It is relatively easy to assess populations of larger flies, such as the face fly and stable fly, and apply a pour-on treatment when they become problematic. However, it is not necessarily so when it comes to midges. The midges which are capable of infecting cattle and sheep with the bluetongue virus are much smaller than most flies (typically only 3mm long) and subsequently much harder to see, even at high populations.
The lifecycle of the culicoides midge necessitates more frequent treatments. While users of Intervet’s Butox SWISH would normally expect 8 to 10 weeks of cover from a single application, when it comes to midge control, treatments need to be applied to cattle every four weeks.
In this important pre-vaccination period, an enquiry recording form has also been set up by Intervet to allow vets to collect the names and details of anyone making enquiries about vaccination.  Simply inform the practice of the number of sheep and cattle that the vaccine is required for; this information will help your vet to estimate how much vaccine needs ordering.

Be vigilant for early signs

As we head into Autumn, all livestock producers should be aware that this is the time when bluetongue disease may show itself in unvaccinated stock. Intervet/Schering-Plough Animal Health is therefore, keen to encourage further uptake of the vaccine, Bovilis® BTV8 – particularly as supplies are currently plentiful.

But the manufacturers also want to alert people to the many other diseases which BTV can easily be confused with.  As experience in Europe has shown, early recognition of this devastating virus is essential if vets are to make a prompt diagnosis and offer appropriate treatments.

Despite its name, a blue or purple colouration of the tongue is reported in only 20% of cases of bluetongue in sheep and fewer than 6% in cattle. The most significant and worrying disease it can be confused with is foot and mouth disease (FMD) – especially in cattle when there is a lot of drooling saliva.

In sheep, FMD symptoms are relatively mild, usually temporary lameness. In comparison, the classic sign of BTV in sheep is a swollen face – absent in FMD. Also typical of FMD, is the fast spread of disease within the herd with the majority of animals suffering from clinical signs. In bluetongue outbreaks, only a small number of animals are affected.

Look through the check-list below of diseases with similar symptoms, then contact your vet for more information and log on to www.bluetongue-info.co.uk

SHEEP
Orf
This condition can cause swelling of lips and muzzle which could be confused with bluetongue.
Haemonchosis (and chronic liver fluke infestations)
Cases with ‘bottle jaw’ may be confused with swollen head symptom of BTV. Lameness
All causes of lameness with swelling and lesions of the coronet may be confused with BTV.
Cobalt/vitamin B12 deficiency
A typical clinical sign is a swollen face (usually chronic cases) which may be confused with BTV.
Photosensitisation and facial eczema
BTV often looks like a case of photosensitisation or severe facial eczema however, with photosensitisation and eczema, there are no lesions inside the mouth.

CATTLE
IBR
This is primarily a respiratory disease without the lameness or teat lesions often seen in cases of BTV.
Mucosal disease
The most common clinical sign of mucosal disease is diarrhoea, but this is not present in BTV cases.
Photosensitisation
As for sheep above.