Bluetongue

The NSA organised two Bluetongue meetings recently in the West Country, one in Devon and one in Somerset. I attended the one in Exeter. Considering the importance of the topic, it was very disappointing to see only 100 people at the meeting. I hope you find these notes useful as background information. Please, however, do keep up to date with developments. I’m sure that strategy and tactics will change to meet the evolving situation.

There were two main speakers, Robert Ankorn (Intervet, vaccine producers) and Peter Morris (NSA).

1. Robert Ankorn, Intervet

What is Bluetongue?
• Viral disease, 24 strains, BTV8 is the one in the UK
• Affects cattle, sheep, goats, camelids and wild ruminants
• No risk to human health
• Notifiable disease

Clinical Signs
• Cattle and goats are only mildly affected
• Sheep are particularly affected
• The virus attacks blood vessels
- inflamed gums
- lesions around the mouth
- salivation
- conjunctivitis
- red band around top of hoof
- blue tongue (in the end)
• Starts with high temperature, miserable, apathetic, off food
• Stock in such a bad way that they need intensive nursing
• Up to 70% death rates
• Easily confused with many other diseases, including FMD

Other effects
• Infertility – around 20% in surviving animals
• Foetal defects and abortion

How is it spread?
• No animal-to-animal spread
• Stock only affected after being bitten by a midge
• 1000 species of midge worldwide but only 6 carry BTV
• Un-infected midge takes (infected) blood from animal…into midge’s gut…virus replicates…next bite/feed passes the virus to the next sheep
• Infection within 3-5 days
• Goats have the virus for up to 38 days, sheep up to 54 days, cattle up to 100 days.

Treatment
• Viral disease, so antibiotics don’t work (on the virus, but are of great help in curing the effects (secondary infections)).
• Stock need lots of fluids
• Anti-inflammatories can help alleviate symptoms
• Nursing is very important..use soft bedding, keep out of the sun….

Control
• Reality – total removal of midges is impossible. Also midges fly 2 km a day and can be taken up to 200 km a day by the wind. Thus rapid spread is inevitable.
• Local vector (midge) numbers can be reduced somewhat by use of insecticide. Also, animals can be housed at the times of highest midge numbers, ie dawn and dusk.
• The only insecticide which contains the right chemical (deltamethrin) and is licensed for sheep in the UK is Spot On. Another product (Swish) is licensed for cattle.
• This chemical works for up to 28 days BUT although it can kill the midge which bites the particular sheep (and stop it spreading disease to further sheep) the act of biting gives the disease to that first sheep. Since there are ‘a lot’ of midges, control by this method is not good (as proved in Germany in 2007).
• Vaccination is the only feasible control method. There is no Plan B.

Vaccination
• The vaccine is serotype-specific, ie for BTV8. It is being developed by Intervet, Merial and Fort Dodge.
• Defra have ordered 22.5 million doses for England and Wales (20 million for England, 2.5 million for Wales) from Intervet (called Bovilis BTV-8). It is an inactivated product (not live), which is the only type allowed in Northern Europe.
• Cattle require 2 doses, sheep 1 dose under the skin.

Why Do We Have Bluetongue Now?
• Before 1998, only 2 incursions into Europe.
• Since 1998, there have been 11 more incursions, the present one being the most serious with over 30,000 cases.
• The reasons may be climatic (temperature changes, different rainfall patterns, increased windyness).
• So, we have a longer vector season (period when midges are active), increased vector range, more vectors, and the disease spreads though midge gut walls more efficiently at higher temperature.

Where Does It Go In Winter?
• After all, midges die….
• Scientists not really sure but it probably remains in previously infected animals that were not culled.

What Next?
• Dutch experience says that the second year is much worse than the first.
• Vaccination is the only realistic control method.
• IF every susceptible animal were vaccinated, we might (theoretically) get rid of BTV8 but even 90-95% vaccination would mean that there would be relatively few infected animals acting as a reservoir for midges to bite and spread the disease. If vaccination levels are around 80% (which is what Defra currently are projecting) then BTV8 is here ‘forever’. It will be endemic in Great Britain (even if it doesn’t make it to Ireland). It won’t just go away……
• A vector-free period was declared on 21st December 2007 and, until midge activity starts again, stock can (after a blood test) be moved from a higher risk area to a lower one. When the vector-free period ends, this will no longer be possible. So, if you want to move animals in this way, do so asap.

2. Peter Morris, NSA

While we have no experience of BTV in most of the British Isles, IT IS OUR PROBLEM. The arrival of this disease has the potential to do more damage to the sheep industry than FMD.

We need to take advantage of the opportunity we have (that was not available to Continental sheep keepers this year). The vaccine will be available at about the same time of the year as Bluetongue will begin to spread. If we vaccinate, our stock will be safe.

In 2006, BTV arrived in a mild way in Holland. There were just 1 or 2 fatalities. In May/June 2007, the disease re-emerged and by the summer it had snowballed in Germany, Holland and France. 40,000 cases were reported but it is thought that this was the tip of the iceberg. There were thousands of dead sheep (up to 70% of infected flocks) and the rest were totally miserable. The level of intensive care required was very high. Of the sheep that survived, 20% were barren.

At the moment, the disease is bottled up in the S/SE of the country. The policy will be:
• Stage 1 – try to keep it out of the UK – we failed and are past this stage now.
• Stage 2 – bottle the disease up – instigate Control and Surveillance Zones.
• Stage 3 – when the vaccine becomes available, vaccinate stock in the Control Zone.
• Stage 4 – as more vaccine becomes available, move the boundary of the Control Zone in steps, vaccinating stock in the new area that has come into the Control Zone. Continue to expand the Control Zone until ‘the whole country’ is one Control Zone with all (or as many as possible) animals vaccinated.

Things to note:
• You are only allowed to vaccinate in a Control Zone, so the zone must be made bigger and bigger to allow stock to be vaccinated.
• The reasons for expanding the Control Zone in stages are: (i) the vaccine will only become available over a 2-3 month period and (ii) if the zone was expanded to include a large part (or all) of Great Britain then free movement would be possible without blood tests and the disease reservoirs (mostly infected cattle) would move through the country this spring and, when the disease re-emerges, spread would be catastrophically bad.
• As the Control Zone is expanded, the Surveillance Zone will move ahead of it, with so ‘disease-free’ parts of England and Wales will come into the Surveillance Zone in early summer and into the Control Zone in mid-Summer. Presumably, though we were not told at the meeting, the zone boundaries will move into Scotland from mid-Summer onward.
• To give vaccine producers confidence, Defra have ordered on our behalf 22.5 million doses of vaccine: 20 million for England and 2.5 million for Wales and all of this should be delivered by late July. Currently (I believe) no orders have been placed by anyone for vaccine for Scotland or Ireland….There are obviously more stock than this in the country (remember to include lambs and calves) so the number presumably reflects the fact that either Defra do not believe that everyone will vaccinate or that they believe that ‘market forces’ will provide the rest of the vaccine.
• Vaccination will not be compulsory.
• Vaccine availability and price will be widely publicised.
• One day the vaccine MAY be available as part of our normal annual 8-in-1 injection.
• Exports to the northern part of the Continent (France, Belgium, Netherlands, Germany) will be allowed, even if the Control Zone is widened – you are allowed to move stock from a lower-risk to a higher-risk area and these countries are effectively one large Control Zone.
• There will be a problem exporting to Ireland. As soon as Surveillance Zones (and later Control Zones) extend into currently clean areas, export from there to a lower-risk area will be prohibited.

Peter Morris’s advice:

1. ORDER YOUR VACCINE ASAP
(Note that it will only be available through your vet.)

2. VACCINATE AS SOON AS YOU CAN,
IE, AS SOON AS YOUR AREA IS DECLARED A CONTROL ZONE.!

3. BE POSITIVE.
ASSUMING THE VACCINE IS AVAILABLE WHEN PREDICTED
WE HAVE AN EXCELLENT CHANCE
OF ‘BEATING’ THE DISEASE!

John Adams, Feb 2008.