Last month’s article from the team at Homefield Farm Vets focussed on the serious impact of the hot weather on livestock – and now another huge challenge for livestock keepers in Dorset has arrived.Bluetongue, a viral disease mainly spread by midges, causes significant disease in ruminants.
It has seen a sharp increase in cases in the South West since 1st July.
The APHA website lists the number of cases at the date of writing (2nd September) as 825, with 14 cases confirmed in Dorset. However, due to the high number of samples submitted to the lab, there are 2,462 potential cases currently under investigation – figures are at least two weeks out of date. A ‘case’ is defined as a premises on which at least one bluetongue-positive animal has been confirmed, so these numbers are not representative of the number of individual animals affected.
This outbreak is a result of the BTV-3 virus that was circulating at the end of last year, resulting in clinical cases here without the need for infected midges to be blown over from continental Europe, as we have seen in previous years. The midges that spread bluetongue (Culicoides) can be active at temperatures as low as 4ºC, but activity rises rapidly over 15ºC, and above 25ºC the viral replication time within the midge is significantly decreased, to as little as four days. That is probably the reason for the seemingly sudden explosion in reported cases: the virus overwintered in a livestock-dense area here in the South West.
First seen in the UK in autumn 2007 as strain BTV-8, bluetongue is a notifiable disease. This current strain (BTV-3) is causing significant disease in sheep and mortality within infected flocks. Cases of sick cows have also been reported, but signs are less obvious and may be restricted to reduced production and fertility.
Vaccination is the only effective measure for reducing risk to stock. There are three different vaccines for BTV-3: Bultavo-3, Syvazul BTV 3 and Bluevac-3. Due to the high demand, vaccine availability has been affected, but ordering doses for your stock will ensure you receive your allocation when it arrives. At the time of writing, we expect each vaccine will be back on the market over the next few weeks, although possibly in limited quantities.
We have learnt a lot from our fellow vets working in Devon and Cornwall, where the outbreak began, and have hopefully been able to act quickly to ensure we don’t suffer the same devastating problems in Dorset seen on farms there. The key to survival of affected animals is prompt treatment and excellent nursing. These animals have very sore mouths, so ensuring easy access to water and soaked feed is essential. Please speak to your vet about the most appropriate pain relief and anti-inflammatory treatment.
How infectious is bluetongue?
One bite from an infected midge will infect an animal. The animal will typically show symptoms within two to four days of infection. A sheep will stay infected for one month, and cattle for two months, even if clinical symptoms have resolved. Not all midges will become infected after feeding on an infected (viraemic) animal.
What are the main symptoms of bluetongue?
- Very high temperatures
- Swollen head
- Crusting around nose and mouth
- Ulcers in mouth
- Drooling and discharge from nose and eyes
- Lameness and redness around the corium
- (top of the hoof)
- Lethargy
- Milk drop
- Lesions on teats
- Mortality
Is it still worth vaccinating?
Yes! Although the vaccine licences say full immunity takes three weeks for sheep, and three weeks after the second dose for cattle, anecdotal evidence from Devon has shown that by 10 to 14 days post-vaccination, animals have milder symptoms and mortality is reduced. There has been less uptake of vaccine in dairy and beef stock. However, while cattle mortality has been lower, and fewer cases have been reported – perhaps due to the more subtle clinical signs – significant milk loss has been seen, and fertility will be affected. Animals that become infected during pregnancy are at risk of early embryonic death, abortions, stillbirth and deformities, and ‘dummy’ calves and lambs can be born. These calves and lambs can be born alive with almost a complete absence of brain tissue. Therefore, protecting stock is essential for healthy animals on the ground next spring.
Can the vaccine be used in breeding males?
Yes! In fact, they are some of the first stock that should be vaccinated, as bluetongue infection could result in infertility for up to six months, and protection from this is key. It is also reported that infected males could transmit the virus via their semen to females (because germinal products such as semen, embryos and ova can also carry and transmit the virus). Reassuringly, there is no evidence that the vaccines themselves will affect fertility. All the available vaccines are inactive vaccines, so are less likely to cause the transient increase in temperature seen with some live vaccines for other diseases that have been linked to short-term reduced fertility.
What do I do if I suspect Bluetongue on my farm?
As a notifiable disease, animal keepers have a legal requirement to notify DEFRA of suspected cases. If bluetongue can’t be ruled out by discussion with a case vet, you will be given a code to allow free testing of up to three animals on your holding.
Unfortunately, at present this will not cover the cost of your vet visit to take samples, or to post them. We are endeavouring to keep these costs to a minimum, and offer advice and support where we can.
With the large number of confirmed cases in the South West, it may feel unnecessary to report cases – however, it is very important that other notifiable diseases that can have similar symptoms – foot and mouth disease, for example – are ruled out.
A positive result on your farm does not result in any sanctions against the individual animal or the holding. As the whole of England and Wales are within the restricted zone, movement of stock in this area does not require negative test samples. There is no enforced culling for bluetongue-positive animals.
Can I use an insecticide to protect my stock?
No. At best, you may get a few hours of protection from midges, assuming you manage to get sufficient coverage on all parts of the animal. Unfortunately, the products on the market rely on contact for effect. By then it is too late, since the midges have already bitten.
How can we help?
We are always at the end of the phone and happy to answer any further questions or worries you may have with regard to bluetongue. We have heard devastating accounts of what has occurred in flocks and herds in Devon and Cornwall, and have investigated positive cases locally.
We are hoping that through both active communication and a proactive response to acquiring vaccine, we won’t see the same level of devastation that other areas of the country have sadly experienced. We were really pleased with the attendance at the emergency bluetongue meeting that we put on at the beginning of August. We did this as a result of keeping a close eye on how the disease was progressing, and we were overwhelmed with thank-you messages the next day. While the meeting was somewhat sobering and scary, one lady commented that ‘forewarned is to be forearmed!’. That is the exact kind of proactive response and support we strive to offer local farmers.
Upcoming events:
Tackling TB in Dorset – deer management and control of TB – Tuesday 8th September
Cattle (dairy and beef) Heat Stress Meeting – Thursday 17th September
Calving and lambing courses – visit our website for details on all our upcoming events
homefieldfarmvets.co.uk
Quick Q&A with Kim Frampton:
My Role: Office administrator at Homefield Farm Vets. I am a qualified registered veterinary nurse, and among many other things in the practice I co-ordinate the lab sample testing, and also use my nursing knowledge to pack and stock the vet’s surgical kits.
My Favourite Farm Animal: Chickens! I also had a lovely pet Oxford and Sandy pig called Dora.
My Favourite Tractor: John Deere
My Favourite Flower: Lily
My Favourite Hobby: Horse riding or drinking gin!
