While no one doubts the importance of bluetongue, it
seems messages are mixed regarding the risks. And according
toMerial Animal
Health's vet adviser Brian Rice,
vaccination has become a victim of its own
success.
"People don't seem to see a risk if they haven't seen the
disease. A bluetongue outbreak can last up to five years, so just
because we haven't seen it doesn't mean it won't crop up," says Mr
Rice. Results of a survey taken on behalf of
Merial show farmers in the
north of England believe they are at lesser risk because of the
cooler weather. "Although in the past this may have had some truth,
climate change is having a big impact on rate of spread, with BTV8
just identified in Norway," he says.
Since 2004 every year there has been an additional serotype
incursion into Europe, but last year there were three new serotypes
arriving in to Europe - BTV1, 6 and 8 - with another 18 bluetongue
serotypes still known to exist, according to Mr Rice.
 |
|---|
| Wating for a local outbreak before taking the decision
to vaccinate is too late, so plan for bluetongue
now. |
"This disease is far from over and we must take action against BTV8
first as this is causing most widespread damage in the UK with a
vaccine available to control it. And with 20,000 individual
holdings going down with BTV8 in France last year this demonstrates
the seriousness of the disease," he says.
But it seems other diseases are registering as of higher
importance than bluetongue, with farmers in the south-west
regarding TB as more important. "Despite this, most farmers do seem
to understand the implications of bluetongue, with abortions, loss
of fertility and reduced milk yield in dairy cattle all real
problems," say Mr Rice.
"An outbreak of bluetongue would mean major financial losses,
with dairy farmers recognising milk losses could be as high as
40-50%. But several factors seem to be discouraging people from
vaccinating."
Low incidence of cases, cases confined to imported animals,
geographic locations and concerns regarding abortion risk and cost
seem to be the main factors hindering vaccination.
"The perceived risk of abortion from vaccination is a major
concern and despite vets being quick to dispel the risk, the
uncertainty has still impacted on the timing of vaccination, with
some farmers reluctant to vaccinate pregnant animals.
"Farmers would be naïve if they were waiting for a local
outbreak before taking action to vaccinate. Vaccines take several
weeks before they are fully effective, with several doses needed in
cattle. So by the time bluetongue is recognised in the local area
it will probably be too late," says Mr Rice.
But as well as vaccination the advice from experts is to begin
regular vector control programmes sooner, rather than later, as the
milder weather brings a rise in midge activity.
Farmers should not be lulled in to a false sense of security
thinking that the cold weather will have killed the midges capable
of spreading bluetongue, according to
Intervet/Schering Plough
animal health vet manager, Alasdair King.
"It is likely some midge larvae and possibly adults too have
survived February's cold spell. It only takes a few days of daily
temperatures to average above 12C for them to start breeding to
large numbers, with midges at their most active at 15-30C.
Bluetongue action |
|---|
| Assess risk |
| Plan time for vaccination |
| Vector control |
This is worrying when the south of England has seen several days
with temperatures between 9-11C recemtly. And although vaccination
remains the only way to protect cattle and sheep from the virus,
vector control can help reduce midge numbers helping cut the risk
of BTV.
"Treating with certain insecticides can be effective against the
midge helping to cut the breeding midge population. Vets in last
year's protection zone say application of an insecticide before
vaccinating in May and continued monthly applications through the
season also resulted in lower cases of summer mastitis and New
Forest Eyes as a result," says Mr King.
"Starting control strategies early prevents flies (including
midges) building up to high levels. Insecticide use should form
part of a management programme inclduing measures such as fencing
of stream banks and removing midge breeding areas such as stagnant
water and dung heaps," adds Mr King.