FRANCE - The latest Bluetongue (BTV) outbreak in central France has the potential to engulf Europe again, a leading expert has told TheCattleSite.
Vaccine doses currently available to French authorities so far are "not enough" to contain the virus, according to Professor Peter Mertens, Head of Pirbright Institute's Vector-borne Viral Disease Programme.
A package of 1.3 million doses was released on Monday, which will be focused on animals intended for export.
"The vaccine requires two doses to work in cattle," said Professor Mertens, meaning the number of cattle that could be safeguarded is only in the hundreds of thousands.
"They can't hope to vaccinate all of the cattle now. Measures such as movement restrictions, increased surveillance and testing and vaccinating animals for export are being rolled out."
On discovering the virus on a sheep and cattle farm at Les Brulards in central France, French authorities imposed a 150 kilometre protection zone, containing 4.6 million cattle, 700,000 sheep and 160,000 goats.
Very Wind Dependent
BTV can be spread by Culicoides midges or via the movement of infected sheep, goats or cattle.
Likened to "aerial plankton", Professor Mertens said midge clouds, that may include infected insects, will usually only move at up to ten kilometres an hour, the limit of their tolerance to wind.
"...at wind speeds of 10km per hour they could potentially be travelling up to 160 kilometres, easily reaching the UK from France in a single night"
Commenting on this speed of travel, he said: "Midges often fly at dusk or dawn and their activity and movement depends on both temperature and wind speed, although their movement over land is relatively slow.
"The assumption is that midges have a mechanism to stop them landing in water, so when they reach the English Channel they could spend up to 10 to 16 hours in the air, and at wind speeds of 10km per hour they could potentially be travelling up to 160 kilometres, easily reaching the UK from France in a single night."
The Met office is monitoring and modelling wind conditions and keeping Pirbright and Defra informed about the risks.
Discussion with vaccine manufacturers are taking place, although there are also concerns with BTV serotype 4, which has re-emerged in South Eastern Europe, he added.
Official reports of cases of serotype four were released in Romania and Hungary earlier this month. A year ago, BTV-4 swept across the Balkans northwards from Greece before cooler weather led to a drop in notifications through the winter.
An Aggressive Strain?
Scientists know the French strain to be serotype eight, an aggressive form of the virus that hit Europe in 2006 causing massive losses, particularly to the sheep industry, with Belgium losing a third of its national flock during the late summer of 2007.
Serotype eight killed around 25 per cent of sheep and around one per cent of cattle back in 2006/7/8, also decimating farms in the Netherlands and much of France and Germany.
Although fatality rates in cattle were much lower, the cattle industry was hit by movement restrictions, loss of trade, reduced milk yield, decreased reproductive performance, as well as surveillance and vaccination costs.
“There’s no reason to think that this strain would not be just as damaging and while we know it is serotype eight we are currently undertaking a genome analysis with French colleagues to assess if the strain is in any way different,” said Professor Mertens.
But Professor Mertens added it can have a “disastrous effect” in gestating cattle.
“Deformities known as dummy calf syndrome are caused by the virus infecting the foetus, causing defects in the central nervous system, and as a consequence the calf can be born with no brain at all,where the cerebral hemispheres are virtual absent and replaced by fluid-filled fragile translucent sacs.”
Anyone keeping ruminants should be aware of the potential risk posed by BTV and be wary of lameness, swelling around the head and mouth , loss of appetite, excessive salivation, conjunctivitis, mouth ulcers, reduced weight gain, as well as other signs of depression and poor condition.
“If a shepherd knows their animals, they’ll spot it, but it is not as obvious in cattle,” advised Professor Mertens, meaning dairy farms should monitor for drop in milk yield.
Monitoring milk production two or three times each day means dairy farms can pick up on a less obvious subclinical sign, said Jules Dare of Westpoint Veterinary Group.
He noted that bulk milk tanks can be sampled for antibody levels and virus presence.
“Watch out for swelling around the mouth and teeth,” he stressed. “People have to keep an eye for it -if there’s any doubt, call your vet.”
Clinical samples would then be sent by the veterinary services via official routes, for laboratory testing and confirmation at the Pirbright Institute.
UK: Lessons Learnt
Animal health advisers in the UK have said that the main lesson learnt from the 2007 was that Defra’s decision to administer 22 million doses was a major success, preventing the re-emergence of the disease in the UK during 2008.
Rob Howells of Merial said: “The outbreak in 2007 showed the companies were very good at reacting, although the vaccination response can only be as good market uptake.
He said he was confident of vaccine production to respond “fairly quickly” if required.
He warned that clinical BTV signs, while apparent, could be missed for something else: “We had farmers thinking they had foot and mouth disease back in 2007, and runny noses and lethargic behaviour could also suggest a pneumonia outbreak.”
A Defra spokesperson said:“Bluetongue serotype 8 has been confirmed in central France and the authorities there have already brought in disease control measures required by EU rules.
“We are carefully monitoring the situation and have robust disease surveillance procedures in place, including testing consignments originating in areas under restriction.
“We urge animal keepers to remain vigilant and to report suspicion of notifiable disease to APHA immediately.”