Worried livestock farmers across the East of England put their bluetongue concerns to government experts as cases of the dangerous animal virus continued to rise.

The potentially-fatal disease, which is spread by infected biting midges, affects ruminants including cattle, sheep, goats and deer, as well as camelids such as llamas and alpacas.

Since the UK's first case of the summer was confirmed in the Broads village of Haddiscoe on August 26, the virus has now affected more than 40 premises across the East of England.

Most are in the Restricted Zone (RZ) which now covers Norfolk, Suffolk and Essex - although new cases have also recently prompted control zones in Yorkshire and north-East Lincolnshire.

Animal movement restrictions in the RZ were among the key topics discussed with veterinary and disease control experts at an industry webinar this week.

Andy Smith, of Defra's exotic disease policy control team, explained that animals can move into or within the RZ with no restrictions - unless they show clinical signs of bluetongue on the day of transport. But licences are required to move out of the zone.

This prompted a question from a rare breeds keeper, who was concerned that while local livestock markets within the RZ can continue to operate, farmers cannot take their animals out of the zone to specialist rare breeds sales elsewhere in the country.

Mr Smith said: "In terms of sales direct to individual buyers, that is something that can be licensed, but for movements out to markets I am afraid that cannot be licenced at the moment.

"We are working with the Livestock Auctioneers Association and others to find ways we can authorise these movements into markets and we are conscious there will be demand for that, but it is not something that is practical, or that the risk of spread can be controlled, at the moment."

Sascha van Helvoort, veterinary lead for outbreak delivery at the APHA (Animal and Plant Health Agency), warned that not all movement licence applications would be successful.

"It is important that everyone understands that although a specific licence is available for the move being undertaken, it may still not be approved if the risks associated with an individual request are too high," she said.

Applications for complex and high-risk movements will need extra time to process, she added.

In response to a question about culling infected animals, Mr Smith said: "In the RZ we have found circulation of bluetongue [in native midges] and culling animals in that situation does not give much disease control benefit. So, in almost all cases, it is very unlikely we are going to be killing any animals in that zone as a disease control measure."

Farmers were encouraged to speak to their private vets about three new vaccines approved by Defra last week, which can help alleviate bluetongue symptoms and reduce mortality rates - but do not prevent animals becoming infected or infectious.

The APHA is carrying out tracing and surveillance visits in the RZ to understand how the disease is spreading.

Farmers were told that not all farms in the RZ are being sampled - but should a farm be selected for a surveillance visit, the APHA will sample up to 35 cattle over six months of age.

Bluetongue does not affect human health or food safety, but it is a notifiable disease and livestock keepers must report suspected cases to the APHA on 03000 200 301.

For guidance on bluetongue disease and RZ movement restrictions and licences, see ruminanthw.org.uk/bluetongue-virus or www.gov.uk/guidance/bluetongue or call the BTV hotline 024 7771 0386.