Bluetongue Disease Latest

BTV Update 24 November 2010

Changes to Bluetongue Post Import Testing

Our testing regime has been revised to move from single post import testing for all bluetongue virus (BTV) susceptible animals entering GB at 5-7 days to a risk-based regime as for other diseases whereby imports will be tested depending on the risk assessment of each susceptible consignment.

These changes will take effect from Friday 26th November 2010.

The changes to our post import testing have been made following a reassessment of the risk from incursion of disease from Continental European Imports.

Background to Post Import Testing

1. At present, every bluetongue (BT) susceptible domestic animal imported from continental Europe is blood tested for bluetongue after arrival in GB. This surveillance requirement allows us to assess disease incursion/spread through movement of infected animals from the continent.

2. BTV cases have decreased significantly across Europe in 2009 and 2010. GB is also part of a Low Risk Zone which means that all imports arriving from another country within a BTV Protection Zone (PZ) are vaccinated or naturally immune.

3. In 2010, 20,185 susceptible animals have been imported and tested in GB for BTV since 1/11/2009. None have tested positive.

   
   Rationale for the Change
   
   
4. BTV Experts recently met and considered the need for BTV post-import testing. They concluded that the threat of disease incursion from legally compliant imports was considered to be very low. Due to the considerable drop in risk, our policy on post import testing should change from testing every susceptible consignment for BTV to a more risk based approach.

5. A move to risk based testing would bring BTV testing in line with other diseases (eg Brucella). For diseases other than BTV in domestic animals, Government has recently moved to a system of risk based post import checks (e.g. based on country of origin), which allows Animal Health to identify and prioritise consignments of animals at higher risk.
   

6. Given the change in risk from BT and the significant costs of ongoing testing, Government will stop 100% post import testing and move to a risk based testing approach, based on
   
   - the BTV status of the country of origin
   - the level of midge activity in the country of origin which would vary by season.
   - random tests prioritising animals perceived to be at higher risk.
   
   These risks will be regularly reviewed so that alterations to the checking regime can be made in response to any emerging risks.
   
   Going Forward

7. Defra is currently carrying out national BT surveillance across the whole of GB during November 2010 similar to the surveillance they carried out in 2009.

8. In order to meet the requirements for the Lower Risk Zone, Defra with help from Animal Health and livestock holders has also carried out additional monthly surveillance in high risk areas of the Midlands and South East for BT between June and October this year. All of these samples returned negative for BT.

9. By the beginning of 2011 GB could be in a position to officially declare freedom from BTV8 if all of our surveillance shows that we remain free from circulating disease.

10. The Commission has also recently indicated that they wish to amend the BT Directive and Regulation to make the use of vaccine easier in order to provide member states with more flexibility in dealing with the threat of infection. (Currently vaccination is only allowed within a zone).

11. We will need to consider the detail of any new proposals from the Commission along with the results of our surveillance before deciding on how to go forward in 2011.

12. On 10th November Denmark also changed to a Lower Risk Zone for BTV8. Like most other member states Denmark has had no circulating disease in 2010 and is implementing the necessary surveillance to implement the change.

13. In the meantime it continues to remain important for all livestock farmers to
    remain vigilant for signs of disease and report any suspicion of a notifiable
    disease.

14. We will keep you updated on future policy options.
    
    
    Bluetongue Core Group

BLUETONGUE
Guidance on the disease vector and potential mitigation measures

The following guidance provides information on the vectors that spread Bluetongue and the mitigation measures that may be appropriate for some situations. Farmers and veterinarians may wish to consider the following advice.

The Culicoides Midge

The Bluetongue virus is spread by Culicoides species of midge.

There are 47 different species of Culicoides but only a few species are able to carry the virus. Some of these species are present throughout the UK. The risk of virus transmission is related to the number of midges present.

Culicoides behaviour

• Populations fluctuate, and peak in May/June and September/October.

• Daily activity peaks at dusk/dawn.

• Some of the most widespread UK species breed around animal dung.

Culicoides mitigation measures

• No insecticides are authorised specifically to act against Culicoides

• Deltamethrin-based compounds have performed best in tests, however, they only offer limited coverage of animals and provide 1-2 days protection at best.

• Generic repellents are only effective for a few hours at best.

• Because they do not entirely remove the risk of an animal contracting bluetongue and their short period of protection, in addition to economic and environmental considerations, the Scottish Government does not advise insecticide use against Culicoides on farms as a practical and cost-effective control measure against Bluetongue.

• Although the Scottish Government does not advise the use of insecticides as a control measure, it supports it application for short-term protection of animals transiting through BTV restricted zones. Animals and their vehicle must be sprayed prior to travel.

• However, in the event of an outbreak insecticide treatments may be required for certain specific livestock movements.

• Any insecticides should be used in accordance with the manufacturers instructions.

Culicoides breeding sites can be potentially reduced by:

• Moving dung heaps away from livestock (>50m where possible), or covering heaps with a plastic, watertight cover.

• Scrape the perimeters of heaps/slurry pits regularly to a depth of 6-10cms (where the majority of larvae reside).

• Housing of animals in an enclosed space (where the means are available to close doors, and cover entrances with mesh) during peak periods of Culicoides activity may reduce biting rates to a greater or lesser extent,

• No one measure will prevent midges biting animals. However, the use of a combination of the measures listed above will sequentially reduce the risk of midge bites and hence reduce the risk animals becoming infected with BTV.