Chief Veterinary Officer’s statement on low pathogenic avian influenza
The following is an update on the current situation on the outbreak of low pathogenic avian influenza in Norfolk and provides information about our approach.
Summary of recent events
On 28 April H7N3 Low Pathogenic Avian Influenza was confirmed on a poultry farm in Dereham, Norfolk. The Veterinary Laboratories Agency have since carried out further investigation and confirmed on 4 May 2006, that no highly pathogenic virus was present.
On 29 April positive results were reported for avian influenza in chickens on two free range farms near Dereham in Norfolk. The birds on these farms have been culled out on suspicion of a notifiable avian disease. On all three premises culling of the birds has been completed using containerised gassing units. The birds have been disposed of, and cleansing and disinfection is being carried out.
A 1km restriction zone is in place around each of the premises. Movements of poultry and poultry products may only take place under licence from the State Veterinary Service. The necessary surveillance is being carried out within the restriction zones and movements and contacts are being traced and all appropriate worker protection measures have been put in place.
Publication of the epidemiological report
A preliminary report into the epidemiology of the outbreak was published on 3 May and states that it is not possible to say at this stage whether any of the 3 flocks was the index case and that other premises may be involved. It is not possible to determine whether the 3 flocks were infected by a common source. As a result wild birds and another possibly infected premises continue to be investigated. However the report does explain that it is likely that one of the free range flocks was infected first around 20 March: some 11 days later the virus infected the second free range flock. The flock that was confirmed with H7N3 on 28 April and owned by a different company was infected between 15 and 18 April. Any links or movements between the premises involved are being investigated.
Difference between H7N3 and H5N1
Birds
Many subtypes of avian influenza exist. The severity of symptoms depends upon the strain of virus and type of bird infected, birds infected with highly pathogenic H5N1 may die suddenly or show a range of clinical signs including respiratory signs, swollen heads, dullness, a drop in egg production, and a loss of appetite. It can also spread rapidly through poultry flocks, causes disease affecting multiple internal organs, and can kill up to 100% of the infected birds, often within 48 hours. Low pathogenic H7N3 however, commonly causes only mild symptoms, ruffled feathers, a drop in egg production, respiratory signs and may go undetected.
Humans
The Health Protection Agency advises that the virus H7N3 is not the same as the H5N1 virus in that the human health effects are far less severe. However like H5N1, the H7 virus does not transmit easily from birds to people and does not readily pass from person to person. In almost all cases of human H7 infection to date, the virus, in both low and high pathogenic forms, has only caused mild disease such as conjunctivitis. This is a virus which has only extremely limited implications for human health. The Health Protection Agency views the risk to the general public as very low .
Food safety
The Food Standards Agency advises that avian flu does not pose a food safety risk for UK consumers. The risk of people getting avian influenza from eating poultry meat and eggs is low. Evidence from countries where people have caught the disease indicates that direct contact with infected birds is the main risk factor. Eating infected chicken or eggs has not been identified as a cause of their illness. Further information is available on the Food Standards Agency website.
Current policy on dealing with H7N3
Our objective, working closely with partners in Government and elsewhere, is to assess and close down all risk pathways arising from the case, resolving current uncertainties as rapidly as possible; and to stamp out and eradicate the infection through proportionate and evidence-based control measures which:
- ensure maximum protection of human safety, particularly workers’ safety;
- provide due protection for the welfare of birds affected;
- minimise the impact on international trade, the rural economy and the sustainability of industry.
Culling
Our policy is to take a proportionate, evidence and risk based approach. Culling is an important disease control measure. Based on the available epidemiological evidence our policy to date has been to cull on suspicion of active infection.
Surveillance
The State Veterinary Service are carrying out inspections on all three premises as well as tracing all poultry movements and other relevant contacts onto and off the premises. This is our priority for detecting the potential source and any spread of disease. In the 1km restricted zones our assessment is proportionate to the risk posed by the infected and suspect premise. Surveillance of commercial poultry flocks comprises clinical inspection and check of production records and sampling for each epidemiological unit, in line with the draft diagnostic manual. ‘Poultry’ are defined as in the 2005 AI Directive and by ‘commercial’ we mean those flocks where there is a legal requirement to register on the Great Britain Poultry Register. Any dead or dying wild birds in the risk area will also be tested as a priority. We are also carrying out additional surveillance activities around the area. This will be kept under active review, and revisited as new evidence emerges or should the situation change.
Housing
Poultry keepers within the restricted zones have not been asked to house their birds, however good biosecurity measures continue to be encouraged. This, as with all other disease control measures, is being kept under review.
Precautionary approach
In the light of our current understanding of the disease spread, the primary focus continues to be on the eradication of the disease. However, as our understanding of the virus develops particularly in respect of seropositive flocks (flocks that develop antibodies to the disease) we will continue to consider our strategy and response to the disease.
Further information is available on our avian influenza webpages.
Page published: 11 May 2006