HPAI H7N7 DEFRA Epidemiological Report ( 08/06/28 ) | |||||
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Part | Charger | doctorysu | date | 08/06/28 | |
The import risk assessment division issued an guideline on 'HPAI H7N7 DEFRA Epidemiological Report' as
a focus on risk analysis on 19th June.
The contents are as follows :
Executive summary
1. Following a report of suspected avian notifiable disease in laying hens in
Oxfordshire on 2 June 2008, highly pathogenic (HP) H7N7 avian influenza (AI)
infection was confirmed on 4 June 2008. At the time of writing (11 June), three
further reported cases, from across GB, have been negated either on clinical
grounds or after laboratory examination of samples, and three are under
investigation.
2. On 11 June, it appears that the infection is confined to a single premises.
Infection has been ruled out at both premises of origin of the affected birds.
Investigations to date have found no evidence of infection on any contact or
geographically close premises, and there has been no evidence of spread of
infection to any other premises to date, however investigations continue.
3. Clinical evidence, from the farm’s records, supports virology opinion that HPAI
infection derived from a pre-existing Low Pathogenic AI infection (LPAI). However
the possibility of an HPAI introduction has not been completely ruled out. Further
analyses of the virus and on the infected premises (IP) continue.
12.30 11June08
4. Seven hypotheses for source have been considered and the evidence to date
suggest two of these are much more likely than the others.
5. The two likely hypotheses for the source of the outbreak continue to be
investigated and are
i. Unidentified AI in domestic poultry premises in Great Britain, associated
either by proximity or potential contact, or
ii. AI in wildlife in contact with the IP
6. Movements of live domestic birds, which represent a medium to high risk of
transmission of AI, have been ruled out as a possible source of infection for the
IP, and as a potential means of spread of AI from the IP.
7. The network of contacts associated with the IP that might act as the source of
infection, or be at risk of spread of infection, is made up in the main by the other
premises connected to the large commercial egg production business of which
this farm was a part. The main risk of exposure to AI virus was on premises
associated with egg collection routes, feed lorry deliveries, disposal of
carcasses/manure and personnel contacts.
8. Investigations to date indicate a good standard of biosecurity is practiced in the
chain between egg production and final packaging. At the time of writing,
investigations of premises at risk due to potential contact (tracings) or proximity
(within the protection zone, PZ) have revealed no further infected premises. The
absence of positive findings from this line of inquiry seems to rule out associated
premises as the source of infection at the present time. However further
investigations including laboratory testing are in progress on premises at risk, in
case LPAI has been missed, as clinical signs can be few and non-specific.
9. Wild bird activity in general was low around the IP. However mallard ducks were
introduced onto a pond near one of the mobile sheds (shed 1) in 2007. Moreover,
shed 1 was moved near to the pond, a public footpath and a stream source
immediately before the current batch of 3000 birds were introduced. Current
evidence suggests that infection most likely started in Shed 1, and further
investigations in to the possibility of a wildlife source are in progress.
Update at 9am Monday 16 June
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