Wild Birds with H5N1 in England 2008

[Oracle]

Re: Abbotsbury Swannery

Not to put a damper on matters, but..


The record population of mature swans and cygnets at the Dorset Swannery should NOT be lauded. <i>This is a wake-up call. </i>

The growing density of swans at Abbottsbury is strong risk factor for disease outbreak.

Swans are NOT social birds, especially breeding pairs. Swans are naturally aggressive and territorial when breeding. These swans have developed unusual behavioral mechanisms to diffuse this natural aggression in a colony setting.

This crowding exerts an immunosuppressive effect on the colony, putting young birds and those already infected with mild bacterial disease at risk.

There are only two such large breeding aggregates in the world.

PAY ATTENTION DEFRA.

[cartski]

Re: Wild Birds with H5N1 in England 2008

Seems that DEFRA has pulled the report. I got the googel entry, but no page listed in DEFRA:

[PDF] Epidemiology report - Highly Pathogenic Avian Influenza H7N7 ...File Format: PDF/Adobe Acrobat
HPAIH7N7 Defra Epi Report. 15.30 23June08. Highly Pathogenic Avian Influenza H7N7, June 2008. Epidemiology Report. Situation at 12.30 Wednesday 11 June ...
https://www.defra.gov.uk/animalh/dis...080617v1-1.pdf -

[Gert van der Hoek]

Re: Wild Birds with H5N1 in England 2008

Still available via these links:

http://216.239.59.104/search?q=cache:C9mtfiQQAXEJ:influenza.bvsalud.org/lildbi/docsonline/7/8/087-HPAI_H7N7_Oxfordshire_NEEG_June_2008.pdf+Highly+Pathogenic+Avian+Influenza+H7N7&hl=nl&ct=clnk&cd=2&gl=nl

and PDF:

http://influenza.bvsalud.org/lildbi/docsonline/7/8/087-HPAI_H7N7_Oxfordshire_NEEG_June_2008.pdf

[cartski]

Re: Wild Birds with H5N1 in England 2008

Thanks, Dutchy.

Below is an excerpt about the apparent development of an LP virus into a HP virus:

We suggest that after a period of approximately 7-10 days following the observed
onset of clinical signs in Shed 1 a mutation to virulence of the presumed LP H7 virus
to the highly pathogenic form occurred in Shed 3 during successive rounds of viral
replication and transmission cycles in a partially immune poultry population. During
these replication and transmission cycles random mutations to the virus genome can
occur. Whether or not these mutations become fixed in the population depends on a
number of factors, some described below. Acquisition of this genotype may have
been driven by synergistic host: pathogen interactions, including:
i. Adaptation and selection of the virus by serial passage within the
poultry host population.
ii. The combination and inter-relationship of viral genes, not least the HA
and NA.
iii. Host immune function and status - a partially immune poultry
population providing a further selection pressure in proximity to a fully
susceptible poultry population
This presumed progressive mutation and host adaptation of the LP virus during
onward transmission from Shed 1 to other Sheds was also proposed during the LPAI
H7N3 outbreak in Dereham, Norfolk during May 2006 (Defra, 2006).
34. Spread of H7N7 HPAI virus may then have occurred between Shed 3 and Shed 4,
infecting a fully susceptible population with the resultant acute and severe clinical
presentation. Coincident with the spread of HP virus infection from Shed 3 to Shed 4,
spread of the HP virus apparently also occurred to (and possibly between) Shed 1
and Shed 2 resulting in H7 super-infection.
35. Analysis to confirm the order of infection of the sheds, considering the virology
results, the seroprevalence at the time of culling in comparison to that two days
earlier, and the husbandry routine on farm is in progress. Further hypotheses, i.e. the
unique introduction of HPAI in the premises without involvement of LPAI, have not
been ruled out at the time of writing.

[Oracle]

Re: Wild Birds with H5N1 in England 2008

The proximity to the pond (see Fig 1) and stream of the primary infected sheds and the poultry operation owners idiocy in stocking the pond with 100 mallards for hunting the previous year (hundreds of them, of which some 30 remained prior to HPAI outbreak report) made for interesting reading. Note that the farm otherwise employed recommended biosecurity measures.

Wildfowl proximity, known HPAI carrier (Mallards) to affected sheds in order of infection. Check.

Colluding factors: (1) proximity to large flock of ducks and pheasants on adjacent property. "The adjacent premises keeps 2150 pheasants and 600
ducks", and (2) foxes were known to frequently visit the affected farm.

Former is more likely to be a source of LPAI to the target farm, rather than the latter, although foxes might carry HPAI asymptomatically, especially if there are one or more females with litters living nearby. See: cats and Q-Fever citations, PubMed).

"The most significant feature of the last two weeks of May was the heavy rainfall which occurred between 25 and 28 May (Appendix 4). Rainfall was recorded on 66 hours out of a maximum of 96 hours. On these four days alone around 130% of an average May rainfall was recorded."

Weather conditions, period of heavy rainfall with heavy winds. Check.

Slow response to report preliminary flock symptoms (egg drop and deaths (two weeks, AGAIN, see Fig 3). "Birds in shed 1 appeared to recover" - despite the concurrent onset of die off in another shed. BS excuse by owner for late reporting. Check.

But here is the kicker that probably pushed LPAI to HPAI (see item 55): bird dropping fell through the mesh floor to the ground below, where it was allowed to collect until the grow-up cycle was finished, when the shed was simply picked up and moved to another location. The birds are STANDING over the viral-infected fecal matter and piss, plus feathers.

Retention of contaminated fecal/bedding materials within shed immediate to LPAI-to-HPAI transition. Check.

Interesting conclusion (item 35): did they find evidence of AI co-infection?

[JJackson]

Re: Wild Birds with H5N1 in England 2008

I am confused

32. Preliminary molecular analyses have shown that phylogenetically the virus clusters with known, contemporary poultry and wild bird H7 isolates from Europe and that the haemagglutinin gene of the virus has undergone progressive mutations with successive rounds of replication and adaptation in the poultry host.

and then

35. Analysis to confirm the order of infection of the sheds, considering the virology results, the seroprevalence at the time of culling in comparison to that two days earlier, and the husbandry routine on farm is in progress. Further hypotheses, i.e. the unique introduction of HPAI in the premises without involvement of LPAI, have not been ruled out at the time of writing.

They obviously have some sequences if they can generate phylogenic analysis and if they have enough to state
"the Haemagglutinin gene of the virus has undergone progressive mutations with successive rounds of replication and adaptation in the poultry host."
then why - when the rest of the report is so comprehensive - is this vital data not included. They talk as if they dont know if it was LP going to HP, or two independent introduction, but if they have before and after (LP & HP) sequences this should be obvious.

[gsgs]

Re: Wild Birds with H5N1 in England 2008

can anything ever be really "ruled out" ?
I mixture of viruses may have entered and evolved independently