Questions about Avian Flu
- From: Peter Duncanson <mail@xxxxxxxxxxxxxxxxxx>
- Date: Sun, 19 Feb 2006 14:11:23 +0000
I'm trying to get a coherent general understanding of the mechanisms
involved in the spread of Avian Flu and the appropriate biosecurity
measures.
It seems that an important biosecurity measure is moving poultry
indoors. This lead me to find out how the virus is transmitted between
birds (wild and/or domestic).
An article dealing with AIV in general, not specifically H5N1 is:
http://www.vetmed.ucdavis.edu/vetext/INF-PO_AI.html
3. Spread between birds
Contact with infected fecal material is the most important mode
of bird-to-bird transmission. Wild ducks often introduce AIV into
domestic flocks raised on range or in open flight pens through
fecal contamination. Within a poultry house, transfer of the virus
between birds can also occur via airborne secretions.
4. Spread between premises
The feces of infected birds are the most important source of avian
influenza virus (AIV). Fecal shedding for 7-14 days after infection
is the most common, but shedding has been documented for up to 4
weeks after infection. The virus can survive in the manure for up to
105 days, especially in high moisture and low temperature
conditions. Mechanical transmission by anything that can walk,
crawl, or fly from farm to farm can and will occur. Vectors are
agents of disease spread. Rodents, insects (including flies) and
wild birds (like sparrows) can act as vectors for AIV by carrying
the virus on their bodies from place to place. AIV can also be found
on the outer surfaces and inside of shell eggs. Transfer of eggs is
a potential means of AIV transmission. Airborne transmission of
virus from farm to farm probably does not occur under usual
circumstances. The spread of avian influenza between poultry
premises almost always follows the movement of contaminated people
and equipment.
The article then goes on to give detailed recommendations for preventing
the spread of the disease, and the cleaning and disinfection of
buildings and equipment of all types.
Would I be right in assuming that the most likely method of infection of
domestic birds is from infected wild birds defecating on the land on
which they are kept? I also assume that the wild bird need not land.
This would appear to leave us with a situation in which land on which
poultry are normally kept must, if there have been any cases of AI in
the vicinity, be considered contaminated for at least 105 days after the
last case of AI infection has been detected.
Back to the article again:
The influenza virus is extremely sensitive to almost any
disinfectant. However, it is very difficult to inactivate the virus
if it is in organic material, such as feces.
Disinfectants that will kill avian influenza virus
1. One-Stroke EnvironR
2. Any detergent
3. Formaldehyde
4. Bleach
5. Ammonia
6. Acids
7. Heating to 90ºF for 3 hours, 100ºF for 30 min.
8. Drying
9. Iodine containing solutions
Is there is any reliable, practical, method of cleaning or disinfecting
a field that would allow poultry to be returned to it in less than the
105 days for natural die-off of the virus?
--
Peter Duncanson
UK (posting from ukba)
.
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