Avian Influenza (AI) Information Clearinghouse
for Bird Owners
Quickies:
- The natural reservoir of Avian Influenza is waterfowl. In some areas (Mekong Delta), 70% of waterfowl are infected with HP-H5N1.
- Migrating waterfowl can spread bird flu to new areas, but much of the spread of HP-AI appears to be along trade routes. It appears that humans have been transporting infected animals.
- The highly pathogenic form (HP-AI) is of critical concern to poultry producers because 80-100% of infected birds die within 2 days.
- HP-AI is extremely contagious in waterfowl (ducks, geese, swans, etc) but the mortality rate in waterfowl of some highly pathogenic strains appears to be declining. This means infected birds are living longer and, presumably, can transmit the virus for a far longer period of time. It also means the virus has more opportunities to combine with other viruses and evolve different characterists.
- Other animals can be infected. Birds other than fowl can be infected. Mammals are rarely infected but, in 2006, domestic cats and zoo tigers that ate infected animals died from H5N1.
- Vaccination of birds is not currently recommended because the vaccine reduces symptoms but does not prevent the bird from having an active infection..
- Control of an HP-AI outbreak involves the depopulation (slaughter) of domestic birds at the location and within a small radius, typically 3 km (approximately 2 miles).
- HP-AI continues to mutate. The 2005 Qinghai Lake mutation is more infective to wild birds than previous strains but is currently NOT easily transmissible to humans.
- The Indonesian strain seems to have a higher fatality rate in humans than the Quinghai strain.
- Human cases have occurred in areas where people are handling live, dead (uncooked) infected fowl (ducks, swans, chickens, etc.), their feathers, or droppings.
UC Davis Veterinary Medicine ExtensionAI Info
Dr. Carol Cardona, Poultry Extension Veterinarian
I. Sources and Spread of Avian Influenza virus (AIV)
1. Signs of diseaseAvian influenza can vary from a very mild to a highly fatal disease depending on the strain of the virus and host factors. In cases of mild infection, no symptoms of illness may be recognized, but the flock will develop an antibody titer (seroconvert), demonstrating a previous infection. Decreased food consumption, and drops in egg production in laying birds, are among the earliest and most predictable signs of disease. Symptoms may include any or all of the following: coughing, sneezing, ruffled feathers, fever, swollen heads, depression or diarrhea. In some cases, birds die so rapidly that no clinical signs of disease are seen. Viruses that cause no disease in one species (e.g. ducks) may cause serious mortality in another species (e.g. turkeys).
2. Sources of virus
All avian (bird) species are susceptible to infection by AIV. However, most
AIV are isolated from wild waterfowl including shorebirds, gulls, geese, terns,
etc. and especially wild ducks. Wild ducks carry the AIV virus without any
signs of illness and are considered the major reservoir for AIV infections
in domestic poultry. Live bird markets have historically been an important
source of AIV. Co-mingling of birds from different sources, fecal material
of crates and vehicles and purchase of birds with unknown AIV status all contribute
to the chance that AIV will be carried to the home farm.
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.
USGS
Quick Facts:
* Numerous subtypes (16 HA and 9 NA) of type A avian flu occur naturally in birds. Most subtypes have no apparent affect on birds and do not spread to humans.
* However, in 1997, one subtype – known as H5N1 or Highly Pathogenic Avian Influenza (HPAI) –led to the death of thousands of domesticated and wild birds in Asia.
This virus can also infect humans, often with lethal consequences.
Potential Movement of H5N1 to Alaska:
* Many species that breed in Alaska migrate and winter throughout parts of Russia and Asia.
* Birds could be exposed to H5N1 in Asia or Russia during winter or on migration and carry the virus to Alaska in spring along migratory corridors (see flyway mapsand migratory bird pathways between Alaska and Asia).
* Adults may pass the virus on to young.
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