Spread
of Avian Influenza Viruses among BirdsAvian
influenza viruses circulate among birds worldwide. Certain birds, particularly
water birds, act as hosts for influenza viruses by carrying the virus in their
intestines and shedding it. Infected birds shed virus in saliva, nasal secretions,
and feces. Susceptible birds can become infected with avian influenza virus when
they have contact with contaminated nasal, respiratory, or fecal material from
infected birds. Fecal-to-oral transmission is the most common mode of spread between
birds. Most often,
the wild birds that are host to the virus do not get sick, but they can spread
influenza to other birds. Infection with certain avian influenza A viruses (for
example, some H5 and H7 strains) can cause widespread disease and death among
some species of domesticated birds. (For more information, see "Low
Pathogenic versus Highly Pathogenic Avian Influenza Viruses.") Avian
Influenza Outbreaks in PoultryDomesticated
birds may become infected with avian influenza virus through direct contact with
infected waterfowl or other infected poultry, or through contact with surfaces
(such as dirt or cages) or materials (such as water or feed) that have been contaminated
with virus. People, vehicles, and other inanimate objects such as cages can be
vectors for the spread of influenza virus from one farm to another. When this
happens, avian influenza outbreaks can occur among poultry. Avian
influenza outbreaks among poultry occur worldwide from time to time. Since 1997,
for example, more than 16 outbreaks of H5 and H7 influenza have occurred among
poultry in the United States. The U.S. Department of Agriculture ( http://www.aphis.usda.gov/lpa/issues/issues.html)
monitors these outbreaks. Low
pathogenic forms of avian influenza viruses are responsible for most avian influenza
outbreaks in poultry. Such outbreaks usually result in either no illness or mild
illness (e.g., chickens producing fewer or no eggs), or low levels of mortality.
When highly pathogenic
influenza H5 or H7 viruses cause outbreaks, between 90% and 100% of poultry can
die from infection. Animal health officials carefully monitor avian influenza
outbreaks in domestic birds for several reasons: - the
potential for low pathogenic H5 and H7 viruses to evolve into highly pathogenic
forms.
- the potential
for rapid spread and significant illness and death among poultry during outbreaks
of highly pathogenic avian influenza.
- the
economic impact and trade restrictions from a highly pathogenic avian influenza
outbreak.
- the possibility
that avian influenza could be transmitted to humans.
When
avian influenza outbreaks occur in poultry, quarantine and depopulation (or culling)
and surveillance around affected flocks is the preferred control and eradication
option. Centers
for Diseases Control and Prevention
http://www.cdc.gov/
More
Information … |
SUSCRIBASE 
