- Please note that we are initially talking about NON H5N1
virus, namely A(H3N2) in Ohio.
-
- Viruses also are carried farm to farm via shoes, tires
of trucks, etc. Another vector (unwitting) is the farm veterinarian.
Extra care and infection control methods were taken during the Foot and
Mouth Disease outbreak in the UK by Vets as they traveled farm to
farm.
-
- Patricia Doyle
-
-
- Viruses Keep Surprising
Scientists
By Regina McEnery
Cleveland Plain Dealer Reporter
1-31-5
-
- Late last January, the owners of a turkey farm in western
Ohio noticed something strange.
-
- Thousands of their 34-week-old hens, bred to produce
meatier, tastier turkeys, suddenly stopped laying eggs. Hens normally
produce
80 to 100 eggs over a 25-week laying cycle, but these turkeys were idle
and oddly quiet.
-
- By mid-February, state veterinarians linked the odd
behavior
to a mild strain of influenza commonly found in pigs and humans. The virus
subtype known as A(H3N2) had infected more than 12,000 birds.
-
- Scientists conducting the investigation pinpointed two
potential sources -- an open-air hog farm and a turkey stud farm, both
less than a mile away. They surmised that the pathogen probably traveled
from farm to farm through the air because pigs typically expel the virus
from their respiratory tracts.
-
- The pathogen posed no threat to human health and the
affected turkeys were slaughtered.
-
- What health officials couldn't say was how the wily agent
managed to jump species. The H3N2 virus had been detected in North American
swine and humans since 1998, but never in turkeys.
-
- For Ohio's animal disease detectives, retracing the steps
of roving pathogens like influenza isn't just a day's work, it's a lifetime
of detective work.
-
- Viruses are creative molecules that mutate to survive,
and preventing their spread can be tricky.
-
- It's a job that has increased in scope ever since a
deadly
strain of avian influenza began striking Asians in 1997 with increasing
regularity. During 2004, the virus subtype known as A(h5N1) caused
widespread
poultry disease in eight Asian countries and infected at least 44 people,
killing 32. Most became sick after coming in contact with live
birds.
-
- A New England Journal of Medicine study released last
week detailed what appears to be the first documented case that the
dangerous
avian flu can be transmitted between humans. The report, released early
to coincide with a bioterrorism preparedness conference in Michigan,
concluded
that an 11-year-old girl in Thailand most likely transmitted avian flu
to her mother and aunt last summer.
-
- While the United States has never encountered any human
cases of the highly pathogenic bird flu, in the wake of the Asia situation
world health authorities are now calling for preventive measures to avoid
a possible pandemic should the bird flu merge with a human strain of
influenza.
-
- "There is a saying among influenza
researchers,"
said Dr. Mo Saif, the veteran researcher who isolated the pathogen.
"Anytime
you can stand up and say anything about influenza, you'll be proven
wrong."
-
- Saif directs Ohio State University's Animal Health
Research
Program in Wooster. The eight virologists and microbiologists in the lab
study a spectrum of diseases that afflict food-producing animals, from
E. coli and mad cow disease to severe acute respiratory syndrome (SARS)
and influenza. Poultry and swine live in disease-free pens that scientists
must enter wearing biohazard suits, gloves and surgical masks.
-
- Saif's laboratory was called to the turkey farm case
because its owners didn't know what was devastating their flocks.
-
- Saif has been studying turkey influenza for 35 years.
His office is filled with studies on this perennial nuisance, and he
clearly
loves to talk about it.
-
- He is considered an international authority on animal
influenza, so the notion that viruses will land where you least expect
them doesn't perplex him much. How they get there does.
-
- Researchers know that influenza viruses adapt to new
hosts through a gene-sharing process known as reassortment. What they have
never been able to figure out is the mechanism that gets them in the door.
(I BELIEVE THAT DR. WILEY WAS WORKING ON JUST THAT AT THE TIME OF HIS
DEATHS. EDITED BY Patricia Doyle) All they know is that it happens and
that when it does, there can be deadly consequences. "Viruses can
make fools of us," Saif said.
-
- Like the legions of doctors who each year call in
suspected
flu cases to health agencies, scientists and veterinarians keep a close
watch on flulike illnesses in Ohio's domestic poultry population. They
do it for a number of reasons.
-
- Not only can major outbreaks be disastrous economically
to commercial farmers, but also the peripatetic tendencies of influenza
viruses are increasingly worrisome to animal- and human-health
experts.
-
- Scientists know that influenza viruses can jump the
species
barrier without warning, exposing vulnerable populations - be they birds,
pigs or humans - to deadly germs. The 1968 pandemic that killed 35,000
Americans arose from an avian strain that people had no immunity to.
-
- Though such events are highly unusual, world health
officials
are pressing for closer surveillance of influenza viruses to prevent a
new pandemic. While virologists scan the globe for new human viruses that
might be percolating in the atmosphere, animal laboratories are keeping
an eye on birds and swine. Though most of the U.S. animal outbreaks have
been fairly benign, in recent years Delaware, Texas and Pennsylvania
discovered
cases of bird flu in their poultry populations that could potentially
mutate
into highly lethal strains.
-
- The turkey outbreak in Ohio was considered mild and posed
no risk to human health. But it also appears to be on the move. No sooner
had Saif's lab wrapped up its work on the Ohio case than the same subtype
of influenza turned up at a turkey farm in Illinois. Saif's laboratory
is investigating that case as well.
-
- Theoretically, up to 135 combinations of influenza A
can occur. Because the virus mutates at a feverish pace, scientists are
constantly on the lookout for new variations and new vaccines, not just
for humans but for animals as well.
-
- Swine are widely believed to be the melting pot for
viruses
that eventually find their way to the human population, so vaccinations
are widely used on commercial hog farms to control the spread of disease.
Breeder hens are also inoculated against common strains of avian
influenza.
-
- But there wasn't much veterinarians could do last year
when the turkey outbreak surfaced in Ohio, because birds didn't have any
natural immunity to that strain of flu.
-
- Instead, people involved with animal health set about
finding out as much as they could about the genetic makeup of the subtypes.
State veterinarians sent samples of blood, fecal matter and saliva to
Saif's
lab, where they managed to sequence the virus after several failed
attempts.
The results were shipped to the national laboratory in Ames, Iowa, to
measure
the virulence of the subtype. The Ames lab confirmed that it was a
relatively
mild subtype of influenza that contained genetic segments from humans and
swine.
-
- Dr. David Swayne, an animal influenza expert with the
U.S. Department of Agriculture, said turkey influenza is extremely rare
because most turkeys are raised indoors, where the risk of disease is low.
Problems can arise, however, when diseased birds arrive from other
countries
where avian flu is widespread.
-
- "It's not like Asia," said Swayne, laboratory
director for the Southeast Poultry Research Laboratory in Georgia.
"Our
whole strategy of raising poultry is to keep viruses out."
-
- Animal surveillance has taken on greater importance
because
overpopulation, overdevelopment and international travel keep pushing the
limits of disease. The threat of bioterrorism is also driving this push
for greater accountability.
-
- Still, animal health scientists would probably not be
so nervous were it not for events unfolding halfway around the
world.
-
- In early 2004, a handful of people in Thailand and
Vietnam
contracted a deadlier form of influenza known as A(H5N1) directly from
infected birds. All 23 became infected after coming in contact with live
chickens; none of the people had transmitted the virus.
-
- Concerns escalated in the fall after infectious-disease
specialists in Vietnam uncovered the first case of human-to-human
transmission
of H5N1.
-
- While the virus doesn't seem to be able to circulate
swiftly or efficiently in humans, the World Health Organization is worried
that the avian flu will eventually mutate into a lethal, fast-moving strain
that could create the next pandemic.
-
- Dr. Richard Slemons, a veterinary preventive medicine
professor at Ohio State University who made history 30 years ago when he
isolated the first avian influenza virus in wild ducks, said the recent
events in Asia have prompted U.S. officials to step up surveillance
efforts.
-
- Before 1997, there were only three known instances of
avian influenza viruses in humans. Though there have been no human cases
of this deadly bird flu in the United States, two people, one in New York
and one in Virginia, were exposed to another strain of avian influenza
considered to be lethal.
-
- One developed antibodies; the other actually became ill
but recovered.
-
- Even in Asia, where human cases of avian flu occur
regularly,
the virus doesn't spread from person to person efficiently. Compared with
the thousands of people who contract and die of human flu every year, the
number of cases is minuscule.
-
- " 'This doesn't represent a public health threat.'
That would have been my standard pat answer a few years ago," Slemons
said.
-
- "But because of what we are seeing in Asia, we have
to look closer."
-
- To reach this Plain Dealer reporter:
- rmcenery@plaind.com, 216-999-5338
-
- © 2005 The Plain Dealer. Used with
permission.
-
- Patricia A. Doyle, PhD
-
- Please visit my "Emerging Diseases" message
board at:
- http://www.clickitnews.com/ubbthreads/postlist.php?Cat=&Board=emergi
ngdiseases
-
- Zhan le Devlesa tai sastimasa
- Go with God and in Good Health
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