Viruses Keep
Surprising Scientists
From Dr. Patricia Doyle, PhD
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
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:, 216-999-5338
© 2005 The Plain Dealer. Used with permission.
Patricia A. Doyle, PhD
Please visit my "Emerging Diseases" message board at: ngdiseases
Zhan le Devlesa tai sastimasa
Go with God and in Good Health



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