#243
In a latter day version of Who Do You Trust?, which my older readers may recognize as originally a TV game show from the late 1950’s (Pre Tonight Show) hosted by an impossibly young Johnny Carson, flu watchers are once again called upon to decide which expert to believe on a critical avian flu issue.
At odds here are statements made by Dr. Robert Webster, considered by many to be the father of modern influenza virology, and the hero behind the eradication of the H5N1 outbreak in Hong Kong in 1997, and David Swayne, director of the USDA's Southeast Poultry Research Laboratory. We can also add in Professor John Oxford, virologist at Barts and the London Queen Mary's School of Medicine and Dentistry, for good measure.
The subject is pigeon feces. No joke.
Early on, these denizens of city parks, town squares, and office window ledges (the pigeons, not our esteemed scientists) have been feared as being vectors of the H5N1 virus. After all, what is more ubiquitous in cities today than pigeon poop? With reports indicating that the virus can remain viable for days in bird feces, these concerns appeared to casual observers to have merit.
This set off alarm bells in cities around the world.
Thousands of people flock to the Piazza San Marco in Venice, Italy each day to admire the architecture, after all, and being badly outnumbered by the pigeon population, they might reconsider their itinerary. The pedestrians on sidewalks in New York City frequently find they are in a free fire zone, when it comes to bird droppings. If pigeon feces were infectious, cities would have a real mess on their hands. . . and feet . . . and clothing.
We were immediately told that pigeons were immune to the H5N1 virus, and therefore were of no threat to humans.
This from the BBC’s Q&A on the bird Flu threat, from April of this year. LINK
Q. I HAVE HANDLED AN INJURED PIGEON. AM I IN DANGER?
Craig Senior, Pontefract, West Yorkshire
A. Professor Oxford: Pigeons are not thought to be carriers. But again, it is best to wash your hands.
And in more detail, this article on pigeons and the bird flu virus, published in SEED magazine on May 22, 2006, entitled The Invincible, Flu Immune Pigeon.
"Generally, you can't even infect pigeons, even with high doses [of the flu]," said David Swayne, director of the USDA's Southeast Poultry Research Laboratory. "If you give them high doses, occasionally you can get infected pigeons, but they usually don't shed very much virus."
Swayne has made it his business to shoot obscenely large doses of avian flu into pigeons' noses, using three strains of H5N1 in his experiments: The first, a strain found in Hong Kong in 1997, failed to infect even one pigeon, even when he gave them a far higher dose than they would ever encounter in nature. His other two strains were both found in birds isolated in Thailand in 2004, one a dead pigeon, the other, a dead crow. He nasally administered a high dose of the Thai strains to six pigeons each. Only one of these birds died. Six showed signs of infection but never became sick, and Swayne couldn't even detect the virus in the other five.
While seemingly putting the question of pigeon poop as a bird flu hazard to rest, many flu watchers expressed doubts. In February of this year, a 14 year old pigeon handler in Iraq reportedly died of the H5N1 virus, and in West Jakarta, a 39 year old man died in May, after reportedly cleaning pigeon feces from blocked roof gutters at his home.
Still, if pigeon poop was a problem, it wasn’t a big one, as we saw no outbreaks among humans residing in areas frequented by pigeons.
Adding to the debate, we get this report from Reuters yesterday, warning poultry growers to isolate their flocks from small birds, including pigeons.
(excerpt)
Leading virologist Robert Webster told Reuters his laboratory infected sparrows, starlings and pigeons with strains of the H5N1 virus isolated in Vietnam, Thailand and Hong Kong recently.
His team confirmed the birds shed the virus in their stools and can therefore infect poultry.
"They were infected and shedding the virus in their faeces and from their respiratory tracts. The sparrows died, so they are not as big a threat," Webster said on the sidelines of a conference on avian flu and other infectious diseases in Singapore.
"The bigger threats are the starling and the pigeon. The starling didn't die, but shed plenty of virus," said Webster of the St Jude Children's Research Hospital in the United States.
The virus replicated very well in the starling and less well in the pigeon, he added.
For now, the debate continues. My money is on Dr. Webster, as his research is both the latest, and his track record is impeccable. But our knowledge of the bird flu virus, and its pandemic potential, evolves constantly.
What we think we know today, may well prove to be erroneous tomorrow.
Nowhere does this article indicate that pigeon droppings constitute a hazard to humans. It only references the danger to poultry flocks. One must presume that pigeon feces poses at least some danger, however, given the two cases of human infection already documented.
Still, I consider bird droppings, even in infamous bombing ranges like the Piazza San Marco, to be a relatively minor threat. If wholesale spreading of the virus were occurring through that route, we’d have seen hundreds of cases by now.
At greater risk are pigeon handlers, and those whose job it is to clean up the mess left behind by these aerial bombardiers. The danger, in my estimation, from bird droppings is overrated.
Today’s blog entry isn’t designed to invoke fear of pigeons, or inspire a rush to buy umbrellas.
It simply illustrates another conflicting data point in the continually evolving world of avian influenza.
Related Post:
Widget by [ Iptek-4u ]