Made in the USA New York City live bird market Bird flu viruses have been detected every year in the United States since the mid-1960s.2084 In just the last five years, more than a dozen outbreaks of viruses with the potential to mutate into highly pathogenic forms have been discovered.2085 But the largest to date still remains the 1983 Pennsylvania outbreak that spread down through Maryland and Virginia2086 and led to the deaths of 17 million domestic birds2087 at a cost to the nation of more than $400 million.2088 Investigators speculate that the H5N2 virus responsible for this outbreak may have started out in a flock of wild ducks that landed in a pond on a chicken farm in eastern Pennsylvania.2089 Duck feces on the boots of a farmer may have first brought the virus inside the broiler sheds.2090 The virus, like essentially all wild waterfowl viruses, started out benign, causing a drop in egg production or mild upper respiratory symptoms, but soon started “racing though giant commercial chicken warehouses.”2091 The now resident director of the University of Pennsylvania’s poultry laboratory explained that “with that many opportunities to mutate under those intensive conditions” the virus changed from one that gave chickens the sniffles to the “bloody Jell-O” virus Webster called “chicken Ebola,” causing birds to hemorrhage throughout their bodies.2092 Webster’s team performed genetic analyses of the H5N2 virus before and after it turned lethal. To their surprise, the two differed by only a single amino acid. Amino acids are building blocks strung together in chains that make proteins. The H5 hemagglutinin protein is more than 500 amino acids long.2093 All it took was a tiny point mutation in the viral genetic material to change the 13th amino acid in the H5 chain from an amino acid named threonine to one called lysine—a mutation that, in Webster’s words, “change[d] that benign virus into one that was completely lethal.”2094 “That such a tiny change in the virus could enable it to wreak so much havoc,” Webster and colleagues later wrote, “was an awesome discovery.”2095 The U.S. Department of the Interior‘s 127-year-old U.S. Geological Survey (USGS) represents the nation’s leading governmental authority on the biological sciences.2096 Reflecting on the evolution of low-grade to high-grade strains of bird flu, the USGS echoes other world authorities in implicating industrial poultry practices not only as providing an “excellent opportunity” for rapid spread (particularly when “poultry are housed at high densities in confined quarters”) but in part playing an “ideal” role in possibly sparking the next human pandemic.2097 H5N2 resurfaced two years later in low-grade form in Massachusetts, New Jersey, Ohio, and again in Pennsylvania,2098 all traced back to live poultry markets in New York City. A survey of live markets in 1986 found 48 harboring the virus,2099 suggesting to investigators that live poultry markets may have been the critical mixing point between ducks or geese and chickens that triggered the original Pennsylvania epidemic.2100 Efforts to purge bird flu viruses from live poultry markets over the years have been unsuccessful,2101 despite periodic quarantine, depopulation, cleaning, and disinfection. In 2004 an outbreak of highly pathogenic H5N2 was discovered in a 7,000-chicken broiler flock in Texas after the owner introduced a chicken from a live poultry market in Houston into his flock.2102 Considering the Hong Kong outbreak and other U.S.2103 and Italian outbreaks traced to live poultry markets,2104 USDA poultry researchers describe live bird markets as the “missing link in the epidemiology of avian influenza.”2105
Posted on: Fri, 23 Aug 2013 07:04:50 +0000
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