The postmarks on the deadly letters laced with anthrax made clear from the start that they came from Trenton. But tracing the origin of the strain of anthrax that killed five people last fall has been a far murkier venture. And it now turns out that scientists and investigators have been on the wrong trail all along.
Federal investigators have found in recent weeks that the so-called Ames strain was first identified not in Ames, Iowa, its reputed home, but a thousand miles south, in Texas. The strain of the bacteria was found on a dead cow near the Mexican border in 1981, and the geographic gaffe was the result of a clerical error by a scientific researcher.
It was of little consequence until last October, when investigators determined that the anthrax in the nation's first major bioterrorism attack matched the "Ames strain." Then the clerical error wound up taking the investigation on several wrong turns.
Investigators spent considerable effort trying to find the genesis of the strain in Iowa, issuing a subpoena to Iowa State University, which was known to have a sizable library of anthrax samples. Investigators persisted, even though Iowa state officials said they could find no evidence of the Ames strain.
The discovery of the true origin of Ames "looks like it gets Iowa off the hook," a senior law enforcement official said yesterday.
The criminal investigation also focused on the possibility that the anthrax used in the attacks was left over from the nation's bioweapons program, which was shut down in 1969. A scientific paper published in 2000 said Ames anthrax was a strain used in the program. But now, with the discovery that Ames emerged from Texas in 1981, that part of the investigation has also lost steam.
The discovery of the error also sheds a disturbing light on the prevalence of the virulent Ames strain. Until recently, Ames was seen as a germ that had an uncertain origin in nature and was locked away in several laboratories around the country. But now scientists and veterinary doctors say they believe that Ames is common throughout Texas.
This raises a possible public health concern and increases the possibility that last fall's bioterrorist could have simply dug anthrax out of the dirt in Texas.
"We isolate a lot of anthrax here," said Lelve G. Gayle, director of the Texas Veterinary Medical Diagnostic Laboratory in College Station. He said the Ames strain now appeared to be widely scattered in natural settings. It was found in a dead goat on a Texas ranch in 1997.
The new history of Ames, some of which was reported yesterday in The Washington Post , is being investigated by the F.B.I. along with the National Intelligence Council, which does federal threat assessments, and the Central Intelligence Agency.
"This one is the true Ames," a C.I.A. analyst said of the Texas germ. He added that the anthrax that panicked the nation last fall "all came from Texas."
That history starts in late 1980 when Gregory B. Knudson, a biologist working at the Army's biodefense laboratory at Fort Detrick, Md., was searching for new anthrax strains to use in tests of the military's vaccine. In December 1980, he wrote Texas A&M veterinary officials, according to documents obtained from Dr. Knudson.
"Unfortunately, I have discarded all my pathogenic cultures," Howard W. Whitford replied in January 1981. But he said warmer weather would probably bring new outbreaks.
Indeed, in May 1981, the disease struck a herd of 900 cows at a ranch near the Mexican border.
"This heifer in excellent flesh was found in the morning unable to rise," Michael L. Vickers, a veterinarian in Falfurrias, Tex., wrote in his case report. "By noon she was dead."
In an interview, Dr. Vickers said: "This is a very lethal strain of anthrax we have down here. It's nothing to play with. I've seen as many as 30 head of cattle die a day until they're inoculated."
Dr. Vickers sent anthrax specimens to the Texas Veterinary Medical Diagnostics Laboratory, an arm of Texas A&M. The Texas laboratory, remembering Dr. Knudson's request, sent a sample along to Fort Detrick.
