Bacteria’s Mode of Transmission Is Key to Its Severity

Anthrax spores, which killed a man in Florida last week, gave a mere sore to an NBC employee in New York, who is recovering.

Experts say the same spores can cause different types of infection, depending on how they enter the body.

“If you’re unlucky, you’re going to shake it up and inhale some of the stuff,” said Raymond Zilinskas, senior scientist at the Monterey Institute of International Studies. “If you’re lucky, you’ll have broken skin somewhere and you’re going to get some spores into that. The organism doesn’t change, though.”

Unlike inhaled anthrax, which is almost always fatal if not treated early, cutaneous infection--entry through a break in the skin--usually resolves itself, even without medications. A third way to contract anthrax is to eat food contaminated with it. None of the forms can be passed from person to person.

Some experts believe that past cases of cutaneous anthrax have gone untreated, dismissed as a skin blister. The immune system usually repairs the damage on its own.

“The vast majority of cases, 80% to 95%, of cutaneous anthrax [recovers] without treatment; the body will win out over this and it will kill the organism,” said Glenn Songer, professor of veterinary science and microbiology at the University of Arizona. “It is certainly conceivable that a person could develop cutaneous anthrax and recover and never be diagnosed.”

Now, with the heightened state of alert, anthrax cases are more likely to be identified and correctly diagnosed.

“There is a much higher index of suspicion among the health providers than before,” Zilinskas said.

Typically, there is no crime involved in anthrax transmission. About 2,000 people worldwide contract anthrax annually through the skin, most from handling contaminated wool, hides or leather. Accurate numbers are not available in the United States.

In West Texas, a man became infected this summer while skinning a dead plains bison on a ranch, according to Martin Hugh-Jones, an anthrax researcher at Louisiana State University. The man was bitten by a horsefly, and a lesion developed at the site of the bite.

Hugh-Jones said the man could have developed the infection from the horsefly bite or by scratching the bite with fingers contaminated by the animal’s blood, or both.

Another case was reported to the Centers for Disease Control and Prevention in August 2000, during an outbreak among cattle in North Dakota. The infected person was a 67-year-old North Dakota man who helped dispose of five infected carcasses.

He was the only person out of 62 workers handling the animals to become infected, suggesting that the disease is difficult to contract.

The first sign of an infection--occurring two to five days after exposure--is a tiny blister.

Over the next few days, the blister grows slowly bigger, and the bacteria multiply in the center. Meanwhile, the bacteria make a toxin that oozes out, causing damage to the tissues around the blister.

The blister, which grows darker in the middle, eventually scabs over and falls off.

The course--and seriousness-- of the infection depend on the health of the infected person, how many spores entered the body and the particular strain of anthrax. For inhalational anthrax, for example, it takes respiration of more than 2,500 spores to become infected.

Individuals can be treated with the antibiotics Cipro, doxycycline and penicillin.

In rare cases, a cutaneous anthrax infection spreads to the bloodstream and causes a serious, systemic infection that usually is fatal.

Inhalation anthrax, by contrast, is fatal in 90% of cases unless treated with antibiotics before symptoms appear.

Outside the body, anthrax becomes dormant in the form of spores. It is quite hardy. One group of researchers found spores of anthrax that had survived 250 years.

More commonly, Hugh-Jones said, an infected cow buried in soil probably contaminates the area for 20 years. When dried, the spores take the form of a white or beige powder.

Anthrax is more common in animals than humans, with American bison being the most susceptible, followed by cattle, sheep and goats. Dogs are resistant, said Dr. Norman Cheville, dean of Iowa State University’s College of Veterinary Medicine.

Humans and pigs fall somewhere in between.

Cultures of the rod-shaped bacterium, Bacillus anthracis, are housed at veterinary schools and research centers around the country, although experts say the exact number and locations are kept tightly under wraps. Worldwide, about 46 culture collections contain strains of virulent anthrax, Zilinskas said.

Contraband supplies of anthrax have not been found in this country but if they exist, they would be extremely hard to locate.

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Times staff writer Marlene Cimons in Washington contributed to this report.