Autumn 2001 Public Health Magazine: An invisible threat

An invisible threat

Bacillus anthracis sounds like the scientific name of a delicate flower, like Queen Anne’s Lace. It is, in fact, a big, boxy monster of a bacterium with a long history of killing man and beast. Called anthrax for short, it is many times larger than a virus and most other bacteria and can survive for decades under spartan conditions. When oxygen is in short supply, the rod-shaped organism curls up and secretes a shell around itself—like a marble. While in this “spore” phase of its life cycle, Bacillus anthracis resists sunlight, radiation, heat, and disinfectants. It requires no nutrients and can lie dormant for years. If stirred up into the air, it can then be inhaled and spring to life.

Inside lymph nodes near the lungs, anthrax spores have oxygen, moisture, and warmth—everything they need to flourish. In this “vegetative” stage, they reproduce and emit toxins that the immune system cannot fight on its own. Without intensive treatment, patients suffer tremendous difficulty breathing, sepsis, massive perspiration, a high temperature, lethargy, shock, unconsciousness, and almost certain death. Anthrax’s stability, portability, and killing power make it an extremely attractive bioweapon, says Philip Brachman, RSPH professor of international health. Brachman’s acquaintance with Bacillus anthracis dates back to the 1950s, when the US Army was developing an anthrax vaccine to protect soldiers during the Korean War.

“When I joined CDC in 1954, one of my first projects was to look at anthrax surveillance data from past years and develop a more sensitive surveillance program for new cases,” he says. “The Army had already tested its anthrax vaccine for safety on its lab workers, but they had never done an efficacy study to determine if it would prevent disease. It was my job to find a population within the United States in which to field–test it.”

After several years of watching the numbers, Brachman identified four goat hair processing mills in New Hampshire and Pennsylvania where sporadic cases of anthrax cropped up. In the days before synthetic fabrics, processed goat hair was used to make the inner linings of men’s suits, backing for ties, and the undersides of carpets.

“These four mills averaged 1.2 cases of cutaneous anthrax per 100 employees a year, so we decided to proceed with vaccine field trials in that population. We went to the mills and asked for volunteers. Two–thirds of the employees agreed to participate. Half of the volunteers were randomly selected to receive a placebo. We vaccinated them and followed them for several years.”

Follow-up revealed a total of 21 cutaneous anthrax cases among those in the trial—13 in people who had received the placebo, two in people who had received some of the placebo but dropped out of the trial, and one case in someone due for the first booster shot of vaccine. Two additional cases occurred in people who had missed some doses of vaccine, and three occurred among unvaccinated people not enrolled in the study. “When we looked at the statistics, only one case occurred among those vaccinated,” says Brachman. “Our vaccine showed an efficacy of 92.5%.”

During the vaccine trials, an anthrax epidemic erupted in the goat hair mill in Manchester, New Hampshire—five inhalational cases and four cutaneous. “Of the five inhalational anthrax cases, three occurred in unvaccinated people, and two occurred in people who had received the placebo,” says Brachman. “None of those fallen ill had received the actual vaccine.”

With the advent of synthetic fabrics, goat hair went out of vogue, and occupational anthrax nearly disappeared. Before this past fall, the last case of inhalational anthrax was seen in 1976, in a California tapestry artist using imported yarn containing goat hair.

“Once we vaccinated in the mills, they never had any more cases,” says Brachman. “They made vaccination a condition of employment. That reduced the cases to only a few a year in other industries like tanning and agriculture. Today the goat hair industry no longer exists in the United States, and we see only rare cutaneous cases in people working with animals.”

After the CDC anthrax vaccine trials concluded, Brachman investigated occasional isolated reports of anthrax. He remembers one particular case with parallels to the recent death of a 94-year-old Connecticut woman thought to have contracted inhalational anthrax from an extremely small dose of bacteria from cross-contaminated mail. Brachman theorizes that smaller doses may sicken those with suppressed immune systems more easily.

“During the 1950s, I investigated a case in Philadelphia in which a young man with a compromised immune system contracted inhalational anthrax through what must have been a very small dose of bacteria. He had sarcoidosis, an inflammatory lung condition, and he was on a small dose of steroids, which inhibits the immune response. On his daily walk to and from work, he passed by a tannery. It was summer time, and the doors of the tannery were open. It is possible that a breeze came from the back to the front and out the tannery door just as this young man was walking by. That breeze could have carried a cloud of Bacillus anthracis from some of the hides they were processing, and the young man may have inhaled at just the wrong time. I cultured the environment in the tannery and found B. anthracis.”

But following the trail of anthrax spread intentionally through the mail is “a different bag,” says Brachman. “This is the first bioterrorist attack ever in which anthrax was successfully used, and we have learned quite a bit from it. We learned a lot about anthrax as an infectious agent and a lot more about bioterrorism than we knew before. We also know firsthand the fear and disruption that bioterrorism can cause.

“Maybe most important, we now know that bioterrorism using anthrax can work and that we must seriously prepare for such events in the future.”

Goat hair mills were the most common site of anthrax outbreaks before the industry declined in the 1960s. While working at the CDC in the 1950s, Philip Brachman led the only clinical trial of anthrax vaccine ever conducted to test the effectiveness among civilians. Before vaccination became a mandatory condition of employment, mill workers suffered 1.2 cases of anthrax per 100 people each year. After vaccination, there were almost no cases at all.