(This column was first published in the November 5, 2001 Buffalo News.)
Anthrax has earned headlines lately as a vicious killer. But how many realize that this bacterium occurs in nature throughout most of the world including here in the United States?
The World Health Organization considers it epidemic in Peru, in Spain, Greece and Turkey, in an east-west band across central Africa, and in Kazakhstan, Mongolia, Indochina and Cambodia. It is prevalent in Mexico and in southern South America. Closer to home it occurs regularly in the western United States and Canada. Although it is rarely found in the east, there was an outbreak in Ontario in the 1990s just north of the St. Lawrence River.*
While it mostly infects grazing animals -- cows, sheep, goats, pigs and horses, and among wildlife deer and buffalo -- we can also be infected as can all mammals, especially carrion feeders.
Severe cattle and deer outbreaks have occurred in west Texas. In fact anthrax killed over 1600 animals there this year. But according to Texas Animal Health Commission epidemiologist Terry Conger, ranchers consider it simply another occupational hazard along with drought, low beef prices and coyotes. He adds, "There has been anthrax around for as long as there have been people and animals, all the way back to the Bible. We've just learned to live with it."
Anthrax occurs in nature in two forms: when oxygen is available as spores and in a vegetative phase in the lymph nodes of infected animals. When animals die of the disease the putrefaction process soon destroys the internal vegetative form but spores escape through body openings into the soil and early-arriving blowflies carry the disease to other animals.
In the soil these spores can be remarkably persistent. For this reason, today anthrax-killed animals are burned and, when possible, the ground on which they lay is disinfected by heat-treatment or applications of a strong formaldehyde solution.
According to another Texas epidemiologist, Julie Rawlings, one source of the modern infestations is spores in the ground along the routes of 19th century cattle drives like the Chisholm and Goodnight-Loving trails. The drovers simply abandoned diseased cattle and their anthrax spores migrated into the soil to wait, unaffected by time and weather, for foragers to ingest them. "That's where you'll find anthrax outbreaks even today," says Rawlings.
Most of the resulting infections of browsing animals are of the gastrointestinal form, but it is not enough simply to ingest spores. Many animals and humans, especially tannery workers, have anthrax spores in their systems. Apparently two requirements must be fulfilled to become ill: many spores -- literally millions of them -- and cuts or ulcers to allow entry to other parts of the body. Thankfully, for these reasons and because the animal anthrax is rarely the more lethal airborne variety, deaths among humans have until now been very rare.
One theory about fatalities among grazing animals is that during periods of drought, they are forced to browse short, dry, spiky grass right down to the ground. In the process they ingest the bacillus from the soil and the sharp grass edges cut their digestive tracts fulfilling both requirements.
Anthrax spores are maintained in a few agricultural labs for use in identification of the disease in submitted samples. It may be that one of these labs was the source for those used by bioterrorists, but clearly the spores are also available to those who purvey evil in nature as well. (This is, of course, not true of smallpox.)
I close with a request. Fear of anthrax is widespread despite its having killed less than a dozen people. Flu kills 20,000 people each year in this country alone. Please get flu shots.-- Gerry Rising
* Dr. Jim Clark of the Ontario, Canada Animal Health and Production Network kindly provided the following information about this brief outbreak. His comments clearly support the long term viability of spores. He wrote, "There was a confirmed anthrax diagnosis in cattle in the vicinity of Iroquois , Ontario in 1996. There was a history of anthrax on the same farm about 65 years earlier. The father of the current owner remembered the outbreak. There was also a fairly generalized outbreak in the farms in the immediate vicinity. In this latest case, apparently, the owners of the farm were doing some reconstruction on an in-ground manure storage pit to enlarge the holding. They may have disturbed a burial site from the previous outbreak. Also, in the neighborhood of the farm, there had been recent pipeline construction and road reconstruction activities. Two cattle died during the outbreak. One was disposed of through dead stock before anthrax was suspected. The second, on which the diagnosis was made, was incinerated at the laboratory where the carcass was sent for post mortem."
Other sources for this column include an article by David Klassen in the October 28, 2001 Edmonton Journal and another by Ross E. Milloy in the October 29, 2001 New York Times. Much information about naturally-occurring anthrax may be obtained from the 1996-97 Global Anthrax Report by Martin Hugh-Jones of Louisana State University and from a World Health Organization report, Guidelines for the Surveillance and Control of Anthrax in Humans and Animals, by a team of authors headed by P. C. B. Turnbull of the Centre for Applied Microbiology and Research in England.