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Anthrax and Cattle

Terror on the Prairies.

Aug 15, 2006

<i>Bacillus anthracis</i> on laboratory media, J. Arbique

The latest threat to Canada's beef industry, following mad-cow disease is potential hysteria over the recent outbreak of anthrax infection.

Like most people, when I think of anthrax, I think of white powder, mail and terrorism plots. If I was the extremely paranoid type, the recent news reports of cattle dying of anthrax infection on farms in Saskatchewan and Manitoba might have me wondering whether our food-chain is now being targeted by terrorists.

The latest threat to Canada's beef industry, following the mad-cow hysteria of the past few years, is anthrax. As of August 10, 2006, the Canadian Food Inspection Agency (CFIA) has reported 644 dead animals on 136 farms in Manitoba and Saskatchewan, most of these cattle. Why? Did terrorists tire of licking envelopes? Are they frustrated with the speed at which snail-mail is delivered? No. This recent outbreak of infection in cattle is naturally occurring, unrelated to any sort of conspiracy.

Anthrax is a zoonotic infection, primarily infecting grazing animals (herbivores) who ingest spores of the bacteria, Bacillus anthracis, found in soil. Bacillus anthracis in its spore form is extremely resistant to harsh environmental conditions such as drying, heat, cold and chemical exposure. This is the reason that anthrax spores have been popular throughout history as an agent of biowarfare and bioterror.

Not all bacteria have the ability to form spores, but for those that do, when environmental conditions become uninhabitable, the bacteria enters into a dormant or nonactive state. Once conditions improve, such as when the spore is inhaled into a nice warm moist nutritious body, animal or human, the spore changes back to its vegetative or active state and begins to grow and multiply. As Bacillus anthracis multiplies, it produces toxins that cause damage and are potentially life-threatening. Infected cattle die quickly once infected so that sick animals are not often seen.

The current outbreak is the largest recorded outbreak of zoonotic anthrax occurring over the largest area in Canada. The last largest outbreak reported by the CFIA was in 2000, involving 28 cattle - 24 in Manitoba, 3 in Ontario and 1 in Saskatchewan. There were also 10 deaths in other animals - 6 in bison (5 in Alberta and 1 in the North West Territories) and 4 in black bears, moose and wolves in Alberta. However, deaths are sporadically seen most years across the Prairie provinces. Why are we seeing so many deaths in livestock this year? The abundant rain and flooding in Saskatchewan and Manitoba this spring and early summer have been extremely favorable for bringing anthrax spores to the surface of fields and meadows where animals graze. Spores reportedly can live in the soil for 50 years or more. Once ingested by animals grazing in spore-rich areas, the bacteria causes a severe gastrointestinal infection, which very often leads to death.

What is the threat to humans? Check in next week to find out whether there is reason for concern.

The copyright of the article Anthrax and Cattle in Microbiology is owned by Judy Arbique. Permission to republish Anthrax and Cattle in print or online must be granted by the author in writing.

Comments

Aug 16, 2006 9:57 AM

Rosemary Drisdelle :

<p></p>Hi Judy! Welcome to Suite 101.

A question about anthrax spores - how do they get in the soil to begin with? Do animals usually have the gastrointestinal form and pass spores in their droppings, or do the spores get left behind when a dead animal decays?

Aug 18, 2006 12:42 PM

Judy Arbique :

Good question Rosemary...animals do not pass the spores in their droppings, because the bacteria is quite happy in the human body and has no need to sporulate. A bacterium that is capable of forming spores does so when the environment is not to its likely. Generally bacteria capable of causing human disease like moist environments with lots of nutrition and a temperate climate...hmmmm, much like humans themselves. Just writing that got me thinking about planning a winter trip to Mexico or Cuba or the Dominican Republic or....Whoops, got distracted there!

Spores are likely to be deposited in the soil from dead animal carcasses.

Have I answered your question adequately?

judy

Aug 24, 2006 7:25 AM

Rosemary Drisdelle :

Hmmm. It's really a pity that the spores live so long in the soil - otherwise, we could get them off agricultural lands simply by clearing away dead animals promptly (and most people do that, I think).

Aug 24, 2006 5:24 PM

Judy Arbique :

Although it doesn't seem to be as simple as that, because the spores get carried to other areas by animals feeding off the carcasses, and by spores getting deposited in the soil. It is recommended that the first 20 cm of soil is removed with the carcass AND it is recommended that carcasses are incinerated, not buried as they used to be. Buried carcasses were often dug up by animals who then fed off the infected carcasses.

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