Season 3, Episode 9: Let It Burn

The British Columbia wildfires uncover not only glanders, but also anthrax. The NorBAC team suspects bioterrorism remnants from World War II. Based on Bob’s analysis of the weather, David suggests a controlled burn to disperse the spores over the Pacific Ocean. At the same time, Bob’s vision worsens from pressure-induced optic nerve damage similar to glaucoma and David scrambles to find the best available treatment to save Bob’s sight.

IS IT POSSIBLE FOR ANTHRAX BACTERIA TO SURVIVE 60 YEARS IN THE WOODS?

Image provided courtesy of Shaftesbury Films.		Carlos prepares to take samples from the infected firefighters.

Where is anthrax found?

Anthrax is a disease caused by the bacterium Bacillus anthracis. B. anthracis normally lives in soil and commonly is carried by ruminants (goats, sheep, cattle). It can infect humans as well, but cannot be transmitted from human to human. Human infection occurs through cuts on the skin, ingesting contaminated meat, or by inhaling anthrax spores, which are the dormant, non-reproducing form of the bacteria.

B. anthracis can survive in its spore state for many years in soil. When the spores are ingested, the bacteria “awaken” and start feeding on and multiplying inside the animal; if left untreated, the bacteria will eventually kill the host organism. The bacteria would then continue to feed on and multiply in the carcass until all the nutrients are used up. At that point, they revert once again to a dormant spore state.

How can anthrax be eradicated?

Because anthrax spores are so hardy, they are difficult to kill. Common clean-up techniques in laboratories include using chemicals like peroxide, which slowly destroys bacterial spores.

So ...

Yes, it is possible for anthrax to survive as spores in the soil in forests for 60 years or longer, but the bacteria cannot reproduce in that state.

IS IT POSSIBLE TO REBUILD OPTIC NERVES?

		Dr. Turnbull explains the experimental eye procedure to Bob and David using graphics of a normal eye (A)
		and damage to the optic nerve (B),
		and explains how the nerve can be treated with a solution containing peptides that self-assemble into trellis-like structures (C),
Images provided courtesy of AXS Studio Inc and Shaftesbury Films.		which enable nerve growth (D).

What does glaucoma do to the optic nerve?

Glaucoma is term for a group of diseases that cause vision loss by damaging the optic nerve. The optic nerve is a bundle of nerve cells that collectively transmit information gathered by the eye into the brain. Increased pressure in the eye can put pressure on the optic nerve, which may result in permanent damage. While higher than average pressure in the eye increases one’s risk for developing glaucoma, there are forms of the disease called “normal tension glaucoma” that occur without high pressure.

How is glaucoma treated?

Medicated eye drops can be used to reduce pressure in the eye. A more radical treatment is surgery to drill holes in the eye to release pressure. Implants that help drain fluid from the eyes also are available. However, none of these treatment options restore lost vision once damage to the optic nerve has occurred.

Can the optic nerve regenerate?

A nerve cell, like those that make up the optic nerve, cannot regenerate, meaning it cannot divide to produce another identical cell. Nerve cells also generally are not able to re-grow or repair themselves if they are badly damaged. However, scientists have been able to coax damaged optic nerves to re-grow a bit in rats by using gene therapy and taking advantage of the rats’ immune systems.

In experiments on rats with damaged optic nerves, scientists began by simulating eye infections in the rats in order to recruit the rats’ immune cells to their eyes. Once at the site of an infection – whether real or simulated – immune cells naturally secrete growth factors that can signal to damaged or injured cells to repair themselves. However, nerve cells make so-called inhibitory proteins that prevent themselves and neighboring nerve cells from growing. Scientists have used gene therapy to block these inhibitory proteins, allowing damaged optic nerves to repair themselves and grow. But, the new nerve growth did not extend all the way back into the brain, so the rats still were blind.

So ...

We’re not quite there yet. There is a lot of research going on to find chemicals, both naturally occurring and synthetic, to enable injured nerve cells to regenerate and repair after injuries like those caused by glaucoma. While some tests have shown promise in getting nerves to grow, these approaches are experimental and are still being tested on animals.

- by Audrey M. Huang, Ph.D.

Want to read and learn more?

To learn more about anthrax, visit:
http://www.phac-aspc.gc.ca/ep-mu/anthrax_e.html
http://www.bt.cdc.gov/agent/anthrax/

To learn more about glaucoma, visit:
http://www.cnib.ca/en/your-eyes/eye-conditions/glaucoma
http://www.glaucoma.org/treating/

To read about experimental nerve regeneration in rats, and some related work, have a look at the studies cited on this page:
www.jneurosci.org/cgi/content/abstract/24/7/1646?ck=nck