Anthrax and Botulinum: Worrisome Bioterrorist Agents


By Barry C. Fox, M.D.University of Wisconsin

The Centers for Disease Control, or CDC, categorizes bioterrorist agents into three categories. These are based on the availability of the agent, its potential for infection or death, and how easily it could be disseminated. The most concerning agents are Category A, of which anthrax and botulinum are a part of. These agents have characteristics that make them particularly worrisome.

Image of Bacteria Bacillus anthracis, the causative agent of anthrax disease.
Category A includes the most concerning agents like anthrax. (Image: Kateryna Kon/Shutterstock)

Deadly Bioterrorist Agents

The agents in Category A can be produced on a large scale, they can be aerosolized, making them easily transmittable, there is usually a lack of effective treatment or vaccines, and the attacks could result in many casualties with a high mortality rate.

The big 6 in Category A include anthrax, smallpox, plague, botulinum toxin, tularemia, and hemorrhagic viral fevers like Ebola. Three scenarios pose the greatest threats to us in a bioterrorism attack: An attack by an airborne agent like anthrax, a smallpox attack, and a release of botulinum toxin in the food supply, such as milk.

What makes it advantageous to plan a bioweapons attack as compared to others of mass destruction? For one thing, biological agents are likely to be smaller and more difficult to detect. They can be portable and easy to carry on different modes of transportation. And terrorists could disperse a bioweapons agent and leave the scene of the crime before anyone showed symptoms of an illness. The acquisition expense is also likely to be much cheaper.

This is a transcript from the video series An Introduction to Infectious DiseasesWatch it now Wondrium.

A for Anthrax

Let’s explore anthrax in more detail. Anthrax spores are easily found in nature or can be produced in a lab. It can be released in several forms, in the form of powder, like the 2001 attacks sent through the mail. Or spore forms could be aerosolized and released into the air, and spread by the wind. 

It can be put into food and water, attacking people when they eat contaminated food or drink. Inhalational anthrax is the most serious form of the disease and would need immediate treatment for any chance at survival. It is odorless and invisible, and since the spores hitch a ride on the dust particles in the air, they have been known to spread for up to 60 miles.

Two grams of anthrax-laden powder contain nearly one trillion spores. A 1993 estimate predicted that 100 kg of aerosolized anthrax over a city would cause up to 3 million deaths, as lethal as a hydrogen bomb.

Learn more about the outbreak of Ebola in 2014 in West Africa.

Symptoms of Anthrax

Let’s look at the characteristics of Anthrax. Anthrax is an oxygen-loving, gram-positive, and spore-forming bacterium that lives in the soil and can contaminate wild animals. The anthrax bacterium looks like a bamboo rod with joints. Spores germinate when they find a welcoming host—like the tissue or blood of animals or humans. It also may take only 1 to 3 spores to cause infection. 

In Africa, cases of skin disease caused by anthrax have occurred from animal hides that are made into bongo drums. If inhaled in the lung, the bacteria divide and produce a lethal toxin that can enter the circulation. This results in sepsis syndrome.

Syringe with Anthrax ؤaccine written on it
Luckily, Anthrax is treatable with antibiotics today. (Image: Novikov Aleksey/Shutterstock)

There’s Good News After All!

Let’s explore the initial medical investigation of the first victims of the anthrax attacks. Blood samples are taken and cultured in an incubator to enhance bacterial growth. If germs are detected in the blood, a gram stain can be done to look at the morphology of the bacteria. 

If they look like bamboo rods, the situation is highly suspicious for anthrax. Next, biochemical testing can be done to identify the specific bacteria, but this usually takes another 12 to 24 hours. 

Usually, we initiate antibiotic therapy before the germ is completely identified, for example, after the gram stain is done on the blood since the mortality consequences of waiting for confirmation could be dire. 

Anthrax is treatable with antibiotics, especially when recognized early. Today, we usually use ciprofloxacin, in part because it was rumored that Russia had developed a penicillin-resistant form of anthrax for use as a bioweapon.

Learn more about influenza.


BOTULISM written on different glasses for research
Botulism toxin is one of the most poisonous substances for humans. (Image: felipe caparros/Shutterstock)

Let’s move on to another of the deadliest agents, botulism. There are some very good reasons we worry about Botulism toxin—by weight—it’s the most poisonous substance known to man. One gram that is aerosolized has the potential to kill one million people. Like anthrax, the bacteria also germinate from spores. 

The clostridium bacterium is easily obtained from soil, could be cultivated to produce toxins, and could be put in our food supply. Well, how does botulism cause illness, and how can it be treated? Bacteria produce the toxin, which can enter into the bloodstream from the mucous membranes, the intestines, or cuts in the skin. The toxin will then bind to nerve endings. 

Normal nerve conduction to activate muscle contraction depends on acetylcholine, a neurotransmitter. The botulism toxin blocks acetylcholine, which prevents muscles from contracting. Paralysis ensues, usually starting from the head and progressing down towards the legs. When the disease is clinically recognized, the antidote is botulism antitoxin injected into the body.

Scientists speculate that with a master’s degree in Biology and $2,000 worth of equipment, an individual could hypothetically make enough toxin to kill thousands of people. So we should be concerned about this scenario, especially in civilian populations that are unprepared. The only comforting news is that it seems to be poorly suited for delivery via a bomb or missile since it degrades quickly when exposed to heat.

Common Questions about Anthrax and Botulism

Q: What are the biggest threats in the event of a bioterrorist attack?

The bioterrorist agents in Category A are the most dangerous to humans. Anthrax, botulinum toxin, and smallpox are very poisonous and more worrisome than others.

Q: How is Anthrax identified?

If somebody is identified as a potential candidate for having this bioterrorist agent in their blood, a blood sample will be taken, and if any germs are identified, they will be grown in an incubator. The results take around 12-24 hours.

Q: Why is botulinum toxin considered an inappropriate agent to use for bioterrorist goals?

This bioterrorist agent degrades quickly when exposed to heat, so it would be hard to use it in a missile or bomb.

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