Anthrax

Anthrax

Bacillus Anthracis

Anthrax is a bacterial disease caused by bacillus anthracis, a large, gram-positive, rod-shaped bacterium. The bacterium was discovered in 1850 by German physician Robert Koch. Koch grew cultures of the anthrax bacteria and injected it into healthy animals to prove that it in fact was the cause of the disease. Later, Louis Pasteur used compromised anthrax bacteria to develop a vaccine for the disease that was proven to be successful in animals. The defining characteristic of bacillus anthracis is its ability to form spores, “dormant” or inactive bacteria that cause no significant problems in this form. Anthrax spores are commonly found in soil, where they can remain dormant for prolonged periods of time (years or perhaps decades) and can survive harsh conditions. They may also be found in the feces of certain animals including horses, deer, cows, sheep and goats as well as animal products such as hide and wool. Since the spores have such a long and durable lifespan, it is no surprise that animals may become infected from soil or plants long after the bacteria are settled in the ground. Once the spores enter a susceptible individual (or animal), they have the ability to germinate and form the active, disease-causing bacteria.

Anthrax infects warm-blooded animals and people of all age, race and gender. It is most common in agricultural areas where there is a large population of animals that have not been vaccinated. Some animals such as birds, dogs, cats, and swine are very resistant to the bacteria. In humans, infection is most commonly found when there is a high rate of exposure to animals or animal products. Rarely, human infection occurs from eating contaminated meat products that are not properly prepared.

There are three types of anthrax infection. The most common type is cutaneous (“skin”) anthrax. Cutaneous infection usually comes from handling infected animals or animal products where spores are transferred into cuts or skin abrasions. This type can also occur, as we witnessed in 2001, if someone intentionally releases a large number of spores into an environment where they will be transmitted by skin contact, such as the postal system (although the majority of infections in this case were inhalation infection, which will be covered later). Signs of cutaneous infection are itching skin lesions at the location of contact which develop into vesicles and quickly cause the tissue to become necrotic and turn black. Death is rare with this type of infection; however it can occur if left untreated. The second type of infection, gastrointestinal, is much less common but slightly more deadly. It is the result of eating contaminated meat, or infected meat that is not properly prepared. Signs of GI infection normally manifest within 1-7 days of ingestion and include expected abdominal symptoms (nausea, vomiting, pain and diarrhea) as well as abnormalities on CT scans and X-rays, ascites (swelling and tightness due to fluid in the abdomen) and hematemesis (vomiting blood). Death can result within 2-5 days of the onset of these symptoms if not treated. The last type of anthrax infection is by far the most feared and the most deadly. Inhalational infection occurs when a large number of spores, at least 5000 to 6000, are inhaled and remain in the respiratory system. Symptoms begin rapidly and abruptly, usually within 1-3 days of exposure. Probably the primary reason for the fatal outcome of this type of infection is that its symptoms mimic the flu. The initial symptoms are fever and a slight cough. As the infection progresses, extreme fever, shortness of breath and cyanosis (bluish coloring of the skin) are classic signs. People may also experience sweating, hematemesis and extreme chest pain that is compared to that of a heart attack. This progression occurs so quickly that early detection is vital to prevent death, and even so death may be inevitable. Inhalational anthrax usually progresses to infect the liver, spleen, kidneys, and sometimes the bloodstream (septicemia) or spinal region (meningitis).

Inhalation anthrax has become an international threat due to its potential to be used as a biological weapon. In 2001, terrorist groups intentionally released spores in a powdered form throughout the United Stated postal system. This triggered 22 cases of cutaneous and inhalational infection which resulted in 5 deaths. If terrorists were to release anthrax spores in larger quantities, the result would likely be an infection and fatality rate of catastrophic proportion. The concern is that anthrax spores can be concentrated and released into the atmosphere via missiles, rockets, or aerial bombs. The process would be similar to that of an aerosol released from an aircraft, however the effects would be detrimental. As the Military Vaccine Agency points