Anthrax is caused by infection with Bacillus anthracis, a hardy, spore-forming bacterium that can survive in extreme conditions for a long time. The bacterium is highly toxic.
Anthrax is common in livestock, and a potentially serious infectious disease in humans. The spores occur naturally in soil, but anthrax only becomes active when it enters the body.
Bacillus anthracis (B. anthracis) gained notoriety as a biological weapon in the 2001 in the United States (U.S.), when anthrax powder was mailed in packages, leading to 22 cases of infection, including 5 fatalities.
However, the disease is not unusual in the agricultural regions of the Caribbean, central and southwestern Asia, Central and South America, southern and eastern Europe and sub-Saharan Africa. How dangerous it is depends on the type.
It is rare in the U.S., but outbreaks occur very occasionally in grazing animals such as deer. It is more likely in countries that do not routinely vaccinate animals against the disease.
It cannot pass from one human to another.
Fast facts on anthrax:
Here are some key points about anthrax. More detail is in the main article.
- Anthrax is a potentially fatal bacterial infection that is rare in the U.S. but more common elsewhere.
- There are four types, depending on how it is transmitted.
- Anthrax can be spread through animals and animal products.
- Treatment is with antibiotics, which must be started soon after infection.
- There is a possibility that anthrax could be used as a biological weapon.
- A vaccine exists for people who are at risk, but not for the general public.
B. anthracis bacteria produce resilient spores that can cause a potentially deadly infection in people and animals.
There are four different forms of anthrax infection:
Each type is caused by the B. anthracis bacteria entering the human body in a different way. Each route of entry leads to a unique set of symptoms.
Anthrax infection happens when the bacterium B. anthracis enters the body through inhaling, swallowing, injecting, or through skin contact.
Anthrax spores are resistant to many environmental stresses and normally lie dormant. If they enter the body of a person or an animal, they can develop into active growing cells, due to the presence of water, sugars, and other nutrients.
Once active, the bacteria multiply throughout the body, creating toxins that can cause severe illness.
Anthrax consists of three proteins. None of these proteins is toxic on its own, but combined, they can make a lethal mix, disrupting cellular signaling pathways and stopping cells from working properly, shutting down the host's immune system, and leading to death.
The most common form of anthrax, cutaneous anthrax, mostly spreads through contact with contaminated animal products such as hides and hair. People have developed anthrax after using the hides of infected animals to make traditional African drums.
If a person deliberately releases a virus or bacteria that can lead to sickness or death, this is known as a biological attack.
According to the Centers for Disease Control and Prevention (CDC), if a biological attack were to occur, the anthrax bacteria is "one of the most likely agents."
There are several reasons for this, for example:
- anthrax is easy to find in nature and easy to grow in labs
- an attack would be hard to detect
- it has previously been used as a weapon
Federal agencies and health departments in the U.S. work together to ensure preparedness for such an event. However, they would not know it had happened until a pattern of infection emerged. This is because it is rare, symptoms take a while to show, and they are also similar to symptoms of other conditions, such as flu.
Each form of anthrax has its own range of symptoms. For most forms, the symptoms appear within a week of exposure to B. anthracis, but the symptoms of inhalation anthrax can take over a month to develop.
The most common form of anthrax is cutaneous anthrax.
The symptoms are as follows:
- small itchy blisters or bumps
- a painless swollen sore with a black center
- swelling in nearby lymph glands and tissue
This is considered the mildest form. With treatment, it is rarely deadly. Without treatment, it may be fatal in 20 percent of cases.
This can come from eating raw or undercooked meat from an infected animal.
The symptoms of gastrointestinal anthrax are:
- abdominal pain and swelling
- fever and chills
- flushing face and red eyes
- loss of appetite
- nausea and vomiting
- sore throat with painful swallowing
- swelling of neck and neck glands
Without treatment, half of patients die, but with treatment, 60 percent will survive.
The initial symptoms of inhalation anthrax are:
- chest discomfort
- coughing up blood
- nausea and vomiting
- pain when swallowing
- flu-like symptoms
As the disease progresses, the individual is likely to experience:
- breathing difficulties
- low oxygen in blood
This is the most deadly kind of anthrax. Without treatment, it is fatal in 85 to 90 percent of cases.
This has affected people who inject heroin in Europe, but it has not been reported in the U.S.
The initial symptoms of injection anthrax are:
- abscesses in and around the injection site
- blisters and bumps around the injection site
- a swollen sore near the injection site
As the disease progresses, the following may develop:
- organ failure
The effects probably depend on how deep they are, but symptoms can also be confused with those of other infections.
Anthrax shares many symptoms with more common conditions, such as flu and pneumonia. A health care provider will rule these out first before considering anthrax, unless there is a specific reason to suspect it.
If other conditions are ruled out, then tests specific to anthrax may follow.
An anthrax diagnosis can only be confirmed by measuring antibodies or toxins in the blood or other tissue. The type of tissue sample and other types of test will depend on the suspected form of anthrax.
- a skin biopsy to test for cutaneous anthrax
- stool testing for gastrointestinal anthrax
- chest x-rays or CT scans to detect inhalation anthrax
- lumbar punctures to reveal anthrax meningitis
In 2014, researchers researchers that a "glow test" can detect the presence of deadly anthrax bacteria in hours instead of days. This could significantly cut the time it takes to respond to a potential bioterrorism attack.
Anthrax must be treated as quickly as possible, before the levels of toxins and harmful bacteria within the body become too high for drugs to eliminate.
The standard treatment for anthrax is with antibiotics and antitoxins. The type of antibiotics will depend on how the infection occurred, the individual's age and medical history.
Antitoxin therapies are currently being developed that target the toxins released by B. anthracis, rather than the bacteria themselves.
Recently, surgical removal of infected tissue has been used successfully to treat injection anthrax.
Tips for avoiding anthrax include:
- only eating meat that has been suitably slaughtered and cooked
- avoiding contact with raw animal hides, especially those of cows, sheep, and goats
People who work with fur, hides, and wool, especially if these are imported, should take extra care.
If anyone is exposed to the bacteria, antibiotics can prevent the symptoms of anthrax from developing before the B. anthracis spores have time to activate.
The U.S. Food and Drug Administration (FDA) have approved a vaccine for anthrax, to be used prior to exposure by adults who could be at risk.
These include laboratory workers, handlers of animals and animal products, and some military personnel. It is not available to the public.
The vaccine can also be given after exposure, alongside antimicrobial therapy.
Anthrax remains rare in the U.S. If a person has symptoms that resemble anthrax, it is most likely a more common illness.
If a person shows signs and symptoms after exposure to animals or animal products from parts of the world where anthrax is common, however, it is best to contact a health care provider.
To be effective, treatment for anthrax must begin as soon as possible.