Anthrax, also called malignant pustule or woolsorters disease, acute, infectious, febrile disease of animals and humans caused by Bacillus anthracis, a bacterium that under certain conditions forms highly resistant spores capable of persisting and retaining their virulence for many years. Although it is most commonly affects grazing animals such as cattle, sheep, goats, horses, and mules, humans can develop the disease by eating the meat or handling the wool, hair, hides, bones, or carcasses of affected animals.
When anthrax its name derived from the Greek word for coal attacks a person’s skin, a sore with a coal-black center develops. Anthrax spores can also be produced inexpensively and converted into either a powder or a liquid, allowing anthrax to be used in a variety of weapons systems. Its potential use as a biological weapon has made anthrax a prime concern of countries seeking to control the spread of terrorism.
It is uncommon in Western Europe, but the disease is not uncommon in the Middle East, the Indian subcontinent, Africa, Asia, and Latin America. In 1958, approximately 100,000 cases of anthrax occurred worldwide. Exact figures do not exist because of reporting difficulties in Africa. It is endemic in Africa and Asia despite vaccination programs.
Sporadic outbreaks have occurred as a result of both agricultural and military disruptions. During the 1978 Rhodesian civil war, failure of veterinary vaccination programs led to a human epidemic, causing 6500 cases and 100 fatalities. A mishap at a military microbiology facility in Sverdlovsk in the former Soviet Union in 1979 resulted in at least 66 deaths. Human anthrax often is associated with agricultural or industrial workers who come in contact with infected animal tissue.
Race, sex, and age-related differences in incidence
There is no racial, sexual, or age predilection for anthrax. However, because anthrax is often related to industrial exposure and farming, the disease most often affects young and middle-aged adults. Persons of any age can, of course, be affected if anthrax is used as a bioterrorist weapon.
It can target various body parts, including:
Cutaneous anthrax- Skin is the most commonly affected body part, occurring in about 95 percent of cases. The bacteria enter the body via a cut or graze. The skin becomes itchy then develops a sore that turns into a blister. The blister (vesicle) may break and bleed. Within two to seven days, the broken blister becomes a sunken, dark-colored or black scab which is usually painless. Without treatment, the infection can spread to the lymph nodes or blood (septicemia). Death is rare with the right antibiotic treatment. The mortality rate from untreated cutaneous anthrax is 5–20 percent.
Pulmonary (inhalation) anthrax- A rare lung infection that can occur when bacterial spores are inhaled. At first, the infection seems like a mild upper respiratory tract infection, such as a cold or flu. The person’s health rapidly deteriorates over the next few days with severe breathing problems and shock. Without treatment, the mortality rate is 70 to 80 percent. In many cases, pulmonary anthrax is fatal even when treated.
Intestinal anthrax- Very rare in developed countries. It occurs if a person eats the undercooked meat of an infected animal, usually one that has died in the field. Early symptoms include nausea, vomiting, vomiting blood, diarrhea, and high temperature. If the infection spreads to the blood (septicemia), the death rate is between 25 and 60 percent.
Anthrax risk factors
To contract anthrax, you must come in direct contact with anthrax spores. This is more likely if you:
- Are in the military and deployed to an area with a high risk of exposure to anthrax
- Work with anthrax in a laboratory setting
- Handle animal skins, furs or wool from areas with a high incidence of anthrax
- Work in veterinary medicine, especially if you deal with livestock
- Handle or dress game animals in the United States, seasonal outbreaks of anthrax are common among livestock and game animals, such as deer
- Inject illegal drugs, such as heroin
Causes of Anthrax
It is caused by Bacillus anthracis bacteria. There are three types of infection:
Cutaneous (skin) anthrax: This can occur when spores enter your body through a break in the skin. Half of the cases in the 2001 U.S. terrorist attacks were this type. In Canada, the more recent occurrence of anthrax in people was a case of cutaneous anthrax that was found in a Saskatchewan man in July 2006. Many livestock animals were also infected in the same area during that time.footnote.
Inhalational (lung) anthrax: This can occur when you breathe in spores. It is the most serious type of infection. Half of the cases in the 2001 attacks were this type.
Gastrointestinal (digestive) anthrax: This can occur when you eat food contaminated with anthrax spores. This has occurred in developing regions of Asia, the Middle East, and Africa, but not in North America.
The illness does not seem to spread from person to person. People who come in contact with someone who has anthrax don’t need to be immunized or treated unless they were exposed to the same source of infection.
Symptoms of anthrax differ depending on the type of anthrax.
Symptoms of cutaneous anthrax start 1 to 7 days after exposure:
- An itchy sore develops that is similar to an insect bite. This sore may blister and form a black ulcer (sore or eschar).
- The sore is usually painless, but it is often surrounded by swelling.
- A scab often forms, and then dries and falls off within 2 weeks. Complete healing can take longer.
Symptoms of inhalation anthrax:
- Begins with fever, malaise, headache, cough, shortness of breath, and chest pain
- Fever and shock may occur later
Symptoms of gastrointestinal anthrax usually occur within 1 week and may include:
- Abdominal pain
- Bloody diarrhea
- Mouth sores
- Nausea and vomiting (the vomit may contain blood)
Symptoms of injection anthrax are similar to those of cutaneous anthrax. In addition, the skin or muscle beneath the injection site may get infected.
The most serious complication of anthrax is inflammation of the membranes and fluid covering the brain and spinal cord, leading to massive bleeding (hemorrhagic meningitis) and death.
Diagnosis and test
Tests to detect and diagnose anthrax include:
- A skin biopsy where a small tissue sample is extracted from the lump in your skin to check for microscopic evidence of cutaneous anthrax
- Sputum testing that involves adding respiratory secretions to culture to test for the presence of anthrax bacteria
- Blood tests to check for the presence of anthrax bacteria
- Chest X-rays or computerized tomography (CT) scans may be conducted to help diagnose inhalation anthrax, which often has a very characteristic appearance on the chest X-ray image
- Endoscopy and stool samples can be used to diagnose intestinal anthrax. Stool samples can be tested for the presence of anthrax bacteria
Treatment and medications
All types of anthrax infection can be treated with antibiotics. The antibiotics selected for treatment are based on the type of infection and the patients’ medical history. It is pivotal to get medical care as soon as possible for the best chance of a full recovery.
Antitoxins can be used to treat anthrax because antitoxins target anthrax toxins in the body. Antitoxins can also be used in conjunction with other treatment options.
Sometimes other drugs
The longer anthrax treatment is delayed, the greater the risk of death. Thus, treatment is usually started as soon as doctors suspect that people have anthrax:
- Skin anthrax is treated with ciprofloxacin, levofloxacin, or doxycycline given by mouth for 7 to 10 days.
- Inhalation, gastrointestinal, or severe skin anthrax is treated with a combination of two or three antibiotics, including intravenous ciprofloxacin or doxycycline plus another antibiotic, such as ampicillin, clindamycin, rifampin, or others.
- Inhalation anthrax can also be treated with a combination of antibiotics and injections of raxibacumab or obiltoxaximab (monoclonal antibodies that bind anthrax toxins in the person’s system) or with a combination of antibiotics and intravenous anthrax immune globulin.
- If the brain and meninges are affected or if the fluid has accumulated around the lungs, corticosteroids may help.
Other treatments may include mechanical ventilation to help with breathing and fluids and drugs to increase blood pressure.
Anthrax spores can survive for over 20 years in dry pasture and soil. Precautionary measures people can take include:
- Wearing long sleeves and protective gloves if handling infected animals.
- Isolating infected cattle and vaccinating herds against anthrax.
- Human vaccination is available for those at significant risk of developing the disease.
For people who have been exposed to anthrax but don’t have symptoms, prophylactic treatment with an antibiotic should be given to reduce the risk of infection. A 60-day oral course of penicillin, tetracycline or quinolone is recommended.