Anthrax

Anthrax is a rare and potentially fatal disease caused by Bacillus anthracis, a bacterium that most commonly occurs in wild and domesticated animals such as cattle, sheep, goats, horses and deer. Humans are only occasionally infected.

The bacteria form spores, which are tough shells that help the microbes survive in unsuitable conditions. These spores remain infectious for long periods. They can live in soil for many years, and may also be present in hair, hides and wool. Processed skins and hides from infected animals can carry spores for years. Outbreaks among animals occur from time to time in some regions.

How people become infected#

Humans can become infected by handling products from infected animals or by breathing in anthrax spores from infected animal products. Illness usually develops within two to seven days of exposure.

People who work with livestock or their by-products are most likely to be exposed, including abattoir and knackery workers, tanners, veterinarians and farmers.

Anthrax is a relatively rare human infection. Among animals it is found worldwide, but tends to be more common in certain places, including parts of Africa, Asia, the Caribbean, Central and South America, Eastern and Southern Europe, and the Middle East.

Symptoms and types of infection#

Symptoms in humans depend on how the disease was contracted, and can include skin lesions, fever, general malaise, headache, joint pains, gastrointestinal upsets such as vomiting, cough, chest pain and flu-like symptoms.

Cutaneous (skin) anthrax#

The skin is the most commonly affected body part, occurring in about 95 per cent of cases. The bacteria enter the body through a cut or graze. The skin becomes itchy and 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 or black scab, which is usually painless.

Without treatment, the infection can spread to the lymph nodes or blood (septicemia). The mortality rate from untreated cutaneous anthrax is 5 to 20 per cent, but death is rare with the right antibiotic treatment.

Pulmonary (lung) anthrax#

This rare lung infection can occur when spores are inhaled. At first it seems like a mild upper respiratory tract infection, such as a cold or flu. The person’s health then rapidly deteriorates over the next few days, with severe breathing problems and shock.

Without treatment, the mortality rate is 70 to 80 per cent, and in many cases pulmonary anthrax is fatal even when treated.

Intestinal anthrax#

This is 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 per cent.

Is anthrax contagious?#

Direct person-to-person spread of anthrax is extremely unlikely. However, an infected person is usually isolated in hospital as a precaution while undergoing treatment. Contagiousness is not a concern when caring for or visiting people with pulmonary anthrax.

Second attacks can occur but are very rare, and recovery is usually followed by prolonged immunity.

Diagnosis and treatment#

Anthrax is diagnosed using a number of tests, including skin tests, blood tests, chest x-rays and a spinal tap (lumbar puncture) of the cerebrospinal fluid.

Treatment must be started urgently and includes antibiotics and hospitalization in intensive care. The antibiotics ciprofloxacin, doxycycline and amoxycillin are all possible treatments, with amoxycillin particularly used for children.

Controlling anthrax in the environment#

Once a person has been diagnosed, it is important to find and isolate the source of infection. Health and agriculture authorities work together to investigate cases. Measures to eliminate anthrax from the environment include:

• Treating symptomatic animals with antibiotics.
• Vaccinating all at-risk animals and re-immunizing them annually.
• Deeply burying animal carcasses with quicklime at the site of death, if possible, or cremating them.
• Not performing an autopsy.
• Not burning carcasses in an open field.
• Decontaminating soil on infected farms with five per cent formalin.
• Seizing suspected animal products.
• Incinerating infected animal products.
• Using formaldehyde to disinfect contaminated premises and machinery.
• Sterilizing imported bonemeal before use as animal feed.
• Sterilizing wool, hair, hides and other infected products with ethylene oxide gas or ionizing (gamma) radiation.

If you suspect livestock have died from anthrax, do not move the carcass, and report it immediately to your local animal health or agriculture authority.

Anthrax and bioterrorism#

If one or more people are infected with anthrax with no evidence of exposure to infected animals or their products, a deliberate release of anthrax organisms must be considered as a possible source.

In 2001, a number of human cases of anthrax occurred after the intentional release of highly refined anthrax spores through mailed postal items. In the months that followed, there were many thousands of incidents related to powders considered ‘suspicious’, but none of these were shown to involve anthrax.

The use of anthrax as a bioterrorism agent remains a hypothetical risk. However, the likelihood that an individual or group could prepare and disseminate anthrax is considered low.

A vaccine for anthrax exists, but its availability is restricted. Vaccination involves six doses: three given two weeks apart, followed by three additional injections at six, 12 and 18 months after the first dose. An annual booster is required to maintain ongoing immunity.

Key points#

• Anthrax is caused by Bacillus anthracis, a bacterium that most commonly occurs in wild and domesticated animals such as cattle, sheep, goats, horses and deer.
• Among animals it is found worldwide, but is more common in certain regions.
• Symptoms in humans depend on how the disease was contracted and can include skin lesions, fever, headache and joint pains.
• Without treatment, the infection can spread to the lymph nodes or blood (septicemia).
• Death is rare with the right antibiotic treatment.

Where to get help#