Anthrax

Overview

Anthrax is a serious infectious disease caused by a bacterium called Bacillus anthracis. This bacterium is capable of forming highly resilient structures called spores, which can survive in soil for decades and withstand extremely harsh conditions. Anthrax is primarily a disease of animals, but humans can become infected through contact with infected animals, animal products, or in rare cases through deliberate release as a biological agent.

Anthrax does not spread from person to person. The form the illness takes depends on how the spores enter the body. The skin form is the most common and tends to be the least severe, while the inhaled form can be far more serious. Infection through the digestive system may occur when undercooked meat from an infected animal is eaten.

The vast majority of anthrax cases worldwide occur in people who work with livestock or animal products. It tends to be seen more frequently in parts of Central Asia, Africa, and the Middle East. In many countries, including some parts of Europe, outbreaks in animals are still occasionally reported and can sometimes result in human cases.

When diagnosed early, anthrax can be successfully treated with antibiotics. However, particularly in the inhaled form, the condition can deteriorate very rapidly if diagnosis is delayed. For this reason, people in at-risk groups who develop relevant symptoms should seek medical attention promptly.

Types of Anthrax

Anthrax can present in different ways depending on how the spores enter the body.

• Cutaneous (skin) anthrax. The most common form, accounting for the large majority of anthrax cases worldwide. Bacillus anthracis spores enter through a small cut, abrasion, or insect bite on the skin. A small, painless, itchy bump may develop within one to five days, which can progress to an ulcer with a characteristic black centre. When treated promptly, cutaneous anthrax tends to follow a relatively mild course.
• Inhalation anthrax. The most severe form, which can develop after breathing in anthrax spores. Early symptoms may resemble a mild flu-like illness, but the condition can deteriorate very rapidly over a matter of days, potentially leading to severe respiratory failure. This form is extremely rare under natural circumstances but has historically been the main concern in relation to anthrax used as a biological weapon.
• Gastrointestinal anthrax. This form may develop after eating undercooked or raw meat from an infected animal. Abdominal pain, nausea, vomiting, diarrhoea, and fever are among the possible symptoms. In severe cases, intestinal bleeding and shock can occur.
• Injection anthrax. Cases have been reported among people who inject drugs, particularly heroin injected under the skin or into muscle. This form can resemble cutaneous anthrax in some ways but may spread more rapidly and follow a more severe course.

Symptoms

The symptoms of anthrax can vary considerably depending on the type and the route of entry into the body.

Possible symptoms of cutaneous anthrax include:

• A raised, painless spot or bump. A small, non-irritating bump may appear at the site of contact, usually within one to five days. It often causes no itching or pain in the early stages, which can make it easy to mistake for an insect bite.
• Blisters and ulcer formation. The initial bump may enlarge over several days, develop surrounding small fluid-filled blisters, and then progress to a central ulcer.
• A black scab (eschar). The development of a painless black crust at the centre of the ulcer is the most characteristic feature of cutaneous anthrax. It is this appearance that gave the disease its name, derived from the Greek word for coal.
• Swelling of surrounding tissue. Significant swelling and tissue oedema around the lesion may develop and can sometimes be quite pronounced.
• Fever and general malaise. Particularly as the infection progresses, fever and a feeling of being unwell may develop.

Possible symptoms of inhalation anthrax include:

• Early-stage symptoms. In the first few days, mild fever, muscle aches, fatigue, and a slight cough may appear, resembling a flu-like illness. At this stage it can be difficult to distinguish from influenza or a common cold.
• Rapid deterioration. Within a few days the condition may worsen very quickly. Severe breathlessness, chest pain, high fever, sweating, and shock can develop. By this stage the situation can become very difficult to manage.

Possible symptoms of gastrointestinal anthrax include:

• Abdominal pain and cramping
• Nausea and vomiting (which may be bloody)
• Fever
• Severe diarrhoea (which may be bloody)
• Throat or mouth pain and difficulty swallowing (in the oropharyngeal form)

When to See a Doctor

Anthrax is a rare condition in everyday life, but people in at-risk groups who recognise the symptoms early and seek help promptly are in a much better position.

It is worth seeing a doctor if:

• You have had contact with a sick or dead animal and an unexplained sore or ulcer has developed on your skin afterwards
• You work with animal hides, wool, or bone products and have noticed a suspicious skin lesion
• You are in or have recently visited an area where anthrax has been reported and have developed fever or general malaise
• You have eaten undercooked or raw meat and have since developed severe abdominal pain, vomiting, or diarrhoea

Call emergency services or go to the emergency department immediately if:

• You have been in an environment associated with anthrax risk and develop sudden severe breathlessness, chest pain, or high fever
• A skin lesion is accompanied by rapidly developing and spreading swelling around it
• Your general condition is deteriorating quickly

Causes and How It Spreads

The Bacillus anthracis bacterium that causes anthrax can form spores that may remain viable in the soil for many decades. Transmission to humans can occur in several ways.

• Direct contact with infected animals. Anthrax primarily affects herbivorous animals such as sheep, goats, cattle, horses, and camels. Direct contact with the skin, blood, or tissue of an infected or anthrax-killed animal can create the conditions for cutaneous anthrax. The risk may be higher if there are cuts or abrasions on the skin at the time of contact.
• Contact with infected animal products. Working with unprocessed animal hides, wool, hair, bones, or horns can increase the risk of contact with spores. Transmission has also been reported from products such as animal-skin drums and traditional instruments that have not been adequately sterilised.
• Eating infected meat. Consuming undercooked or raw meat from an animal that died of anthrax may lead to gastrointestinal anthrax. Thoroughly cooked meat is thought to largely eliminate this risk.
• Inhaling spores. Breathing in dust or material containing anthrax spores can lead to inhalation anthrax. Under natural conditions this is very rare, but anthrax's historical use as a biological weapon has made this form an ongoing area of concern.
• No person-to-person spread. Anthrax does not pass from one person to another. Being in contact with a person who has anthrax, or sharing the same environment, does not put you at risk of infection.

Risk Factors

Factors that may increase the risk of anthrax include the following:

• Working with livestock. Farmers, shepherds, veterinarians, and abattoir workers who have regular direct contact with herbivorous animals may be at higher risk, particularly in regions where anthrax still occurs in animals.
• Working with animal products. Those who process animal hides, wool, bone meal, or animal-based fertilisers may have an increased risk of exposure to spores.
• Living in or travelling to anthrax-endemic areas. Parts of Central Asia, the Middle East, Africa, and South America are still considered endemic for anthrax in animals. People living in or visiting these areas may face an elevated risk.
• Working in biological threat environments. Military personnel, emergency responders, and those working in biological defence may be at potential risk of exposure.
• Injecting drugs. Cases of injection anthrax have been reported, particularly in Europe, among people who inject heroin subcutaneously or intramuscularly.

Diagnosis

Anthrax is diagnosed through a combination of clinical findings and laboratory tests. Because the condition is rare, diagnosis can sometimes be delayed — which is why sharing any relevant exposure history with your doctor is so important.

Methods that may be used to diagnose anthrax include the following:

• Culture and bacteriological examination. Swabs taken from skin lesions, blood samples, or other body fluids can be examined in the laboratory to attempt to grow and identify Bacillus anthracis. This is among the most definitive diagnostic methods available.
• Blood tests. Inflammatory markers in the blood may be elevated. Specialised antibody tests can also provide findings that support a diagnosis of anthrax.
• PCR testing. Genetic material from the bacterium may be detected in a sample using PCR testing, which can produce rapid and reliable results.
• Imaging. In inhalation anthrax, a chest X-ray or CT scan may show fluid accumulation in the chest cavity or enlarged lymph nodes, which can be suggestive findings in this context.
• Clinical assessment. In cutaneous anthrax, the characteristic appearance of a painless black-crusted ulcer combined with a relevant exposure history can be strongly suggestive of the diagnosis. Your doctor will also consider your occupational history, animal contact, and geographic circumstances.

Treatment

When diagnosed early, anthrax can be treated with antibiotics. Starting treatment as quickly as possible can be life-saving, particularly in the inhaled form.

• Antibiotic treatment. Ciprofloxacin and doxycycline are among the antibiotics most commonly used in anthrax treatment. Amoxicillin may also be used in some situations. The duration of treatment can vary depending on the type and severity of the illness — inhalation anthrax typically requires a considerably longer course. Antibiotic treatment can also be started as a preventive measure after a known or suspected exposure, before illness has developed.
• Antitoxin treatment. Biological agents such as obiltoxaximab, raxibacumab, and anthrax antitoxin may help neutralise the toxin that the bacteria produce in the body. These treatments are used particularly in severe inhalation anthrax cases, usually alongside antibiotics.
• Supportive care. In severe cases, hospital-based care including fluid replacement, respiratory support, and other supportive measures may be needed. Intensive care support can be critically important in inhalation anthrax.
• Skin lesion care. In cutaneous anthrax, cutting open or draining the lesion is not recommended as this could potentially spread the infection. With appropriate dressings and antibiotic treatment, most skin lesions can be expected to heal.

Prevention

Preventing anthrax is largely possible through occupational precautions and vaccination for those at higher risk.

• Vaccination. An anthrax vaccine is available for people in high-risk occupational groups. In various countries it is recommended for certain groups including veterinarians, farmers, and military personnel. It is not part of routine vaccination programmes for the general public.
• Protective measures when working with animals. Wearing gloves, a mask, and protective clothing when working with sick or dead animals can help reduce the risk of exposure. Following appropriate hygiene practices during animal slaughter is also important.
• Care when handling animal products. Using protective equipment when working with unprocessed animal hides, wool, or bone, and working in well-ventilated environments, may help reduce the risk of exposure.
• Thoroughly cooking meat. Particularly in areas where anthrax occurs in animals, cooking meat thoroughly is thought to substantially reduce the risk of gastrointestinal anthrax.
• Reporting suspicious animal deaths to the authorities. Slaughtering or processing an animal suspected of having died from anthrax can carry a significant risk. If such an animal is discovered, informing a veterinarian or the relevant authorities is strongly recommended.
• Post-exposure preventive antibiotics. If exposure to anthrax spores is suspected, a course of preventive antibiotics prescribed by a doctor may prevent the illness from developing.

Preparing for Your Appointment

If you are attending a doctor or emergency department with a concern about possible anthrax, having certain information ready may help speed up the assessment process.

What you can do:

• Note when symptoms began and how they have developed
• Mention any contact with animals or animal products in the past few weeks
• Mention any travel abroad or time spent in areas where anthrax has been reported
• Describe your occupation and any relevant work-related exposures
• List all current medications

Questions you may wish to ask your doctor:

• Could this be anthrax?
• Which tests would be needed to find out?
• Which antibiotic would I need and for how long?
• Could my family members or colleagues also be at risk?
• Does this need to be reported to the health authorities?
• Should I consider anthrax vaccination given my work?

Questions your doctor may ask:

• Have you had contact with animals or animal products recently?
• Do you work with livestock, in farming, or with animal-derived products?
• Have you been to an area where anthrax has been reported?
• When did the symptoms start and how have they changed?
• If there is a skin lesion, when did you first notice it and how has it changed?
• Are other people around you experiencing similar symptoms?