Anthrax: Symptoms, Causes & Emergency Treatment Guide

What Is Anthrax and What Causes It?

Anthrax is a serious bacterial infection caused by Bacillus anthracis, a spore-forming bacterium. The disease primarily affects grazing animals like cattle, sheep, goats, and horses, but humans can become infected through contact with infected animals or their products. As spores, the bacteria can survive in soil for many decades, remaining infectious throughout this time.

Anthrax has been known since ancient times and is one of the oldest documented diseases affecting both humans and animals. The name comes from the Greek word "anthrakis," meaning coal, referring to the characteristic black skin lesion (eschar) that develops in cutaneous anthrax. The disease occurs worldwide but is most common in agricultural regions with inadequate public health infrastructure and veterinary programs.

The bacterium Bacillus anthracis is particularly dangerous because of its ability to form highly resistant spores. When conditions become unfavorable for bacterial growth, the bacteria transform into dormant spores that can withstand extreme temperatures, desiccation, radiation, and even some disinfectants. These spores can persist in contaminated soil for 50 years or more, creating long-term reservoirs of infection in endemic areas.

Understanding the biology of anthrax is essential for effective prevention and treatment. The bacteria produce three main toxins that cause the severe symptoms of the disease: protective antigen (PA), lethal factor (LF), and edema factor (EF). These toxins work together to disable the immune system and cause tissue damage, leading to the characteristic symptoms of anthrax infection.

Where Does Anthrax Occur?

Anthrax is endemic in many parts of the world, particularly in regions where livestock vaccination programs are inadequate. The disease is most common in sub-Saharan Africa, Central and South Asia, the Middle East, and parts of Southern Europe. However, sporadic cases and outbreaks can occur anywhere in the world.

In developed countries, anthrax is rare but not absent. Historical contamination sites, such as old tanneries, wool processing facilities, and burial sites for infected animals, can harbor viable spores for many years. Climate change and environmental disturbances can sometimes bring dormant spores to the surface, leading to unexpected outbreaks even in areas that have been free of anthrax for decades.

How Does Anthrax Spread to Humans?

Humans can contract anthrax through three main routes: through the skin (cutaneous anthrax) when spores enter through cuts or wounds, by breathing in spores (inhalation anthrax), or by eating contaminated undercooked meat (gastrointestinal anthrax). Anthrax does not spread from person to person, so caring for an infected patient does not put others at risk of infection.

The most common route of human infection is through the skin, known as cutaneous anthrax. This typically occurs when people handle infected animals or contaminated animal products such as wool, hides, hair, or bone meal. Spores can enter the body through small cuts, abrasions, or other breaks in the skin. Workers in agriculture, veterinary medicine, and industries that process animal products are at highest risk.

Inhalation anthrax occurs when a person breathes in airborne anthrax spores. Historically, this form was known as "woolsorter's disease" because it primarily affected workers who processed contaminated wool and animal hides. Inhalation anthrax is the most serious form of the disease and was responsible for the anthrax letter attacks in the United States in 2001. The infectious dose for inhalation anthrax is estimated to be between 8,000 and 50,000 spores.

Gastrointestinal anthrax results from eating undercooked or raw meat from infected animals. This form is more common in developing countries where food safety standards may be inadequate and where consumption of animals that died suddenly of unknown causes occurs. The bacteria or spores enter the digestive tract and can cause infection anywhere from the mouth to the intestines.

A fourth, less common form called injection anthrax has been identified among people who inject drugs. This form was first recognized in Europe in 2009 and is associated with contaminated heroin. Injection anthrax can cause deep soft tissue infections that are particularly difficult to treat.

Anthrax as a Notifiable Disease

Anthrax is classified as a notifiable disease in virtually all countries, meaning that healthcare providers are legally required to report cases to public health authorities. This is essential for disease surveillance, outbreak investigation, and preventing further spread. In many jurisdictions, anthrax is also a legally mandated reportable animal disease, requiring veterinarians to report suspected cases in livestock.

What Are the Symptoms of Anthrax?

Anthrax symptoms depend on how you become infected. Cutaneous anthrax causes a painless skin sore that develops into a characteristic black ulcer. Inhalation anthrax begins with flu-like symptoms and rapidly progresses to severe breathing difficulties. Gastrointestinal anthrax causes fever, nausea, vomiting, and abdominal pain. Symptoms typically appear within 1-7 days after exposure.

The clinical presentation of anthrax varies significantly depending on the route of infection. Early recognition of symptoms is critical because prompt treatment dramatically improves outcomes. In all forms of anthrax, the incubation period (time between exposure and symptom onset) is usually 1 to 7 days, though it can occasionally be longer, particularly with inhalation anthrax where symptoms may appear up to 60 days after exposure.

Cutaneous Anthrax Symptoms

Cutaneous anthrax is the most common and least dangerous form of the disease, accounting for approximately 95% of naturally occurring human cases. The infection begins when spores enter through a break in the skin. Initially, a small, painless, itchy bump appears, similar to an insect bite. Over 1-2 days, this develops into a blister (vesicle) filled with clear or bloody fluid.

The characteristic feature of cutaneous anthrax is the development of a painless ulcer with a distinctive black center called an eschar. This black scab is caused by tissue death and is the hallmark sign that gives anthrax its name (from the Greek word for coal). The ulcer is typically surrounded by significant swelling (edema) that may extend well beyond the immediate lesion. Despite the dramatic appearance, the lesion remains remarkably painless.

Without treatment, approximately 20% of cutaneous anthrax cases may progress to systemic infection. However, with appropriate antibiotic therapy, the mortality rate drops to less than 1%, making cutaneous anthrax highly treatable when recognized early.

Inhalation Anthrax Symptoms

Inhalation anthrax is the most dangerous form of the disease and requires immediate medical attention. The disease progresses in two distinct phases. The initial phase presents with non-specific flu-like symptoms including fever, fatigue, muscle aches, mild chest discomfort, and a non-productive cough. This phase can last from hours to several days.

The second phase begins suddenly and is characterized by severe respiratory distress, high fever, drenching sweats, and shock. Patients develop mediastinal widening (visible on chest X-ray) due to hemorrhagic lymphadenitis. Without treatment, inhalation anthrax is almost always fatal, with death occurring within 24-36 hours after the onset of severe symptoms. Even with aggressive treatment, mortality remains high at approximately 45%.

Gastrointestinal Anthrax Symptoms

Gastrointestinal anthrax can affect the upper or lower digestive tract. When the infection affects the throat and upper gastrointestinal tract (oropharyngeal anthrax), symptoms include sore throat, difficulty swallowing, fever, and swelling of the neck due to enlarged lymph nodes.

When the lower gastrointestinal tract is affected (intestinal anthrax), patients experience nausea, loss of appetite, vomiting, fever, abdominal pain, and bloody diarrhea. The disease can progress rapidly to acute abdomen, septic shock, and death. Mortality for gastrointestinal anthrax ranges from 25-60% depending on the rapidity of treatment initiation.

Systemic Anthrax and Sepsis

Regardless of the initial route of infection, anthrax bacteria can spread through the bloodstream and cause sepsis (blood poisoning). Septic anthrax is characterized by high fever, rapid heart rate, and dangerously low blood pressure. The bacteria can also spread to the brain, causing anthrax meningitis, which is associated with severe headache, altered consciousness, and a high mortality rate.

When Should You Seek Medical Care?

Seek medical care immediately if you develop a painless skin sore with a black center, sudden severe breathing difficulties, or severe abdominal symptoms after potential exposure to anthrax. If you know or suspect you have been exposed to anthrax, contact healthcare services even before symptoms appear, as preventive antibiotics can prevent the disease from developing.

Early medical intervention is the most important factor in surviving anthrax. The disease responds well to antibiotic treatment when started early, but becomes increasingly difficult to treat as it progresses. Do not wait for symptoms to worsen before seeking care – early treatment can be lifesaving.

Contact a healthcare provider or go to an emergency department immediately if you experience any symptoms consistent with anthrax, particularly if you have potential occupational exposure through work with animals, animal products, or potentially contaminated materials.

If you believe you have been exposed to anthrax but have not yet developed symptoms, you should still seek medical attention. Post-exposure prophylaxis (preventive antibiotics) can prevent the disease from developing even after exposure. This is particularly important for inhalation exposure, where the disease can have a delayed onset but rapid progression once symptoms begin.

How Can You Prevent Anthrax Infection?

Prevention of anthrax involves avoiding contact with infected animals and contaminated products, proper handling of animal hides and wool, good hygiene practices when working with animals, and vaccination for high-risk individuals. If you suspect exposure, preventive antibiotics can be given before symptoms develop.

For most people, the risk of anthrax exposure is extremely low. However, those who work with animals or animal products should take specific precautions. Understanding how the disease spreads is the first step in effective prevention.

Occupational Prevention Measures

Workers in high-risk industries should follow established safety protocols. These include wearing appropriate personal protective equipment (PPE) such as gloves, masks, and protective clothing when handling potentially contaminated materials. Workplaces that process animal products should have adequate ventilation systems and dust control measures to minimize airborne spore exposure.

Proper decontamination procedures are essential. Workers should thoroughly wash hands and any exposed skin after handling animals or animal products. Contaminated clothing should be properly cleaned or disposed of. Work areas should be regularly cleaned and decontaminated using appropriate disinfectants that are effective against anthrax spores.

Food Safety

In endemic areas, ensuring that meat is thoroughly cooked is important for preventing gastrointestinal anthrax. Avoid consuming meat from animals that died suddenly of unknown causes. In many countries, public health inspections and regulations help ensure that meat entering the food supply is safe.

Vaccination

An anthrax vaccine is available but is generally only recommended for high-risk groups due to limited supply and the need for multiple doses. Those who may benefit from vaccination include:

• Certain laboratory workers who work with Bacillus anthracis
• Some military personnel
• People who handle potentially infected animals or animal products in high-risk regions

The vaccine requires a series of doses over 18 months for full protection, followed by annual boosters. It is not available to the general public and is not routinely recommended for travelers to endemic areas.

How Is Anthrax Diagnosed?

Anthrax is diagnosed through bacterial culture from wound samples, blood, or respiratory secretions. PCR tests can rapidly detect Bacillus anthracis DNA. Blood tests may show elevated white blood cell counts and markers of systemic infection. Chest X-rays or CT scans can reveal the characteristic mediastinal widening in inhalation anthrax.

Accurate and rapid diagnosis of anthrax is crucial for effective treatment. When you seek medical care, your healthcare provider will take a detailed history including any potential exposures to animals, animal products, or suspicious materials. They will perform a physical examination looking for characteristic signs of anthrax.

Laboratory Tests

The definitive diagnosis of anthrax requires identifying Bacillus anthracis in clinical specimens. This can be done through:

• Bacterial culture: Growing the bacteria from samples taken from skin lesions, blood, respiratory secretions, or stool. Culture remains the gold standard for diagnosis but may take 24-48 hours.
• Polymerase chain reaction (PCR): A rapid molecular test that can detect anthrax DNA within hours. PCR is particularly useful for early diagnosis when bacterial numbers may be low.
• Blood tests: Complete blood count, inflammatory markers, and other tests can help assess the severity of infection and guide treatment.
• Serological tests: Blood tests for antibodies against anthrax can be useful for confirming past infection but are less helpful for acute diagnosis.

Imaging Studies

For suspected inhalation anthrax, chest X-rays or CT scans are important diagnostic tools. The characteristic finding is mediastinal widening – an enlargement of the central chest structures due to hemorrhagic inflammation of the lymph nodes. Pleural effusions (fluid around the lungs) are also commonly seen.

How Is Anthrax Treated?

Anthrax is treated with antibiotics, typically ciprofloxacin or doxycycline. Early treatment is crucial for recovery. Cutaneous anthrax responds well to antibiotics with nearly 100% survival when treated promptly. Inhalation and gastrointestinal anthrax require aggressive treatment with multiple antibiotics and supportive care. Anthrax antitoxin may be used in severe cases.

The cornerstone of anthrax treatment is antibiotic therapy. The choice of antibiotic and duration of treatment depend on the form of anthrax and severity of disease. Treatment should be started immediately upon clinical suspicion, even before laboratory confirmation, because delays in treatment significantly worsen outcomes.

Antibiotic Therapy

For cutaneous anthrax without systemic involvement, oral antibiotics for 7-10 days are usually sufficient. Ciprofloxacin and doxycycline are the preferred agents. For more severe disease or when systemic involvement is present, intravenous antibiotics are used, often in combination.

Inhalation anthrax requires aggressive treatment with multiple intravenous antibiotics. A typical regimen includes a fluoroquinolone (such as ciprofloxacin) plus another agent with good activity against Bacillus anthracis (such as clindamycin, rifampin, or penicillin). Treatment is continued for a total of 60 days due to the risk of delayed spore germination.

Antitoxin Therapy

For severe systemic anthrax, antitoxin medications may be used in addition to antibiotics. These include raxibacumab and obiltoxaximab, which are monoclonal antibodies that neutralize anthrax toxin. Anthrax immune globulin, derived from vaccinated donors, is another option. These therapies can help neutralize the toxins that cause much of the damage in severe anthrax.

Supportive Care

Patients with severe anthrax often require intensive supportive care. This may include:

• Intravenous fluids to maintain blood pressure and organ perfusion
• Mechanical ventilation for respiratory failure
• Vasopressor medications for shock
• Drainage of pleural effusions
• Management of complications such as meningitis

Treatment During Pregnancy and Breastfeeding

Anthrax can be life-threatening and requires treatment even during pregnancy. Ciprofloxacin, though not typically a first-choice antibiotic in pregnancy, is recommended for anthrax because the benefits clearly outweigh the risks. Healthcare providers will weigh the specific risks and benefits for each individual case.

What Is the Outlook for Anthrax?

Prognosis depends heavily on the form of anthrax and how quickly treatment begins. Cutaneous anthrax has an excellent prognosis with treatment, with survival rates exceeding 99%. Inhalation anthrax is much more serious, with approximately 45% mortality even with treatment. Gastrointestinal anthrax has intermediate mortality of 25-60%.

The outcome of anthrax infection varies dramatically based on several factors. The form of disease, time to treatment initiation, and the patient's overall health all influence prognosis. Modern medical care has significantly improved outcomes, but prompt recognition and treatment remain essential.

For cutaneous anthrax, the prognosis is excellent when treated with appropriate antibiotics. The skin lesion will typically heal over several weeks, though it may leave a scar. Without treatment, approximately 20% of cutaneous anthrax cases can progress to systemic disease and potential death.

Inhalation anthrax remains challenging to treat despite advances in medical care. The 2001 anthrax letter attacks in the United States demonstrated that survival is possible with aggressive treatment – 6 of 11 patients with inhalation anthrax survived. However, mortality rates remain high, particularly if treatment is delayed until the second (fulminant) phase of the disease.

Long-term sequelae from anthrax infection can include persistent fatigue, memory and cognitive issues in survivors of severe systemic disease, and scarring from cutaneous lesions. However, most patients who survive acute anthrax infection go on to make a full recovery.