Anthrax: Causes, Symptoms and Treatment

Table of Contents

What is Anthrax?

Anthrax is a zoonotic disease mainly affecting herbivores and domestic animals, with humans infected through animal contact.
It is a rare but serious illness caused by Bacillus anthracis, a Gram-positive, spore-forming, non-motile bacterium found naturally in soil worldwide.
Anthrax spores can survive for decades in the environment.
Human infection occurs through skin contact, inhalation of spores, or gastrointestinal exposure from contaminated meat.

Why Anthrax is a Public Health Concern?

Anthrax can cause serious illness and death in humans and animals.
The spores of anthrax survive in soil for many years, making outbreaks hard to prevent.
Humans can get infected through contact with animals, meat, or animal products.
Anthrax outbreaks can lead to public health and economic problems in affected communities.
It can be used in bioterrorism.

What are the Causes of Anthrax?

Bacillus anthracis: Structure and Spore Formation

Anthrax is a serious infectious disease caused by the spore-forming, gram-positive bacterium Bacillus anthracis.
It primarily affects livestock and wild herbivores, with human infection occurring through contact with infected animals, contaminated animal products, or by inhaling spores.
anthracisis a large, rod-shaped Gram-positive bacterium that forms spores.
Anthrax spores can persist in soil for decades in a dormant state.
Once ingested, the spores are activated, and the bacteria begin to reproduce.

Virulence Factors and Anthrax Toxins

Bacillus anthracis has two primary virulence factors:
An extracellular poly-D-glutamate (D-PGA) capsule
Anthrax toxin complex
- Protective antigen: It is bundung domain of anthrax toxin and is necessary for entry of the bacteria into the host cell.
- Lethal factor: It inactivates nitogen-activated protein kinase, leading to the inhibition of intracellular signaling.
- Edema factor: It acts by converting Adenosine triphosphate to cyclic adenosine monophosphate.
These virulence factors are induced under physiologic conditions found in mammalian hosts, including:
- Body temperature (37 °C)
- Increased CO₂ levels
- Bicarbonate concentration

Types of Anthrax

1. Cutaneous Anthrax

Most common form of anthrax
Caused when spores enter through cuts or break in the skin from handling infected animals or products
Usually appears on the head, neck, forearms, and hands

2. Inhalational Anthrax

Severe form caused by breathing in spores
Common in wool mills, slaughterhouses, or tanneries
Can lead to serious respiratory illness

3. Gastrointestinal Anthrax

Occurs from eating contaminated meat
Symptoms include abdominal pain, vomiting, and diarrhoea

4. Injection Anthrax

Happens from injecting contaminated drugs
Causes severe soft-tissue infections

How Does Anthrax Transmit?

How Anthrax Spreads from Animals to Humans?

Anthrax is usually spread in the form of a spore.
Anthrax spreads to humans in three main ways:
Skin contact: Touching contaminated animal products such as wool, hair, hide, bone, or skin
Inhalation: Breathing in anthrax spores from contaminated materials
Ingestion: Eating infected meat that is not properly cooked.

What are the Risk Factors of Anthrax?

Occupational Risk Groups for Anthrax

Laboratory workers handling anthrax bacteria
People working with animals or animal products like farmers, veterinarians, livestock workers
People traveling to endemic areas
Welders and metalworkers
In case of bioterrorism:
- Mail handlers
- Military personnel
- Emergency and disaster response workers

Environmental Persistence of Anthrax Spores

Anthrax spores can survive in soil for decades
Spores resist heat, drying, and disinfectants

What are the Signs and Symptoms of Anthrax?

Clinical Features of Different Types of Anthrax

1. Cutaneous anthrax

Cutaneous anthrax begins as a small red bump (papule) 5–7 days after spores enter through cuts or scrapes, usually on the hands, arms, neck, or face.
The bump becomes a blister that may itch and eventually bursts, forming an open wound.
The wound develops a black, hard scab (eschar), and more lesions may appear nearby

2. Gastrointestinal Anthrax

In this type, you can get anthrax in your throat (oesophagus) or your stomach:
- Throat/oesophagus infection: trouble swallowing, sore throat, swelling of throat/neck, difficulty breathing
- Stomach/intestine infection: abdominal pain and swelling, diarrhoea (sometimes bloody), nausea, vomiting (sometimes bloody), malaise, red face and eyes

3. Inhalational Anthrax

In this type, symptoms occur in two phases;

Phase 1 (Early / Flu-like symptoms):
- Fatigue
- Fever
- General malaise (feeling unwell)

Phase 2 (Severe / Advanced symptoms):
- Chest pain
- Coughing, sometimes coughing blood (hemoptysis)
- Confusion
- Excessive sweating (diaphoresis)
- Fast, shallow breathing (tachypnea)
- Rapid heartbeat (tachycardia)
- Severe headache
- Nausea
- Trouble breathing (dyspnea)

4. Injection anthrax

Injection anthrax is similar to cutaneous anthrax, but deeper.
Early symptoms include:
- Bumps that might itch in the area of injection.
- Swelling around the sore.

What are the Complications Caused Due to Anthrax?

Meningitis or meningoencephalitis – can occur from any form
Sepsis – from any form
Pleural effusion, pneumonia, or mediastinitis – mainly from inhalational anthrax
Spreading skin infections like vasculitis, cellulitis – especially cutaneous or injection anthrax
Stomach ulcers – from gastrointestinal anthrax

What are the Warning Signs Requiring Emergency Care?

Black, painful skin sores that spread quickly
Trouble breathing, chest pain, or coughing blood
Severe stomach pain, vomiting, or diarrhoea
Red, swollen, or infected injection sites
High fever, confusion, or signs of serious infection

How Is Anthrax Diagnosed?

Anthrax is diagnosed by identifying Bacillus anthracis from clinical specimens and by detecting specific antibodies or bacterial DNA in the blood.
Depending on which type of anthrax, the tests include:
Cutaneous anthrax:
- Skin lesion swab or skin biopsy
- Gram stain
- Capsule staining
- Culture of lesion material
- PCR

Inhalation anthrax:
- Chest X-ray or CT scan
- Blood culture
- PCR testing

Gastrointestinal Anthrax
- Stool or blood culture
- PCR
- Serologic tests

For all form of anthrax
- Lumbar Puncture,
- Blood test like PCR, ELISA

Challenges in Early Detection

Because Early symptoms can look like common respiratory or stomach illnesses.
Anthrax is rare, so healthcare workers may not suspect it at first.
Low awareness among communities and healthcare providers can delay recognition.

What is the Treatment for Anthrax?

Antibiotic Therapy for Anthrax

Anthrax is treated with antibiotics such as ciprofloxacin, doxycycline, or penicillin, which are most effective when given early.
Antibiotics help kill Bacillus anthracis and prevent disease progression.
Oral antibiotics are used for mild cases and post-exposure prophylaxis.
Intravenous (IV) antibiotics are used in severe or systemic anthrax cases.

Role of Antitoxin and Supportive Care

Antitoxin neutralizes circulating anthrax toxins, especially the protective antigen, and helps reduce toxin-mediated tissue damage.
It improves survival in severe or systemic anthrax and is always used along with antibiotics, not alone.
Supportive care includes continuous fluid drainage (such as pleural effusion drainage) to reduce breathing difficulty.
Mechanical ventilation is provided in cases of respiratory failure to maintain adequate oxygenation.

Post-Exposure Prophylaxis (PEP)

Given to individuals who have been exposed to anthrax but have no symptoms.
Involves oral antibiotics for 60 days to prevent bacterial growth.
Anthrax vaccine may be added in high-risk exposures for better protection.

What are the Prevention and Control Mechanisms for Anthrax?

Anthrax Vaccination: Uses and Effectiveness

The anthrax vaccine (Anthrax Vaccine Adsorbed) is made from a laboratory-grown strain of Bacillus anthracis.
It is highly effective (about 92.5%) in preventing infection.
Recommended for adults 18–65 years at risk of exposure.
Administered as 3 doses, followed by boosters for ongoing protection.
Can be used before exposure for high-risk people and after exposure with antibiotics to prevent disease.
Works by stimulating protective antibodies against anthrax.

Animal Vaccination and Veterinary Control

Anthrax in animals is controlled through vaccination, early detection, reporting, quarantine, and treatment.
The Sterne live vaccine is commonly used, given 2–4 weeks before outbreak season.
Annual vaccination of grazing animals is recommended in endemic areas.
During outbreaks: restrict movement, quarantine, and enforce emergency measures.
Exposed animals may receive long-acting antibiotics, followed by vaccination after 7–10 days.
Prompt disposal of carcasses by burning or deep burial is essential.
Isolation of sick animals, disinfection, and good hygiene should be strictly maintained.

Infection Prevention and Control Measures

Early detection and reporting of suspected human or animal cases.
Isolation of infected or suspected cases and restriction of movement.
Use of personal protective equipment (PPE) by healthcare workers, veterinarians, and handlers.
Safely dispose of infected animals and products by burning or deep burial.
Clean and disinfect contaminated areas and equipment.
Provide post-exposure antibiotics to the exposed individual.
Vaccination of animals and high-risk occupational groups where indicated.
Environmental control, including control of insects and scavengers.
Raise awareness about safe animal handling and meat consumption.
Collaboration between human and animal health sectors (One Health) is essential.

Public Health and Biosecurity Related to Anthrax?

Anthrax Outbreaks and Case Studies

Anthrax outbreaks continue to occur worldwide, especially in areas with low livestock vaccination coverage and close human–animal contact.
Anthrax occurs more frequently in certain regions, including parts of South and Central America, Europe, Asia, Africa, the Caribbean, and the Middle East.
In April 2025, an outbreak in Virunga National Park, Democratic Republic of the Congo, killed around 50 hippopotamuses and other wildlife, likely due to long-persisting spores in the soil.
Between 1–4 May 2025, Thailand reported four confirmed cutaneous anthrax cases, including one death, following exposure during cattle slaughter.

Anthrax as a Bioterrorism Threat

Anthrax (caused by Bacillus anthracis) is considered a high-priority bioterrorism agent because of its unique biological and epidemiological features.
Occurs naturally but can be produced in laboratories.
Forms spores that survive for long periods in the environment.
Can be released secretly into the air, food, water, or mail.
Airborne spread can infect many people at once.
Even small amounts can cause large outbreaks.

Surveillance, Reporting, and Emergency Preparedness

Surveillance:

Anthrax surveillance means regularly monitoring human and animal health to identify suspected cases early.
It helps in early detection of outbreaks, especially in livestock, and reduces the spread of the disease to humans.

Reporting:

Anthrax is a notifiable disease. If Bacillus anthracis is suspected or confirmed, it must be reported immediately to local or national public health authorities.
Mandatory reporting helps authorities take quick control measures and protect the community.

Emergency Preparedness:

Emergency preparedness for anthrax focuses on preventing human exposure, protecting healthcare and response workers, and detecting outbreaks as early as possible.
This includes trained staff, proper laboratory facilities, availability of antibiotics and vaccines, and coordination between human and animal health sectors.

Frequently Asked Questions (FAQ’s)

Is Anthrax Contagious?

Anthrax does not spread from person to person.
Humans usually become infected through contact with infected animals, animal products, or spores in the environment.

Can Anthrax Be Treated Successfully?

Anthrax can be treated successfully with antibiotics, especially when diagnosed and treated early.

Key Takeaway

Anthrax is a serious zoonotic disease caused by Bacillus anthracis, affecting animals and humans.
Transmission occurs through skin contact, inhalation, or eating contaminated meat.
Anthrax does not spread from person to person.
Antibiotics are essential for treating anthrax.

Public Health Notes

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