“Anthrax!”, the word itself invokes a sense of danger, of imminent threat. Anthrax can indeed be potentially devastating for those who are affected by it. If you would like to know more about the effects and dangers of anthrax, please read on below. 

What is anthrax?

Anthrax is an illness caused by specific bacteria. These bacteria are called Bacillus anthracis. and can be found in the soil, in water and in infected animals.¹

It is important to distinguish between different strains of Bacillus anthracis. Some strains are virulent (harmful) and cause anthrax. These dangerous strains are sometimes also called anthrax strains. Other Bacillus anthracis strains are harmless and do not cause any illness.^2,3

Infection with one of the virulent anthrax strains results in anthrax and its various symptoms. The severity of these symptoms depends on several factors:

• The individual characteristics of each person’s immune system
• The level of potency of the given anthrax strain
• The number of Bacillus anthracis bacteria in the infection¹

Additionally, the way by which the infection enters the body greatly influences what kind of symptoms will arise. It also determines the chance of severe symptoms leading up to death.^1,3

In this article, only the effects of the virulent Bacillus anthracis strains (anthrax strains) causing anthrax will be discussed.

How do we get anthrax?

We get anthrax by being exposed to bacteria of a virulent Bacillus anthracis strain (anthrax strain). There are generally two sources of Bacillus anthracis infection.¹ 

Water and soil

The first source is inanimate natural resources, in this case, water and soil. Bacillus anthracis can be present in both but only in the form of spores. These spores are a very hardy form of these bacteria, capable of surviving in soil and water for years.^1,3,4 

By drinking water containing Bacillus anthracis spores or breathing in dust filled with Bacillus anthracis spores, we get infected.¹ In our bodies, the Bacillus anthracis will then develop from its spore form into its biologically active vegetative form. This process is called germination. In its vegetative form, an anthrax strain produces its two characteristic toxins. These toxins are capable of disrupting the cell function of nearly every cell they encounter, resulting in the typical symptoms of anthrax (see further below).^1,3,5

Animals and animal products

The second source of Bacillus anthracis infections are infected herbivores (plant eaters) and animal products derived from these herbivores. Herbivores which can be infected include both farm animals (cattle, goats, sheep e.t.c.) and wild animals (for example zebras, elephants and buffalos). Due to their infection, they can carry both forms of Bacillus anthracis. The vegetative form can be found in their blood. The spore form on the other hand can be present in their flesh, on their skin and in their hair.¹  

Infection occurs when one or both forms of Bacillus anthracis:

• Come into contact with broken skin (the break being through at least the top layer of the skin)
• Are breathed in
• Are ingested (for example eating contaminated meat that is raw or not cooked well enough)^1,3

This allows an anthrax strain to enter our bodies and wreak havoc.

In rare cases, people have acquired anthrax in hospital while being there for unrelated reasons.¹

Clinical forms of anthrax

Generally, the clinical forms of anthrax are categorised by how the anthrax strain originally entered the body (route of infection).³ 

Getting anthrax through breaks in the skin is referred to as cutaneous anthrax.^1,3 

Developing anthrax by breathing in anthrax strain spores is called inhalational or inhalation anthrax.¹

Being infected by anthrax after drinking or eating things containing an anthrax strain is referred to as gastrointestinal or ingestion anthrax.¹ 

A fairly newly described fourth clinical anthrax form is called ‘injectional anthrax’, which is caused by injection of heroin contaminated with anthrax strain spores.¹ 

Symptoms of the clinical forms of anthrax

Initially, the symptoms of the clinical forms of anthrax tend to be restricted to the area where the infection first occurred. In some cases, especially in the absence of successful treatment, the anthrax bacteria will start spreading further and can also cause more serious symptoms.^1,3

Symptoms of cutaneous anthrax

The incubation period (time from infection to the first appearance of symptoms) for cutaneous anthrax is usually between 2 and 7 days.¹ 

Cutaneous anthrax gives rise to papules (small bumps) on the skin. These are mostly found on the face, neck, arms and hands. Subsequently, these papules turn into vesicles (blisters). They are accompanied by erythema (reddening of the skin) and oedema (swelling).^1,3 Oedemas of the neck and the face can sometimes restrict the airway, resulting in breathing difficulties (dyspnoea). Fever and swollen lymph nodes (lymphadenopathy) are often seen as well.³

The blisters then turn into ulcers containing dead tissue called black eschar. This black eschar tends to fall off after 2 to 3 weeks.³

In rare cases, the anthrax bacteria will spread into the bloodstream which results in toxaemia/septicaemia (blood poisoning). This can lead to sepsis and thereby septic shock, two dangerous conditions which can be fatal.^1,3

Symptoms of inhalation anthrax

Inhalation anthrax has a very high mortality rate at  85 - 87%. Symptoms usually appear 1 to 7 days after infection. Inhalation anthrax has 2 stages.^1,6

During the first stage, inhalation anthrax can result in the following symptoms:

• Mild fever
• Malaise (feeling generally unwell)
• Dry cough 
• Myalgia (muscle pain)
• Chest pain
• Stomachache¹

When not treated successfully, inhalation anthrax progresses to the second stage. At this stage, it can cause:

• High fever
• Toxaemia/septicaemia (blood poisoning)
• Cyanosis (skin and lips turning blue)
• Dyspnoea (shortness of breath)
• Hypothermia (very low body temperature)
• Hypotension (low blood pressure)
• Meningitis (infection of the layers surrounding and protecting the brain)
• Haemorrhagic mediastinitis (chest inflammation with internal bleeding)
• Septic shock
• Death^1,3

The second stage of inhalation anthrax often leads to death, sometimes within the first 24 hours of entering this stage.^1,3

Gastrointestinal anthrax

Gastrointestinal anthrax starts causing symptoms about 3 to 7 days after infection. 

It is subdivided into oropharyngeal and intestinal anthrax.¹

Oropharyngeal anthrax

Oropharyngeal anthrax affects the oropharynx – the part of the throat immediately behind the mouth. This form of anthrax can cause:

• Fever
• Dysphagia (difficulty swallowing)
• Pharyngitis (sore throat)
• Ulcers
• Lymphadenopathy (swollen lymph nodes that are also painful)
• Swelling located in the neck^1,3

Intestinal anthrax

Intestinal anthrax impacts the digestive tract. Similar to inhalation anthrax, intestinal anthrax has two stages.¹

The first stage of intestinal anthrax can result in:

• Fever
• Anorexia (loss of appetite)
• Nausea (feeling sick)
• Vomiting
• Diarrhoea¹

The second and final stage of intestinal anthrax can lead to:

• Stomachache 
• Ulcers
• Lymphadenopathy (swollen lymph nodes)
• Bloody diarrhoea
• Haematemesis (throwing up blood)
• Ascites (accumulation of fluid in the belly)
• Blockages in the digestive tract 
• Gastrointestinal perforation (a hole in the digestive tract)
• Toxaemia/septicaemia (blood poisoning)
• Septic shock
• Death^1,3

Injectional anthrax

While cutaneous anthrax infects the top layers of the skin, injectional anthrax infects the deeper layers of the skin or the tissue inside a muscle. Due to this, it is estimated that injectional anthrax has a higher chance of causing septic shock and leading to death.³

Injectional anthrax can lead to:^1,3

• Oedema (swelling) at the injection site
• Bleeding at the injection site
• Formation of dead tissue at the injection site
• Thrombocytopenia (lack of blood platelets)
• Coagulopathy (excessive bleeding due to reduced blood clotting)
• Meningitis (infection of the layers [meninges] surrounding and protecting the brain)
• Toxaemia/septicaemia (blood poisoning)
• Sepsis 
• Septic shock
• Death

Summary

Anthrax is a devastating illness caused by a bacterium called Bacillus anthracis. These bacteria can be found in the soil,  water and infected plant-eating animals. People can get infected by Bacillus anthracis in numerous ways, which is reflected in the categorisation of the clinical forms of anthrax. The bacteria can be breathed in (inhalation anthrax) or enter the body through the skin (cutaneous anthrax).

Drinking water containing Bacillus anthracis or eating meat from infected animals also allows these bacteria to infect someone (gastrointestinal anthrax). Finally, people injecting themselves with heroin contaminated with Bacillus anthracis spores also results in anthrax (injectional anthrax). The severity of the resulting symptoms and the probability of a fatal outcome heavily depends on the clinical form.

For example, inhalation anthrax has a very high chance (85 - 87%) of proving fatal, far more so than the other three clinical forms of anthrax. Initially, all the clinical forms of anthrax tend to primarily affect the site of infection, resulting in relatively mild symptoms. Over time, some of these clinical anthrax forms will progress, spreading further and causing more severe symptoms. This can lead to sepsis and septic shock. These two conditions are highly dangerous and often result in death.