Introduction

Anthrax is an infectious disease caused by spore-forming bacteria called Bacillus anthracis (B. anthracis).¹ B. anthracis is derived from the Greek word “anthrakis” which means black, relating to the black marks seen in the affected individuals.¹ B. anthracis is a small, aerobic, rod-shaped bacteria.¹ B. anthracis is found in the soil worldwide and exists as a spore in the environment lying dormant for decades² before resurfacing when the soil is disturbed due to flooding, rain or landslides.¹ 

Anthrax is a zoonotic disease that can be transmitted to humans from animals like cows, goats, sheep.¹ Anthrax can be fatal in animals and humans due to the toxins produced by the bacteria.

Once animals or humans inhale the spores, they germinate and replicate, producing toxins which make animals and humans very sick. Anthrax can be transmitted by:¹

• Insects infecting other animals
• Contaminated animal feed containing bone meal from infected animals
• Human contact with infected animals

Studying the history of anthrax cases is of significant importance for understanding how the bacteria behave, the geographical location, the frequency of outbreaks, and the transmission patterns. It also provides data to be analysed to improve public health strategies against anthrax and prevent transmission. 

Anthrax poses a major public health concern as it has the potential to be used as a bioweapon and has been used in the past. Understanding the previous attacks can prevent future threats from taking place.² 

This article will discuss the historical background of anthrax, including the early mentions of anthrax, the discovery of anthrax bacteria and the historical uses of anthrax in warfare and bioterrorism. It will also discuss major outbreaks of anthrax, both in humans and animals and the lasting impact and the responses to historical cases of anthrax. The article will end with a discussion of the lessons learnt from historical cases and their influences on shaping the current public response to anthrax. 

Historical background of anthrax

Early mentions of anthrax in history

Anthrax has been around for thousands of years, as far back as ancient Egypt, with the first recorded case in 1491 B.C.³ It is also believed that the 5th and 6th Egyptian Plagues in the Biblical Book of Genesis are caused by the bacteria B. anthracis.³ 

Anthrax’s symptoms affecting animals such as sheep, cattle, horses and wild animals have been described in early Hindu and Greek literature³ and there is some evidence that a plague in Athens in 430-427 BCE may have been caused by anthrax spores.⁴ 

Throughout the Middle Ages, anthrax remained a major problem for the population, targeting both animals and humans and remained a problem until the 19th century when there was a breakthrough in the discovery of anthrax bacterium.⁴ 

Discovery of the anthrax bacterium

Pierre Raver and Casimir Joseph Davaine discovered in 1850 a small rod bacterium circulating the blood of sheep, and Davaine suggested that the presence of these bacteria in the blood was the cause of the disease in sheep. Anthrax was further researched in the 1870s by Robert Koch and Louis Pasteur.⁴ 

In 1876, there was a farm animal epidemic suffering from anthrax that influenced Koch to find the cause.³ Koch was able to complete the life cycle of the bacteria, and he discovered that the bacteria were able to form spores that remained healthy in a range of environments⁴ and, more importantly, that the spores were able to form back into bacteria.³ 

He also expressed that anthrax disease can only be transmitted with the transfer of bacteria from one host to another.⁴ In 1881, Pasteur developed the first anthrax vaccine for animals that contained attenuated live bacteria.⁴ 

Historical use of anthrax in warfare and bioterrorism

Anthrax is a dangerous pathogen that has the potential to be used as a bioweapon since World War 2 and is classified as a Category A pathogen by the Centers for Disease Control & prevention.² 

Anthrax was used in a bioterrorism attack in 2001 in the anthrax letter events in the US, where anthrax spores were sprayed on letters, leading to more than 800 infections and leading to the death of 5 individuals.⁵ The attack caused a disruption of the mail services in the US and the evacuation of several buildings, including the Supreme Court.⁵

Anthrax was also used in a bioterrorism attack in Japan during 1993, where a Japanese religious cult (Aum Shinrikyo) released aerosolised B. anthracis alongside botulinum neurotoxin gases as an attempt to trigger a “nuclear holocaust”.⁶ The anthrax spores were released from an eight-story building, but fortunately, no anthrax cases were reported.⁶

Anthrax bacteria is an attractive choice for bioterrorism as it is easy to obtain, relatively easy to grow and can be dispersed from an aerosol or as dry powder.⁶ It is highly toxic and can be almost 100% fatal if the spores are inhaled and there is no medical treatment provided.⁵ More importantly, the spores are durable and can remain viable and dormant for years until they are disrupted and can, therefore affect more individuals.⁵

Major historical outbreaks of anthrax

Outbreaks in livestock

In 1709, there was an anthrax epidemic that caused the death of half of the sheep in Europe, lasting for almost a century.⁷ This led to enormous economic loss that impacted farmers and ranchers. This would have also impacted jobs involved in butchering, tannery, and textiles due to the low availability of animal products. The remaining animal products might have also been of lower quality, making them less valuable to sellers and reducing overall productivity, impacting the economy. Agriculture was also affected by the outbreaks of anthrax.^2,3 

Human outbreaks

Human anthrax outbreaks have existed for thousands of years, not only among individuals with direct contact with infected animals but also indirectly, like workers who work with animal products.⁶ The Greeks and Romans were familiar with anthrax as the symptoms associated with anthrax were detailed in the writings of Homer, Hippocrates, Virgil, and Galen.⁸ 

Within the 17th century, there was a widespread anthrax outbreak in Europe called “black bane” where both animals and humans were infected.⁸ In 1613, it is estimated that 60,000 died due to anthrax infection.⁸ Outbreaks continued in the 18th century, where an intestinal anthrax outbreak in 1770 in Saint-Domingue (modern Haiti) killed 15,000 people.⁹

This outbreak was triggered by an earthquake that destroyed most of the cities, closing down bakeries and storehouses leaving individuals on the island with the threat of famine.⁹ At the same time, cattle were also dying off anthrax, leaving only infected meat available to the inhabitants of the island. This meant that the people of Saint-Domingue only had available uncooked contaminated beef to eat, which unfortunately led to their deaths.⁸ 

In Victorian England, inhalation anthrax was very common in mill workers and was known as woolsorters disease as the workers were exposed to spores from infected sheep's wool.⁴ Workers involved in textiles were also at risk of developing anthrax infection.⁷ 

The development of anthrax vaccines for animals decreased anthrax outbreaks. Pasteur vaccine initiated the vaccination of animals, and this decreased anthrax cases. However, some batches of the Pasteur vaccine did not successfully prevent anthrax in immunised animals.⁶ In 1939, Max Sterne, in South Africa, was able to develop a vaccine that can safely vaccinate animals, therefore preventing anthrax cases in animals and thus in humans.⁶

Response & management of historical anthrax outbreaks

Early response to anthrax outbreaks included quarantine measures where the infected animals were isolated from other animals to prevent the spread of the disease by moving animals to another site. Infected animals were also killed off and their carcasses burned in an attempt to prevent the spread of anthrax. 

Since Koch’s work in the 19th century and Louis Pastur’s vaccine, the response to anthrax outbreak has changed. Widespread vaccines were used to control outbreaks and prevent anthrax outbreaks in animals.^6,7,9 

Lessons learned from historical cases

Impact on development of microbiology and medicine

Anthrax outbreak on a farm in 1876³ inspired Koch to investigate the cause of the disease, which made anthrax the inspiration for Koch’s postulates in the transmission of infectious disease. Due to the rivalry between Koch and Pasteur, Koch’s discovery inspired Pasteur to develop a vaccine that is vital for controlling anthrax in animals and therefore protecting us from anthrax cases.⁴

Influence on public health

Historical cases of anthrax have taught us important lessons in regards to public health and to control the transmission of anthrax. This includes:⁵

• Importance of vaccinating animals and how it prevents human cases
• Early detection is vital in controlling anthrax outbreaks
• Continual surveillance is important, especially considering the threat of anthrax as a bioweapon

Summary

Anthrax is an infectious disease caused by spore-forming bacteria called Bacillus anthracis (B. anthracis). It is a zoonotic disease which means the disease can be transmitted to humans from animals like cows, goats, and sheep. Anthrax has been around for thousands of years, as far back as ancient Egypt, with the first recorded case in 1491 B.C.

Throughout the Middle Ages, anthrax remained a major problem for the population, targeting both animals and humans and remained a problem until the 19th century, when there was a breakthrough in the discovery of anthrax bacterium. 

It wasn't until the development of the anthrax vaccine that anthrax cases decreased in both humans and animals. The historical outbreaks provide us important lessons in the importance of public health whilst providing a breakthrough in medicine and microbiology.