Overview

Anthrax is a rare infectious disease caused by a spore-forming bacteria called bacillus anthracis.¹ This bacterium is naturally found in soil worldwide and most commonly affects livestock and wild animals but can be passed to humans through direct contact with contaminated animals or animal products. Anthrax spores can enter the body by breathing them in, eating food or water that is contaminated or through cuts and scrapes in the skin. 

Anthrax is preventable with the use of vaccines and can be treated with antibiotics. There are specific control measures that are necessary to control the spread of the disease, such as proper disposal of infected animal carcasses, quarantining and treatment of diseased livestock, adequate cleaning, and disinfection of the premises.⁴

Types of anthrax 

There are four types of illness caused by anthrax characterised by how the spores have entered the body: skin, lungs, or gastrointestinal system.¹ All types of anthrax are serious and can be fatal if left untreated. 

Cutaneous anthrax 

Anthrax spores can enter the skin through cuts and scrapes when someone handles an infected animal or contaminated animal products, such as wool or hides. This type most commonly presents on the hands and forearms but can also affect the head and neck. Cutaneous anthrax is the most common type of anthrax infection and is thought to be the least dangerous, however every form of anthrax infection should be treated with antibiotics as soon as possible.

Inhalation anthrax

This type of anthrax infection occurs when the anthrax spores are breathed in. It is regarded as the deadliest form due to how quickly it can spread throughout the body, beginning in the lymph nodes and circulating to the rest of the body. 

Gastrointestinal anthrax

Anthrax spores can enter the gastrointestinal tract by the consumption of raw or undercooked contaminated meat, causing nausea, vomiting and severe diarrhoea in the later stages of infection. The anthrax spores can cause lesions and ulcerations in the throat and intestines.²

Injection anthrax

This form of anthrax is similar to cutaneous anthrax as the anthrax spores enter the body through the skin and cause infection deep under the skin or in the muscle after injection.³ Injection anthrax is a very uncommon form of anthrax-related illness and has only been found in drug users.

Anthrax and the health of the public

Anthrax was the first infectious disease known to be caused by bacteria and has now been researched for over 150 years,⁵ leading to characterisation as both a human and animal disease. Anthrax bacteria naturally occurs in soil and the spores can remain in the environment for a number of years⁶, it is thought to be a seasonal disease with higher instances of contraction taking place during dry spells and droughts. The human form of anthrax is uncommon in Western countries where the rates of animal anthrax are low. Cases of human anthrax are highest in Africa, Asia and the Middle East, possibly due to the higher temperatures and dry land causing a high number of animals to be infected with anthrax bacteria. 

Anthrax spores have been used as a biological weapon in the past, which is where anthrax has gained fear from the general public. It is speculated that humans are naturally resistant to anthrax bacteria to an extent and that an obscenely large dose is required for infection to take place.⁷ Anthrax poses the biggest risk to public health in the context of biological warfare. For example,s the anthrax postal attack in the United States of America, in 2001, occurred when a massive dose (millions of spores) was artificially created in an act of bioterrorism.

Surveillance of anthrax cases

Surveillance of anthrax collects, collates and analyses health data in order to put together a prevention and control protocol. This requires established veterinarians, health care professionals and laboratory scientists to detect and diagnose the disease, along with aid from the general public to report new cases of anthrax. Because anthrax was used in a bioterrorism attack, it has been placed on a national notifiable disease list and all cases, animal or human, should be reported. 

The use of a surveillance system is put in place to reduce the loss of livestock and reduce the risk of human disease. Detection and successful reporting of cases should be immediately followed up with a system to control the disease, such as appropriate storing and disposal of animal carcasses, vaccination, and treatment. Local health authorities are required to investigate, identify and control the outbreak by determining the source of infection and acting appropriately to reduce the morbidity and mortality of the population.⁸

There are diagnostic techniques carried out in laboratory testing to confirm the presence of anthrax, such as: 

• Isolating bacillus anthracis from a specimen (animal or human) by collecting tissue from an affected site
• Blood samples

How is anthrax prevented?

There are vaccinations available to prevent anthrax -these can be used in both humans and animals. Anthrax vaccination in humans is typically offered when at risk of inhalation anthrax and should be offered as 3 doses, with a follow-up booster dose after 6 months. 

Anthrax in livestock is controlled by the use of vaccination programs, providing the livestock with a live strain of bacillus anthracis to build up their immunity. This method has been in use since 1939.⁹ 

There are specific control measures put in place for those who handle livestock that are especially important in controlling the spread of infection, such as: 

• All animals should be quarantined until all animals are vaccinated and infected carcasses are disposed of by incineration
• Carcasses should not be opened, as this will allow the bacteria to become spores when coming into contact with oxygen
• Clean and disinfect the premises to prevent rodents and pests from contracting and carrying the disease

Vaccination is very important in areas where anthrax rates are typically high even if rates fall, it is beneficial to continue vaccinating livestock due to the long life of anthrax spores. 

Summary

Anthrax is a rare disease caused by the spore-like bacterium bacillus anthracis It most commonly affects livestock but can be spread to humans through the consumption of contaminated meat, handling of wool or hides or via inhalation of anthrax spores. Anthrax spores can enter the body in four different ways -cutaneous, gastrointestinal, inhalation and injection. Anthrax bacteria naturally occurs in the soil worldwide and is thought to be worst in hot, dry countries where the soil is dry and dusty. It is also considered to be a seasonal disease due to these qualities. 

In the past, anthrax has been used as a biological weapon where items have been purposefully contaminated with large quantities of anthrax spores, posing a threat to not only specific individuals but the health of the public. Whilst anthrax can be a fatal disease, it is typically rare and uncommon for people in western countries to contract it. There have since been appropriate surveillance and control methods put in place to report and record outbreaks of anthrax in communities, with local health authorities being required to investigate and control the source of infection, by implementing the quarantining and treatment of susceptible animals, along with the appropriate disposal of contaminated animal carcasses. Diagnosis of anthrax is carried out in a laboratory by isolating bacillus anthracis from affected tissue from an animal or human specimen, or via a blood test. Trained veterinarians can diagnose anthrax in animals by some telltale signs, such as fever, convulsions, bleeding from orifices and sudden death. 

Prevention of anthrax relies on veterinary intervention of vaccinations for livestock in locations of high anthrax cases, although vaccinations should be continued even when cases drop It is highly important for individuals with close proximity to livestock or industrial settings, where they may come into frequent contact with animal products (meat, hides, etc.), to be aware of anthrax and report any instances of the disease to the appropriate authorities.