Anthrax, an ancient and resilient bacterial infection, continues to captivate scientists and health professionals due to its unique survival mechanisms and deadly potential. Caused by the Bacillus anthracis bacterium, anthrax can lie dormant in the environment for decades until it finds a host in humans or animals, where it rapidly activates and multiplies. While often linked to those working with animal products, anthrax poses broader risks, notably through its potential for use in biological warfare. This article explores the nature of anthrax, its modes of transmission, and the ongoing threats posed by both natural outbreaks and weaponized strains.
Anthrax is a bacterial infection caused by Bacillus anthracis, a Gram-positive bacterium. Identified in 1875 by Robert Koch, anthrax was named after the ancient Greek word for coal, derived from the jet-black lesions found on infected skin. Often appearing in infected animal products, anthrax (also known as Hide Porter or Woolsorter’s disease) is spread by contact with the bacterial spores through inhalation, ingestion or through a skin abrasion or injection site. Anthrax does not typically spread directly between people but many workers who deal with wool and animal hides are routinely exposed to low levels of anthrax spores, although most exposure levels are not sufficient to develop infections. However, vaccination is available for those who are at high risk and immunization of animals is also recommended in areas where previous outbreaks have occurred.
Although a rare disease, human anthrax occurs mostly in Africa, Asia, and Southern Europe with around 2000 cases occurring annually. The disease is uncommon in Northern Europe and North America. Of the several types of anthrax, the cutaneous form is the most common, occurring in greater than 90% of all anthrax cases. This form presents as a boil-like lesion that eventually forms an ulcer with a black center (Figure 1). However, cutaneous anthrax is the least dangerous form with a low mortality if treated but increases up to 20% mortality if left untreated.
Figure 1. Cutaneous anthrax showing an ulcer with a coal black center
Respiratory anthrax is rare but has a higher mortality even when treated. In respiratory disease, the lymph nodes in the chest become infected first before spreading to the alveoli in the lungs (Figure 2). Symptoms include high fever, extreme shortage of breath and rapid death occurring within days in fatal cases. Ingesting anthrax spores through the consumption of infected meat causes gastrointestinal infection and this is the rarest form of anthrax. Lesions can be found in the intestines and in the mouth and throat of those infected. The bacterium can spread to the bloodstream and throughout the body while continuing to make toxins. These infections can be treated, but usually result in fatality rates of up to 60%, depending upon how soon treatment commences.
Figure 2. Respiratory anthrax affects the lymph nodes and the alveoli of the lung
Anthrax and biological warfare
Historically, anthrax spores have been used as a weapon of war and as far back as 1916, it was reported that Nordic rebels in Finland used anthrax against the Imperial Russian Army. During the 1930s, anthrax was tested by the Japanese and involved intentional infection of prisoners of war with thousands of them dying as a result. During the Second World War, the Vollum strain of anthrax was developed as a biological weapon and used during the British bioweapons trial of 1942 that took place on the Scottish island of Gruinard (Figure 3). The island only become safe in 1990 following decontamination by the Ministry of Defense. Although it had been used to develop vaccines, the Vollum strain is still highly dangerous and is thought to have been the strain in possession of the Iraqi government during the Gulf war.
Figure 3. Gruinard Island located off the northwest coast of Scotland
In modern times, many countries have signed the treaty of the Biological Weapons Convention banning the production, development, and stockpiling of toxic weapons. However, despite signing the 1972 agreement, the Soviet government had an active program and as a result of an accidental release of anthrax from a biological weapons complex near Sverdlovsk in 1979, many people died. A ‘battle strain’ of anthrax was also later developed by a former Soviet bioweapons designer. Known as Strain 836, it was reported as being the most virulent and vicious strain of anthrax known to man.
However, one strain that has probably received the most news coverage is the virulent Ames strain. This strain was used in the 2001 anthrax attacks in the United States that occurred within weeks of the disaster on September 11th at the World Trade Centre. In this attack, seven letters containing the Ames strain of anthrax were sent to several media outlets and politicians. Five people died and 22 more were infected as a result. Years later, the US Department of Justice proclaimed that Bruce Ivins, a senior biodefence researcher employed by the United States government was the perpetrator. More recently, in May 2015, the Pentagon acknowledged that samples of live anthrax of the Ames strain had been sent from a laboratory in Utah to another in Maryland. The samples were eventually distributed to laboratories in every US state as well as to several countries overseas. Although no deaths or serious illnesses were reported in shipping the anthrax samples to laboratories for testing, many civilians and military personnel were treated with antibiotics as a precaution. In the US, the virulent Ames strain is used as the gold standard in the development and testing of anthrax vaccines.
Since anthrax infections are difficult to control, outbreaks can be very difficult to predict. Occupational anthrax infections may be found in butchers, farmers and veterinarians who are more likely to come in contact with or handle infected animals or carcasses. Industrial exposure may also lead to inhalation of the spores from aerosols produced in the processing of animal hides, hair and wool. Laboratory workers too, are also at risk when testing samples that are known to be infected. Nevertheless, the use of anthrax spores to intentionally cause human suffering has heightened the awareness of it. If recognized early, cutaneous anthrax is readily treatable with antibiotics. However, anthrax disease caused by inhalation or ingestion are associated with a high mortality rate even with appropriate antibiotics and modern supportive care.
Anthrax remains a serious, though rare, health threat worldwide. With effective early detection and treatment, certain types of anthrax infections are manageable, though respiratory and gastrointestinal infections still pose significant mortality risks. Furthermore, its history as a bioweapon serves as a potent reminder of anthrax’s dangerous potential when harnessed with harmful intent. The heightened awareness and continued development of vaccines underscore the importance of vigilance in managing and controlling this ancient disease.
Further reading
https://www.cdc.gov/anthrax/
https://www.cdc.gov/anthrax/bioterrorism/index.html
https://www.mayoclinic.org/diseases-conditions/anthrax/symptoms-causes/syc-20356203
https://en.wikipedia.org/wiki/Gruinard_Island
Dr. Phil Bryant
Wales, UK
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