Scotland’s Anthrax Island

Howard Fischer
Uppsala, Sweden


Graphic anthrax lesion predating Anthrax Island
Cutaneous anthrax lesion on the neck, May 25, 1953. Centers for Disease Control and Prevention Public Health Image Library. Via Wikimedia. Public domain.

“They make a desolation and call it peace.”
— Agha Shahid Ali (1949–2001)


During World War Two, the British government purchased from its owners the Gruinard Island, a one by two km island off the Scottish coast. The one inhabitant was evicted, and the island became the site of secret tests to weaponize anthrax spores.1

Anthrax is a disease known since antiquity. Of the ten plagues of Egypt mentioned in the Old Testament, it has been proposed2,3,4 that the sixth plague, an outbreak of “festering boils…on men and animals” (Exodus 9:8-9) might have been anthrax. However, this idea is not universally accepted.5 Anthrax means “coal” in Greek, and the lesions of cutaneous anthrax are black as coal. The disease is caused by a bacterium, Bacillus anthracis, which under unfavorable conditions transforms itself into a spore with a hard outer capsule of protein. This spore can remain dormant in the soil for centuries, can withstand ten minutes of boiling, and survive dry heat of 140° C for three hours.6 It is not affected by visible or ultraviolet light,7 nor by some noxious chemicals. The “danger and durability of anthrax spores”8 makes anthrax, unfortunately, “God’s gift to germ warfare.”9

Humans may develop four different forms of anthrax: cutaneous, inhalational, ingestional (oro-pharyngeal or intestinal), and injectional. Cutaneous anthrax is the most common infection (95% of cases) in humans. It is contracted by contact with the wool, hair, or hide of infected animals. The spores enter the skin through cuts or abrasions. After one to five days incubation, a rash forms and develops characteristic black scabs. Without treatment, mortality rate is about 20%.10,11

Inhalational anthrax is the rarest manifestation of anthrax (about 1% of cases), but it has a 50% mortality rate even with appropriate, aggressive treatment. The illness is biphasic. First, the patient has fever, cough, malaise, sweating, and sometimes a feeling of pressure in the chest. It is often thought to be a simple upper respiratory tract infection. This phase lasts from one to several days. The second phase of anthrax pneumonia is marked by shortness of breath, cyanosis, pleural effusion, and rales on chest auscultation. This phase may end in death within twenty-four hours.12

Ingestional anthrax (1-2% of infections) may produce neck swelling, hoarseness, and facial flushing (oro-pharyngeal infection), or fever, abdominal pain, diarrhea, and vomiting (in a gastro-intestinal infection). The source of the infection is undercooked infected meat. Mortality is about 40% with treatment.13,14

Users of heroin have been infected by injection of anthrax-contaminated heroin. They develop fever, chills, and lesions at the injection site.15

Gruinyard Island was the site of testing of weaponized anthrax spores in 1942. Sheep were used as test animals, since they weigh about as much as humans, are very susceptible to anthrax infection, and were available in large numbers. They were placed in individual crates with their heads exposed and the rest of the body covered with canvas. They were not near the sheep in neighboring crates. These precautions were to prevent skin infection or ingestion of anthrax spores. A bomb containing anthrax spores was detonated on a framework at a height of four feet. The animals began to die on the third day. All but two of the fifteen sheep used in this first experiment died. Blood smears and necropsies were performed (“autopsies” are only performed on humans), which confirmed anthrax as the cause of death. Repeated experiments showed the same results. An anthrax bomb dropped from a plane produced the same effect.16

The British military had plans to drop anthrax-contaminated cattle feed on six German cities if the British position looked desperate. They did not, however, have enough spores for this attack, and the US could not produce enough until mid-1945.17 By then the war in Europe had ended.

It is not necessary to inhale many spores to develop anthrax. The LD50 (the dose of a substance that is lethal to one-half of the individuals exposed) for anthrax spores is 8,000 to 10,000.18 This is not very much.

Attempts to decontaminate Gruinard Island started before the end of the war. In 1943 the island was set on fire. When soil samples were taken afterward, there were still many spores in the soil.19 The government decided to quarantine the island permanently. Periodic soil sampling showed persistent contamination. In 1981 a group calling itself “Operation Dark Harvest” sent messages to British news agencies that they had collected 300 pounds of soil from Gruinard Island and sent it to the laboratory that was the successor of the organization that did the 1942–3 experiments. The soil still contained anthrax spores.20 The public reaction was such that the government felt compelled to decontaminate the island.

Luckily, there had been a successful decontamination of a factory in the US that could be used as a model for their approach. In 1957, a textile mill in the state of New Hampshire was contaminated by anthrax spores in a shipment of goat hair from Pakistan. After trying various techniques, formaldehyde, which has powerful germicidal qualities, was vaporized to decontaminate the building.

Decontamination of Gruinard Island started in 1986. First the island was sprayed with an herbicide, then the dead vegetation was burned. Next, a system of “irrigation” was built on the island, through which 5% formaldehyde in seawater was pumped. Every square meter of soil received fifty liters of this solution over two months. On re-testing, some spores were still found, and the treatment was repeated in 1987. The island had received, in total, 280 tons of formaldehyde in 2000 tons of seawater. The island was declared safe in 1990, and the quarantine was ended.21 The decontamination cost $1.8 million in today’s money (0.5 million pounds sterling in 1986).22

Anthrax infection is treated with antibiotics. In addition, there is an anthrax vaccine for use in animals, which was developed by Pasteur in 1881.23 An acellular anthrax vaccine is used in humans.24

In 2011, researchers from the Russian Academy of Science noted that the temperature of the surface of the Siberian permafrost was increasing. Since millions of anthrax-infected reindeer were buried there, some as recently as 1925, they wondered if the thawing would lead to “the release of viable anthrax organisms.”25

They were right.26



  1. Ed Regis. The Biology of Doom. New York: Henry Holt and Company, 1999.
  2. Sarah O’Donohue. “Anthrax: real threat or useful scare tactic?” Vanderbilt Undergraduate Research Journal, 5(1), 2009.
  3. Mehmet Dogany and Hayati Demiraslan. “Human anthrax as a re-emerging disease,” Recent Patents in Anti-infective Drug Discovery, 10, 2015.
  4. NA. “Biological warfare: Dark Harvest,” Time, 19 Nov 1981.
  5. Margaret Lloyd Davies and Trevor Lloyd Davies. The Bible: Medicine and Myth, Cambridge: Silent Books, 1991.
  6. Joanne Thwaite and Helen Adkins. “Bacillus: Anthrax,” In Medical Microbiology (18th ed), Daniel Greenwood, Richard Slack, Mike Barer, et al (eds), London: Churchill Livingstone, 2012.
  7. Dogany. “Human anthrax.”
  8. Leonard Cole. The Anthrax Letters: A Medical Detective Story, Washington, D.C.: Joseph Henry Press, 2003.
  9. Regis. “Doom.”
  10. NA. Anthrax, Centers for Disease Control, ND.
  11. O’Donohue. “Real threat.”
  12. Sheldon Campbell. “Anthrax is a bio-war environment,” 1990.
  13. O’Donohue. “Real threat.”
  14. CDC, “Anthrax.”
  15. CDC, “Anthrax.”
  16. Regis. “Doom.”
  17. Julian Lewis. “The plan that never was: Churchill and the anthrax bomb,” Encounter, 1982.
  18. Dogany. “Human anthrax.”
  19. Regis. “Doom.”
  20. Gruinard Island. Wikipedia.
  21. Cole. “Letters.”
  22. Kate Aaron. “Operation dark harvest: The story of Scotland’s ‘Anthrax Island’,” History of Yesterday, 2021.
  23. Regis. “Doom.”
  24. Thwaite. “Bacillus.”
  25. Boris Revisch and Marina Podolnaya. “Thawing of the permafrost may disturb historic cattle burial ground in East Siberia,” Global Health Action, 4, 2011.
  26. Alec Luhin. “Anthrax outbreak triggered by climate change kills boy in the Arctic Circle,” Guardian, 1 Aug 2016.

There is a now-declassified film, “Gruinard Island X-Base Anthrax Trials 1942-43,” eighteen minutes long, on YouTube. It shows some parts of the first anthrax experiment.



HOWARD FISCHER, M.D., was a professor of pediatrics at Wayne State University School of Medicine, Detroit, Michigan.


Winter 2022  |  Sections  |  Infectious Diseases