Anthrax: what it is, symptoms, treatment and UK risk

UKHSA describes anthrax as a rare infection caused by Bacillus anthracis, a large, spore-forming bacterium. By forming spores, the bacteria can survive in harsh conditions such as dry environments and can persist in the soil for many decades. Spores begin to grow when they reach a nutrient-rich environment, such as the tissues or blood of an animal or human.

The Department for Environment, Food and Rural Affairs (Defra) says anthrax affects mammals and some species of birds, including cattle, pigs, horses, sheep and humans. In Great Britain the previous outbreak in livestock was in 2015, and anthrax is a notifiable animal disease, which means suspected cases must be reported immediately.

Defra says anthrax is spread when its spores are inhaled, ingested, or come into contact with skin lesions. The spores can survive for decades or even centuries and are found on infected animal carcasses, wool, hair and hides. People can also be infected by drinking contaminated milk.

UKHSA says anthrax in humans is very rare in the UK and has largely been associated with imported contaminated animal products. The most significant UK outbreak in humans was of injectional anthrax in 2009 to 2012, associated with the use of contaminated heroin.

UKHSA says the clinical picture and incubation period depend on the route of infection. Defra summarises the risk to humans: symptoms begin with a flu-like illness, then followed by respiratory difficulties, and direct contact can cause raised boil-like lesions on the skin that develop a black centre.

UKHSA says anthrax is treated with commonly used antibiotics, but it is really important that they are given as soon as possible. Cutaneous anthrax is often treated with tablets, but other types need admission to hospital for intravenous antibiotics and other supportive treatment. A combination of antibacterial drugs is usually used, and suitable drugs include amoxicillin, clindamycin, doxycycline and ciprofloxacin.

For anthrax related to injection of drugs into the muscle, surgical removal of the affected area may be required to control the source of infection and prevent fatal systemic disease. Defra says the skin form normally responds to early treatment with antibiotics.

UKHSA says there is no person-to-person transmission of anthrax. People catch it from spores in animal products, contaminated drugs or the environment, not from another person with the disease.

Laboratories handle samples carefully because the bacterium is classed as a hazard group 3 organism, and UKHSA says potentially infectious material should be handled in containment level 3 conditions. This is a laboratory safety matter and does not mean the infection spreads between people.

UKHSA says that if there is a known exposure, giving antibiotics before illness develops (prophylaxis) can prevent severe infection, and that post-exposure prophylaxis with antibiotics is recommended for people without symptoms who have a convincing exposure history. If you think you have been exposed, seek medical advice urgently, because antibiotics work best when started early.

An anthrax vaccine is available to people in high-risk specialist roles. The Green Book chapter is written for public health professionals and describes immunisation, including advice on booster doses for occupational groups. For livestock keepers, Defra advises talking to your vet before moving or disposing of carcasses after a sudden or unexplained death, practising strict biosecurity and not moving, skinning or opening the carcass of any suspect animal.

UKHSA says testing for Bacillus anthracis requires isolation of the bacteria or spores in a clinical sample, which can be blood, a skin lesion swab, cerebrospinal fluid or respiratory secretions. Tests such as PCR (a DNA test) can be done on specimens or cultured colonies, and testing is available at the Rare and Imported Pathogens Laboratory.

UKHSA says clinicians can contact the Imported Fever Service if there are concerns about a suspected case.

UKHSA stresses that antibiotics must be given as soon as possible, so anyone with these symptoms after possible exposure should seek urgent medical advice (NHS 111, or 999 if very unwell or struggling to breathe) and tell the clinician about the exposure. The features to look out for are a black-centred skin ulcer or boil-like lesion after contact with animal products, a flu-like illness followed by breathing difficulty, bloody diarrhoea with abdominal pain after eating suspect meat, or a swollen, painful injection site after injecting drugs.

Defra describes the progression of inhalation anthrax as a flu-like illness followed by respiratory difficulties, which is why early assessment matters.

Anthrax is so rare in the UK that there is no routine patient pathway. UKHSA says testing is available at its Rare and Imported Pathogens Laboratory and that clinicians can contact the Imported Fever Service about a suspected case, and the treatments it describes, intravenous antibiotics and supportive care, are given in hospital. For exposure through work with animals or animal products, occupational health and the local health protection team can advise on vaccination and antibiotics.