Anthrax

Anthrax is a zoonotic disease that occurs on all continents throughout the world and can cause high mortality among domestic and wild herbivores. It can be passed on to humans and carnivores. Outbreaks continue to be reported from many countries worldwide, specifically where livestock vaccination programmes are inadequate or have been disrupted. Humans generally acquire the disease directly or indirectly from infected animals, or through occupational exposure to infected or contaminated animal products. Anthrax is a seasonal disease and its incidence is related to temperature, rains or drought, although conditions that predispose to outbreaks vary from one area to another. A One Health approach including animal, environmental and human health is essential to prevent anthrax outbreaks.

The following are standard case definitions to allow national health authorities to interpret data in an international context. However, during an outbreak case definitions may be adapted to the local context and the Red Cross Red Crescent should use those agreed/established by national health authorities. NB: Consider that during community-based surveillance, volunteers should use broad (simplified) case definitions (referred to as community case definitions) to recognize most or all possible cases, provide relevant risk communication and appropriate actions and encourage them to seek care. Other actors such as healthcare workers or investigators studying the cause of a disease, on the other hand, can use more specific case definitions that may require laboratory confirmation.

As with other zoonotic diseases, control of anthrax among humans is highly dependent on the integration of the human health and veterinary surveillance and control systems. The following include case definitions for human surveillance and exclude case definitions for veterinary surveillance. For more information on veterinary surveillance or clinical presentations, please visit OIE’s page on anthrax.

Clinical description: An illness with acute onset characterized by several clinical forms 

• Cutaneous: skin lesion evolving over two to six days from small bumps or blisters, evolving to black skin lesions/ulcer accompanied by oedema (typically painless skin sores)
• Gastrointestinal: abdominal distress characterized by nausea, vomiting, loss of appetite and followed by fever. Additional symptoms can include sore throat, hoarseness, painful swallowing, or watery or bloody diarrhoea
• Pulmonary (inhalation): brief prodrome resembling acute viral respiratory illness, followed by rapid onset of low level of oxygen in the blood, difficulty breathing and high temperature, with X-ray typical evidence
• Meningeal: acute onset of high fever possibly with convulsions and loss of consciousness, meningeal signs and symptoms

Suspected case: A case that is compatible with the clinical description and has an epidemiological link to confirmed or suspected animal cases or contaminated animal products.

Probable case: A suspected case that has a positive reaction to allergic skin test (in non-vaccinated individuals).

Confirmed case: A suspected case that is laboratory-confirmed.

WHO case definition source of information: https://www.who.int

• People who work with animals (farmers, veterinarians, livestock breeders) or animal products such as wool, hides or hair (butchers, weavers).
• People who eat raw or undercooked meat from infected animals.
• People who inject drugs.
• People living in known anthrax endemic areas with low vaccination rates among livestock, and/or lack of infection prevention and control measures during and after a known outbreak are at higher risk.
• Communities where opening dead animal carcasses (including after unusual illness) is common practice as exposure to oxygen allows the bacteria to form spores.

Attack rates will vary from one outbreak to another. In case of an outbreak, consult the latest information provided by health authorities.

Generally low and depends on the type of exposure.

• People with gastrointestinal and pulmonary anthrax have an increased risk of severe illness and poorer prognosis.
• Older people.
• People with weakened immune systems.
• Immunosuppressed persons such as those receiving chemotherapy, transplant recipients or HIV carriers.
• People with chronic diseases such as renal disease, cancer, chronic lung or liver disease and diabetes.

Bacillus anthracis (bacterium). When conditions are not conducive to growth and multiplication of the bacilli, they tend to form spores able to outlast many years and resistant to heat and usual disinfection. Within the infected host the spores germinate to produce the vegetative forms which multiply, eventually killing the host.

Zoonotic disease: domestic and wild animals such as cattle, sheep, goat, antelope and deer. Animals typically become infected when they ingest or inhale the bacterial spores present in the soil where they are feeding. Carnivores or humans can also (more rarely) become infected by eating meat from infected animals. Insects can spread the bacteria to other animals.

People get infected with anthrax when spores get into the body. This can happen via:

• Airborne spread: People breathe in spores (pulmonary anthrax).
• Vehicle-borne transmission: Animals may become infected by eating contaminated feedstuff, or inhaling/ingesting spores from the soil as they feed. Humans may be infected by eating food or drinking water that is contaminated with spores or when injecting drugs. Carcasses pose a risk both to humans and animals through their meat, hides, hair, wool or bones.
• Contact transmission: Getting spores in a cut or scrape in the skin (cutaneous anthrax).

The disease is generally regarded as being non-contagious as human-to-human infection is rare (cutaneous anthrax only).

One to seven days but can be as short as a few hours and as long as several weeks (or up to two months for inhaled anthrax) depending on the transmission pathway.

Humans are not infectious.

• Cutaneous or skin anthrax is the most common form. It is usually contracted when a person with a break in their skin, such as a cut or abrasion, comes into direct contact with anthrax spores (including through injection). The resulting itchy bump rapidly develops into a black sore. Some people can then develop headaches, muscle aches, fever and vomiting. Cutaneous anthrax must be treated quickly. Appropriate medical evaluation and treatment are essential. Without treatment cutaneous anthrax has a mortality rate up to 20 per cent, but with proper treatment is reduced to under two per cent.
• Gastrointestinal anthrax is caught from eating meat from an infected animal. It causes initial symptoms similar to food poisoning but these can worsen to produce severe abdominal pain, vomiting of blood and severe diarrhoea. Without treatment more than 50 per cent of those infected with gastrointestinal anthrax die. Appropriate medical evaluation and treatment are essential to reducing mortality.
• The most severe form of human anthrax is called inhalation or pulmonary anthrax. This form of the disease is caused when a person is directly exposed to a large number of anthrax spores suspended in the air, and breathes them in. The first symptoms are similar to those of a common cold, but this can rapidly progress to severe breathing difficulties and shock. Appropriate medical evaluation and treatment are essential. Without treatment inhalation or pulmonary anthrax is almost always fatal. With proper treatment mortality is reduced to approximately 50 per cent.
• Meningeal anthrax can occur in rare cases when the bacteria passes the blood-brain barrier and affect the central nervous system. Clinical signs and symptoms include neck pain, headache, changes in mental state, vomiting and high fever. Meningeal anthrax infections are very dangerous with fatality rates of over 90 per cent.

Boil (early lesion), arachnid bites, ulcer (especially tropical); erysipelas, glanders, plague, syphilitic chancre, ulceroglandular tularaemia; clostridial infection; rickettsial diseases; orf disease, vaccinia and cowpox, rat bite fever, leishmaniasis, diphtheria, tonsillitis, streptococcal angina, food poisoning, acute abdomen, pneumonia.

• Demonstration of Bacillus anthracis in a clinical specimen by microscopic examination of stained smears of vesicular fluid, blood, cerebrospinal fluid, pleural fluid, stools, etc.
• Isolation of B. anthracis from a clinical specimen (e.g. blood, lesions, discharges).
• Positive serology (Enzyme linked immune-sorbent assay (ELISA), Western blot, toxin detection, chromatographic assay, fluorescent antibody test (FAT)).
• Polymerase chain reaction (PCR).

Please refer to the appropriate local or international guidelines for clinical management. All clinical management including the administration of a treatment or vaccine should be conducted by a health professional.

• All types of anthrax can be prevented and treated with antibiotics.
• There is a vaccine licensed to prevent anthrax, but it is only recommended for routine use in certain groups of at-risk adults.

Anthrax infection results in long-term immunity.