Biological weapons, Anthrax: what is it and how is it transmitted?

By Cristiano Antonino On Dec 3, 2022

Anthrax is an acute infectious disease caused by Bacillus anthracis, a sporigenous, Gram-positive bacterium whose spores are highly resistant to the action of chemical and physical disinfectants

In nature, the disease affects various species of herbivorous animals, which become infected by ingesting spores present in the soil.

Humans can become infected through direct contact with infected animals or contaminated animal products.

The spores are very resistant in the environment, and in some types of soil they can survive for decades.

Anthrax, how it is transmitted

When used as a biological weapon, B. anthracis can be spread basically by two ways

by dissemination in the air (e.g. by aircraft similar to those used to spread agricultural herbicides), with the formation of a colourless and odourless aerosol, and therefore absolutely invisible;
by impregnation of commonly used materials and objects, such as writing paper, fabrics or textiles, in the form of a light dust.

Sources of contagion are therefore any material that is contaminated by spores, and can occur in three ways

direct skin contact
by the air, by inhaling the spores;
by the digestive route, through ingestion of contaminated food.

It is extremely important to establish the mode of transmission, as this leads to very different clinical pictures.

Human-to-human contagion does not occur, so there is no need to isolate sick persons.

Clinical pictures

The incubation period may vary, depending on the infecting dose and the mode of transmission, from 1 to 7 days; however, most cases manifest themselves within 2 to 5 days.

Clinical manifestations depend on the route of transmission. three forms of the disease can be observed:

Cutaneous anthrax

This is the most common form, observed in more than 95% of cases, and occurs by penetration of the germ spores through the skin. The most frequent sites are the hands, arms and head.

It manifests itself as a papular skin lesion, which within 24 to 48 days develops into a vesicle and then an ulcer; the lesion is usually surrounded by a large area of inflammation.

After about 2-6 days, a black eschar, usually painless, forms, which detaches within 2-3 weeks and normally leaves no scarring.

This form usually responds well to therapy, and the prognosis is good.

Inhalation anthrax

The initial symptoms may appear to be those of a common flu syndrome (fever, cough, muscle aches, general malaise), while after a few days very high fever and symptoms of severe respiratory impairment (dyspnoea, cyanosis) quickly appear.

This form has a mortality rate of practically 100%.

Ingestion anthrax

This is the rarest form of the disease.

It is secondary to eating food contaminated with spores of B. anthracis, and is characterised by an acute inflammation of the intestinal tract.

The initial symptoms are nausea, lack of appetite, vomiting and fever, which are quickly followed by the onset of very intense abdominal pain, profuse diarrhoea and gastroenteric haemorrhages (presence of blood in vomit and faeces).

Mortality is high, despite adequate antibiotic therapy.

Prevention

In the event of exposure to suspicious material, either through direct contact or inhalation, antibiotic prophylaxis can be carried out, which should be continued for a period of at least two months.

It can be discontinued if microbiological investigations carried out on the suspect material prove negative for the presence of germ spores.

A vaccine is available in the United States, which is usually only used for military personnel.

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