Different Forms of Anthrax Infection

There are three forms of anthrax that affects humans: cutaneous anthrax, gastrointestinal anthrax, and inhalational or pulmonary anthrax, all of which differ in their mode of entrance to the human body.

Cutaneous Anthrax

A person may acquire cutaneous anthrax if his skin comes into contact with anything that contains Bacillus anthracis endospores. Ninety percent of reported anthrax cases are cutaneous anthrax. If endospores enter wounds in the skin they can germinate into active vegetative bacterial cells, resulting in the formation of small bumps or round protuberances on the skin. The small bumps grow into vesicles which eventually rupture and create a depressed, ulcerated region that is enclosed by a dark scab. (Note that the word “anthrax” is derived from the Greek word for coal.) Most often, bacteria do not enter the bloodstream and the patient experiences only fever and a feeling of discomfort. But if the bacteria entered the bloodstream and the appropriate antibiotic is not administered, there is a 20% probability that the patient will die. The probability decreases to 1% if the patient takes the needed antibiotic (Madigan 2006; Talaro 2008).

Gastrointestinal Anthrax

An individual may get gastrointestinal anthrax by eating poorly-cooked food (e.g. meat and poultry products) that contain B. anthracis spores. A patient having this form of anthrax experiences “nausea, abdominal pain, and bloody diarrhea.” Once the bacteria enters the gastrointestinal tract, they create ulcerative lesions in areas of the mouth, the throat and the esophagus; although the bacteria create more damage to the small intestine (producing symptoms which include bloody diarrhea). People with this form of anthrax have a 50% probability of survival (Madigan 2006; Talaro 2008).

Inhalational Anthrax

Also called pulmonary anthrax, this form of anthrax is considered by scientists as the most dangerous and most deathly. People will get anthrax once they inhale endospores floating in the air. This is the preferred method of terrorists in inflicting anthrax disease to their targets because the incubation period of the infection is less than cutaneous and gastrointestinal anthrax. The incubation period is less because the anthrax endospores immediately enter the bloodstream once they reach the lungs. The endospores germinate in the blood and reproduce at an exponential rate; the increase in the amount of toxins produced is also exponential.

The initial symptoms are usually not alarming (mild fever, coughing, and chest pain) and doctors may not immediately suspect anthrax. If the patient takes antibiotics, the progression of the disease stops. However, there are instances that antibiotics are not immediately administered if the doctor’s diagnosis is incorrect; it is already too late when antibiotics are given and the patient is dying due to extreme septic shock. The mortality rate for pulmonary anthrax is extraordinarily high - almost one hundred percent (Madigan 2006; Talaro 2008).

References:

Madigan, Michael. 2006. Brock Biology of Microorganisms. Upper Saddle River, N.J. : Prentice Hall/Pearson Education.

Talaro, Kathleen. 2008_. Foundations in microbiology: basic principles_. Boston: McGraw-Hill Higher Education.