Threat of anthrax today is through a bioterrorist attack.
Anthrax is an infection caused by the bacterium Bacillus anthracis. It can occur in four forms: skin, lungs, intestinal, and injection.Symptoms begin between one day and two months after the infection is contracted. The skin form presents with a small blister with surrounding swelling that often turns into a painless ulcer with a black center. The inhalation form presents with fever, chest pain, and shortness of breath. The intestinal form presents with diarrhea which may contain blood, abdominal pains, and nausea and vomiting. The injection form presents with fever and an abscess at the site of drug injection.
Anthrax is spread by contact with the bacterium's spores, which often appear in infectious animal products. Contact is by breathing, eating, or through an area of broken skin. It does not typically spread directly between people. Risk factors include people who work with animals or animal products, travelers, postal workers, and military personnel. Diagnosis can be confirmed based on finding antibodies or the toxin in the blood or by culture of a sample from the infected site.
Cutaneous anthrax, also known as hide-porter's disease, is when anthrax occurs on the skin. It is the most common form (>90% of anthrax cases). It is also the least dangerous form (low mortality with treatment, 20% mortality without). Cutaneous anthrax presents as a boil-like skin lesion that eventually forms an ulcer with a black center (eschar). The black eschar often shows up as a large, painless, necrotic ulcer (beginning as an irritating and itchy skin lesion or blister that is dark and usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection. In general, cutaneous infections form within the site of spore penetration between two and five days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain. Nearby lymph nodes may become infected, reddened, swollen, and painful. A scab forms over the lesion soon, and falls off in a few weeks. Complete recovery may take longer.
Bacillus anthracis is a rod-shaped, Gram-positive, facultative anaerobic bacterium about 1 by 9 μm in size. It was shown to cause disease by Robert Koch in 1876 when he took a blood sample from an infected cow, isolated the bacteria, and put them into a mouse. The bacterium normally rests in spore form in the soil, and can survive for decades in this state. Herbivores are often infected whilst grazing, especially when eating rough, irritant, or spiky vegetation; the vegetation has been hypothesized to cause wounds within the GI tract, permitting entry of the bacterial spores into the tissues, though this has not been proven. The production of two powerful exotoxins and lethal toxin by the bacteria causes death. Veterinarians can often tell a possible anthrax-induced death by its sudden occurrence, and by the dark, nonclotting blood that oozes from the body orifices. Most anthrax bacteria inside the body after death are outcompeted and destroyed by anaerobic bacteria within minutes to hours post mortem. However, anthrax vegetative bacteria that escape the body via oozing blood or through the opening of the carcass may form hardy spores. These vegetative bacteria are not contagious.
Occupational exposure to infected animals or their products (such as skin, wool, and meat) is the usual pathway of exposure for humans. Workers who are exposed to dead animals and animal products are at the highest risk, especially in countries where anthrax is more common. Anthrax in livestock grazing on open range where they mix with wild animals still occasionally occurs in the United States and elsewhere. Many workers who deal with wool and animal hides are routinely exposed to low levels of anthrax spores, but most exposure levels are not sufficient to develop anthrax infections. A lethal infection is reported to result from inhalation of about 10,000–20,000 spores, though this dose varies among host species.
Journal of Bioterrorism & Biodefence,