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Exposure to Anthrax

The usual pathway of exposure of anthrax for humans is occupational exposure to infected animals or their products. Workers exposed to dead animals or 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.

The last fatal case of natural inhalational anthrax in the United States occurred in California in 1976, when a home weaver died after working with infected wool imported from Pakistan.1

In November 2008, a drum maker in the United Kingdom who worked with untreated animal skins became the latest person to die from anthrax.2

Anthrax mode of infection

Anthrax can enter the human body through ingestion (intestines), inhalation (lungs), or cutaneously (skin) and causes distinct clinical symptoms based on its site of entry. An infected human will usually be quarantined. However, anthrax does not usually spread from an infected human to a noninfected human. However if the disease is fatal the deceased person’s body and its mass of anthrax bacilli becomes a potential source of infection to others. Special precautions should be used to prevent further contamination. Inhalational anthrax, if left untreated until obvious symptoms occur, may be fatal.

Anthrax can be contracted in laboratory accidents or by handling infected animals or their wool or hides. It has also been used in biological warfare agents by terrorists to intentionally infect humans, as occurred in, for example, the 2001 anthrax attacks in the United States.

Cutaneous (skin) anthrax

Cutaneous (on the skin) anthrax infection in humans shows up 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. Cutaneous infections generally form within the site of spore penetration between 2 and 5 days after exposure. Unlike bruises or most other lesions, cutaneous anthrax infections normally do not cause pain.3

Cutaneous anthrax is rarely fatal if treated,4 but without treatment about 20% of cutaneous skin infection cases progress to toxemia and death.

Gastrointestinal (gastroenteric) anthrax

Gastrointestinal infection in humans is most often caused by eating anthrax-infected meat and is characterized by serious gastrointestinal difficulty such as vomiting of blood, severe diarrhea, acute inflammation of the intestinal tract, and loss of appetite. Some lesions have been found in the intestines and in the mouth and throat. After the bacteria invades the bowel system, it spreads through the bloodstream throughout the body, making even more toxins along the way. Gastrointestinal infections can be treated but usually result in fatality rates of 25% to 60%, depending upon how soon treatment begins.3

Pulmonary (pneumonic, respiratory, or inhalational) anthrax

Respiratory infection in humans initially presents with flu-like or cold symptoms for several days, followed by severe (and often fatal) respiratory collapse. Historical mortality was 92%, but when treated early, such as with the 2001 anthrax attacks, observed mortality was 45%.4 Illness progressing to the fulminant phase has a 97% mortality regardless of treatment.

A lethal infection is reported to result from inhalation of about 10,000–20,000 spores, though this dose varies amongst host species. 5 Like all diseases there is probably a wide variation to susceptibility with evidence that some people may die from much lower exposures; there is little documented evidence to verify the exact or average number of spores needed for infection. Inhalational anthrax is also known as woolsorters’ or ragpickers’ disease as these professions were more susceptible to the disease due to their exposure to infected animal products. Other practices associated with exposure include the slicing up of animal horns for the manufacture of buttons, the handling of hair bristles used for the manufacturing of brushes, and the handling of animal skins. Whether these animal skins came from animals that died of the disease or from animals that had simply laid on ground that had spores on it is unknown. This mode of infection is used as a bioweapon. 5

Anthrax Resources

Anthrax, Centers for Disease Control and Prevention (CDC)
Anthrax factsheet from European Centre for Disease Prevention and Control, agency of European Union
Agent Fact Sheet: Anthrax, Center for Biosecurity
– “Anthrax“. CDC Division of Bacterial and Mycotic Diseases. Retrieved June 17 2005.
Bioterrorism Category A Agents – Information Resources

References
1.Suffin, S. C.; Carnes, W. H.; Kaufmann, A. F. (September 1978). “Inhalation anthrax in a home craftsman”. Human Pathology 9 (5): 594–597. http://www.ncbi.nlm.nih.gov/pubmed/101438.

2.”Man who breathed in anthrax dies,” BBC News, 2 November 2008. Retrieved 2 November 2008.

3.a b “Anthrax Q & A: Signs and Symptoms”. Emergency Preparedness and Response. Centers for Disease Control and Prevention. 2003. 4.Bravata DM, Holty JE, Liu H, McDonald KM, Olshen RA, Owens DK (2006), Systematic review: a century of inhalational anthrax cases from 1900 to 2005, Annals of Internal Medicine; 144(4): 270–80.

5.”Anthrax, Then and Now”. MedicineNet.com., http://www.medicinenet.com/script/main/art.asp?articlekey=18812&page=2. Retrieved 2008-08-13.

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