Anthrax

What is Anthrax?

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Skin, LungsAnthrax is caused by Bacillus anthracis. Bacillus anthracis is a bacteria which is found in the environment in soil. The spores of these Gram-positive bacilli are extremely hardy and withstand extremes of temperature and humidity. This disease primarily affects herbivores, although infection in humans can occur - most often involving the skin (cutaneous anthrax), or the lungs (inhalation anthrax), and rarely gastro-intestinal anthrax.

Statistics on Anthrax?

United States:Anthrax infection is rare. From 1955-1994, US cases totaled 235, with 224 cases of cutaneous anthrax, 11 cases of inhalational anthrax, and 20 fatalities. The last fatal case during this period occurred in 1976, when a home craftsman died of inhalational anthrax after working with yarn imported from Pakistan. Before October 2001, the Centers for Disease Control and Prevention (CDC) investigated several threats in the United States, including Indiana, Kentucky, Tennessee, and California. Since October 2001, 22 confirmed or suspected cases of anthrax infection, disseminated through the US postal system, have been identified. Cases were reported from Florida, New York, New Jersey, the District of Columbia, and Connecticut. There were 11 confirmed cases of inhalational anthrax and 11 cases of cutaneous anthrax, of which 7 are confirmed and 4 are suspected. Internationally:In 1958, approximately 100,000 cases of anthrax occurred worldwide. Exact figures do not exist because of reporting difficulties in Africa. Anthrax is endemic in Africa and Asia despite vaccination programs. Sporadic outbreaks have occurred as a result of both agricultural and military disruptions. During the 1978 Rhodesian civil war, failure of veterinary vaccination programs led to a human epidemic, causing 6500 anthrax cases and 100 fatalities. A mishap at a military microbiology facility in the former Soviet Union in 1979 resulted in 66 deaths. Human anthrax often is associated with agricultural or industrial workers who come in contact with infected animal tissue. Mortality/Morbidity:Anthrax is primarily zoonotic, that is it is a disease which is transferred from animals to humans. Most anthrax disease is cutaneous (95%). The remaining cases of the disease are inhalational (5%) and GI (<1%).

Risk Factors for Anthrax

Anthrax infection is rare as a result of vaccination of herds. Risk factors include:

Handling contaminated animal products
Animal hair processing
Contact with livestock
Products from livestock

Occupations at risk are:

Veterinarians
Animal handlers
Abattoir workers
Laboratorians

Progression of Anthrax

The incubation period is 1-10 days.

By far the most common form is cutaneous anthrax. The small, erythematous, maculopapular lesion is initially painless. It may subsequently vesiculate and ulcerate, with formation of a central black eschar. The illness is self-limiting in the majority of patients, but occasionally perivesicular oedema and regional lymphadenopathy may be marked, and toxaemia can occur.
Respiratory involvement (inhalation anthrax) follows inhalation of spores. A febrile illness is accompanied by non-productive cough and retrosternal discomfort; pleural effusions are common. Untreated, the mortality is about 90%.
Gastrointestinal anthrax is due to consumption of contaminated meat. It presents as severe gastroenteritis; haematemesis and bloody diarrhoea can occur. Toxaemia, shock and death may follow.

How is Anthrax Diagnosed?

Cutaneous anthrax: culture of the skin lesion;Inhalation anthrax: Chest x-ray, arterial blood gases, blood cultures, sputum cultures.

Prognosis of Anthrax

The prognosis of cutaneous anthrax treated with antibiotics is excellent. However, in the absence of antibiotics, up to 20% of individuals may die as anthrax may spread into the bloodstream.The prognosis of inhalation anthrax once it reaches the second stage is poor, even with antibiotic therapy. Up to 90% of cases in the second stage are fatal.The prognosis of gastrointestinal anthrax is also poor with a high proportion of individuals dying of this disease.

How is Anthrax Treated?

Penicillin or ciprofloxacin are the best treatments. In mild cutaneous infections, oral therapy for 2 weeks is adequate. In more severe infections high doses of intravenous antibiotics are needed, along with appropriate supportive care.
Vaccination of animals as well as burning or burial of infected animal carcasses is important to control disease in animal herds.

A Human vaccine is available to those at a high risk.