Anthrax overview: Difference between revisions
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==Overview== | ==Overview== | ||
'''Anthrax''' ([[Greek language|Greek]] Άνθραξ for ''coal'') is an [[Acute (medical)|acute]] [[infectious disease]] in humans and animals that is caused by the [[bacterium]] ''[[Bacillus anthracis]]'' and is highly lethal in some forms. Anthrax is one of only a few [[bacteria]] that can form long lived [[spores]]. When the [[bacteria]] s life cycle is threatened by factors such as lack of food caused by their host dying or by a change of temperature, the [[bacteria]] turn themselves into a dormant [[endospore|spore]]s to wait for another host to continue their [[life cycle]]. | |||
'''Anthrax''' ([[Greek language|Greek]] Άνθραξ for ''coal'') is an [[Acute (medical)|acute]] [[infectious disease]] in humans and animals that is caused by the bacterium ''[[Bacillus anthracis]]'' and is highly lethal in some forms. | |||
When [[breathing]], [[ingesting]] or getting anthrax [[spores]] in a cut in the [[skin]], these spores reactivate themselves and multiply in their new host very rapidly. The anthrax [[spores]] in the soil are very tough, can live many decades and are known to occur on all continents except Antarctica. Anthrax most commonly occurs in wild and domestic grass eating mammals (ruminants) who ingest or breathe in the [[spores]] while eating grass. Anthrax can also infect [[human]]s when they are exposed to dead [[infected]] animals, eat tissue from [[infected]] animals, or are exposed to a high density of anthrax [[endospore|spore]]s from an animal's fur, hide, or wool. Anthrax [[spores]] can be grown outside the body and used as a biological weapon. Anthrax cannot spread directly from human to human; but anthrax [[spores]] can be transported by human clothing, shoes, among others. If a person dies of anthrax their body can be a very dangerous source of anthrax [[spores]]. The word ''anthrax'' is the [[Greek language|Greek]] word for ''coal'', the germ's name is derived from ''anthrakitis'', the Greek word for ''[[anthracite]]'', in reference to the black skin [[lesion]]s victims develop in a cutaneous [[skin]] [[infection]]. | |||
==Historical Perspective== | ==Historical Perspective== | ||
Revision as of 01:00, 18 July 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Anthrax (Greek Άνθραξ for coal) is an acute infectious disease in humans and animals that is caused by the bacterium Bacillus anthracis and is highly lethal in some forms. Anthrax is one of only a few bacteria that can form long lived spores. When the bacteria s life cycle is threatened by factors such as lack of food caused by their host dying or by a change of temperature, the bacteria turn themselves into a dormant spores to wait for another host to continue their life cycle.
When breathing, ingesting or getting anthrax spores in a cut in the skin, these spores reactivate themselves and multiply in their new host very rapidly. The anthrax spores in the soil are very tough, can live many decades and are known to occur on all continents except Antarctica. Anthrax most commonly occurs in wild and domestic grass eating mammals (ruminants) who ingest or breathe in the spores while eating grass. Anthrax can also infect humans when they are exposed to dead infected animals, eat tissue from infected animals, or are exposed to a high density of anthrax spores from an animal's fur, hide, or wool. Anthrax spores can be grown outside the body and used as a biological weapon. Anthrax cannot spread directly from human to human; but anthrax spores can be transported by human clothing, shoes, among others. If a person dies of anthrax their body can be a very dangerous source of anthrax spores. The word anthrax is the Greek word for coal, the germ's name is derived from anthrakitis, the Greek word for anthracite, in reference to the black skin lesions victims develop in a cutaneous skin infection.
Historical Perspective
Anthrax, caused by Bacillus anthracis, is thought to have originated in Egypt around 1250 BC. Described as being a disease affecting horses, camels and sheep, anthrax had an impact on great civilizations, such as the Greek and Roman. It was described clinically for the first time by Maret in 1752 and Fournier in 1769. In 1877, based upon his studies with Bacillus anthracis, Robert Koch was able to demonstrate what became known as Koch’s postulates. In 1881, Louis Pasteur worked to create a vaccine for anthrax, which he was able to test with success in animals. In 1900, due to the great amount of knowledge gathered during the 1800s, anthrax cases were well documented in the US, UK and Germany. In 1944, penicillin was first used to treat anthrax. The first commercial vaccine to prevent anthrax in humans was created in 1950s. In the past 10 years there have been a few reported cases in the US, specifically in 2006 in NYC, 2009 in Connecticut and in 2011 in Florida. Anthrax has also been used throughout history as a biologic weapon and there has been efforts to create and enforce legislation to avoid disastrous outbreaks of the disease. For that, a Convention on the Prohibition of the Development, Production, and Stockpiling of Biological and Toxin Weapons and on Their Destruction was created and later ratified in April of 1972, with more than 100 nations signing it, including Iraq, the United States, and the Soviet Union.
Pathophysiology
Causes
Differentiating Anthrax from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
The symptoms of anthrax infection depend on the mode of anthrax exposure in the patient (cutaneous, ingestion, inhalation, injection). The cutaneous type of anthrax is characterized by a skin blister that evolves into an ulcer with a black center, muscle pains, fever, and vomiting. The gastrointestinal type may include symptoms of fever, chills, sore throat, painful swallowing, and abdominal pain. The symptoms of the inhalation type of anthrax are fever, chills, fatigue, sore throat, and shortness of breath. The symptoms of the injection type are usually similar to those of cutaneous anthrax; however, the disease may spread through the body faster. The symptoms of the injection type of anthrax include fever, chills, skin ulcer, and subcutaneous or muscular abscess.
Physical Examination
The physical findings of anthrax infection depend on the mode of anthrax exposure in the patient (cutaneous, ingestion, inhalation, injection). Common findings associated with cutaneous anthrax infection include fever, tachycardia, skin rash with formation of a typical scar, edema and lymphadenopathy; with gastrointestinal anthrax infection include fever, tachycardia, mucosal ulcer and edema in case of oropharyngeal lesion and edema and pallor in more severe cases; with inhalation anthrax infection includes: fever, tachycardia, bradypnea in severe cases, pallor, cyanosis and decreased heart and lung sounds in the presence of pleural effusion; and with anthrax infection due to injection include fever, typical skin scar at the site of injection, edema and subcutaneous and/or muscular abscess.
Laboratory Findings
When systemic anthrax is present, abnormalities in laboratory tests include anemia, thrombocytopenia, and leukocytosis particularly in the latter stages of the disease. Other laboratory findings are hyponatremia, increased BUN, elevated transaminase levels, hypoalbuminemia, and elevated troponin. Cell cultures from blood, CSF, or pleural fluid can identify the organism and possibly the toxins. In injection anthrax, the typical laboratory finding is an inflammatory pattern with a low CRP. A normal PT/PTT at admission does not exclude coagulopathy nor DIC.
Chest X Ray
Chest X-ray is a sensitive diagnostic test for inhalation anthrax. Chest X-ray abnormalities associated with inhalation anthrax include mediastinal widening, paratracheal fullness, pleural effusions, parenchymal infiltrates, and mediastinal lymphadenopathy.
CT
The chest CT scan findings in anthrax include mediastinal widening, hyperdense lymph nodes, and edema of the mediastinal fat.
Other Diagnostic Studies
Several studies are used for the diagnosis and monitoring of anthrax. The polymerase chain reaction (PCR) test is ordered to confirm the virulence of the organism. In addition, lumbar puncture should be performed on admission when it is not contraindicated to search for the organism in the cerebrospinal fluid (CSF) and to to exclude other alternative diagnoses. Other diagnostic studies include an electrocardiogram and an echocardiogram to assess possible complications of anthrax such as atrial fibrillation and pericardial effusion.
Treatment
Medical Therapy
Medical therapy of anthrax infection includes antibiotic and antitoxin drugs. Patients should be treated with a multiple antibiotic regimen (≥3 drugs) for 60 days to avoid the creation of drug resistant species and ensure the elimination of remaining spores of the bacteria. These patients should be monitored at all times to evaluate the need for supportive care measures, such as hemodynamic support, mechanical ventilation, corticosteroids, procedures, and surgical interventions in certain occasions.