Anthrax is an acute infectious disease generally an environmentally-stable and ubiquitous organism caused by the spore-forming bacterium Bacillus anthracis a small aerobic or facultatively-anaerobic, gram-positive or gram-variable, encapsulated spore-forming rod. It is usually a disease in wild and domestic animals, including cattle, sheep, and goats. However, human infection, while rare, does occur. Human infection usually results from contact with infected animals or their products. However, anthrax has become of interest because of the possibility that a nation or terrorist group might attempt to use it as a weapon of warfare or terrorism. This commonly presents with nonspecific prodromal symptoms such as fever, nausea, vomiting, and sweats which progress to dyspnea and ultimately a respiratory failure and hemodynamic collapse.
Types
There are three types of anthrax:
- Cutaneous (through the skin) – Bubonic plague, lymphocutaneous tularemia, cat scratch disease, brown recluse spider bite, primary syphilis, abscess, erythematous granuloma annulare
- Gastrointestinal /Respiratory – Influenza, pneumonia, pneumonic plague, hemopneumothorax, pneumothorax, PE, ACS, AAA, PUD
- Inhalational/ GI – PUD, Boerhaave syndrome, peritonitis, perforated viscus, shigella, amebic dysentery, ulceroglandular tularemia, bubonic plague
Inhalational anthrax presents following an incubation period of approximately 1 to 6 days post-exposure, with a non-specific prodromal phase including fever, sweats, nausea, vomiting, malaise, chest pain, and nonproductive cough. The second stage of illness occurs as bacterial replication in mediastinal lymph nodes results in hemorrhagic lymphadenitis and mediastinitis, and progression to bacteremia. Fever, dyspnea, and stridor from increasing lymphadenopathy impacting the airways, and ultimately a respiratory failure and hemodynamic collapse occur. Meningitis also occurs in up to 50% of inhalational cases, with a headache, confusion, and progression to coma. Chest x-rays classically demonstrate a widened mediastinum (the result of significant lymphadenopathy) without pulmonary infiltrates, though pleural effusions and/or pulmonary infiltrates both of which may be hemorrhagic can also be seen. The time from onset of symptoms to death ranges from 1 to 10 days.
GI anthrax results from ingestion of contaminated, undercooked meat or ingestion of spores inhaled into the nasopharynx and can include oropharyngeal and/or intestinal symptoms. Patient with oropharyngeal anthrax develops ulcers of the posterior oropharynx and associated dysphagia, cervical swelling, and regional lymphadenopathy. Patients with intestinal anthrax develop fever, nausea, vomiting, and diarrhea. They can progress to an acute abdomen-like presentation with bloody diarrhea, hematemesis, and massive ascites. Intestinal involvement more frequently involves the terminal ileum and cecum. Untreated patients will progress to septicemia. Mortality ranges from 25% to 60%.
Cutaneous anthrax presents 1 to 10 days post-inoculation with a pruritic papular lesion that progresses over several days into a painless ulcer. The lesion may have associated satellite vesicles and will progress into a necrotic and blackened center with surrounding non-pitting edema. The painlessness of the lesion is characteristic of cutaneous anthrax and a distinguishing feature from other diagnoses. As the lesion heals, the eschar will dry, and slough off after 1 to 2 weeks. Without appropriate treatment, the mortality rate can approach 20%.
Injection drug anthrax presents as a grouping of small vesicles or papules at the injection site, with progression to painless ulcerative lesion similar to cutaneous anthrax. Injection anthrax may make it more difficult to recognize and may progress more rapidly to systemic illness than cutaneous anthrax.
Causes
Anthrax is primarily a disease of animals, specifical herbivores such as cattle, goats, and sheep. Animal cases of anthrax tend to occur in the summer and fall seasons and are most frequent in grazing mammals including domestic sheep, goat, and cattle and wild deer and antelope. Human transmission occurs via contact with infected animals through butchering and working with hides or ingestion of raw or undercooked meat. Skin contact results in cutaneous anthrax while inhalation or ingestion of the spores leads to inhalational or gastrointestinal (GI) anthrax.[rx] They contract the disease after coming into contact with B. anthracis spores, which are present in the soil around the world. The rare cases when humans are infected typically occur when people come into contact through their occupations with infected animals or when people eat undercooked meat or other products from infected animals. Its occurrence is most likely in developing countries, although animal products imported from those countries may pose a risk.
Human infection sometimes results from contact in an industrial setting. In the United States, there have been occasional episodes in industrial settings resulting from, for instance, processing contaminated animal fibers such as goat hair.
Infection may also occur among those who work in agricultural jobs. These infections typically occur among people who have had direct contact with animals sick with anthrax or those who have died with the disease.
Cutaneous anthrax occurs after spores come into contact with skin that is broken as a result of a wound or lesion. Gastrointestinal anthrax occurs as a result of eating poorly cooked or raw meat from animals that are infected with the disease. Inhalational anthrax occurs as a result of breathing in (inhaling) the spores.
There have been no confirmed cases of person-to-person transmission of cutaneous, gastrointestinal, or inhalational anthrax. For this reason, it is believed unnecessary to immunize or treat the family members, friends, or co-workers of those who become ill with anthrax unless it is possible that they have been exposed to the same original source of the infection.
Diagnosis
Cutaneous anthrax may be diagnosed by the characteristic signs, such as the raised area on the skin and detection of the presence of the anthrax bacilli in the area of the lesion. A history of exposure to livestock or other possible animal sources also is important. Gastrointestinal anthrax is more difficult to diagnose. In the first, mild phase of inhalational anthrax, symptoms resemble a common cold or upper respiratory infection. With the sudden onset of the more severe symptoms of the second phase, radiographic examination of the chest may show characteristic changes.
Treatment
Antibiotics, such as penicillin, are used to treat all forms of anthrax. However, to be effective, treatment must be started as soon as possible after exposure. Once symptoms begin, there is a significant decline in the likelihood that treatment will be successful.
An antibiotic known as ciprofloxacin (Cipro) was approved in August 2000 by the U.S. Food and Drug Administration for treating people who have been exposed to inhalational anthrax. However, Cipro, too, needs to be taken soon after exposure, and before symptoms begin, to be effective. Taking this or other antibiotics before exposure, as a preventive measure, is not recommended and may cause harm. Before being approved for this purpose, Cipro had been used for several years to treat a variety of infections, including cutaneous anthrax.
Once symptoms have begun, antibiotic therapy is rarely successful against the gastrointestinal or inhalational forms of the disease.
The CDC has concise treatment recommendations based upon anthrax disease manifestations, including multiple alternative agents that may be considered in select patients.[rx][rx][rx]
Well-appearing patients diagnosed with cutaneous anthrax can be treated as an outpatient with ciprofloxacin or doxycycline for 7 to 10 days.
In brief, treatment for inhalational anthrax requires a multidrug regimen with one bactericidal agent + 1 protein-synthesis inhibitor. Intravenous ciprofloxacin + clindamycin or linezolid are the preferred agents. In patients with meningitis, a 3-drug regimen comprised of 2 bactericidal agents from different drug classes (fluoroquinolone + beta-lactam) + 1 protein-synthesis inhibitor is recommended. For cutaneous anthrax, oral ciprofloxacin or doxycycline are effective, except in cases with extensive edema or head and neck involvement, when a multidrug intravenous regimen is recommended.
All other patients should be treated with intravenous (IV) ciprofloxacin 400 mg every 12 hours or doxycycline 100 mg every 12 hours plus at least 2two other antibiotics (e.g., imipenem, clindamycin, rifampin, or an aminoglycoside). Treatment must continue for at least 60 days or until 3 doses of the anthrax vaccine can be given.
An antitoxin product may be recommended as a treatment adjunct together with a multidrug antimicrobial regimen, and there are multiple products that have been developed including both monoclonal and polyclonal antitoxins.
Anthrax immune globulin should also be considered with CDC consultation as adjunctive therapy for systemic anthrax treatment.
The vaccine may also be recommended more broadly to exposed community members as a component of a public health response after a bioterrorism event.
Post-exposure prophylaxis guidelines
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All individuals with inhalation exposure should be treated for 60 days, regardless of their vaccination status.
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Multiple agents should be used instead of monotherapy
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Quinolones have been approved for inhalational anthrax. Doxycycline and ciprofloxacin are the first line treatment.
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Anthrax meningitis should be managed with triple antibiotics
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Cutaneous anthrax can be treated with doxycycline or a quinolone
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Treatment of pregnant and post partum patients is the same as non pregnant females.
References
Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices.
