Anthrax

Anthrax (malignant carbuncle, Anthrax, Pustula Maligna, rag-disease, sorter sorter disease) is an acute saprozonotic infectious disease with a predominantly contact mechanism for the transmission of the pathogen. Most often occurs in benign cutaneous form, less often in generalized form. Take to dangerous infections. The causative agent of anthrax is considered as a biological weapon of mass destruction (bioterrorism).

ICD-10 codes

• A22.0. Cutaneous form of anthrax.
• A22.1. Pulmonary form of anthrax.
• A22.2. Gastrointestinal form of anthrax.
• A22.7. Siberian septicemia.
• A22.8. Other forms of anthrax.
• A22.9. Anthrax, unspecified.

What causes anthrax?

Anthrax is caused by Bacillus anthracis. It is a toxin-producing encapsulated facultative anaerobic. Anthrax, often a fatal disease for animals, is transmitted to a person by contact with infected animals or their products. In humans, infection usually occurs through the skin. The transmission of infection by airborne droplets is more rare. Oropharyngeal, meningeal and gastrointestinal infections are rare. With inhalation and gastrointestinal infections, the initially non-specific symptoms after a few days are followed by acute systemic manifestations, shock and often death. Empirical treatment is performed with ciprofloxacin and doxycycline. There is vaccination against anthrax.

In developed countries, the occurrence of anthrax has significantly decreased. However, the possibility of using the pathogen as a potential biological weapon increased the alertness for this pathogen.

The causative agent quickly forms spores when dried. Spores are stable and can remain viable decades in the hair and hair of animals. In those cases where spores enter a medium containing a large number of amino acids and glucose, they begin to germinate and multiply rapidly. In humans, infection usually occurs through the skin, but there may be cases of infection with the use of contaminated meat, in particular when there is a defect in the mucosa of the pharynx or intestine, which facilitates the invasion. Inhalation of spores, especially in the presence of acute respiratory disease, can lead to inhalation of anthrax (shepherd disease), which often leads to death. Bacteremia can occur with any form of anthrax and almost always accompanies fatal cases.

After penetration into the body, spores enter the macrophages, where they germinate. Together with macrophages, bacteria enter the lymph nodes, where they multiply. With the inhalation form of anthrax, spores are deposited in alveolar spaces where they are absorbed by macrophages, which usually leads to hemorrhagic mediastinitis. Gastrointestinal infection is usually the result of eating improperly prepared contaminated meat. Only the cutaneous form of anthrax is contagious (contagiosity - medium). Infection occurs by direct contact, with bite of lice and with detachable affected skin.

The bacterium secretes several exotoxins, which are considered in accordance with their virulence. The most important toxins are edematous toxin and lethal toxin. Protective antigen binds to target cells and facilitates intracellular penetration of edematous or lethal toxin. Ointment toxin causes the formation of massive local edema. The lethal toxin triggers a massive release of cytokines by macrophages, which in turn can lead to sudden death. Sudden death with anthrax occurs quite often.

Anthrax is a dangerous animal disease. It can occur in goats, cattle, sheep and horses. Anthrax can also occur in representatives of wildlife, for example in armadillos, elephants and buffalo. This disease rarely occurs in humans, and mostly in countries that are not involved in prevention in the industrial and agricultural industries to prevent people from contacting sick animals and their products. For military purposes, as well as for the purposes of bioterrorism, spores are prepared in a very fine powder form.

What are the symptoms of anthrax?

In most cases, the symptoms of anthrax appear 1-6 days after contact, but for an inhalation form of anthrax, the incubation period may be more than 6 weeks.

Anthrax dermal form begins with the appearance of a painful itchy red-brown papule. The papule increases, and around it a zone of brown erythema and a delimited edema form. Vesiculation and induration are also present. Then comes the central ulceration with serous bloody exudation and the formation of a black scab (malignant pustule). Often there is local lymphadenopathy, which is sometimes accompanied by general malaise, myalgia, headache, fever, nausea and vomiting.

The initial symptoms of anthrax inhalation form are non-specific and resemble influenza. Over the next few days, fever accrues, develops an acute respiratory distress syndrome, which accompanies cyanosis, shock and coma. Develops acute hemorrhagic necrotizing lymphadenitis, which extends to the adjacent structures of the mediastinum. There are serous-hemorrhagic transudate, pulmonary edema and pleural effusion. Typical bronchopneumonia does not develop. Hemorrhagic meningoencephalitis and gastrointestinal anthrax can develop.

Gastrointestinal anthrax varies from asymptomatic to lethal. When spores are absorbed, they can cause damage in any area from the oral cavity to the caecum. The released toxin causes hemorrhagic necrosis, which spreads to the mesenteric lymph nodes. Frequent fever, nausea, vomiting, abdominal pain and diarrhea with an admixture of blood. Intestinal necrosis and septicemia may develop, potentially leading to a toxic fatal outcome.

Oropharyngeal anthrax is represented by a mucocutaneous lesion in the oral cavity. In this case, there are sore throat, fever, adenopathy and dysphagia. Obstruction of the airways may develop.

How is anthrax diagnosed?

To diagnose anthrax, a professional anamnesis with carriers of infection is important. Gram stain and culture should be performed from the clinically damaged lesions; skin areas, pleural fluid, cerebrospinal fluid, stools. With the help of sputum examination and Gram staining, it is unlikely to diagnose an anthrax. They can help in the diagnosis of PCR and immunohistochemical methods of investigation. Taking smears from the nose in order to detect a dispute with people who are likely to have been exposed is not recommended, since the expected value of the method is unknown.

Radiography of the chest (or CT) should be performed in cases where there are symptoms from the respiratory system. In typical cases, using an X-ray study, it is possible to define an enlarged mediastinum (due to enlarged hemorrhagic lymph nodes) and pleural effusion. Pneumonic infiltrates are not common. Lumbar puncture should be performed in cases where there are meningeal symptoms or a change in mental status. Enzyme-linked immunosorbent assay is available, but confirmation requires a 4-fold change in the antibody titer in samples from an acute period to recovery.

How is anthrax treated?

People who were in the inhalation form require oral ciprofloxacin 500 mg (10-15 mg / kg for children) or doxycycline 100 mg (2.5 mg / kg for children) for 60 days. In cases where ciprofloxacin and doxycycline are contraindicated, amoxicillin 500 mg (25-30 mg / kg for children) becomes the drug of choice. Treatment of anthrax within 60 days after exposure provides optimal protection. It is necessary to appoint a vaccination, even after the exposure.

An anthrax of the dermal form is treated with ciprofloxacin 500 mg orally (10-15 mg / kg for children) or doxycycline 100 mg orally (2.5 mg / kg for children) for 7-10 days. Treatment of anthrax is prolonged up to 60 days if there was a probability of inhalation exposure. In the treatment of deaths occur rarely, but the damage will progress through the phase of the scab.

Anthrax inhalation and other worms, including cutaneous with significant edema and skin symptoms, require treatment with 2 or 3 drugs: ciprofloxacin 400 mg intravenously (10-15 mg / kg for children) every 12 hours or doxycycline 100 mg intravenously (2.5 mg / kg for children) every 12 hours along with penicillin, ampicillin, imipinem-cilastatin, meropinem, rifampin, vancomycin, clindamycin or clarithromycin. Glucocorticoids may be useful for the treatment of anthrax, but at the moment they are not adequately evaluated. With early diagnostics and intensive care, including mechanical ventilation, fluid transfusion and vasopressors, mortality can be reduced to 50%. The likelihood of a fatal outcome is high if treatment is delayed (usually due to late diagnosis).

Resistance to antibiotics is the topic of theoretical disputes. Despite the fact that the pathogen is nominally sensitive to penicillin, beta-lactamases induced by Bacillus anthracis are detected, so treatment with a single drug, penicillin or cephalosporin is not recommended. Military researchers may have created multi-resistant strains of anthrax, but so far these strains have not manifested themselves clinically.

How is anthrax prevented?

For people at high risk for anthrax (military personnel, veterinarians, laboratory technicians, textile workers who handle imported wool of cattle), an anthrax vaccine may be used. The vaccine against anthrax is a mixture of wallless culture filtrates. It is necessary to carry out a second vaccination, in order to create a reliable protection. Local reactions may appear on the administration of the vaccine. CDC recommends that vaccination be combined with prophylactic antibiotic therapy in patients who underwent exposition with spores. Some evidence suggests that the cutaneous form of anthrax does not lead to the formation of acquired immunity, especially in cases where previously there was effective antimicrobial treatment. Inhalation form can lead to the appearance of acquired immunity, but data on this are too scarce.

What is the prognosis of anthrax?

Anthrax has 100% lethality, provided that the inhalation and meningeal forms of the disease are not treated. When skin form of anthrax lethality fluctuates within 10-20%. In gastrointestinal form, approximately 50%. With oral form 12.4-50%.