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Anthrax

Anthrax or splenic fever, as it was formerly called, is an infectious disease caused by Bacillus anthracis, a Gram-positive, rod-shaped bacterium. It mainly affects herbivores and infected animals may serve as a source of infection for humans, rendering anthrax a zoonotic disease. In recent years, the disease has attracted considerable attention as a potential bioterrorist threat. Clinically, there are three types of anthrax: cutaneous, gastrointestinal and inhalational. Initial symptoms differ between those variants of the disease, but all may lead to sepsis and death if not treated accordingly.


Presentation

Depending on the port of entry, inhalational, gastrointestinal, or cutaneous anthrax may be developed. Some authors also describe a fourth form of the disease, namely injectional anthrax [1].

The classical variants of anthrax manifest as follows [2]:

  • Contrary to other forms of splenic fever, inhalational anthrax is not characterized by local disease before systemic spread. From the lungs, bacteria reach regional lymph nodes and the bloodstream. Non-specific symptoms like malaise, fatigue, fever, chills, dyspnea and non-productive cough, nausea and vomiting may precede the acute phase of the disease [3]. The latter is marked by sudden dyspnea, cyanosis, coma and death.
  • The ingestion of Bacillus anthracis spores may lead to oropharyngeal or, more commonly, to gastrointestinal anthrax. In case of oropharyngeal anthrax, an initial lesion that may measure several centimeters in diameter can be observed in the oral cavity or pharyngeal mucosa. This lesion is usually covered by a pseudomembrane, frequently ulcerates and is surrounded by extensive edema. It causes dysphagia and may be associated with regional lymphadenopathy [4]. Similarly to oropharyngeal anthrax, ulcerative lesions may be encountered in other parts of the gastrointestinal tract, and this condition is known as gastrointestinal anthrax. Hemorrhages from such lesions may be profound and provoke hemodynamic failure. Gastrointestinal perforation is another dreaded complication of this form of splenic fever. It is accompanied by unspecific symptoms like fever, nausea, vomiting, diarrhea, and abdominal pain, that frequently don't raise suspicion for anthrax, but rapidly develop into hematemesis, bloody diarrhea, and severe ascites [4].
  • Cutaneous anthrax manifests up to three days after the inoculation of the pathogen in form of a single papule, less frequently of multiple skin lesions. Subsequently, vesicles develop around that papule and fluid builds up in the surrounding skin. Regional lymphadenopathy may be noted at this point, but otherwise neither pain nor pus are reported. During the following days, ulceration occurs and eschar forms, and associated edema may expand to adjacent body regions and exert mass-like effects that may require emergency procedures. Patients presenting with anthrax eschar frequently claim constitutional symptoms like malaise, fever, and headaches, too. If the disease takes a self-limiting course, skin lesions start to resolve about one week after the initial appearance of the papule.

Anthrax meningitis may complicate any of the aforementioned variants of the disease. Patients developing anthrax meningitis suffer from high-grade fever, changes of their mental state, neck pain, and vomiting. All forms of anthrax may eventually give rise to toxemia, bacteremia, septicemia, septic shock, coma and death. Mortality is significantly higher, though, in pulmonary and gastrointestinal splenic fever than in cutaneous anthrax.

Cervical Lymphadenopathy
  • In oro-oesophageal anthrax, the clinical manifestations include sore throat, dysphagia, fever, cervical lymphadenopathy, and oedema.[pubmedcentral.nih.gov]
Fever
  • Gastrointestinal perforation is another dreaded complication of this form of splenic fever.[symptoma.com]
  • These symptoms can occur within 7 days of infection: Fever (temperature greater than 100 degrees F). The fever may be accompanied by chills or night sweats.[web.archive.org]
  • The former was admitted to the hospital with complaints of headache, vomiting, fever, and decreased level of consciousness. The latter presented with abdominal pain and distension, vomiting, and fever. Both cases were proven by animal inoculation.[ncbi.nlm.nih.gov]
  • Symptoms of inhalation anthrax: Begins with fever, malaise, headache, cough, shortness of breath, and chest pain Fever and shock may occur later Symptoms of gastrointestinal anthrax usually occur within 1 week and may include: Abdominal pain Bloody diarrhea[nlm.nih.gov]
Fatigue
  • Initial symptoms after inhalation might include mild fever, malaise, fatigue, coughing and, occasionally a feeling of pressure on the chest.[news.bbc.co.uk]
  • If the Bacillus anthracis spores are inhaled, the initial signs of disease are usually flu-like symptoms including fever, sore throat, feeling unwell, body aches, fatigue, cough and chest discomfort.[ccohs.ca]
  • More severe symptoms include a cough, shortness of breath, fatigue, and may progress to shock which can be fatal. Seek medical attention immediately if you suspect exposure to Anthrax. Treatment includes antibiotics.[iamat.org]
Malaise
  • Patients presenting with anthrax eschar frequently claim constitutional symptoms like malaise, fever, and headaches, too.[symptoma.com]
  • Initial symptoms after inhalation might include mild fever, malaise, fatigue, coughing and, occasionally a feeling of pressure on the chest.[news.bbc.co.uk]
Pathologist
  • The Investigation Finally, in 1992, after collapse of the Soviet Union, a group of scientists, including pathologists and epidemiologists, was allowed to visit Sverdlovsk to perform an on-site investigation.[web.archive.org]
  • Yet neither the clinicians nor the pathologists had identified the cause of the epidemic. Moreover, as you can imagine, the members of the pathology department were frustrated and overburdened with work. So, on this day, Dr.[medicinenet.com]
  • Journal of clinical pathology : JCP ; the journal of the Association of Clinical Pathologists London : BMJ Publ.[zdb-katalog.de]
  • The organs or tumors were postfixed for 24 h in 4% (wt/vol) paraformaldehyde, embedded in paraffin, sectioned, stained with hematoxylin/eosin, and subjected to microscopic analysis by a pathologist unaware of treatment or animal genotype (two to eight[doi.org]
Anorexia
  • Signs may include fever, chills, severe colic, anorexia, depression, weakness, bloody diarrhea, and swellings of the neck, sternum, lower abdomen, and external genitalia. Death usually occurs within 2–3 days of onset.[merckvetmanual.com]
  • The symptoms for intestinal infection include fever, nausea, abdominal pain, vomiting, and anorexia.[rarediseases.org]
  • Gastrointestinal anthrax presents with severe abdominal pain, fever, fatigue, anorexia, hematemesis, and bloody diarrhea. In some cases there may be lesions in the nose, mouth, and throat.[medical-dictionary.thefreedictionary.com]
  • In abdominal anthrax initial symptoms are nausea, vomiting and anorexia, and fever.[pubmedcentral.nih.gov]
Sore Throat
  • Inhalation anthrax: Initial symptoms may resemble a common cold – sore throat, mild fever, muscle aches and malaise. After several days, the symptoms may progress to severe breathing problems and shock. Inhalation anthrax is usually fatal.[web.archive.org]
  • The chances that your sore throat and aching muscles are due to anthrax are extremely small.[mayoclinic.org]
  • Initially, there is a flu-like illness with a nonproductive nausea, vomiting, sore throat, cough, sweats, fever, confusion, headache and myalgia.[patient.info]
  • If the Bacillus anthracis spores are inhaled, the initial signs of disease are usually flu-like symptoms including fever, sore throat, feeling unwell, body aches, fatigue, cough and chest discomfort.[ccohs.ca]
Pleural Effusion
  • Of these, 127 control subjects (67.6%) had infiltrates, 43 control subjects (22.9%) had pleural effusions, and 15 control subjects (8.0%) had mediastinal widening.[citeseerx.ist.psu.edu]
  • If inhalation anthrax is suspected, chest X-rays or CT scans can confirm if the patient has mediastinal widening or pleural effusion, which are X-ray findings typically seen in patients with inhalation anthrax.[cdc.gov]
  • B. anthracis can be cultured from blood, ascitic fluid, cerebrospinal fluid, pleural effusion or skin lesion. Blood culture is almost always positive. Culture of skin lesion is positive in only 60-65% of cases.[patient.info]
Dyspnea
  • A blind 65-year-old man, living in a rural area, was admitted with respiratory infection, fever, dyspnea, loss of appetite, and myalgia. The patient was treated with outpatient antibiotics a week ago.[ncbi.nlm.nih.gov]
  • Non-specific symptoms like malaise, fatigue, fever, chills, dyspnea and non-productive cough, nausea and vomiting may precede the acute phase of the disease. The latter is marked by sudden dyspnea, cyanosis, coma and death.[symptoma.com]
  • […] inhalation anthrax , pulmonary anthrax , ragpicker's disease , ragsorter's disease , woolsorter's disease , woolsorter's pneumonia a form of anthrax infection acquired by inhalation of dust containing Bacillus anthracis; initial symptoms (chill and cough and dyspnea[vocabulary.com]
  • […] prodrome of fever, chills, nonproductive cough, chest pain, headache, myalgias, and malaise, with more distinctive clinical hallmarks of hemorrhagic mediastinal lymphadenitis, hemorrhagic pleural effusions, bacteremia and toxemia resulting in severe dyspnea[web.archive.org]
  • Inhalation anthrax starts with a brief prodrome that resembles a viral respiratory illness followed by hypoxia, dyspnea, fever, muscle aches, headaches, and fatigue.[medical-dictionary.thefreedictionary.com]
Respiratory Distress
  • Abstract A 10-year-old boy presented with facial swelling, thick exudates in the nasal cavities with membranes covering the nasopharynx, shock and respiratory distress. X-ray of the paranasal sinuses showed opacification of both maxillary sinuses.[ncbi.nlm.nih.gov]
  • In a few days, however, the illness worsens and there may be severe respiratory distress with shortness of breath and pain in the chest and/or muscles. Some patients may begin coughing up blood. Shock , coma , and death follow.[medicinenet.com]
  • Acute respiratory distress syndrome. Am J Respir Crit Care Med. 1998 ; 157 : 1332 – 47. DOI PubMed Demirdag K, Ozden M, Saral Y, Kalkan A, Kilic SS, Ozdarendeli A.[doi.org]
Dry Cough
  • In such cases the main clinical signs are: high temperature, shivering or twitching harsh dry cough blood in dung or in nostrils decrease or complete loss of milk fits bright staring eyes colicky pains dejection and loss of appetite In pigs and horses[gov.uk]
  • He had a mild sore throat and occasional dry cough.[cdc.gov]
  • Inhalational anthrax typically begins with one to three days of fatigue, low-grade fever, and dry cough.[rarediseases.org]
Vomiting
  • The former was admitted to the hospital with complaints of headache, vomiting, fever, and decreased level of consciousness. The latter presented with abdominal pain and distension, vomiting, and fever. Both cases were proven by animal inoculation.[ncbi.nlm.nih.gov]
  • Non-specific symptoms like malaise, fatigue, fever, chills, dyspnea and non-productive cough, nausea and vomiting may precede the acute phase of the disease. The latter is marked by sudden dyspnea, cyanosis, coma and death.[symptoma.com]
  • (the vomit may contain blood) Symptoms of injection anthrax are similar to those of cutaneous anthrax.[nlm.nih.gov]
Nausea
  • Hours after receiving dose 3 he experienced fever, chills, nausea, vomiting, and neck, hand, and shoulder pain. The vaccination series was terminated after the third dose.[ncbi.nlm.nih.gov]
  • Non-specific symptoms like malaise, fatigue, fever, chills, dyspnea and non-productive cough, nausea and vomiting may precede the acute phase of the disease. The latter is marked by sudden dyspnea, cyanosis, coma and death.[symptoma.com]
  • Shortness of breath Nausea Coughing up blood Pain when you swallow An uncomfortable feeling in your chest Dizziness or confusion Sweating If it worsens, you could also have other symptoms like shock or trouble breathing, or develop a condition called[webmd.com]
Abdominal Pain
  • The latter presented with abdominal pain and distension, vomiting, and fever. Both cases were proven by animal inoculation.[ncbi.nlm.nih.gov]
  • Patients also develop pallor or cyanosis, dyspnoea, tachycardia, abdominal pain and pleuritic chest pain. Abrupt onset of respiratory failure may develop 2-4 days later.[patient.info]
  • The symptoms include fever, chills, swelling of neck or neck glands, abdominal pain, fever, nausea, loss of appetite, vomiting and diarrhea.[ccohs.ca]
Dysphagia
  • It causes dysphagia and may be associated with regional lymphadenopathy. Similarly to oropharyngeal anthrax, ulcerative lesions may be encountered in other parts of the gastrointestinal tract, and this condition is known as gastrointestinal anthrax.[symptoma.com]
  • Symptoms for oropharyngeal illness may include fever, sore throat, difficulty in swallowing (dysphagia), collection of fluid (edema) in the tissues of the throat, and swelling of the lymph nodes.[rarediseases.org]
  • Symptoms include hoarseness, sore throat, fever, and dysphagia. Airway obstruction may occur. Inhalation anthrax begins insidiously as a flu-like illness.[merckmanuals.com]
  • Clinical Cervical oedema, lymphadenopathy (causing dysphagia), respiratory difficulty. Anthrax meningitis A rare, usually fatal complication of GI or inhalation anthrax, with death occurring 1 to 6 days after onset of illness.[medical-dictionary.thefreedictionary.com]
  • In oro-oesophageal anthrax, the clinical manifestations include sore throat, dysphagia, fever, cervical lymphadenopathy, and oedema.[pubmedcentral.nih.gov]
Hematemesis
  • Neither had abdominal pain, tenderness, diarrhea, hematemesis, melena, or other expected signs and symptoms of anthrax.[ncbi.nlm.nih.gov]
  • […] hypoxia and septic shock; gastrointestinal anthrax may result in pharyngeal lesions with sore throat, dypshagia marked neck swelling and regional lymphadenopathy, or intestinal infection characterized by fever, severe abdominal pain, massive ascites, hematemesis[web.archive.org]
  • It is accompanied by unspecific symptoms like fever, nausea, vomiting, diarrhea, and abdominal pain, that frequently don't raise suspicion for anthrax, but rapidly develop into hematemesis, bloody diarrhea, and severe ascites.[symptoma.com]
  • Gastrointestinal anthrax presents with severe abdominal pain, fever, fatigue, anorexia, hematemesis, and bloody diarrhea. In some cases there may be lesions in the nose, mouth, and throat.[medical-dictionary.thefreedictionary.com]
Jaundice
  • On the second day of anthrax treatment, the patient was complicated with jaundice, elevation of liver enzymes, and a significant drop in hemoglobin, hematocrit, and platelet despite lack of obvious bleeding and was complicated with respiratory distress[ncbi.nlm.nih.gov]
Chest Pain
  • Cutaneous anthrax begins as a pruritic papule or vesicle that enlarges and erodes (1-2 days) leaving a necrotic ulcer with subsequent formation of a central black eschar; inhalation anthrax may begin as a prodrome of fever, chills, nonproductive cough, chest[web.archive.org]
  • Symptoms include bumps and blisters (after skin contact), difficulty breathing and chest pain (after inhaling spores), and abdominal pain and bloody diarrhea (after eating contaminated meat).[msdmanuals.com]
  • Symptoms of inhalation anthrax: Begins with fever, malaise, headache, cough, shortness of breath, and chest pain Fever and shock may occur later Symptoms of gastrointestinal anthrax usually occur within 1 week and may include: Abdominal pain Bloody diarrhea[nlm.nih.gov]
Cyanosis
  • Later symptoms include an abrupt onset of a high fever and severe respiratory distress (cyanosis, dyspnea, stridor). Treatment is a 60-day course of antibiotics such as ciprofloxacin, levofloxacin, doxycycline, and penicillin.[medical-dictionary.thefreedictionary.com]
  • Patients also develop pallor or cyanosis, dyspnoea, tachycardia, abdominal pain and pleuritic chest pain. Abrupt onset of respiratory failure may develop 2-4 days later.[patient.info]
  • The latter is marked by sudden dyspnea, cyanosis, coma and death. The ingestion of Bacillus anthracis spores may lead to oropharyngeal or, more commonly, to gastrointestinal anthrax.[symptoma.com]
  • As the disease progresses, there may also be vomiting of blood, bloody diarrhea, toxemia, shock and a bluish tinge to the skin and mucous membranes (cyanosis).[rarediseases.org]
Skin Lesion
  • B. anthracis can be cultured from blood, ascitic fluid, cerebrospinal fluid, pleural effusion or skin lesion. Blood culture is almost always positive. Culture of skin lesion is positive in only 60-65% of cases.[patient.info]
  • After isolation of the Gram-positive bacilli from the skin lesions, prompt antibiotic treatment (intravenous sulbactam-ampicillin 1.5 g every six hours) was initiated.[ncbi.nlm.nih.gov]
  • The only ways to confirm an Anthrax diagnosis are: To measure antibodies or toxin in blood To test directly for Bacillus anthracis in a sample blood skin lesion swab spinal fluid respiratory secretions Samples must be taken before the patient begins taking[cdc.gov]
Skin Ulcer
  • Anthrax infection can be contracted through: Skin lesions where the bacteria invade the blood stream and cause blisters and a skin ulcer characterized by dying skin (black area) in the center.[iamat.org]
  • Symptoms of anthrax exposure include skin ulcers, nausea, vomiting and fever, and can cause death if untreated. The military has ordered all of its labs that have previously received inactive anthrax samples to test them.[bbc.com]
  • It then becomes a skin ulcer with a black center. This doesn’t usually cause pain. The symptoms typically develop within one to five days after exposure. Inhalation People who inhale anthrax usually develop symptoms within a week.[healthline.com]
  • Cutaneous anthrax presents with small, pruritic lesions similar to insect bites that progress to malignant pustules (large, painless boils), vesicles, or skin ulcers with necrotic centers and surrounding brawny edema, usually on an exposed body surface[medical-dictionary.thefreedictionary.com]
Neck Swelling
  • swelling and regional lymphadenopathy, or intestinal infection characterized by fever, severe abdominal pain, massive ascites, hematemesis, and bloody diarrhea.[web.archive.org]
Headache
  • The former was admitted to the hospital with complaints of headache, vomiting, fever, and decreased level of consciousness. The latter presented with abdominal pain and distension, vomiting, and fever. Both cases were proven by animal inoculation.[ncbi.nlm.nih.gov]
  • The most frequently reported side effects were headache, itching (pruritus), upper respiratory tract infections, cough, nasal congestion, hives, and bruising, swelling and pain at the infusion site.[fda.gov]
  • They found a number of local and systemic reactions, including swelling at the injection site (up to 10cm in diameter), muscle aches, headaches, and mild-to-moderate malaise.[thinktwice.com]
  • Initially, there is a flu-like illness with a nonproductive nausea, vomiting, sore throat, cough, sweats, fever, confusion, headache and myalgia.[patient.info]

Workup

Anamnestic data are of major importance in the workup of anthrax cases: Specific symptoms are rare and the confirmation of exposure to livestock or animal products may be one of very view hints on an infection with Bacillus anthracis. A reliable diagnosis of anthrax requires the identification of the etiologic pathogen or its toxins, either by means of conventional techniques (microscopic examination, Gram stain, culture) or molecular biological approach [5]. Samples may consist in fluid specimens of pulmonary or pleural effusion or serum, or may be obtained by means of bronchial biopsy, using oropharyngeal or wound swabs. It should be noted that treatment with antibiotics negatively affects the sensitivity of any method applied to isolate the causative bacterium [2].

In case of inhalational anthrax, chest radiographs may provide vital information before the onset of the acute phase of the disease. Radiographs obtained in this stage typically show pulmonary infiltrates, pleural effusion and mediastinal widening and lymphadenopathy [2]. However, computer tomography is considered more sensitive with regards to the detection of mediastinal lymph node involvement than radiography, and this finding is much more specific for anthrax than mediastinal widening.

Pericardial Effusion
  • An echocardiogram might be needed to identify pericardial effusions, as reported for 3 of 10 patients (postal workers) with inhalation anthrax in 2001 ( 3 ).[doi.org]
Gram-Positive Rods
  • Bacillus anthracis, the causal agent in anthrax, is a Gram-positive rod. Humans can acquire anthrax by industrial exposure to infected animals or animal products.[ncbi.nlm.nih.gov]
  • Anthrax is a serious infectious disease caused by gram-positive, rod-shaped bacteria known as Bacillus anthracis. Anthrax can be found naturally in soil and commonly affects domestic and wild animals around the world.[web.archive.org]
  • Anthrax or splenic fever, as it was formerly called, is an infectious disease caused by Bacillus anthracis, a Gram-positive, rod-shaped bacterium.[symptoma.com]
Pleural Effusion
  • Of these, 127 control subjects (67.6%) had infiltrates, 43 control subjects (22.9%) had pleural effusions, and 15 control subjects (8.0%) had mediastinal widening.[citeseerx.ist.psu.edu]
  • If inhalation anthrax is suspected, chest X-rays or CT scans can confirm if the patient has mediastinal widening or pleural effusion, which are X-ray findings typically seen in patients with inhalation anthrax.[cdc.gov]
  • B. anthracis can be cultured from blood, ascitic fluid, cerebrospinal fluid, pleural effusion or skin lesion. Blood culture is almost always positive. Culture of skin lesion is positive in only 60-65% of cases.[patient.info]

Treatment

In the United States, the Centers for Disease Control and Prevention published the following guidelines on the clinical management of anthrax [6]:

  • Intravenous application of at least one bactericidal agent and one protein synthesis inhibitor is recommended without exception in patients suffering from systemic disease. In case of anthrax meningitis, another bactericidal agent should be added.
  • Patients with anthrax meningitis should receive antibiotics able to penetrate into the central nervous system, e.g., β-lactam antibiotics, carbapenems, quinolones, or vancomycin. In most parts of the world, penicillin G is the drug of choice for anthrax treatment irrespective of whether or not the patient suffers from anthrax meningitis. Bacillus anthracis may show resistance against β-lactam antibiotics, though [7]. Resistances against other types of antibiotics have also been reported [8].
  • Linezolid is preferred over other protein synthesis inhibitors, but clindamycin and rifampin are valuable alternatives. Chloramphenicol and doxycycline may also be applied.
  • System anthrax requires treatment for at least two weeks.
  • Oral monotherapy may suffice to treat cutaneous anthrax, but recommendations as given above should be followed in patients showing severe edema or systemic symptoms.

Some patients have been applied corticosteroids in an attempt to reduce anthrax-associated edema. However, conclusive results as to the efficacy of such an approach have not yet been presented.

Prognosis

If left untreated, all forms of anthrax are potentially life-threatening. However, self-limiting courses are regularly observed in cases of cutaneous anthrax. All possible measures should be taken to assure an early diagnosis and timely initiation of treatment, since progression from local disease to sepsis rapidly ensues death.

Etiology

Anthrax is caused by Bacillus anthracis, a Gram-positive, rod-shaped, obligate pathogen. Bacillus anthracis may be encountered in its vegetative form or in form of spores. The disease is most commonly contracted by the inhalation, oral uptake or cutaneous inoculation of spores [2]. Of note, those spores are extremely resistant to heat, pressure, ultraviolet and ionizing radiation, chemical agents and disinfectants and may survive for decades in soil, i.e., long periods of time may pass between outbreaks [9]. Within the host - either the animal or a human being - the spores germinate, which gives rises to vegetative state Bacillus anthracis that releases three proteins that form two toxins, as described below.

Epidemiology

Anthrax endemic regions comprise the Middle East, West Africa, Central Asia, parts of India, and South America, but outbreaks may occur anywhere even though some countries claim freedom of splenic fever [9]. Indeed, outbreaks have recently been reported in different parts of Europe [10] [11]. Because the disease primarily affects herbivores, people with occupational exposure to susceptible animals like cattle and sheep, but also goats and horses, have a greater risk of contracting anthrax. Similarly, those working with contaminated animal products are more likely to become infected. The overall risk of human-to-human-transmission is considered to be close to cero [2].

In humans, individuals of any age and both genders are affected equally.

Sex distribution
Age distribution

Pathophysiology

The vast majority of infections with Bacillus anthracis is contracted by inhalation, oral ingestion or cutaneous inoculation of the pathogen [2]:

  • For anthrax to develop upon the inhalation of spores, large quantities of spores have to be inhaled. Even in the unlikely scenario of Bacillus anthracis being used in a bioterrorist attack, the overall likelihood of pulmonary infections remains low.
  • The oral ingestion of the causative pathogen is more commonly observed where people use to consume undercooked meat, e.g., in Sub-Saharan Africa and South East Asia.
  • Even though the infectious dose for cutaneous anthrax is considered to be very low, the pathogen is presumably non-invasive, only being able to pass the skin barrier via epidermal lesions. However, such ports of entry cannot be identified in all patients suffering from cutaneous anthrax.

Bacillus anthracis has two major virulence factors: anthrax toxins and an antiphagocytic polyglutamic capsule [12]. In early stages of the infection, anthrax toxins presumably target immune cells like dendritic cells, macrophages and neutrophils, interfere with chemotaxis, release of chemokines, cytokines and reactive oxygen species, among others, and even induce cell death. The pathogen's antiphagocytic capsule also contributes to the evasion of the innate immune response. In sum, both anthrax toxins and capsule largely facilitate pathogen survival at the port of entry and allow for the subsequent dissemination of Bacillus anthracis. In late stages of the disease, anthrax toxins mediate possibly highly life-threatening effects on the cardiovascular system and most likely a variety of other organ systems [1].

Prevention

In 1970, the Anthrax Vaccine Adsorbed has been licensed in the United States. It was initially used to protect those at greater risk due to possible occupational exposure, but may also be applied to immunize military personnel and anyone else considered to be at risk in a specific situation. The vaccine has been proven to be safe and effective [13]. Ongoing research aims at producing better defined vaccines in more convenient formulations and presentations [1].

On the other hand, both antibiotic treatment and vaccination are effective measures in controlling anthrax outbreaks in animals. Infected animals usually respond favorably to antimicrobial therapy and even if its survival cannot be achieved, pathogen loads are significantly reduced.

Summary

Anthrax is an infectious disease usually affecting cattle and sheep or other livestock [14]. People who work with infected animals or contaminated animal products are at risk of inhaling spores of the causative pathogen, Bacillus anthracis. This bacterium may also enter into the human body via skin lesions or upon the ingestion of contaminated, undercooked food. Depending on the port of entry, patients may develop inhalative, cutaneous, or gastrointestinal anthrax. While cutaneous anthrax may run a self-limiting course, all variants of the disease are potentially life-threatening and may lead to sepsis, shock and death. If an early diagnosis is achieved and antibiotic treatment is initiated in a timely manner, the infection can be controlled in most cases. However, progression to sepsis is still associated with particularly high mortality. In industrialized countries, vaccines are available to protect individuals at risk. However, this does generally not apply to developing countries in Africa and Asia, where most cases occur. Still, according to current knowledge, splenic fever may occur in any country. Contrasting opinions exist regarding the real risks of a potential bioterrorist attack involving Bacillus anthracis.

Patient Information

Anthrax or splenic fever, as it was formerly called, is a zoonotic disease: It mainly affects animals, namely cattle, sheep, goats, and horses, and people working with infected animals or processing contaminated animal products are at risk of contracting the disease. The causative agent of the disease is called Bacillus anthracis and it is able to form highly resistant spores that may be inhaled or ingested by human beings, but that may also penetrate the skin in case of wounds:

  • Those who develop pulmonary anthrax after the inhalation of spores may develop malaise, fatigue, fever, chills, dyspnea and non-productive cough, nausea and vomiting, non of which are specific for anthrax. Therefore, it is of utmost importance to inform the attending physician about exposure to possible sources of infection as indicated above.
  • In case of ingestion of Bacillus anthracis, ulcers may form anywhere in the digestive tract: While they are readily visible within the oral cavity or pharynx, they may remain undetected in other parts of this organ system. Symptoms typical of gastrointestinal anthrax are fever, nausea, vomiting, diarrhea, and abdominal pain. This variant of the disease may also follow a life-threatening course, which is why an early diagnosis is as important as in inhalative anthrax.
  • Finally, individuals suffering from cutaneous anthrax will develop a papule at the port of entry. In the following days, vesicles and edematous swelling may become visible. Ulceration and eschar formation occur subsequently. Cutaneous anthrax may follow a self-limiting course, but systemic dissemination cannot be ruled out either.

Combined antimicrobial treatment is recommended in case of infection with Bacillus anthracis. An early diagnosis is essential for a favorable prognosis. Complete recovery is to be expected if treatment is initiated in a timely manner.

References

Article

  1. Williamson ED, Dyson EH. Anthrax prophylaxis: recent advances and future directions. Front Microbiol. 2015; 6:1009.
  2. WHO Guidelines Approved by the Guidelines Review Committee. Anthrax in Humans and Animals. Geneva: World Health Organization. 2008.
  3. Azarkar Z, Bidaki MZ. A case report of inhalation anthrax acquired naturally. BMC Res Notes. 2016; 9:141.
  4. Owen JL, Yang T, Mohamadzadeh M. New insights into gastrointestinal anthrax infection. Trends Mol Med. 2015; 21(3):154-163.
  5. Kim J, Gedi V, Lee SC, Cho JH, Moon JY, Yoon MY. Advances in Anthrax Detection: Overview of Bioprobes and Biosensors. Appl Biochem Biotechnol. 2015; 176(4):957-977.
  6. Pillai SK, Huang E, Guarnizo JT, et al. Antimicrobial Treatment for Systemic Anthrax: Analysis of Cases from 1945 to 2014 Identified Through a Systematic Literature Review. Health Secur. 2015; 13(6):355-364.
  7. Chen Y, Tenover FC, Koehler TM. Beta-lactamase gene expression in a penicillin-resistant Bacillus anthracis strain. Antimicrob Agents Chemother. 2004; 48(12):4873-4877.
  8. Ashley RE, Lindsey RH, Jr., McPherson SA, Turnbough CL, Jr., Kerns RJ, Osheroff N. Interactions between Quinolones and Bacillus anthracis Gyrase and the Basis of Drug Resistance. Biochemistry. 2017; 56(32):4191-4200.
  9. Doganay M, Demiraslan H. Human anthrax as a re-emerging disease. Recent Pat Antiinfect Drug Discov. 2015; 10(1):10-29.
  10. Elschner MC, Busch A, Schliephake A, Gaede W, Zuchantke E, Tomaso H. High-Quality Genome Sequence of Bacillus anthracis Strain 14RA5914 Isolated during an Outbreak in Germany in 2014. Genome Announc. 2017; 5(40).
  11. Orlos Z, Rakoczi E, Misak O, et al. Outbreak of anthrax in adults and adolescents: a review of nine cases in a regional teaching hospital in East Hungary. Clin Microbiol Infect. 2017; 23(1):52-54.
  12. Moayeri M, Leppla SH, Vrentas C, Pomerantsev AP, Liu S. Anthrax Pathogenesis. Annu Rev Microbiol. 2015; 69:185-208.
  13. Institute of Medicine Committee to Assess the Assess the Safety and Efficacy of the Anthrax Vaccine. In: Joellenbeck LM, Zwanziger LL, Durch JS, Strom BL, eds. The Anthrax Vaccine: Is It Safe? Does It Work? Washington (DC): National Academies Press (US); 2002.
  14. Hemming JH. Two Cases of "Charbon" or "Malignant Pustule" Directly Inoculated from a Cow Suffering with "Splenic Fever:" Recovery. Br Med J. 1884; 2(1238):560.

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Last updated: 2019-07-11 22:50