What is Anthrax Infection?
Anthrax is a bacteria that forms hardy spores and is particularly common in tropical soils. It has a lot of characteristics that make it a good choice for use as a biological weapon. These include a high rate of sickness and death, a low amount needed to infect someone, there are no quick diagnostic tests available, there isn’t a widely available effective vaccine, and it can cause a lot of fear and anxiety. The bacteria is also easy to get hold of, easy to produce, can survive well in the environment, and can be made into a weapon.
In recent history, there have been instances of anthrax being used as a biological weapon. For example, in 1979 in Sverdlovsk, Russia, anthrax spores accidentally escaped from a Soviet Union bioweapons facility. This event infected 77 people, of whom 66 died within 1 to 4 days of showing symptoms. Another instance occurred in September 2001 in the United States. A government employee intentionally sent anthrax spores through the postal service. Eleven people who had contact with the contaminated mail later developed inhalational anthrax and sadly, five of them died. There were also eleven additional patients who got anthrax through their skin, but all of them survived.
What Causes Anthrax Infection?
The bacterium called Bacillus anthracis is a specific type of bacteria that doesn’t move and doesn’t destroy blood cells. This bacterium is classified as a “facultative anaerobe,” meaning it can live with or without oxygen. To be harmful, it needs to acquire two small, circular pieces of DNA called plasmids. One of these plasmids provides the instructions to make a protective layer, and the other provides the instructions to produce a harmful substance called exotoxin.
This exotoxin is made of three proteins, which are the protective antigen, the edema factor, and the lethal factor. When anthrax bacteria infect a host, they transform from their dormant spore form into active bacteria inside the cells that absorb foreign particles (called macrophages). Once active, these bacteria produce the exotoxin proteins which leads to effects like cell death, swollen lymph nodes, and fluid accumulation (edema).
Risk Factors and Frequency for Anthrax Infection
Anthrax is a disease that can infect those who consume undercooked meat containing anthrax spores, or those living in rural and farming areas. The risk is especially high for those with professions like veterinarians, farmers, and wool sorters who are often exposed to livestock, infected meat, and contaminated soil.
Interestingly, anthrax is not believed to be transmitted from person to person. Anthrax spores can survive for years in the soil and are often consumed by herbivores like sheep, cattle, and goats, making them the most common carriers. Developed countries seldom report anthrax infections due to effective animal and human vaccination programs.
- It’s estimated that 95% of anthrax infections show up on the skin, 5% affect the respiratory system, and only 1% cause gastrointestinal problems.
- However, these numbers might not be entirely accurate. This is because gastrointestinal anthrax often happens in areas with limited healthcare and testing. Also, the symptoms can vary hugely and are sometimes mild, leading to underreporting. Consequently, the cause of the illness may not be found, and the diagnosis may be missed.
Signs and Symptoms of Anthrax Infection
Anthrax is an infection that usually affects people who live in tropical climates or who work in rural or agricultural environments with grazing animals or animal hides. Those who work in labs around infectious spores or anyone who comes into direct contact with the white powder of Anthrax, contaminated needles, or wounds exposed to soil from tropic regions are also at risk. Depending on how the anthrax entered the body, symptoms can be varied and can affect the respiratory, digestive, or skin systems. It’s essential to keep a high level of suspicion for this disease with these risk factors.
One common sign of anthrax is a painless skin lesion or eschar. If one develops in high-risk individuals, it should be taken seriously. Respiratory symptoms are often vague and can feel like the flu with fever, fatigue, and a dry cough. Severe complications like sepsis, shock, and cardiopulmonary collapse can quickly follow, so it’s essential to pay close attention to any possible exposure risks. Similarly, unexpected belly fluid, inflammation of the peritoneum, or severe gastrointestinal bleeding should also raise suspicions of anthrax.
One form of Anthrax, known as injectional anthrax, typically occurs in those who misuse substances. It happens when the anthrax spores germinate at the site of a subcutaneous injection such as that used for heroin intake. This form of anthrax often presents as swelling and death of surrounding tissues and is linked with a higher risk of septic shock and death when compared to the cutaneous form of the disease.
Testing for Anthrax Infection
For skin-based anthrax, doctors mainly rely on physical exam to make a diagnosis. However, they can use methods such as taking a sample from a skin sore, doing a blood test, or using a small, round blade (termed a ‘punch biopsy’) to take a small piece of skin for testing. Specific mediums such as nutrient agar or blood agar can be used to grow and identify the anthrax bacteria.
In cases of anthrax that is inhaled, traditional imaging, like an X-ray, may not show clear signs of the disease. However, some patients may show a wider than normal area in the chest (mediastinum) along with enlarged lymph nodes in the chest region. A CT scan – a more detailed imaging technique – is recommended if doctors suspect anthrax has been inhaled. Culturing sputum (mucus coughed up from the lower airways), or performing a gram stain and blood cultures could also help in diagnosing the disease. But, these tests are not very useful in the very early stages of anthrax. Other ways doctors can diagnose anthrax include identifying anthrax markers in fluid collected from the chest cavity by a test known as PCR, detecting antibodies to the bacteria in the blood, or by staining tissue samples taken for biopsy.
For anthrax that affects the digestive system, doctors can identify the bacteria by analysing its DNA using a PCR test, performing blood cultures, and examining fluid accumulated in the abdomen. DNA tests and cultures can also be performed on stool samples or swabs taken from the rectum to confirm the diagnosis.
Treatment Options for Anthrax Infection
Traditionally, anthrax has been managed with supportive care and the antibiotic penicillin. However, due to concerns about anthrax being used as a weapon and potential resistance to penicillin, the Centers for Disease Control and Prevention (CDC) now recommend the broader-acting antibiotics ciprofloxacin or doxycycline. This recommendation applies to all patients, regardless of their age, as incomplete treatment can result in a mortality rate of over 50%.
Patients diagnosed with skin anthrax who are in overall good health can be treated at home with ciprofloxacin or doxycycline for 7 to 10 days. All other patients should be treated with intravenous (IV) ciprofloxacin or doxycycline every 12 hours plus at least two other antibiotics such as imipenem, clindamycin, rifampin, or an aminoglycoside. This treatment should continue for at least 60 days or until the patient can receive three doses of the anthrax vaccine, which is typically administered on days 0, 14, and 28. Other treatments, including placement of a chest tube and mechanical ventilation, have not been shown to improve survival rates.
If probable exposure to anthrax occurs, preventive antibiotic treatment is recommended. This could include taking ciprofloxacin or doxycycline twice a day for a total of 60 days, or until at least three doses of the vaccine have been received. It’s important to note that the anthrax vaccine has only been approved by the Food and Drug Administration for adults and not for children.
What else can Anthrax Infection be?
When diagnosing certain diseases, doctors also need to consider other potential conditions that could cause similar symptoms. Here is the breakdown based on different systems:
For skin-related symptoms, some possible conditions could include:
- Bubonic plague
- Lymphocutaneous tularemia (an infection caused by bacteria)
- Cat scratch disease (an infection you can get from getting scratched by a cat)
- Brown recluse spider bite
- Primary syphilis (the first stage of this sexually transmitted disease)
- Abscesses
- Erythematous granuloma annulare (a skin condition that causes ring-shaped bumps)
For issues related to the respiratory system, some possibilities could include:
- Flu
- Pneumonia
- Pneumonic plague
- Hemopneumothorax (a condition where both air and blood fill up the space between the lungs and the chest wall)
- Pneumothorax (a collapsed lung)
- PE, ACS, AAA (medical terms for blood clots in the lung, chest pain due to blocked blood vessels, and a ballooning of the main artery from the heart)
- PUD (Peptic Ulcer Disease causing sores in the stomach lining)
Finally, for gastrointestinal symptoms, the following conditions could be considered:
- PUD (Peptic Ulcer Disease)
- Boerhaave syndrome (a tear in the esophagus)
- Peritonitis (inflammation of the membrane lining the abdominal wall)
- Perforated viscus (a hole in the wall of a part of your gastrointestinal tract)
- Shigella (infectious bacteria that can cause diarrhea)
- Amebic dysentery (a parasitic infection of the intestines)
- Ulceroglandular tularemia (a form of tularemia that forms an ulcer)
- Bubonic plague
It’s important for doctors to consider all these possible conditions when trying to make a correct diagnosis.
What to expect with Anthrax Infection
The exact death rate from inhalational anthrax is unclear, but it’s believed that 50% or more of people will die after the disease begins. Left untreated, gastrointestinal anthrax also has a death rate of 50%, but with appropriate treatment, this rate can drop to less than 40%. The form of anthrax with the best chances of survival is cutaneous anthrax, with a death rate estimated to be below 20%.
Possible Complications When Diagnosed with Anthrax Infection
These are some serious complications that can occur:
- Bleeding in the chest, also known as hemorrhagic mediastinitis.
- Rapid and severe bleeding in the digestive tract, known as fulminant GI bleeding.
- Inflammation of the membranes surrounding the brain and spinal cord, called meningitis.
- A life-threatening condition where blood pressure drops dangerously low due to a severe infection, known as septic shock.
