Introduction
Anthrax is caused by a bacillus, called Bacillus anthracis, which is extremely infectious for live stock such as cattle, horses, sheep and goats.
It has gained a lot of publicity in 2001 when in the US envelops had been mailed with anthrax spores. The reason anthrax is so dangerous is that it is deadly once the spores get into the body as it can grow anaerobically (without oxygen) in the depth of any tissue and it also forms spores as a storage form that live in the soil for decades.
Once an animal has been infected in a herd, the decomposed body’s bacilli will be transformed into spores the moment the carcass has dried up. The healthy animals just need a small cut in a hoof or elsewhere in the skin and the spores can enter the body and become live bacilli again. In the U.S. herds are cared for by veterinarians and animals are vaccinated with a live non virulent animal vaccine.
This way the environment is safer as not as many spores are around. However, there are certain high risk occupations such as wool-sorters of imported sheep or goat hair, veterinarians and laboratory technicians who are more likely to be exposed to anthrax bacilli (Ref. 1, p. 1158).
Signs and symptoms
There are three major symptom complexes, namely from skin exposure, from exposure to the lung tissue (by inhalation) and from exposure to the gastrointestinal tract (from swallowing spores).
Skin symptoms
Even though anthrax in man is rare, once it does occur the most common form of it is from skin exposure where even some microscopically small skin abrasion can allow some Bacillus anthracis spores to enter the system. This will within 3 to 5 days lead to an itchy, but painless localized skin elevation with a reddish/brown color.
This grows ring-like in the periphery, but flattens in the center, where it leads to ulceration, leakage of serum and eventually to formation of a black crust. This can be seen in this picture of anthrax (thanks to ca.wiley.com for this image). The next phase is further spread centrally with lymph gland swelling and distribution and absorption of the anthrax toxin produced by the invading Bacillus anthracis. The patient will complain of headaches, muscle aches and pains, sick feeling to the stomach and vomiting. When the bacillus enters into the blood stream the patient gets comatose due to a developing shock and dies. This deterioration occurs mostly very fast within a matter of a few days.
Lung symptoms
If anthrax spores are inhaled the patient develops a flu like symptoms over a few days with a cough and fever, but then there is an acute deterioration. The fever increases, the cough worsens acutely to the point where respiratory distress brings the patient to the hospital. The skin color is bluish (=cyanosis), the patient looks deadly sick and gets into a coma and shock. Inside the body the Bacillus anthracis has infected the lung tissue, has eaten itself into the draining lymph glands in the space behind the chest bone (=mediastinal lymph glands) and produces lots of toxin, which is very noxious to any tissue.
The end result is a necrotizing lymphadenitis, where the lymphatic tissue gets liquefied and blood vessels get destroyed thus leading to internal bleeding and release of toxic substances into the blood stream. The end result is more distribution of the toxin into the whole body, more bleeding into all the vital organs, fluid loss from the vascular system and lack of oxygen in tissues, shock and death. This last deterioration can happen within a matter of hours or perhaps up to 1or 2 days.
Gastrointestinal symptoms
If the mode of infection is via the gastrointestinal tract, there might be symptoms initially reminiscent of a stomach flu with nausea and vomiting. However, very quickly the patient will deteriorate, vomit blood or coffee grounds material (this is blood modified by stomach acid), and have excruciating abdominal pain.
The invading Bacillus anthracis is eating its way from a surface erosion in the stomach or in the small intestine into the mesenteric lymph glands that drain the gastrointestinal region, which leads to a necrotizing lymphadenitis similar as described above. The patient deteriorates very quickly as the toxins go right to the liver, the major metabolic organ, and into the blood stream. Sepsis with Gram negative bacteria (E.coli) ensues, and the patient dies in a coma within only a few days of turning sick.
Diagnostic tests
If the physician thinks that there would be a possibility of anthrax, treatment will be initiated before tests for it are even done to ensure that no time is wasted. For, if anthrax is confirmed later, every minute of stopping the toxin from being produced by the bacillus counts and may save a patient’s life. Cultures are taken from the possible portal of entry such as the infected skin area. This is more difficult in the case of lung or gastrointestinal anthrax, but endoscopic methods (bronchoscopy, gastroscopy) can be utilized to visually diagnose the condition and to get samples for culturing. Throat swabs, samples of vomitus and phlegm samples can all be cultured. If there is no obvious infected lesion with lots of organisms to culture, then tissue samples can be injected into laboratory mice that are sacrificed later to obtain a positive or a negative result. This is a very sensitive and specific test.
Treatment
95% of all cases in the U.S. are the skin type (=cutaneous type). As there is a certain incubation time where the local infection can be treated, there is an excellent prognosis when treated promptly with antibiotics such as high dose penicillin G injection or treatment with doxycycline or ciprofloxacin orally (Ref. 2). Unfortunately, the 5% of other forms of anthrax in the U.S. (gastrointestinal, pulmonary or meningeal anthrax) have a very high mortality rate as the patient is battling the systemic effect of a toxic shock-like condition.
These cases need to be treated in an Intensive Care Unit setting with Swan-Ganz catheters in place, with large bore intravenous lines and the fluid balance has to be measured carefully while a combination of intravenous antibiotics are given as well, combined with corticosteroids to mitigate the toxic reactions of the body to the Bacillus anthracis. It is more important for the long term success to know that the time between the ingestion or inhalation of the spores of Bacillus anthracis to the beginning of the therapy was short than it is to know exactly what antibiotics and other treatment modalities were used in the treatment. Skin lesions of the head and neck have to be treated with intravenous antibiotics as well as the complication rates of these lesions is potentially higher. Usually the patients are treated with antibiotics 7 days beyond he point where they have clinically recovered, just in case.
Prevention
An effective anthrax vaccine for humans exists and has been in use for several years by military personal. It consists of inactivated bacteria (passive immunization) that is given by subcutaneous injection (like a flu injection). Despite many irrational fears this vaccine has been found to be very effective and without many side-effects. Ref. 3 lists as side-effects some local irritation at the site of the injection, a few minor headaches, a mild fever and fatigue. These symptoms were only transitory and this has to be related to the knowledge that the person is now protected against anthrax. Health care personnel working in emergency rooms, soldiers, veterinarians, wool-sorters and laboratory technicians should be vaccinated with this vaccine and occasional booster vaccinations need to be given to maintain antibody titers.
References:
1. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 161.
2. TC Dixon et al. N Engl J Med 1999 Sep 9;341(11):815-826.
3. F Charatan BMJ 2000 Oct 21;321(7267):980.
4. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 43.
5. JR Zunt and CM Marra Neurol Clinics Vol.17, No.4,1999: 675-689.
6. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 162.
7. LE Chapman : Antivir Ther 1999; 4(4): 211-19.
8. HW Cho: Vaccine 1999 Jun 4; 17(20-21): 2569-2575.
9. DO Freedman et al. Med Clinics N. Amer. Vol.83, No 4 (July 1999): 865-883.
10. SP Fisher-Hoch et al. J Virol 2000 Aug; 74(15): 6777-6783.
11. Mandell: Principles and Practice of Infectious Diseases, 5th ed., © 2000 Churchill Livingstone, Inc.
12. Goldman: Cecil Textbook of Medicine, 21st ed., Copyright © 2000 W. B. Saunders Company
13. PE Sax: Infect DisClinics of N America Vol.15, No 2 (June 2001): 433-455.
14. David Heymann, MD, Editor: Control of Communicable Diseases Manual, 18th Edition, 2004, American Public Health Association.
