Anthrax is also known as Wool sorter's disease and is zoonotic in nature. The organism responsible for this disease has been discussed here. The organism has also been used in bioterrorism attacks.

1. BACILLUS
ANTHRACIS
ANJU RANA

2. Anthrax is mainly a zoonotic disease and is transmitted through spores
of B. anthracis – by contamination, inhalation or ingestion. The disease
is not contagious. The organism was first discovered by Robert Koch.
It exists as spores in the soil. It secretes toxins made up of three
proteins – lethal factor, oedema factor and protective factor. These
toxins are the cause of high rate of fatality.

3.  Wool sorter’s disease

4. These are Gram positive spore bearing rods. They are non-motile and
arranged in chains which is surrounded by capsule. They appear as
bamboo sticks under microscope

5. Medusa head colonies
They are aerobes and facultative anaerobes. On nutrient agar,
colonies appear as greyish white, round and irregularly raised.
Under low power microscope, the edges of colonies appear as
tangled mass of hairy curls – called as medusa head.

6. Figure. B. anthracis on PLET medium
polymyxin, lysozyme, EDTA and thallous acetate
are added to heart infusion agar.

10. Pathogenicity of B. anthracis

11. Eschar formation

12. There are following clinical types of anthrax:
Cutaneous anthrax: This type is most prevalent (80% - 90%), and is
common among farmers, animal handlers and veterinary doctors. The
infection starts with a small painless, brownish, itchy papule. The
papule changes to pustule within 2-3 days. Papule gets filled with
haemorrhagic fluid.

13. The inflammatory reactions due to toxin released while
multiplication leads to congestion and oedema in whole area.
Now the pustule changes to a black eschar or ulcer and gets
surrounded by ring of vesicles with serous fluid. The
symptoms include lymphadenitis, headache, myalgia, nausea
and vomiting and fever. If illness is not treated death may
occur due to invasion of the lymph nodes and blood.

14. Injection anthrax: This is the newest form of anthrax seen in intravenous
drug (especially heroin) users in Northern Europe. The incubation period
varies from a few days to months. The symptoms include small
blisters/bumps at the site of injection with itch, fever with chills and
swelling around the blisters. Deep abscesses are formed under the skin.
These blisters later turn into painless sores with dark scab.
Intravenous drugs may induce injection anthrax

15. Pulmonary anthrax: It is also known as wool sorter’s disease because it
was common in workers working in wool factories. Infection is
acquired by inhaling spores. Early symptoms are flu like with pain in
chest. Within a few days situation worsens and patient starts coughing
out blood.

16. Gastrointestinal anthrax: This form of anthrax is rare in humans and
occurs in communities who eat uncooked meat of animals dying due to
anthrax. Patient suffers from haemorrhagic diarrhoea with severe
enteritis. Nausea, abdominal pain, loss of appetite are common
symptoms. The organism invades the intestinal wall and enters the blood
steam. The infection spreads in the body and septicaemia occurs,
followed by shock and coma. These conditions lead to death.

17. Lab diagnosis
Samples are collected depending on the site of infection like sputum,
blood, gastric aspirates or faeces. The samples must be handled carefully.
Under microscope stained preparation show Gram positive bacilli
arranged in chains. Direct fluorescent antibody test is employed for
capsule staining.
For isolation sample is inoculated on PLET (polymyxin lysozyme EDTA
thallous acetate) medium, blood agar and nutrient agar and incubated at
37oC for 24 hours. Medusa head colonies appear which is characteristic
of B. anthracis. Gram staining of the colonies picked from the culture
plate show its morphology.

18. McFadyean’s reaction: To blood films containing anthrax bacilli
polychrome methylene blue is added and viewed under a
microscope after a few seconds. Capsule is stained in purple
colour. The test is used in diagnosis of anthrax.

19. Gelatin stab culture produce inverted fir tree –
characteristic of this organism. Biochemical tests
performed on culture further confirm the
identification. It is catalase, nitrate reduction and
gelatin liquefaction tests positive. Glucose, maltose
and sucrose are fermented with production of acid,
no gas is produced.

20. Diagnosis can also be done by Ascoli’s thermoprecipitation test. The
tissue sample under observation is grounded up in saline and boiled for 5
minutes. It is filtered and filtrate is layered over anti-anthrax serum in a
narrow test tube. A ring of precipitation is formed at the junction of
antiserum and anthrax antigen if present in test sample

21. Treatment
Anthrax can be treated if antibiotics are started early. Tetracycline,
ciprofloxacin and erythromycin are effective in cutaneous form of
anthracis. In pulmonary anthracis intravenous antibiotic therapy
with emergency medical care can save a life. The toxin once formed
cannot be removed only the load of microorganism can be
decreased with antibiotics. This is the reason that patient usually
dies even after giving antibiotics.

22. Prevention
Animals known to have died of anthracis, must be buried in such
way that soil is not contaminated. In epidemics the hides and skin
of animals must be sterilised by gaseous sterilisation method. In
1881, Pasteur prepared live attenuated vaccine by growing anthrax
bacilli at 42oC-43oC. It proved effective in animals. Later Sterne
prepared vaccine from anthrax bacilli’s spores. The spore vaccine
is also effective in animals.

23. Bioterrorism
Anthrax bacilli were spread in U.S. as a bioterrorism attack, in the
form of white powder through postal system. Therefore, in aerosol
exposures (e.g. bioterrorism attack), post-exposure prevention is given
with antibiotics like penicillin G, ciprofloxacin, levofloxacin and
doxycycline. Immunisation with three doses of vaccine –
intramuscularly is also started immediately. Research is going on to
prepare oral vaccine.