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Anthrax

Anthrax

Anthrax is primarily a zoonotic disease. Large epidemics of anthrax acquired by inhalation have reported to cause deaths enormously in the past. The fatal disease anthrax is caused by a pathogenic bacterium, Bacillus anthracis. It has got a lot of credits on its own. It is considered as;
1. The first bacterium to be viewed under microscope
2. First communicable disease spread through inoculation of infected blood
3. First bacilli isolated from pure culture
4. First bacilli to produce spores
5. First bacteria used for preparing attenuated vaccine

It is considered as one of the largest pathogenic bacteria. In culture media, the bacilli shows a characteristic “bamboo stick” appearance. Central, ovoid spores are produced with the same size as that of the bacterial cell. It is non-motile. A specific presumptive diagnostic method called M’Fadyean’s reaction can be done which shows out the capsular material inside the bacilli which is specific for B. anthracis.

Under low power microscope, the edges of the bacterial colony resemble locks of matted hair. This is called ‘Medusa Head’ appearance. Growth in gelatin shows off like a ‘Fir tree’. ‘String of pearls’ reaction is also characteristic of B. anthracis.

Spores of B. anthracis are resistant to environmental factors, physical and chemical agents, and have been isolated from soil after 60years, but the vegetative cells are easily killed at 600C in 30minutes. 4%potassium permanganate is effective against spores as they are killed in 15 minutes. Bacilli are susceptible to sulphonamides, streptomycin, tetracycline and chloramphenicol.Two virulent factors have been identified from the bacillus; the capsular polypeptide which inhibits phagocytosis and the anthrax toxin producing generalized shock and local edema. Human anthrax is contracted from infected animals. Certain biting insects like Stomoxys calcitrans also might transmit anthrax.

The disease can appear in different forms;
1. Cutaneous anthrax: pathogen enters through the skin of the face, neck, hands and arms. Shaving brushes made of animal hair spreads cutaneous infections. The lesions start to appear as an elevation called as papule and later becoming vesicular with clear or blood stained fluid in them.

The whole area becomes overcrowded and edematous. The central main necrotic lesion; malignant pustule, starts to get surrounded by small satellite lesions. The central lesion becomes covered with a black scab resembling that of a burn known as eschar which resembles coal. That is how the name anthrax (meaning coal) has developed. Since this type is seen commonly among dock workers and lesions appears on the back, cutaneous anthrax is also called ‘hide porter’s disease’. Since it resolves spontaneously, most cases go untreated leading to meningitis or fatal septicemia.

2. Pulmonary anthrax: commonly known as ‘wool sorter’s disease’ as it is seen in wool factory workers. It onsets as hemorrhagic pneumonia with high fatality rate.

3. Intestinal anthrax: it is common only in certain primitive human beings who eat animal carcasses. Some of them may have died of anthrax. Aggressive enteritis occurs associated with bloody diarrhea.

4. Industrial: meat packing and or wool workers are prone to industrial anthrax.

5. Non-industrial: these include occupational hazards like those associated with animals. Example, veterinarians, butchers and farmers.

Human anthrax can be prevented by;
1. Improving the factory hygienic conditions
2. Prevent close contact with suspected animals
3. Proper sterilization of animal hide and wool
4. Animals which have been died of anthrax should be buried deep in quicklime or burned.
5. Active immunization
6. Antibiotics are ineffective against toxins.

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