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Synonyms
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In animals: ‘Adaippan noiy’ (Tamil)
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In humans: Woolsorter's disease (pneumonic anthrax or pulmonary anthrax), Rag-picker's disease, Knacker's disease, Hide-porter’s disease (cutaneous anthrax), Malignant edema, Malignant carbuncle, Malignant pustule, Charbon, Milz brand disease, Splenic fever
Type of zoonosis
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Direct anthropozoonosis
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Occupational zoonosis
Definition
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Anthrax ('Anthrakis' is the Greek word, means 'coal', and refering to the blackened eschar skin lesion) is an acute infectious disease of all animals and human beings, caused by Bacillus anthacis. Human infection is clinically characterized by necrotic cutaneous ulcer (Eschar), pulmonay manifestations and gastrointestinal manifestations, or some times meningeal form.
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In animals, anthrax is characterized by septicemia and sudden death, accompanied by the exudation of tarry coloured unclotted blood from the natural orifices (mouth, nose, ear, anus) and the important findings of failure of the blood to clot, absence of rigor mortis and bloaty appearance.
Brief history
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In 1876-1877, the absolute proof of the etiology of anthrax was established by Robert Koch and named it, 'Bacillus anthracis', and the famous "Koch's postulates" was formulated using anthrax as the model infection.
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In 1881, Louis Pasteur produced vaccine against anthrax.
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In 1939, Stern evolved a vaccine called "Stern's vaccine / Spore vaccine" and still used this technique for vaccine production for animals.
Etiology
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Bacillus anthracis, is a Gram-positive, endospore-forming, rod-shaped (square-ended), non-motile and facultatively aerobic bacteria.
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Pathogenecity of anthrax bacilli depends on three factors, are
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Factor I: Edema factor - Inflammatory property
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Fator II: Protective antigen (PA) - Antiphagocytic and immunogenic factor. The capsular polypeptide, poly-D-glutamic acid, which is antiphagocytic in nature. It contains two plasmids px01 and px02, which are responsible for the production of virulence factors. It produces three types of toxins, which are extracellular in nature.
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Factor III: Lethal factor - Inflammatory property
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There are two forms: (a). Vegetative form (capsular form) within the host and (b). Spore form in the environment.
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Spores are formed through sporulation, when exposed to oxygen in the air.
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Spores are resistant against cold, heat, chemicals and drying. They are viable for many years (>60 years) in the soil (if it is at least 15 cm below the soil) with neutral or alkaline pH and in alluvia soil.Such soil/field is called as cursed soil. Acidic soil reduces the survivability of spores.
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Spores can be destroyed by heating at 100°C for 10 minutes, 5% sodium hydroxide, 10% formalin at 40°C for 15 minutes and 3% peracetic acid.
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Vegetative form can be killed at 60°C for 30 minutes.
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Anthrax spores are considered to be one of a number of potential agents for use in biological terrorism.
Reservoir and incidence
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It is distributed worldwide, except Antarctica. It is common in agricultural regions where it occurs in animas.
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Globally it has been estimated that as many as 20000 to 100000 human cases of anthrax occur annually.
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Many regions in India are still enzootic for animal anthrax and sporadic cases of human anthrax have been reported, especially from South India (Tamil Nadu, Puducherry, Anthra Pradesh and Karnataka).
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Tamil Nadu: Vellore, Vaniyambadi, Ambur, Sempattu (Trichy) and Chennai.
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Andhra Pradesh: Chittoor, Cuddapah, Gundur and Prakasam.
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Karnataka: Mysore, Midnapore and Kolar.
- Soil is the reservoir for the infectious agents.
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For man, the source of infection is always infected animals, contaminated animal products (leather, belts, wool, fur, hairs, skin and bone meal) or environmental contamination by anthrax spores.
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Anthrax belt / Anthrax zone / Anthrax district: It is determined by the soil type and climate, which is also termed as "incubator area" of anthrax. It is more common in tropical and subtropical countries than temperate countries. Outbreaks in animals often recorded when there is high rain fall after prolonged draught. The area will be enzootic for anthrax under these circumstances. When the temperature is over 15°C with relative humidity of 60% and higher results in sporulation and soil-borne infection. This relationship to climate has made it possible to predict "anthrax year".
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Outbreaks of anthrax in animals in Tamil Nau, India between 1991-2006
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Transmission
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Herbivorous animals infected by ingestion of spores which are viable in soil for years and contaminated feed or water.
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Man is infected by
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Cutaneous route: contact with contaminated carcasses, wool, hide or hair.
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Ingestion (Oral route): ingestion of under-cooked infected meat.
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Inhalation (Respiratory route): during wool sorting. It needs higher dose (LD50) of 8000 to 10000 viable spores.
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Inhalation of spores along with ingestion of under-cooked infected meat is highly fatal than cutaneous route of infection.
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Mortality may be 20%, 25-60% and 100% respectively in cutaneous, oral and pulmonary route of infection.
Disease in animals
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It primarily affects all warm-blooded animals, especially cattle, sheep, goats, horses and pigs. Algerian sheep and dwarf pigs are naturally resistant to anthrax.
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It is also recorded in dogs, chickens, elephants, camels, tigers, cats, etc.
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The morbidity and mortality are 70 to 80 and 1 to 5% in highly susceptible and less susceptible animals, respectively. But, it is fatal in swine.
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Incubation period 1-5 days. It occurs as peracute, acute, subacute and rarely chronic form. In swine, it may be pharyngeal form, intestinal form and septicemic form.
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Anthrax is characterized by septicemia and sudden death, accompanied by the exudation of tarry coloured unclotted blood from the natural orifices (mouth, nose, ear, anus) and the important findings of failure of the blood to clot, absence of rigor mortis and bloaty appearance.
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Carcass suspected for anthrax MUST NOT BE OPENED. In accidentally opened carcasses, splenomegaly (six time enlarged than the normal spleen) was observed, with "black-berry jam consistency" of spleen.
Disease in man
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Eschar lesion on lower left eye lid
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Eschar lesion on neck
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Diagnosis
Treatment
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Cutaneous anthrax: Procaine penicillin - 1 million units i/m injection for every 12 to 24 hrs for 5 to 7 days.
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Pulmonary anthrax: Penicillin G - 2 million units i/v injection or Penicillin G - 500000 units i/v injection slowly for every 4 to 6 hrs until temperature returns to normal or Streptomycin - 1 to 2 g / day.
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Gastrointestinal anthrax: Ciprofloxacin 400 mg, every 12 hrs i/v injection and ampicilin - 500 mg i/v injection, every 8 hrs for five days, followed by injections ciprofloxacin - 500 mg twice a day and ampicilin - 500 mg at every 8 hrs interval for two weeks.
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Chloramphenicol, tetracycline, doxycycline and erythromycin can also be effective for anthrax.
Prevention and control
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Carcass disposal involves incineration or deep burial. Barns and fences should be disinfected with 10% sodium hydroxide or 3% peracetic acid.
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Protective measures to be taken while handling of infected wool and hide.
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Prevent the contact and ingestion of infected animal products.
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People handling dead carcasses suspected for anthrax must not have skin abrasions, should wear face mask, gum boots and protective clothing.
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In animals:
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Using anthrax spore vaccine in animals can prevent the disease.
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Disinfect wool or hair from animals in endemic areas with 10% formalin, 5% lye or 3% peracetic acid.
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Two to three days before and after vaccination of animals, antibiotics should not be administered.
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Pregnant animals should not be vaccinated.
Disposal of anthrax infected carcass
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When an anthrax case is detected during the clinical examination of the herd or during slaughter or post-mortem examination, immediate restrictions are imposed on all activities to prevent the spread of the disease. In slaghterhouse all the slaughter operations should be stopped and affected and in contact animals are disposed off as per the recommended procedure. The buildings and slaughterhouses are completely disinfected before subsequent use.
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It is legally required that suspected carcass should not be opened or incised. The natural orifices should be plugged with disinfected cotton.
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Contaminated material along with animal should be collected and carried away in a closed vehicle to the site of disposal.
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If necessary, post-mortem inspection can be conducted at the site of disposal.
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The animals should not be dragged or left uncovered for birds and wild animals to feed upon.
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It should be protected from human beings and other domestic animals and it should not contaminate farmhouses, water supplies and pastures.
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Best method of disposal is burning or incineration. If it is not possible, burial should be done in a remote area. The area is declared protected from domestic and wild animals. A 2-meter deep pit is suitable for burial of average sized animal. The carcass should be covered with sufficient quantities of quick lime (caustic soda) and soil.
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The farm buildings, slaughter houses, exposed hospital equipment and clothings, boots and gloves should be disinfected with
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5-10% formaldehyde
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4% warm sodium carbonate
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4-5% lye
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5% phenol
- Disinfect wool or hair from animals in endemic areas with 10% formalin, 5% lye or 3% peracetic acid.
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