Anthrax, Splenic fever, Carbuncle, Malignant pustule, and Woolsorters disease.
All of them refer to only one serious and zoonotic disease that can be transmitted from animals to humans.
Dr. Provet always cares for both animals and the vet's health.
So, DR. Provet decided to discuss this disease through this article.
This article includes:
Epidemiology of Anthrax
- Source and reservoir of anthrax infection.
- Mode of transmission of anthrax to man
- Types of anthrax in man.
- Prevention and control of anthrax in man.
- Diagnosis of anthrax in man.
- Prophylaxis and treatment of anthrax in man.
- Elimination of industrial infection.
Epidemiology of Anthrax
The causative agent of anthrax is Bacillus anthracis, which Is found all over the world, and is the cause of the disease in domestic animals.
The major reason for the continuing presence of the disease is that the organism produces spores in an attempt to resist unfavorable environmental conditions.
Anthrax spores are not normally found in living animals, but once infected fluid, exudates, blood, or tissues are shed into the environment, then spore formation will occur on exposure to the atmosphere.
In man, the disease generally appears as an infection of the skin (Malignant pustule), but may occur in a pneumatic air-borne form Wool sorter's disease”.
Source and reservoir of anthrax infection
This disease has several sources, including:
Blood, fluid, and tissues of animals dying of the disease.
Contaminated animal products as hair, wool, hides, and skins.
Food and dust particles contaminated with anthrax spores.
Cattle, sheep, and goats (e.g., herbivorous animals) are reservoirs of infection to man.
Mode of transmission of anthrax
Anthrax can be transmitted to man through:
Direct contact with animals' secretions and excretions.
Manipulation of animal products contaminated with anthrax.
In the condition of the presence of skin abrasion, scratch, or small wounds on an exposed surface.
It usually occurs during skinning or autopsying infected cattle or during shearing sheep.
Also, a man can be infected by a dog that had fed on a dead sheep.
Inhalation of spores in dust, during wool sorting, or from dried skin or hair, or the use of dried animal fertilizers.
House flies and other insects have been implicated in the transmission of spores mechanically from animals to man.
Bites of pet animals have recently fed on carcasses of animals dead from anthrax.
Man-to-man transmission is rare, although one case was reported in which a child contracted ocular anthrax from his father, who had an anthrax lesion (Malignant pustule).
Workmen in tanneries may also carry the infection to members of their families.
Laboratory infection: accidental infection occurs among laboratory workers from cultures and experimentally infected laboratory animals.
Types of anthrax in man:
According to the occupation, there are Two basic clinical types of infections in man:
Industrial anthrax:
It affects mostly those engaged in industries of animal products such as those handling sheep wool, animal hair, pig bristles, hides, bones, and other products of animal origin.
It takes the form of malignant pustules on skin or acute pulmonary infection, depending on the nature of the industrial treatment of animal products.
Non-Industrial Or agricultural anthrax
It affects farmers, veterinarians, butchers, pathologists, knacker man and those coming in contact with infected animals.
The incubation period is within 7 days but is usually less than 4 days.
In skin form, the lesion is generally evident within 2 days, while in the respiratory form of the disease it is not more than one day.
Malignant pustule:
It represents 98% of human anthrax, the following considerations are noticed:
There is no seasonal incidence with this form of anthrax.
The site of skin lesions will vary according to the nature of the industrial occupation.
Persons carrying hide on their shoulders are frequently infected on the back of the neck.
Slaughterman and pathologists on the other hand are usually infected on the arms, fingers, and wrist.
When spores contaminated shaving brushes(before compulsory sterilization), the infections were confined to the face and front of the neck.
The early symptoms include:
Itching on the exposed surface.
A small macule appears surrounded by an area of erythema.
The macule becomes elevated, and a papule is formed and vesication takes place in which the vesicles contain clear yellow fluid.
The vesicles increase rapidly in size, and the color becomes dark red and finally black.
The lesion may become nearly 5 cm in diameter, surrounded by a wide area of edema, which later becomes hard, but not particularly painful, and if left without treatment, infection tends to spread rapidly to regional lymph nodes and bloodstream resulting in septicemia and death within 5-6 days.
On the other hand, infection through the gastrointestinal route(an intestinal form of anthrax) is rare.
Wool sorter's disease:
Wool sorter's disease is characterized by:
Severe bronchopneumonia.
Patchy areas of Hemorrhagic consolidation in the lungs.
Enlargement of the regional lymph nodes.
Both the pulmonary and intestinal forms of anthrax are almost fatal and lead to death in the majority of cases.
Prevention and control of anthrax in man
Control of anthrax relies upon 3 main factors, including:
Early diagnosis of the disease.
Prophylactic measures.
Effective treatment of infected persons.
Diagnosis of anthrax
The disease is often not diagnosed in animals during life, because they usually die suddenly.
Prophylaxis of anthrax in man:
Protective vaccination of persons in high-risk occupations by sterile alum precipitated anthrax antigen (Wright's vaccine) is available for immunization of man.
It is given three subcutaneous injections, each of 0.5 ml, in a 6 months interval.
Treatment of anthrax in man
Cutaneous anthrax (Malignant pustule) responds very satisfactorily to treatment.
The intestinal and pulmonary forms are almost fatal.
The treatment of cutaneous anthrax in man relies mainly on procaine penicillin therapy.
The dose and the route of administration will depend on the individual case (streptomycin may produce a synergistic response when in combination with penicillin).
Patients with mild edema require 1-1.5 mega units intramuscularly every 12 hours for 2 days.
Extensive edema requires one mega unit of penicillin every 6 hours, especially if the lesion is on the head or neck or when respiratory embarrassment is present.
On the other hand, in the case of pulmonary anthrax, it is essential to make an early diagnosis, and treatment must commence as soon as anthrax is suspected.
The penicillin dosage is 20 mega units over 24 hours, given by continuous drip.
Treatment of pulmonary anthrax requires to be continued for 14 days or more to prevent reinfection bacteremia.
Passive immunity may be conveyed hyperimmune serum is also helpful and frequently used at a dose of 10-20 ml given intravenously.
Elimination of industrial infection.
These rely upon:
Disinfection of raw animal products
Wool disinfection: Preliminary agitation in warm alkali and soap for 20 minutes and then exposure to 2% formaldehyde solution and drying in hot air 30-40 c°.
Hair for shaving brushes: Autoclaved or boiled for 3 hours or exposed to warm formaldehyde gas 10%.
Hides and skins:
The Austrian Schotten Froh method: 2 % Hcl + 10% Nacl for 2 days at 20 c°. This method kills spores but leaves harsh skin which is hard to tan satisfactorily.
The English Segmons-Jones method: 1/5000 Hgcl2 +1% formic acid for one day, then 2 weeks holding period after treatment.
The use of H2s gas: for 7–16 days.
Disinfection of the workplace:
Disinfection of the effluents and wastes in factories dealing with animals also or manufacturing their products.
Exhaust fan ventilation system in wool industries.
Suppression of dust.
Education of the employees:
Health education of workers and prevention of eating in the working room, but they should eat in special halls separated from the working area.
Tannery workers should wash their hands with soap and water before eating and take a shower before changing the street clothes.
Clothing worn by workers in tanneries should not be taken out of the tannery until first disinfected.
Workers should be instructed to pay attention to every skin wound, and no one should work with an unprotected open wound of any kind.
Finally, Dr.provet wanted to focus on the transmission of anthrax to man and how this serious disease can threaten vets and needs perfect control.
Written by: Dr. Mai Foda
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