Anthrax (Splenic fever) (Charbons) is a fatal infectious disease of all animals and man, caused by Bacillus anthracis.
- Let's know more about this serious disease through Dr. Provet article which will include:
- What's anthrax in animals?
- What's the Bacillus anthracis?
- Distribution of Anthrax.
- Susceptibility of Anthrax.
- Sources of Anthrax infection.
- How can anthrax be transmitted?
- Pathogenesis of Anthrax.
- Clinical signs of anthrax in cattle and sheep.
- Clinical signs of anthrax in Equine.
- Clinical signs of anthrax in dogs.
- The postmortem lesions of anthrax.
- Diagnosis of anthrax.
- Differential diagnosis of anthrax.
- Prognosis of anthrax.
- The optimum Control of anthrax.
- Vaccination against anthrax.
It's a fatal disease that threatens all animal species and man.
It's characterized by:
The sudden death of the affected animal.
Exudation of the tarry blood from all-natural orifices of the body.
Failure of blood to coagulate.
Enlargement of the spleen.
Absence of rigor mortis after death.
What's the Bacillus anthracis?
It is Gram-positive, non-motile large bacilli of some specific properties, including:
In animal tissue, it develops a capsule of polyglutamic acid.
It forms central spores when exposed to the air.
Spores are resistant to salting, dryness, and the standard disinfectants.
It remains in the soil for several decades.
The spores are killed by boiling for 10 minutes, 5% phenol for two days, 10% formalin for 10 minutes, and 3% hydrogen peroxide for 30 minutes kills the spores.
Distribution of Anthrax
It is a worldwide, soil-borne infection, so its outbreaks occur after a major climatic change, as heavy rains carry the spores into water holes that act as incubators.
Susceptibility of Anthrax
All animals are susceptible, mostly herbivorous ones.
The susceptibility of domestic animals is the highest in sheep, then cattle, goats, buffaloes, camels, hones, pigs, dogs, cats, and man respectively.
Also, zoos and wild animals are susceptible.
Birds are not susceptible.
Sources of Anthrax infection
This serious disease has many sources of infection, including:
Infected animals.
Soil and infected pastures.
Animal products such as bone meal, wool, hair, hide,s, and fertilizers.
How can anthrax be transmitted?
Bacillus anthracis can invade the body through different modes of transmission, including:
Ingestion of contaminated food.
Skin abrasions.
Inhalation.
Mechanical transmission by biting flies.
Pathogenesis of Anthrax
Spores enter through injuries of the digestive tract, mucous membrane's or skin.
Then spores germinate and are carried by phagocytes to the local lymph nodes where they multiply and form capsules that protect them from phagocytosis.
Then bacilli reach the blood via lymphatics and septicemia develops with the invasion of all animal body tissues.
The bacilli block blood capillaries, resulting in fatal anoxia.
The organism produces three types of toxins:
Edema factor.
Protective factor.
Lethal factor.
Death may be attributed to anoxia, respiratory distress, shock, k, and renal failure.
Clinical signs of anthrax
The clinical signs slightly differ from one animal species to another one.
Clinical signs of anthrax in cattle and sheep
There are 2 forms of anthrax in cattle and sheep, including:
Peracute form
This form is characterized by:
Sudden death without previous clinical signs.
Fever, convulsions, and tremors with death occurring 1-4 hours.
Tarry blood escapes from all-natural orifices after death, which does not tend to coagulate.
Acute form:
This form is characterized by:
Fever, cessation of rumination, and lactation.
Mucous membranes are congested and show petechial hemorrhage.
Edema of the tongue, throat, sternum, perineum, and flanks.
Abortion of pregnant cows.
Bloody milk and urine.
Bloody diarrhea.
Clinical signs of anthrax in Equine
The affected horse usually shows:
Fever.
Enteritis and colic.
Obliteration of supraorbital fossa.
Hot painful subcutaneous edema of the throat, lower neck, the lower part of the abdomen, prepuce and mammary glands
Clinical signs of anthrax in dogs
When a dog is infected by anthrax, it will show:
Fever.
Swelling of the throat.
Hemorrhagic gastroenteritis.
The postmortem lesions of anthrax
It is forbidden to open a carcass of animals suspected to be infected with anthrax.
But generally, the carcass shows:
Exudation of tarry blood from all body orifices and not tend to coagulate.
Absence of rigor mortis.
Rapid decomposition of the carcass.
Gelatinous fluid in subcutaneous tissues.
Body cavities contain bloody stained fluids.
Diagnosis of anthrax
This serious disease can be diagnosed through:
Clinical signs.
Laboratory diagnosis with accurate steps, including:
Sampling
The samples are collected from:
Blood swabs from exuded blood.
Blood smears and aspirated fluid from localized lesions, especially in horses.
Pieces of the ear with cauterization.
Hair, wool, and hides.
Samples should be collected only from fresh carcass submitted on ice and packed in non-breakable containers and labeled “Suspected Anthrax”
Microscopical examination
The blood smears are stained with polychrome methylene blue or Giemsa stain for demonstration of McFadyean's reaction. The capsule is purple, and the bacilli are stained pink.
Isolation of the organism on blood agar media.
The colonies are rough, flat, gray without hemolysis or with weak hemolysis.
Guinea pigs and mice inoculation
These animals are inoculated with blood or tissues suspension, either s/c or I/v.
The animal dies within 24 hours, and Bacillus anthracis can be demonstrated in smears from their spleen and blood.
Ascoli's test (Precipitin test)
It is used for the detection of anthrax bacilli in tissues, hair, hides, or putrefied material.
Boil 2 gm of suspected material in 5 cm saline containing acetic acid 1%, then cool and filter this mixture.
Put 5 cm of anti-anthrax serum in a test tube - and then put the filtrate over it.
If positive, a white ring at the junction of the two fluids will be formed.
Differential diagnosis of anthrax
Anthrax may be confused with other causes of:
Sudden death in cattle and sheep as:
Hemorrhagic septicemia.
Clostridial diseases (Blackleg disease, Black disease, Bacillary hemoglobinuria, Pulpy kidney, and Struck).
Subcutaneous edema in equine confused with:
Strangles.
Glanders.
Hemorrhagic septicemia.
Prognosis of anthrax
The peracute cases are unfavorable.
The subacute cases are favorable if treated immediately after the rising of temperature.
The optimum Control of anthrax
For optimum control of the disease, vets should follow the next strategy, including:
Hygienic measures:
Notification of the veterinary authorities.
Strict quarantine measures against the infected premises.
Isolation of suspected cases and should be given antibiotics and antiserum.
It is forbidden to open infected carcasses and should be disposed of by burning or deep burial with the infected materials at least two meters deep with the addition of quick lime.
Disinfection of stables and the equipment using 5-10% formalin.
Insect control.
Treatment of the diseased animals
Treatment is possible only in the early stages of the disease, including:
Penicillin with 10,000 IU/Kg b.w., I/M twice daily for five successive days.
Streptomycin is given in a dose of eight-gram I/M twice daily for five days.
I/V injection of anthrax antiserum 100-250 ml/animal.
Vaccination against anthrax
The vaccination against this serious disease includes:
Attenuated spore vaccine (Pasteur I&II):
It may produce cases of anthrax
These vaccines are not used nowadays.
A virulent spore vaccine:
It produces good protection for 9-12 months.
It has postvaccinal reactions such as fever, drops in milk yield, and abortion.
Saponified vaccine:
A Pasteur II vaccine suspended in 10% saponin.
It may cause new cases.
Anthrax bacterins:
It gives short immunity.
It is used in uncontaminated areas.
Serovaccination:
The use of Pasteur II vaccine and at the same time inoculation of 10-20 ml of immune sera.