Anthrax:

Syn: Wool sorter’s disease, Splenic fever

• It is an acute infectious disease of livestock that occurs throughout the globe.
• It is zoonotic in nature and human contact infection through infected cattle.
• Cattle and sheep are most susceptible animal.

Etiology:

• Bacillus anthracis
• It is gram +ve, rod-shaped, non-motile organism.
• Organism remains in chains
• Size: 1-1.2 µm in diameter, 4-8µm in length
• Organism produce spores when comes in contact with oxygen. Spores are very resistant to heat, drying, chemicals.
• Spores remain viable in the soil for considerable period of time without endangering the life of animals.

Epidemiology:

• Disease is distributed globally.
• Cattle and sheep are most susceptible animal followed by horse and pig.
• Organism produces three types of toxin
  • Factor I- Edema toxin
  • Factor II- Protective antigen
  • Factor III- Lethal factor

Transmission:

• Through ingestion of contaminated carcass.
• Through ingestion of contaminated feed and water
• Through skin or mucosa; oral, conjunctival
• Inhalation of spores
• Soil is main source of infection in animals

Pathogenesis:

Clinical Signs:

Cattle and buffalo:

Acute case:

• Elevation of body temperature; 104-108°F
• Animal refuse to eat and there is development of bloat.
• Increased pulse and respiratory rate.
• Development of muscle tremor
• At end, animal shows distressed breathing.
• Extreme dyspnoea lead to mouth breathing.
• Following death, there is oozing of blood from all-natural orifices; nose, ear, eyes, anal region, vulva
• Death usually occurs in 48 hours.

Sub-acute case:

• It is characterized by edema.
• Edema is predominantly found in neck, brisket region, thorax, abdomen, flank.
• Jugular pulse noted at terminal stages.
• Abortion in pregnant animals.

Sheep and Goat:

• Sudden death which is characteristic in nature.
• Sometime death is preceded by staggering gait, trembling of body, vertigo, grinding of teeth and labored breathing.
• There is frothy hemorrhagic discharge from mouth and natural orifices.
• Increased temperature, anorexia, depression, drooping of ears
• Convulsion

Horse:

Symptoms are generally acute in nature and follow septicaemic course.

Per-acute form:

• There is sudden death without any clinical manifestation.
• Horse may die while at work or found dead in grazing field.

Acute form:

• High rise of temperature, rapid pulse rate and respiratory distress
• Mucus membrane may show cyanotic changes
• Acute attack of colic with passage of bloody faeces.
• Staggering and signs of spasm
• Death within 5-10 hours following the attack.

Sub-acute form:

• Edematous swelling on lower part of abdomen, thorax, shoulder, legs.
• Intermittent colic, abdominal respiration
• Carbuncles are located on neck, chest, abdomen and limbs.

Pig:

• Disease is either acute or sub-acute in nature.
• Lymph nodes of the neck region are swollen
• Difficulty in respiration and swallowing due to swelling
• Visible mucus membrane turns red.
• Hemorrhagic spots are found scattered over the skin surface.
• Death usually takes place within 2-3 days following infection.

PM lesion:

• Carcass decompose rapidly with formation of gas and distension of abdomen.
• Rigor mortis is absent.
• Discharge of blood- and blood-stained fluid through natural orifices
• Visible mucus membrane remains purple in color.
• Blood is dark red or black in appearance and blood donot clot.
• Yellow gelatinous fluid is found in every part of subcutaneous tissue.
• Spleen is enlarged and soft.
• Congestion of liver and kidney.
• Lungs are congested, swollen and edematous.

Diagnosis:

• Animals died suddenly with bloody discharges from mouth, nostrils, anus must be suspected to have died of anthrax.
• Suspected carcass should not be opened.
• Microscopic examination of blood films; Presence of large square ended blue rods in short chain with pink capsules (Mac-Faydean’s reaction).
• Cultural examination: Samples from suspected tissue should be inoculated in 5% blood agar and incubated aerobically at 37°C for 18-24 hours.
• Cultural examination of sample in nutrient agar reveals medusa-head appearance.
• Animal inoculation test: 0.5 ml of suspension made from small quantity of blood from ear vein are inoculated in thigh of guinea pig SC. The animal will die in 36-40 hours in positive case.
• Serological test: Ascoli’s test is done. Whitish ring at junction of two fluids reveals positive case.
• ELISA

Differential Diagnosis:

1. Lightning stroke:

• Sudden death with singeing marks on hairs of striken area.
• Absence of anthrax organisms in blood smear.

2. Electric Injury:

• There is history of contact with electric cords.
• Number of animals may be found dead in same areas.
• Lesion have a charred appearance.

3. Acute tympany:

• It may produce death of ruminant animals due to respiratory failure.
• It is characterized by distension of abdomen and distressed breathing with extension of head and neck.
• History of excessive carbohydrate ingestion

4. Black quarter:

• Well built calf with adequate development of muscles are the usual victim.
• Emphysematous condition of muscle giving rise to crepitation.
• Spleen is normal.

5. Hemorrhagic Septicaemia:

• High rise of temperature, nasal discharge, distressed breathing
• Swelling of neck region, respiratory embarrasement and death due to asphyxia

6. Acute lead poisoning:

• It is characterized by sudden death.
• Respiratory distress and cyanosis of mucus membrane.
• Animal shows nervous signs

7. Snake bite:

• Dead animal shows principal evidence of fang marks and edema of surrounding bite.

8. HCN poisoning:

• It causes sudden death due to ingestion of cyanogenic plants.
• Animal shows severe dyspnea due to anoxia.
• Spleen not enlarged.

9. Acute leptospirosis:

• Disease is characterized by oliguria, proteinuria with hemoglobinuria.
• Elevation of urine bilirubin and urobilinogen
• Detection of organism in urine or blood by dark filed microscopy

10. Acute infectious anemia:

• This disease may simulate anthrax but causative organism is virus
• No enlargement of spleen
• No oozing of blood from nostrils.

11. Acute swine fever:

• It may produce sudden death in pigs.
• It is characterized by high rise of temperature, coughing.
• Pinpoint hemorrhage in kidney, button ulcers in intestine

Treatment:

• Per-acute cases of anthrax may not allow treatment of animals due to sudden death.
• Penicillin is the drug of choice. Penicillin @10,000 units/kg, b.wt. BID through parenteral route has been proved to be effective against anthrax.
• Streptomycin can also be used @ 8-10 gm in divided doses through IM injection in cattle.
• Apart from these antibiotics; oxytetracycline, erythromycin, chloramphenicol or sulphonamide have been suggested.
• Anti-anthrax serum @ 100-200 cc IV along with a course of penicillin
• Treatment has to be continued for at least 5-7 days.

Control Measures:

• Introduction of animals from disease prevalent area should be restricted.
• Fodder from infected pasture should be destroyed.
• Strict quarantine measures should be followed in anthrax prone areas.
• Dead body should be disposed off properly and safely either by burial or burning method.
• Areas of dead and infected animal should be disinfected by applying 3% peracetic acid or 10% caustic soda or 10% formalin. 3% per acetic acid is considered effective sporicide. Dose; 8 litre/sq.m
• Hides, wools, bone meals, etc should be sterilized through irradiation
• Fly repellant should be used to control insect population.
• Carcass shouldnot be opened as organism forms spore when gets exposed to environment
• Adequate sanitary measures should be adopted while handling the case of anthrax.
• Vaccination of animal in prone areas annually 1-2 months prior to anthrax season.
• Anthrax spore vaccine have been produced by NVPL in Nepal and been used for immunization. Dose is 1ml for cattle, horse, sheep and goat.