Background

Antharx is caused by Bacillus anthracis, a Gram positive bacterium. The bacterium exhibit two forms i.e. the vegetative form and the spore form. Bacterium can survive in the environment for a long period by producing spores on exposure to free atmospheric oxygen, through a process known as sporulation. It is a fatal septicaemic disease affects livestock as well as wild animals. Cattle and sheep are more susceptible than other farm animals. Affected cattle die due to severe septicaemia resulting in haemorrhages and death due to shock. On post mortem examination, dark un-clotted un-oxygenated blood may be seen in the body cavities with incomplete rigor mortis, subcutaneous oedema and splenomegaly. The major virulence factors are the bacterial capsule encoded by pXO2 plasmid and the exotoxin encoded by the pXO1 plasmid which has three major antigenic components i.e. protective antigen, edema factor, a calmodulin dependant adenylate cyclase and lethal factor, a zinc metalloprotease. These three components of anthrax toxin i.e. edema factor lethal factor and protective antigen are released from the bacterium as soluble monomeric proteins. It has also zoonotic importance. Disease is transmitted through ingestion of feed material including fodder, bone meal and water contaminated with anthrax bacilli or inhalation of contaminated air droplets and dust due to infected hide, wool, soil etc. Transmission may also occur due to certain arthropod vectors like Stomoxys spp. and Tabanus spp. etc.

Cause

A bacterial disease caused by a bacteria, Bacillus anthracis

Host Species

Cattle, sheep, goat, horse, pig, dog and cat

• The animals get infection through ingestion, inhalation, and through the skin.
• The animals are generally infected by the ingestion of contaminated food or water.
• The injury of the mucous membrane of the digestive tract also facilitates infection.
• The grazing of animal on pasture grown on contaminated soil and injury of the oral mucosa facilitate the invasion by the organism and increase the incidence of the disease.
• Inhalation of contaminated dust is also important for contracting infection.
• Biting flies like Tabanus sp, mosquitoes, ticks, and other insects also harbor anthrax organisms and transmit the infection during the late summer and autumn seasons due to the increase in the fly population.
• Human beings working in the wool and hair industries may get infection through the inhalation of anthrax spores where cutaneous anthrax is much more common.

Cattle and sheep

The disease is manifested in two forms:

Per-acute and Acute

The per-acute form

• This form of the disease is commonly seen at the initial stage of the outbreak.
• The course of diseases is of 1-2 hours and animals suddenly die without showing any pre-dominant signs.
• The clinical signs like fever, muscle tremor, respiratory distress and congested mucous membranes may be observed.
• The animal immediately collapses, and dies after convulsions.
• The discharges of blood from the mouth, nostrils, anus and vulva are common and pathognomonic

The acute form

• The course of the diseases is of about 48 hours.
• A high rise of body temperature (41 to 42°C), very rapid and deep respiration, congested and hemorrhagic mucosae and increased heart rate are observed.
• Initially, severe depression and listlessness followed by a short period of excitement is also observed.
• Animal do not take food and show ruminal contractions.
• Abortion may occur in pregnant cows.

Pigs

• The disease is acute or sub-acute in nature.
• High rise of body temperature, dullness and loss of appetite
• The swelling and edema of the throat and face may obstruct swallowing and respiration. Bloodstained froth are seen at the mouth.
• Petechial hemorrhages are present in the skin.
• Dysentery is observed when intestine is affected.
• Respiratory distress and signs of pneumonia are also common.
• Death usually occurs after 12-36 hours of onset of disease, although individual cases may linger for several days.

Horses

• The disease is always acute in nature in horse.
• High fever, marked depression and dyspnea due to swelling of the throat and colic due to intestinal irritation are observed.
• The clinical signs vary depending on the mode of infection.
• When infection is by ingestion there will be septicemia, diarrhea and severe colic.
• When horse acquire infection through insect bite, there will be hot, painful, edematous, subcutaneous swellings appear in the throat, lower neck, floor of the thorax and abdomen, prepuce, and mammary gland.
• The course of the disease is usually 48-96 hours.

Management

No scope of treatment in per acute cases.

If fever is detected before other signs, animal may recover with the appropriate treatment

• Non steroidal anti-inflammatory drugs (NSAID) to alleviate fever and pain
• Penicillin (20000 IU/kg BW twice daily), streptomycin (8-10g/day in two doses) intramuscularly for cattle or Oxytetracycline (5-10 mg/kg BW per day) parenterally are effective.
• Antiserum, if available, should also be administered for at least 5 days in doses of 100-250 mL daily but it is expensive.

Preventive measures

• In outbreak of the disease, the farm should be kept in quarantine.
• The discharges and cadavers are to be destroyed properly.
• Survivor animals are to be vaccinated immediately.
• Disposal of infected material and hygiene are most important in the prevention of spread of the disease.
• Infected carcasses should not be opened.
• The carcass along with bedding and soil contaminated by discharges must be burnt or buried.
• If it is not possible immediately, 5% formaldehyde is applied in sufficient quantities on the carcass.
• The premises, hides, bone meal, fertilizer, wool, and hair require to be disinfected.
• Strong disinfectants such as lysol (5%), formalin or sodium hydroxide (5-10%) and peracetic acid (3%) are appropriate disinfectants to destroy spores.
• Special care must be taken to avoid human contact with infected material and, if such contact does occur, the contaminated skin must be thoroughly disinfected.

Control

Regular vaccination is the only effective way to control the disease

Type of vaccines

Anthrax spore live vaccine

Vaccination schedule

First vaccination is done at 6 months of age followed by annual vaccination. The vaccination preferably before monsoon season is recommended.

Dose: 1 mL S/C route or following manufacturer's instructions

Note: Deworming is must at least 15 days before vaccination

Source/manufacturer of vaccine in India

Indian Immunological, Hyderabad

Biomed Pvt. Ltd., Ghaziabad (UP)

State Veterinary Vaccine Institutes e.g. Institute of Veterinary Biologicals, Thiruvananthapuram