ANTHRAX

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Causative Agent(s)

The disease is caused by Bacillus anthracis. It is a large Gram-positive, aerobic, spore-forming, nonmotile rod. The individual bacilli have square ends and are usually 1–5 µm in diameter and 3–8 µm long.

Anthrax is not a common disease in pigs because they are resistant to it. It is an important zoonotic disease, so, livestock farmers, abattoir workers, meat sellers and veterinarians are at risk of contracting it.

Clinical Presentation and Epidemiology

The disease occurs worldwide, though the incidence is low and sporadic. Some countries in the world are free from the disease.

Pigs get infected when they ingest feed contaminated with large numbers of B. anthracis or their spores. However, animal-to-animal transmission is not common. The spores of B. anthracis can survive in the soil or the environment for a period.

The disease exists in three forms, pharyngeal, intestinal, and septicaemic. The clinical signs observed in the pharyngeal form are fever, depression, in appetence, vomiting, cervical oedema, dyspnoea and death. -Although pigs may recover without treatment -but they remain carriers of the bacteria.

The intestinal form manifests vomiting, anorexia, haemorrhagic diarrhoea, and death. The septicaemic form is highly acute affecting mainly young animals and death can occur without premonitory signs. Dead pigs are usually very pale and dehydrated and may have haemorrhagic discharges from the nose. The pharyngeal mucosa is frequently inflamed. The mandibular and suprapharyngeal lymph nodes are usually enlarged, deep brick red  or greyish yellow in colour.

Diagnostic Considerations

The diagnosis of anthrax is based on the culture and isolation of B. anthracis.

The organism can be demonstrated in impression smears and cultures of peritoneal fluid, cervical and mesenteric lymph nodes, spleen, kidney, or intestinal mucosa.

The smears are fixed and stained by polychrome methylene blue or Giemsa stain. The bacteria appear as rods with square ends and centrally situated spore.

Where proper incineration facilities are not available, deep burial is the only option available. A competitive enzyme immunosorbent assay (EIA) should be used to detect the presence of immunoglobulin G (IgG) antibody to the bacterial toxin.

Polymerase chain reaction (PCR) can be used to confirm the diagnosis of this disease.

Management and Treatment

Penicillin, 20,000IU/kg, q24h, 5 days, IM. Oxytetracycline L.A. 20mg/kg, single dose, IM

Other Approaches to Management

Anthrax antiserum can be at the – dose rate of 20–75 ml.