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African Swine Fever (Wart Hog Disease)

African Swine Fever (Wart Hog Disease) is highly contagious hemorrhagic disease of pigs that produce wide range of clinical signs and lesions that closely resembles to those of CSF.

African Swine Fever or Wart Hog Disease is of domestic swine with cyanosis of the skin, haemorrhages of the lymph nodes, kidney, and gastrointestinal mucosa.

Etiology

African Swine Fever (ASF) is caused by African swine fever virus, a large enveloped DNA virus.
It is currently classified as the only member of the family African swine fever like viruses (Asfiviridae).
The virus is highly resistant to wide p^H range, heat, dryness and survives in chilled carcasses for upto 6 months.

Epidemiology

African swine fever is enzootic in African continent and can spread to neighbouring countries.
Occurrence of clinical disease in South Africa has been cyclical with periods of 10-12 years and then absence of disease.
Wart hogs, bush pigs and forest hogs act as reservoirs of the virus.
Morbidity rate: 100% and case fatality rate > 90%.

Transmission

Infection is primarily transmitted to domestic pigs through argasid tick.
Ingestion of contaminated feed and water.
Feeding of uncooked garbage containing infected pig material.

Pathogenesis

Clinical manifestation

Incubation period is 5-15 days.
High fever (105^oF) persist for 4 days without other signs, when fever subsides, marked cyanotic blotching of the skin is noticed.
Depression, anorexia, huddling together.
Disinclination to move.
Extreme weakness of hind quarters with difficulty in walking, dragging of hind legs.
Tachycardia.
Serous mucopurulent nasal discharge, dyspnea and cough.
Vomition, diarrhoea, sometimes dysentery may occur.
Bleeding from nose or rectum.
Purplish discolouration of skin occur on snout, limbs, abdomen and ears.
Death occur in one or two days after onset of obvious clinical signs.

Necropsy Finding

Swollen and hemorrhagic gastrohepatic and renal lymph node.
Subcapsular petechiation of kidney.
Ecchymoses on the cardiac surface.
Hydrothorax.
Splenomegaly.
Gall bladder is edematous and haemorrhagic.
Marked karyorrhexis of lymphocyte in lymphoid organ.

Sample collection

Dead animals-spleen, lymph node, kidney, liver, colon and caecum.

Diagnosis

Based on clinical signs and lesion.
Blood picture: decreased WBC count, lymphopenia and neutrophillia.
Detection of antigen by PCR or ELISA.
Detection of antibodies in serum or tissue fluids by ELISA, CIE and indirect immunoflourescence test.

Differential diagnosis

Treatment

There is no treatment.

Prevention and control

Currently vaccines are not available for control of the disease.
Test and slaughter of all animals.
Disposal of dead carcass properly.
Control of movement.
Heat treatment of waste food.
Serological survey of all pig farms within a specific zone must be conducted.