Special Veterinary Pathology

Classical swine fever

SWINE FEVER

Synonym: Hog cholera ,Swine plague

Definition

• Highly contagious disease of pig characterized by Intestinal disturbances, diarrhoea, pneumonia and skin haemorrhages

Etiology

• Pesti virus – Togaviridae – RNA virus

Incubation period : 1 to 4 days by artificial infection and 7 days in natural infection

Incidence

• First recognized in 1885 in the United States, its viral aetiology was established in 1903
• The disease is seen worldwide including India

Susceptibility

• The pig is the only domestic animal which is naturally infected by the virus

Transmission

• The infection is usually acquired by ingestion, but inhalation is also a possible route

Routes of infection

• Digestive tract
• Respiratory tract
• Conjunctiva
• Nasal mucosa

Pathogenesis

• The virus enters into blood after multiplication in tonsillar tissue and produces various symptoms like temperature, erythematous patches of skin and enteritis

Clinical signs

• Cerebral symptoms like fits, wobbling gait,howling,coma

Gross lesions

• Intestine- Necrotic enteritis - Spherical ‘button ulcers’ – Mucosa of Caecum and colon.

PPR-Abomasum-ulcers

• Erythematous patches in the ventral surface of the abdomen and thorax, ears, inner aspects of thigh, perineum and snout

 

Skin - Erythema

 

• Kidney – Subcapsular haemorrhages and renal cortex shows “ Turkey egg ” appearance due to petechiae.

Turkey egg appearance

• Splenic infarcts
• Swollen lymph node and red in colour

Microscopic lesions

• Haemorrhages may be seen in the bowmans space and interstitial areas.
• Button ulcer - Occurs due to infarction, develops following occlusion of small arterioles by swelling and hydropic changes in its endothelium
• Splenic infarcts
• Disseminated non-purulent meningo-encephalomyelitis
• Croupous pneumonia

Diagnosis

• Symptoms and Lesions
• Agar gel precipitation test
• Fluorescent antibody technique