Synonym of classical swine fever
• Hog cholera, European swine fever.
Introduction
• Classical swine fever is a highly contagious viral disease of pigs of all ages, characterized by rapid and sudden onset, high mortality, and morbidity with generalized hemorrhages of internal organs.
• This disease is caused by the pantropic RNA virus belonging to the genus Pestivirus, family Flaviviridae.
• The virus is closely related to the Bovine viral diarrhea virus.
• The disease was widespread in South African countries, Europe, China, and Japan and prevalent in moderate to severe proportion in India, Myanmar, Nepal, Pakistan, Bangladesh, and the Philippines.
• In India this disease was first reported in West Bengal in the year 1961.
• Swine are the natural host of the virus. All breeds, sex, and ages of pigs are susceptible to this infection.
• Wild pigs often remain as inapparent carriers of the virus.
• Young pigs are more susceptible than adult pigs. Infection is transmitted readily by direct and indirect contact.
• The virus is usually acquired by ingestion of food and water contaminated with discharges and secretions from the infected pigs.
• Urine and nasal and ocular discharges are generally regarded as most infective.
• The isolation of CSFV should be attempted in the pig kidney ( PK-15 ) cell line, or other suitable cell lines.
Clinical symptoms of classical swine fever
- Incubation period is 3-8 days
- The disease may appear in three clinical forms
- Per acute form of classical swine fever
a. Most commonly noticed in young pigs
b. Disease terminates fatally within about 24 hours of developing the disease
c. No appreciable clinical manifestations except high raise of temperature and erythematous patches in the non-hairy parts of the skin - Acute form of classical swine fever
a. Sharp rise of body temperature. Temperature reaction may persist up to 8th day or till death
b. Dullness, depression, anorexia, vomiting, constipation, severe foul-smelling diarrhea, dehydration and loss of body weight
c. Hyperemia of the skin with purplish discoloration of the snout, ears, abdomen, inner side of the legs, a peculiar blotching effect on the ears, small areas vesicular lesions followed by necrotic lesions on the edges of the ears, tail, lips, and vulva
d. Mucopurulent to purulent discharges from eyes with signs of conjunctivitis
e. Severely affected pigs may suck urine and water due to obvious temperature reaction and dehydration
f. Central nervous system may be affected. The signs are wobbling gait, ataxia, tremor, convulsion, paralysis, circling, tremor, and coma
g. Reproductive disorders in sows due to low virulent strain with signs of fever and birth of mummified, stillbirth, abnormal piglets - Chronic form of classical swine fever
a. Chronic diarrhea
b. Chronic pneumonia - Gross lesions
• Degeneration of small blood vessels leading to hemorrhages in kidney, bladder, skin and lymph nodes
• Circular or oval raised button ulcers are most prevalent in the caecum and proximal portion of the colon
• Turkey egg appearance of the kidney is the pathognomonic lesion of the disease.
Diagnosis of classical swine fever
Samples to be collected
• Based on characteristic symptoms and lesions
• Nasal, ocular discharges, blood, spleen, lymph nodes, lungs, and liver
– Virus isolation can be carried out in porcine cell lines using homogenates of the spleen and tonsil.
– The cultures are examined for virus growth by immunofluorescence or immunoperoxidase staining; positive isolates are further characterized by the use of monoclonal antibodies and by partial genetic sequencing.
– Polymerase chain reaction protocols for the identification of CSFV nucleic acid have now gained international acceptance and are being used in several laboratories, both for detection of the agent and differentiation from ruminant pestiviruses.
– Antigen-capture enzyme-linked immunosorbent assays ( ELISAs ) are also useful for herd screening, but should not be used on a single animal basis.
– Serological tests – VNT, ELISA
Differential diagnosis of classical swine fever
Salmonellosis
• common in pigs between 2-4 months of age but swine fever affects pigs of all age groups.
• In salmonellosis diarrhea is the leading feature.
• Bacteriological investigations are able to differentiate salmonellosis and swine fever.
• Button ulcers of the intestine is not present in salmonellosis
Swine erysipelas
• Characterized by diamond markings on the skin.
• In swine fever turkey egg appearance of the kidney is seen, but in swine erysipelas, the kidney is congested and dark red in color.
• Bacteriological examination differentiate the swine erysipelas with swine fever
Colibacillosis
• Enteritis during the first week of age, high fever, and death within 48 hours are the common clinical findings in Colibacillosis.
• Smears from feces and culture will reveal gram-negative E.coli organisms.
Purpura hemorrhagica
• Etiology of the disease is not known. It is a self-limiting disease.
• Postmortem examination will reveal subcutaneous hemorrhage extending to skeletal muscles, heart, lungs, intestine, kidneys, and urinary bladder.
• Laboratory tests will rule out the possibility of swine fever.
Mulberry heart disease
• This disease usually affects the best, healthy pigs exclusively. No fever, lesions confined to heart. Pericardium remains distended with jelly-like fluids.
• Increased creatinine phosphokinase level in the serum is noticed.
Necrotic enteritis
• Predilection site caecum and colon. The lesions are superficial in nature and can be removed
easily. Button ulcers are not present
Aujeszky’s disease
• Widespread nervous manifestations in the young suckling pigs characterized by convulsions and prostration than the nervous manifestations in swine fever
Salt poisoning
• This is an afebrile condition that sets in suddenly and affects a large number of piglets in a pen.
• Grinding of teeth, champing of jaws, frothing of mouth, blindness, head pressing, and vomition are seen. Responds to therapy with ad-libitum water.
Treatment of classical swine fever
• No specific treatment. Prohibit the feeding of uncooked garbage to pigs
• Hyperimmune serum is the only treatment that may have value in the very early stages of the disease if given at the dose level of 50-150 ml per animal.
Prevention of classical swine fever
• If hyperimmune serum is given to the in-contact animals it gives better protection
• Simultaneous method of vaccination: simultaneous administration of hyperimmune serum along with vaccination with virulent swine fever virus
• Vaccinate the pigs after six months of age with attenuated live virus vaccines or inactivated vaccines then annual revaccination to be done