Introduction: Classical swine fever (hog cholera) is a highly contagious viral infection of swine caused by an RNA virus in the genus Pestivirus of the family Flaviviridae. CSF is one of the most economically- damaging pandemic viral diseases of pigs in the world. In a susceptible (unvaccinated) herd almost all the pigs are affected. Fortunately, there is only one serotype of the virus and attenuated vaccines are highly effective. It is a notifiable disease in most countries of the world. Virus is most often transmitted through the ingestion of contaminated feed or garbage. However, the virus may also be spread through open wounds and mucous membranes, contact with bodily secretions or faeces of an infected pig, physical transfer from a contaminated object, sow to piglet transfer or inhalation in close quarters. Also, it does not spread on the wind or on insects or birds so standard precautions of farm bio-security should keep it out. However it persists in uncooked and cured meat and these should not be fed to pigs.
Clinical signs: Clinical signs usually appear first in a small number of growing pigs which show non-specific signs of depression, sleepiness and reluctance to get up to eat. They walk and stand with their heads down and tail limp. Over the following few days these signs get worse and more pigs become affected. Younger piglets may appear chilled, shiver and huddle together.
Clinical signs of the acute form of CSF may include:
• Persistent high fever up to 41°C(105.8°F) • Weakness • Lethargy • Ataxia (in-coordination) • Huddling • Anorexia (unwillingness to eat) • Conjunctivitis (pink eye) • Constipation and/or diarrhoea • Reddish/purplish discoloration of the skin of the abdomen, inner thighs and ears • Abortions • Mortality rate up to 100 % in young pigs.
Sub-acute form
• Signs as above but not so severe • Fluctuating fever • Mortality rate lower
Chronic form
• Fever • Failure to thrive • Diarrhoea • Coughing and difficulty breathing • Skin problems • Death may result from secondary infections • Abortion
Congenital form
• Congenital tremor • Weakness • Runting • Poor growth • Persistent viremia without any disease or anybody response
Post-mortem findings: In the acute form the following may be seen:
• Enlarged and haemorrhagic lymph nodes • Enlarged and necrotic tonsils with pin point haemorrhages • Petechias and ecchymoses on the skin • Haemorrhages in body organs especially kidney, heart, bladder, lung and gall bladder • Oedema of the lungs • Fluids in body cavities • Encephalomyelitis with perivascular cuffing
Sub-acute form
• Lymph node and kidney haemorrhagic • Consolidation of lungs • Haemorrhages of intestinal mucosa
Chronic form
• Enlarged lymph nodes • Atrophy of the thymus • Inflammation around the heart and lining of the chest cavity • Consolidation of the lungs • Poor body condition • Small (button) ulcer in the large intestine • Secondary pneumonia and enteritis
Diagnosis: Clinical signs manifested by CSFV-infected pigs are also seen with other diseases of swine, therefore laboratory confirmation is always required.
Managemental control, prevention and treatment:
• Culling of infected animals and preemptive slaughter of susceptible animals within determined distances from the focus. • Restriction of movement within a well-defined radius from the outbreak is applied to contain spread of the infection. • Prophylactic vaccination with CSF live attenuated vaccines as a tool to control and eradicate CSF in endemic areas. • Emergency ring vaccination around the outbreak is done to prevent further spread of CSFV. • No treatment is available.
Dr. Lily Ngullie Subject Matter Specialist (Animal Science) KVK Longleng ICAR-RC for NEH Region Nagaland Centre
