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Classical Swine Fever (CSF) in Pigs

Introduction

Classical Swine Fever (CSF), also known as hog cholera, is a highly contagious viral disease of domestic pigs and wild boar. It is characterized by fever, hemorrhages, immunosuppression, and high mortality in acute forms. CSF is a major transboundary disease with significant economic impact due to production losses and strict trade restrictions.

Etiology
Causative Agent

CSF is caused by Classical Swine Fever Virus (CSFV), a member of the genus Pestivirus in the family Flaviviridae.

Virus Characteristics
  • Enveloped, single-stranded positive-sense RNA virus
  • Closely related to bovine viral diarrhea virus (BVDV)
  • Moderately resistant in the environment, especially in cold conditions
  • Inactivated by heat and common disinfectants
Epidemiology
Species Affected
  • Domestic pigs
  • Wild boar (important reservoir)
Transmission
  • Direct contact with infected animals
  • Ingestion of contaminated feed (including pork products)
  • Fomites (equipment, clothing, vehicles)
  • Vertical transmission (transplacental infection)
Risk Factors
  • Poor biosecurity
  • Illegal movement of pigs and pork products
  • Swill feeding
  • Contact with infected wild boar
Pathogenesis
Entry and Initial Infection

The virus enters through the oronasal route and initially replicates in tonsils and regional lymphoid tissues.

Systemic Spread
  • Primary viremia spreads virus to lymphoid organs
  • Secondary viremia leads to widespread infection of vascular and immune systems
Pathological Effects
  • Severe immunosuppression due to lymphoid depletion
  • Vascular damage leading to hemorrhages
  • Bone marrow suppression
Clinical Signs
Peracute Form
  • Sudden death with minimal clinical signs
Acute Form
  • High fever (40–41.5°C)
  • Depression and anorexia
  • Conjunctivitis
  • Skin hemorrhages (ears, abdomen)
  • Constipation followed by diarrhea
  • Neurological signs (ataxia, tremors)
  • High mortality
Chronic Form
  • Weight loss
  • Intermittent fever
  • Persistent diarrhea
  • Poor growth
Congenital Infection
  • Weak piglets
  • Tremors (“shaker piglets”)
  • Persistent infection with virus shedding
Summary for Practitioners

CSF should be suspected in pigs showing fever, hemorrhagic signs, and neurological symptoms, especially in areas with known outbreaks or contact with wild boar.

Postmortem Findings
Gross Lesions
  • Enlarged hemorrhagic lymph nodes
  • Splenic infarcts (wedge-shaped necrotic areas)
  • Petechiae in kidneys (“turkey egg kidney”)
  • Button ulcers in colon (chronic cases)
  • Pulmonary congestion
Microscopic Lesions
  • Lymphoid depletion
  • Vasculitis and hemorrhages
  • Bone marrow suppression
Diagnosis
Clinical Diagnosis

Based on fever, hemorrhages, and high mortality in pig populations.

Laboratory Diagnosis
  • RT-PCR for viral RNA detection
  • Virus isolation
  • Serology (ELISA, virus neutralization tests)
Differential Diagnosis
  • African swine fever (ASF)
  • Porcine reproductive and respiratory syndrome (PRRS)
  • Salmonellosis
  • Other septicemic diseases
Summary for Practitioners

Differentiation from African Swine Fever is critical, as both diseases present similarly and require immediate regulatory action.

Treatment
General Consideration

No effective treatment is available for CSF.

Management
  • Culling of infected and exposed animals
  • Proper disposal of carcasses
  • Movement control and quarantine
Summary for Practitioners

Treatment is not feasible. Rapid reporting and containment are essential to control outbreaks.

Control and Prevention
Vaccination
  • Live attenuated vaccines available in endemic regions
  • Marker vaccines used in some eradication programs
Biosecurity
  • Strict control of farm access
  • Disinfection of equipment and personnel
  • Prohibition of swill feeding
Surveillance and Eradication
  • Monitoring of domestic and wild pig populations
  • Stamping-out policies in disease-free regions
  • Zoning and movement restrictions
Summary for Practitioners

Control relies on vaccination in endemic areas and strict eradication measures in disease-free regions. Biosecurity is critical to prevent introduction.

Zoonotic Importance

Classical Swine Fever is not zoonotic and does not infect humans.

Economic Importance

CSF causes severe economic losses due to high mortality, trade restrictions, culling of animals, and disruption of pork production systems.

Summary

Classical Swine Fever is a highly contagious pestivirus infection of pigs characterized by fever, hemorrhages, and immunosuppression. It is a major transboundary disease requiring strict control measures, including biosecurity, surveillance, and in some cases vaccination.