Porcine Reproductive and Respiratory Syndrome

AKA PRRS

Antigenicity

• Isolates vary in virulence
• Some are subclinical

Hosts

• Pigs: aka Blue Ear or Lelystad virus

Pathogenesis

• Infects alveolar macrophages, followed by interstitial pneumonitis
• Persistent infection of Monocytes followed by leukopenia and thrombocytopenia
• Mostly affects piglets
• In adults, cyanotic appearance due to vascular lesions
• Transplacental spread leads to abortion, mummification, or resorption

Epidemiology

• Discovered in Holland in 1990
• Highly contagious
• Survives well on fomites
• Transfer may also be aerosol or via semen
• Exacerbated by immunosuppression (eg by porcine circovirus 2)

Diagnosis

• Clinical signs:
  • Thumping respiration
  • Abortions
  • Flushed skin
  • Eyelid oedema
  • Weak or dying piglets
• ELISA for virus antibody
• Rising antibody titres as a retrospective diagnosis (4X increase)

Control

• Certified Specific Pathogen Free units exclude by quarantine
• Management: all in/all out, screening AI semen
• Vaccine available

Porcine reproductive and respiratory syndrome

• The syndrome is caused by a small enveloped RNA virus which belongs to the new Arteriviridae group
• Replicates in and destroys macrophages and endothelial cells causing vasculitis -> viraemia -> virus shedding (nasal secretions, faeces)
• Clinical signs: respiratory and reproductive failure, weaned pigs, tachypnoea, eyelid oedema, conjunctivitis
• Moderate to severe interstitial pneumonia in the cranial lobe
• Superimposed bacterial infections are common
• Infectious disease in swine that emerged 10 years ago
• Today, PRRS is endemic in many if not all the pig-producing countries

PRRS Porcine reproductive and respiratory syndrome virus (Lelystad virus). There is abortion late in gestation with respiratory tract illness in live piglets (interstitial pneumonia).