Rabbit haemorrhagic disease (RHD, calicivirus disease) is an acute highly contagious disease with haemorrhage in multiple organs, especially lungs and liver. RHDV belongs to the calicivirus family.

It is a disease subject to official control.

Pathophysiology

Infection usually occurs by direct contact with infected animals via oral, nasal, and ocular mucosa. Other routes include carcass, fur, food, bedding, water. Import of contaminated rabbit meat can introduce virus into a naive area. Flies and other insects may vector the virus.

The virus is highly infectious — only a few virions may infect a rabbit.

Replication appears not to occur in carnivores, but predators may shed RHDV in faeces after eating infected rabbits.

Viral replication occurs in liver, lungs, spleen, and intestine with viraemia and diffuse haemorrhages.

No breed predisposition. Rabbits older than 8 weeks are susceptible; under 8 weeks disease is often subclinical. Animals under 4 weeks are not susceptible. Survivors develop durable immunity even to related strains.

Clinical signs

  • Incubation 1–3 days; death may occur 12–36 hours after fever onset;
  • Suspect an outbreak with sudden deaths where animals showed lethargy and fever and necropsy shows liver necrosis or DIC;
  • Hyperacute, subacute, or chronic forms; signs are usually seen in hyperacute form; subacute forms show similar but milder signs;
  • Sudden death without preceding signs;
  • Anorexia;
  • Lethargy;
  • Neurological signs (seizures, ataxia, paralysis, opisthotonus);
  • Vocalisation;
  • Dyspnoea, frothy or bloody nasal discharge;
  • Cyanosis of mucous membranes;
  • Generalised icterus, weight loss, lethargy, death in 1–2 weeks from liver disease.

Risk factors

Contact with sick animals, animal products, equipment, bedding, food, water. Virus may remain viable for months when frozen and in carcasses.

Differential diagnoses

  • septicaemic pasteurellosis;
  • toxicity;
  • heat stroke;
  • atypical myxomatosis;
  • other causes of severe septicaemia.

Blood changes

  • lymphopenia, progressive thrombocytopenia;
  • elevated liver enzymes.

Diagnosis

PCR detects viral RNA in organs, urine, and/or serum.

Treatment / control

Quarantine and disinfect affected premises first. After confirmation, euthanasia of infected and in-contact animals is typically required by regulation.

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