ISSN 2398-2969      

Calicivirus

Clapis

Synonym(s): Rabbit hemorrhagic disease virus (RHDV), Viral hemorrhagic disease virus (VHDV)


Introduction

Classification

Taxonomy

  • Family: Caliciviridae.
  • Genus: Lagovirus.

Etymology

  • Greek: calyx - cup, calicivirus has many cup-shaped subunits on its surface as seen by electron microscopy.

Active Forms

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Clinical Effects

Epidemiology

Habitat

  • Can survive in the environment, eg feed and bedding, for protracted periods of time.

Transmission

  • Direct animal to animal contact via the nasal, oral and respiratory routes.
  • Contact with contaminated food or bedding.
  • Aerosol spread is possible over long distances.
  • Passive transfer by insects, birds, and possibly by foxes or dogs may be highly significant.
  • Rabbit pelts and meat may carry infection.

Pathological effects

  • Antibodies to RHD virus appear to cross-react with some naturally-occurring antibodies in rabbits.
  • This may be due to circulation of non-pathogenic related virus strains.
  • Many wild animals in the UK are seropositive and protected against severe disease.
  • Causes viral hemorrhagic disease of rabbits Viral hemorrhagic disease.
  • Causes an acute, highly infectious and often fatal disease.
  • Incubation period 24-72 h; death occurs 12-36 h post-development of pyrexia.
  • Morbidity and mortality rates may be 90-100%.
  • Disease is usually peracute (sudden death without clinical signs) or acute.
  • Clinical signs are pyrexia, tachypnea and cyanosis, later developing to anorexia and recumbency.
  • Central nervous system signs may develop, including incoordination, opisthotonus, ataxia and frenetic behaviour.
  • The virus induces disseminated intravascular coagulation (DIC).
  • 20% of cases develop frothy nasal hemorrhage.
  • Gross pathology includes severe disseminated necrotic hepatitis with multifocal petechiae in various organs.

Other Host Effects

  • Young rabbits (40-50 days old) are generally unaffected by viral hemorrhagic disease; the reason for this is not known although it is not thought to be related to maternal antibodies.

Control

Control via animal

  • Isolate newly-purchased rabbits for at least 1 week.
  • Avoid contact of domestic rabbits with wild rabbits.

Control via chemotherapies

  • Treatment is rarely instituted early enough to be successful.

Control via environment

  • If a case of RHD has occurred, all infectious material should be removed and the premises disinfected.
  • Disinfect housing with either 1-2% formalin or 10% sodium hydroxide.

Vaccination

  • Inactivated adjuvanted vaccines containing virus antigen are available commercially.
  • Primary vaccination is from 10 weeks of age. If the vaccine is given earlier than 10 weeks then a follow-up dose, 4 weeks later is recommended.
  • Boosters are reccomended every 12 months.
  • A new Myxomatosis-RHD vaccine is now available in the UK and Europe in which a virulence factor (capsid protein gene) from a German isolate of RHDV has been combined into the myxomatosis virus to form a non-adjuvanted combined vaccine with year-long duration of immunity.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Spibey N, McCabe V J, Greenwood N M et al (2012) Novel bivalent vectored vaccine for control of myxomatosis and rabbit haemorrhagic disease. Vet Rec 170 (12), 309 PubMed.
  • Marchandeau S, Bertagnoli S, Peralta B et al (2004) Possible interaction between myxomatosis and calicivirosis related to rabbit haemorrhagic disease affecting the European rabbit. Vet Rec 155 (19), 589-592 PubMed.
  • Thiel H J & König M (1999) Caliciviruses - an overview. Vet Microbiol 69 (1-2), 55-62 PubMed.
  • Motha M X & Kittelberger R (1998) Evaluation of three tests for the detection of rabbit haemorrhagic disease virus in wild rabbits. Vet Rec 143 (23), 627-629 PubMed.
  • Chasey D (1997) Rabbit haemorrhagic disease - the new scourge of Oryctolaguis cuniculus. Lab Anim 31 (1), 33-44 PubMed.
  • Chasey D, Lucas M H, Westcott D G et al (1995) Development of a diagnostic approach to the identification of rabbit haemorrhagic disease. Vet Rec 137 (7), 158-160 PubMed.
  • Fuller H E, Chasey D, Lucas M H et al (1993) Rabbit haemorrhagic disease in the United Kingdom. Vet Rec 133 (25-26), 611-613 PubMed.
  • Chasey D, Lucas M, Westcott D et al (1992) European brown hare syndrome in the UK; a calicivirus related to but distinct from that of viral haemorrhagic disease in rabbits. Arch Virol 124 (3-4), 363-370 PubMed.
  • Smíd B, Valícek L, Rodák L et al (1991) Rabbit haemorrhagic disease: an investigation of some properties of the virus and evaluation of an inactivated vaccine. Vet Microbiol 26 (1-2), 77-85 PubMed.

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