Rabbit Haemorrhatic Disease Virus

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Also known as: Haemorrhagic Viral Disease — Viral Haemorrhagic Disease — HVD — VHD — HDV — RHDV

Introduction

This is a severe viral disease of rabbits caused by Calicivirus. The disease affects only rabbits of the species Oryctolagus cuniculus. Hares are not affected, although they are susceptible to a different rabbit calicivirus (European Brown Hare Syndrome). Many strains exist in rabbits populations. Only a single serotype is known, but there are two subtypes RHDV and RHDVa.

The disease is transmitted by direct contact with infected wild rabbits or their secretions on fomites. Most secretions are thought to contain the virus. Flies and other insects are very efficient mechanical vectors of the disease, and can infect rabbits via the conjunctival route.

The disease was first described in China in 1984 and has been reported in Europe since 1992. It is endemic in Australia, New Zealand, Cuba, parts of Asia and Africa and most of Europe. It is not currently endemic in North American or Canada.

There is very high morbidity rate and fast mortality (within 2 days of contraction). The virus causes a systemic disease syndrome, including haemorrhage, generalised congestion, especially in the lungs and trachea, and liver necrosis.

Clinical Signs

Young rabbits can become infected, but are usually resistant to the disease. Typically, only animals older than 8 weeks show symptoms of the disease. Peracute or acute disease is usually described, but chronic sub-clinical infections also occur.

Peracute disease: fever and death within 36 hours of its onset.

Acute disease: dullness, anorexia, congestion of the palpebral conjunctiva, prostration, bloody nasal discharge, cyanosis, ocular discharge and epistaxis followed by death.

Subclinical infections: milder signs, jaundice, anorexia

Mortality ranges from 40 to 90%, but rabbits that recover may develop jaundice, lose weight and die a few weeks later.

Diagnosis

RHDV should be suspected when several rabbits die suddenly after a brief period of lethargy and fever. It is more difficult to diagnose in an isolated rabbit.

Laboratory tests include: PCR, immunofluorescence, haemagglutination and ELISA to identify the virus in the liver, blood spleen and other organs.

Antibodies can be detected in convalescent rabbits by haemagglutination inhibition or an ELISA.

Post mortem examination findings include: The rabbit is usually in good condition. There is hepatic necrosis and splenomegaly. The liver is usually pale, and has a fine reticular pattern of necrosis outlining each lobule. The spleen in usually black and thickened with rounded edges. The kidneys may be very dark brown. Haemorrhages in the lungs, trachea and thymus are common, and petechiae may be found on the serosal membranes or viscera. Infarctions may be seen in most organs.

Differential diagnoses include:

Acute pasteurellosis
Atypical myxomatosis
Poisoning
Heat exhaustion
Enterotoxaemia due to E. coli or Clostridium spp

Treatment

No treatment is available.

Supportive treatment should be instituted if the rabbit survives the infection.

Control

Until 1996, RHDV was notifiable and slaughter was indicated, however in the UK and other areas where the disease circulates in wild rabbits, eradication is not feasible.

Instead, the disease is controlled in domesticated rabbits with biosecurity measures including disinfection and sanitation, the maintenance of closed colonies, and most importantly, vaccination.

It is generally recommended that all animals should be vaccinated, even if the rabbit is kept indoors, as spread from fomites is possible. More information on the vaccine available in the UK can be found at vaccination for rabbits.


Rabbit Haemorrhatic Disease Virus Learning Resources
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References

Spickler, A. (2010) Emerging and Exotic Diseases of Animals, 4th Edition CFSPH Iowa State University

Miller, L. (2004) Shelter medicine for veterinarians and staff Wiley-Blackwell

Merck and Co (2008) The Merck Veterinary Manual Merial




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