45. Rabbit haemorrhagic disease, European brown hare syndrome.

Question 1

History, Occurrence?

Answer 1

Rabbit haemorrhagic disease (& European brown hare syndrome) - Notifiable

x History, occurrence

• 1984, China: emergence in rabbits imported from Germany
• Spread to Korea (1984)
• Emergence in Italy (1986) ʹ quick spread w/in Europe
• Used as a biological weapon against rabbits ʹ Australia
• RHDV-2 emergence in France (2010) ʹ spread w/in Europe & Australia
• World-wide present (Asia, Europe, Americas, N. Africa, Australia)
• Australia: biological control of rural rabbits
• 1991: lab tests ofsusceptibility
• 1995: Wardang Island virus escaped
• 1996: permitted for rabbit control (pest management)

Question 2

Causative agent of Rabbit haemorrhagic disease virus 1?

Answer 2

Causative agent

• Rabbit haemorrhagic disease virus 1 (RHDV-1, 1a)
• ONLY rabbit (Oryctolagus cuniculus) is susceptible
• Resistant in the environment: for months in chilled/frozen, carcasses (fomite, fly/insect ʹ all 3
• viruses!)
• Cannot be propagated in cell cultures - have to test the vaccine in live animals

Question 3

RHV2 causative agent?

Answer 3

Rabbit haemorrhagic disease virus 2 (RHDV-2)

• Rabbit & hare (Lepus europaeus) are susceptible
• Longer incubation period, lower mortality (?)
• Younger rabbits are also susceptible (?)
• Serologically different from RHDV-1

Question 4

European brown hare syndrome causative agent?

Answer 4

European brown hare syndrome virus (EBHSV)

• ONLY hare susceptible, known EU since 1980s
• Serologically distinct from RHDV
• The disease in hares is very similar to RHD

Question 5

Epizootiology, pathogenesis?

Answer 5

Epizootiology, pathogenesis

• Rabbits susceptible over 1 (2) months of age
• Shedding via faeces, excretes ʹ very contagious
• Direct & indirect transmission (fomites, people etc.) ʹ flies can spread the virus ʹ few viral particles
• necessary for conjunctive route is enough
• PO, air-borne infections: viremia, propagation in liver, vasculitis
• Liver dystrophy, thrombo-embolia in airways & visceral organs ʹ haemorrhages
• Mortality up to 100%

Question 6

Clinical signs?

Answer 6

Clinical signs from 6-8 weeks

• Incubation 1-4 days
• Peracute: no specific clinical signs, depression & fever, death w/in few hours
• Acute: depression, fever, foamy &/or bloody nasal discharge, heavy breathing (edema),
• incoordination, shaking, terminal opisthotonus, die in 12-36 hours

Question 7

Pathology, Histopathology?

Answer 7

Pathology, histopathology

• Haemorrhage: lung, resp tract, everywhere
• Lungs: oedema, emphysema
• Kidney: haemorrhages, infarcts, congested medulla
• Catarrhal enteritis
• Liver: swollen, necrotic cells; necrosis starting from portal area

Question 8

Diagnosis?

Answer 8

Diagnosis

• Clinical signs, high mortality, PM lesions
• Only VESI viruses can be cultured
• Histopathology ʹ liver dystrophy, necrosis
• Virus detection: RT-PCR, HA; serology: HAI, ELISA

Question 9

Control?

Answer 9

Control

• No treatment!
• Sanitary prophylaxis: movement restrictions, humane slaughter & disposal of sick & in-contact
• animals, healthy animals in the same farm may be immunised
• Medical prophylaxis: vaccinations
• Inactivated vaccine (From rabbit liver), recently RHDV-2 vaccine was launched
• Recombinant, myxomatosis virus vectored live vaccine
• Vaccination at 4-5 weeks of age, yearly repetitions