45. Rabbit haemorrhagic disease, European brown hare syndrome.

Question 1

Caliciviridae: Viruses of concern

Answer 1

• Vesivirus
• Lagovirus
• Norovirus
• Sapovirus
• Nebovirus

Question 2

Calicivirus: General introduction

Answer 2

• Ø envelope; +ssRNA genome
• Can survive stomach pH
• Relatively stenoxen

Question 3

Calicivirus: Isolation in cell culture

• Vesivirus
• Lagovirus/Sapovirus

Answer 3

• Vesivirus: Possible
• Lagovirus/Sapovirus: Impossible

Question 4

Rabbit haemorrhagic disease: Causative agent(s)

Answer 4

• Rabbit haemorrhagic disease virus 1 (RHDV-1, 1a)
• Rabbit haemorrhagic disease virus 2 (RHDV-2)

Question 5

Rabbit haemorrhagic disease virus 1 (RHDV-1, 1a): Summary

Answer 5

• Only affecting rabbit
• Resistant in the environment & carcasses → Months
• Ø Propagation in cell cultures → Test vaccine in live animals

Question 6

Rabbit haemorrhagic disease virus 2 (RHDV-2): Summary

Answer 6

• Rabbit & hare are susceptible
• Young are also susceptible
• Longer incubation period & lower mortality
• Serologically different from RHDV-1

Question 7

European brown hare syndrome virus (EBHSV): Summary

Answer 7

• Only hare is susceptible
• Serologically distinct from RHDV
• Very similar to RHD

Question 8

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Epizootiology

Answer 8

NOTIFIABLE DISEASE

• Susceptible age > 1 month (Except RHDV-2)
• Shedding: Faeces → Very contagious
• Direct/indirect transmission; Flies can spread the virus

Question 9

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Pathogenesis

Answer 9

PO/Airborne infection → Viraemia → Prop. in the liver → Vasculitis

• Up to 100% mortality

Question 10

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Incubation & CSx

Answer 10

Incubation period: 1-4 days; Signs appear after 6-8 weeks

• Peracute: Non-specific; depression, fever & death
• Acute: Depression, fever, foamy/bloody nasal discharge, heavy breathing
• Death within 1 day

Question 11

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Pathology

Answer 11

• Haemorrhage: Lung, resp. tract; everywhere
• Lungs: Oedema & emphysema
• Kidney: Haemorrhage, infarcts, congested medulla
• Liver: Swollen, necrotic; Necrosis starting from portal area
• Catarrhal enteritis

Question 12

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Dx

Answer 12

• CSx & PM lesions
• Histopathology: Liver dystrophy & necrosis
• Virus detection: RT-PCR & HA
• Serology: HAI & ELISA

Question 13

Rabbit Haemorrhagic Disease & European Brown Hare Syndrome: Control

Answer 13

Ø Treament

• Sanitary prophylaxis:
  
  • Movement restrict
  • Dispose of sick/in-contact animals
  • Immunise animals on the same farm
• Medical prophylaxis:
  
  • Inactivated vaccine
  • Recombinant & myxomatosis virus vectored live vaccine
  • Vaccinate: 4-5 weeks old; annual boosters