Clinical features of RHD

rhd.jpg

Play video of a young wild rabbit with confirmed RHDV2

RHD has a short incubation period of 1–5 days and death can occur within 12-26 hours. Articles about RHD often describe three clinical courses: peracute, acute or chronic. (Abrantes et al. 2012, OIE 2019) but laboratory and field investigations of RHD often fail to make a distinction between these forms of RHD.

Clinical signs

The following ante-mortem signs of RHD are taken from laboratory investigations (Neimanis et al. 2018, Dalton et al. 2019, Le Minor et al. 2020) a case report (Bonvehi et al. 2019) and a naturally occurring outbreak of RHDV2 (Harcourt-Brown et al. 2020).

  • Pyrexia (>40 degrees centigrade) is a consistent feature of RHD infection although hypothermia can occur just before death. This is the most significant clinical sign.
  • Anorexia
  • Lethargy

In some rabbits

  • Nervous signs (convulsion, ataxia, paralysis, opisthotonos, paddling).
  • Respiratory signs (dyspnoea, frothy and bloody nasal discharge).
  • Signs of haemorrhage (haematuria, vaginal haemorrhage, bleeding from the mouth).
  • Pallor or cyanosis of mucous membranes.
  • Icteric sclera or pinnae
  • Darkening of the iris in albino rabbits
  • Collapse shortly before death.

Anecdotally, in outbreaks of RHDV2 in pet rabbits, underlying diseases can suddenly flare up (e.g. rhinitis or treponematosis) shortly before death, which complicates the diagnosis. The presence of RHDV2 in these rabbits could easily be missed without post-mortem examination.

Blood samples

If blood samples are taken, hypoglycaemia, anaemia, raised liver enzymes and bilirubin levels are highly suggestive of RHD in a pyrexic rabbit.

Some differential diagnoses in the live animal

  • Liver lobe torsion can cause sudden lethargy, anaemia and collapse. Pyrexia is not a feature.
  • Sepsis can cause collapse, hypoglycaemia and pyrexia and intravascular coagulopathy. In some rabbits, a source of infection e.g. a bite wound is obvious.
  • Haemabdomen from trauma or a ruptured, torsed liver lobe can cause collapse and anaemia. Affected animals are not pyrexic.
  • Heatstroke can cause pyrexia and collapse. The conditions in which the rabbit died are suggestive of heat stroke.

Treatment of RHD

There is no specific treatment for rabbits with RHD. The majority of them will die quickly. Generalised supportive care (fluid therapy, syringe feeding, warmth etc.) is indicated. It must be borne in mind that these rabbits are highly infectious to others. Barrier nursing is essential.