RCD / Calici Virus

CAREMEDICALEMERGENCY
Written By Jen Herd

Last Updated April 2021

We recommend all rabbit owners insist their vet uses the Filavac VHD K C+K vaccine in preference to the old vaccination; Cylap.

Filavac protects against V1, K5 and V2. This makes Cylap - which is not effective against V2, redundant.

V1, K5 & V2 Facts
Calici virus aka RCD aka RHDV is a rabbit hemorrhagic virus.
There are three known variants in NZ - V1, K5 and V2.
Incubation is 1-5 days.
Death can occur in 12-26 hours.
V1
New Zealand's wild rabbits have become increasingly immune to V1.
Does not usually kill kits younger than 6-8 weeks of age.
Mortality rate of 70% - 90%.
K5
Korean strain of the existing RHDV1 virus.
Introduced to help overcome immunity to V1 in the wild rabbit population.
Does not usually kill kits younger than 6-8 weeks of age.
Mortality rate of 40%-100%.
Kills faster than V1.
V2
Kills rabbits from around 11 days old.
Less virulent than K5
Affected animals tend to show more subacute to chronic clinical signs.
Variable mortality rate of 5% - 70%

The New Zealand RCD Timeline -
1997 - V1 was illegally introduced to NZ.
2010 - V2 first appeared in Europe.
2017 - samples collected from wild rabbit populations in which V2 was later detected.
2018 - in March/April a Korean variant of V1; K5, was imported into NZ and released by the Govt.
2018 - in May V2; origin unknown, was confirmed in wild rabbit populations in NZ.
2019 - from June Filavac vaccination was made available for domestic rabbits in NZ.

A global timeline for RCD by Frances Harcourt-Brown, can be seen here - History of rabbit haemorrhagic disease (RHD)

Sources -
Rabbit calicivirus RHDV2 strain - MPI
Update for New Zealand veterinarians - MPI

Vaccination
It is essential that all rabbits - regardless of their prior vaccination history, are vaccinated with Filavac to ensure they are protected against the new V2 strain, along with boosting immunity against the existing V1 strains.

For rabbits that have recently been vaccinated with Cylap a two week interval is recommended between revaccination with Filavac.

Cylap vs Filavac

Clyap
- Protects against V1 & K5
- Vaccination at 12 weeks, single dose, yearly thereafter
- Vaccination can be done earlier but will need to be repeated 4 weekly until the rabbit is over 12 weeks of age.
- Can cause significant side effects.
- Safe to use in pregnant rabbits.
- Available in multi dose bottles. Unused vaccine must be discarded within 10 hours of opening.
- Cylap RCD Vaccine - data sheet

Filavac
- Protects against V1, K5, V2.
- Vaccination from 10 weeks, single dose, yearly thereafter
- Vaccination can be done earlier (from 4 weeks) but will need to be repeated 4 weekly until the rabbit is over 10 weeks of age.
- 7-10 days for immunity to develop.
- Minimal side effects however a temporary increase in body temperature of up to 1.6°C can be observed one day after vaccination.
- Available in single dose vials.
- FILAVAC VHD K C+V - LEAFLET

Fliavac use under 10 weeks of age
"Until recently the efficacy of the vaccine in rabbits younger than ten weeks of age had not been demonstrated and its use has been considered off label. However a recent study has stated -
"Although the data sheet for Filavac states that rabbits should be 10 weeks old when they are vaccinated, the manufacturers now have evidence that early vaccination at four to 10 weeks is effective for young rabbits at risk of RHDV2. Revaccination at 10-12 weeks is necessary.
This study is linked here - Preventing rabbit haemorrhagic disease

Unfortunately Filavac is significantly more expensive than the Cylap vaccine, but it is reassuring that NZers now have this vaccine available to protect our pet rabbits against this nasty disease. Filavac is also proven to cause far fewer - if any, side effects compared to Cylap so is a far superior option.

How to reduce the risk of exposure
In addition to Filavac vaccination, to reduce the risk of your pet rabbit becoming infected from a wild rabbits and the environment, we suggest owners follow these preventative measures:

  • Control insects (especially flies and fleas) as much as possible both indoors and outdoors. Flies are the main vector through which the virus is spread. Insect sprays / fly zappers / fly sticker papers / fly screens. Caution must be used when using products containing Permethrins/Permathrins as this substance is a neurotoxin to rabbits. Products such as Dr Pottle's Fly Stop (Dr Pottles) & Effol Fly Repellant Spray (available from Horselands) sprayed on rabbit's hutch, cage, blankets and litter trays will help limit flies from landing on those items.
    Read this file for more ideas - Fly and Mosquito Prevention

  • Remove uneaten food daily to reduce flies.

  • Ensure your rabbit is spotlessly clean - inspect them daily - especially their rear end where droppings & cecotrophes may get caught in fur. No Fly Zone will prevent maggots from hatching if flystrike does occur.

  • Keep pet rabbits indoors where possible.

  • Rabbit-proof backyards to prevent access by wild rabbits.

  • Regularly decontaminate equipment and materials (eg. cages, hutches, bowls) with either 10% bleach or 10% sodium hydroxide. Leave for 10 minutes, then rinse off.

  • Limit contact with and handling of unfamiliar pet rabbits. Take special precautions if attending any events where unfamiliar rabbits are present, such as petting zoos, rabbit shows, feed stores, pet shops and rescue centres.

  • Use good biosecurity measures (eg. wash hands, shoes and clothing) after handling other people’s rabbits.

  • Isolate new rabbits for 7 days before introducing to other rabbits.

  • Rinse all leafy greens well before feeding them to rabbits. While feeding rabbits leafy greens remains a risk for introducing infection, the benefits of feeding these is considered to outweigh the risks.

  • Store new hay for 3 months before using.

What to do if you have an unexplained rabbit death
If you are unfortunate enough to have a suspected death from RCD/RHDV it is important to have a vet determine the cause of death via an autopsy. A liver sample can be sent off to be tested to establish which variant of RCD may be responsible.

Landcare Research are responsible for testing. This requires a fresh or frozen liver sample, which will need to be used with a specific kits which can be procured from Landcare.
A post mortem by a vet or someone who is experienced with pathology is required.  It is best to collect liver samples and store them in sealed bag in the freezer until they can be organised to send off for processing.

This is the form needed to order a testing kit and to submit samples to Land Care Research.
The contact person is Janine Duckworth duckworthj@landcareresearch.co.nz

If the death is of a kit 12 weeks or under or a vaccinated rabbit, it is important that your vet takes a liver sample for testing to ascertain which strain caused the death. This is the only way the cause of death can be confirmed. We understand it is not an easy thing to do at such an awful time, but it is important for other rabbit owner's and their pets.

Whether you have one rabbit or more than one, if you do suffer a death from RCD/RHDV standard protocols dictate that you quarantine yourself and any remaining rabbit/s for 130 days and thoroughly sterilise everything that your rabbit/s and yourself have worn or had contact with.

For outside equipment, housing etc we recommend  a 10% Janola solution can be used. Spray to soaking wet and make sure it stays wet of at least 10 minutes. The rinse off and dry in the sun.

For inside the home, F10SC is safe to use on furnishings, curtains, walls etc etc. Use a clean/new garden sprayer and spray everything - walls, floors, furniture, curtains etc until damp (it must stay damp/wet for 10 minutes) and then leave it to dry.

In a commercial Rabbitry in addition to the 130 day quarantine during an RCD outbreak, the whole environment will be sprayed down at least once a day until two weeks after the last death - this might potentially be for months ...

For a domestic scenario when the property is in the middle of an RCD breakout in the wild rabbit population, the situation is a bit more ‘blurry’ regarding the 130 day stand down. This stand down period is to try to ensure that any on site contamination that has been missed in the sterilisation process becomes inactive. However, if the virus is rampant in your location - lots of dead wild rabbits etc, then the risk of it coming on to the property (until winter arrives) remains very high - be it via visitors, flies, the wind, etc. SO all you can do is your best and use your better judgement. If it is active in your region I would continue the biosecurity measures discussed above for the 130 day period or until winter arrives and if you are visiting places where the risk may be higher or there is a wild rabbit population make sure to have a pair of ‘dedicated’ shoes in the care, F10 them when you get back to your car, again when you arrive home and leave them in the car.

If you’ve had a death at home - when the source of contamination/RCD inside the home is gone, I would say after the initial clean and spray down, a good spray down 2-3 times over a 7-10 days should suffice (there's very little info about protocols for this scenario so I’m just using common sense ... ) - as long as new sources of contamination are controlled via biosecurity measures.

The Clinical ‘Picture’ of RCD
The clinical evolution of the disease can be
- peracute (very severe and of very short duration, generally proving quickly fatal)
- acute (experienced to a severe or intense degree)
- subacute (between acute and chronic) or
- chronic (persisting for a long time or constantly recurring)
Clinical manifestations have been described mainly in the acute infection, as there are usually no clinical signs of disease in the peracute form, and the subacute form is characterised by similar but milder signs.

The incubation period varies between 1 and 5 days depending on the type of causative agent.
Death may occur 12–36 hours after the onset of fever.

During this phase, these signs can be observed in all rabbits
- Pyrexia (onset of fever greater than 40°C)
- anorexia, not wanting to eat
- Lethargy / Apathy
Some may also exhibit the following
- prostration
- nervous signs - convulsion, ataxia (stumbling, falling, and incoordination), paralysis, opisthotonos (spasm of the muscles causing backward arching of the head, neck, and spine), paddling, groans and cries
- respiratory signs - dyspnoea (difficult or laboured breathing), frothy and bloody nasal discharge.
- Signs of haemorrhage - haematuria (presence of blood in urine), vaginal haemorrhage, bleeding from the mouth.
- cyanosis (bluish discolouration) of mucous membranes.
- Jaundiced (yellow colouration) of the whites of the eyes, mucous membranes and ear flaps.
- Darkening of the iris in albino rabbits.
- Collapse just before death.

During an outbreak, a certain number of rabbits (5–10% in the case of RHDV/RHDVa and significantly more if the infection is caused by RHDV2) may show a chronic or subclinical evolution of the disease.
This is characterised by
- severe and generalised jaundice (skin, whites of the eyes and mucous membranes turn yellow)
- loss of  weight and lethargy.
These animals often die 1–2 weeks later, probably due to liver dysfunction, but some rabbits survive showing very high seroconversion (the time period during which a specific antibody develops and becomes detectable in the blood).

A rabbit that is infected with RCD without being killed by it may well succumb to other underlying illnesses.
If blood tests are done to try to determine the cause of a rabbit's illness when there isn't a clear picture the following suggest RCD is involved especially if the rabbit has a high fever
- hypoglycaemia
- anaemia
- raised liver enzymes
- Raised bilirubin levels
Source - Clinical features of RHD

This video explain what a Necropsy involves and why can be a good idea to have one done.

Jen Herd
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