Contents
Understanding rabbit RHD
Rabbit hemorrhagic disease is an extremely lethal and contagious disease that affects both wild and domesticated European rabbits with a new variant strain of this disease, the RHD2, reported in Europe in 2010 and in Nanaimo area located on Vancouver Island in British Columbia in Canada on March 2nd, 2018.[1]
The disease attacks most internal organs making them bleed (causes internal hemorrhage) including the lungs, heart, kidney among others and it was first described in 1984 in China.
The first outbreak of this disease was reported in the People’s Republic of China Jiangsu Province in 1983 and it was mainly spread by the Angora breed causing the death of about 140 million domestic rabbits in a span of less than a year [2].
From there, it later spread to Korea. Up to now, the virus been reported in several countries including the UK, Canada, New Zealand, Cuba, North Africa, Mexico, Australia, and the United States.
However, in Australia and New Zealand, it was deliberately introduced to help reduce the wild rabbit population since they are pests in these two countries.
Rabbit calicivirus or RVHD
This viral disease is at times referred to as viral hemorrhagic disease (VHD) or rabbit calicivirus disease (RCD) and it is caused by the rabbit hemorrhagic disease virus (RVHD or RVHD1), also known as rabbit calicivirus (RCV). This virus belongs to the genus Lagovirus found under the family Caliciviridae.
The RHDV virus can survive at room temperature outside its host for 10-19 months making thorough disinfection very necessary [3] after an outbreak.
It affects mainly adult Oryctolagus cuniculus (European rabbits). Other types including cottontails (Sylvilagus floridanus), volcano rabbits (Romerolagus diazi), Lepus californicus (black-tailed jackrabbits) and are not susceptible. [4]
This virus does not affect hare species such as Lepus europeans (European brown hares), (L. timidus, L. corsicanus, L. capensis among others.
Infection in young rabbits below 6-8 weeks is not severe but the RHD2 can affect those aged above 15 -20 days.
Incubation period RVHD
RHD’s Incubation period is about 1-3 days and death will occur between 12-48 hours after this infection’s various signs have been noticed [5] or between 48-72 hours after infection after infection.
Transmission of VHD in rabbits
The most common means of transmission include the following:
- Direct contact with an infected pet especially their conjunctival, oral or nasal areas or discharges.
- Exposure to dead animal
- Any other thing contaminated and capable of carrying the virus including bedding, skin cells, fur, water, and bedding.
- Infected rabbit meat (blood in the meat can carry the virus)
- Flies, insects, and predators( especially in their feces)
- Recently recovered rabbits may still be harboring the virus
The liver and spleen have the highest virus concentrations and excretions including feces, urine, discharges from the respiratory system or any other body part also have the virus.
Signs and symptoms of VHD
This infection can be peracute, acute, subacute or chronic. Most symptoms are often noted once the disease is acute. Some of the expected symptoms will include the following:
- Depression
- Anorexia – Loss of appetite
- Fever or pyrexia
- Dullness and apathy – lack of interest in anything
- Prostration (lying while stretched on the ground) and side recumbency (lying on its side)
- Nervous problems including paralysis, convulsion, ataxia, paddling, and opisthotonos. [6]
- Cries and groans
- Bloody nasal discharges that may be frothy at times
- Labored breathing – dyspnoea
- A small percentage of rabbits may exhibit lethargy.
In case of any of the above clinical signs, you need to immediately inform your vet and isolate the affected rabbit.
Diagnosis of VHD
Diagnosis is by observing the various clinical signs, electron microscopy, hemagglutination (HA ) test, Virus detection ELISA, immunostaining, Western blotting, RT-PCR, in-situ hybridization among others.
Also, the differential diagnosis may be necessary to rule out poisoning, heatstroke, septicemia due to Pasteurellosis or any other agent that causes septicemia.
Treatment of RCD
There is no cure for this contagious viral disease. However, IV fluid therapy, syringe feeding, painkillers may be helped to relieve associated symptoms. Since the disease causes internal hemorrhage, euthanasia may be advised.
This is a new strain of RVHD. It is also referred as to RHDVb or VHD2 and was first described in France in 2010 and later identified in 2011 in Spain and 2012 in Portugal. The virus has been reported in various countries since then including the UK (2015), Ireland, Medina Count in Us on Sept. 19, 2018, among other locations.
The virus that causes RHD2 is antigenically and genetically variant to the RHDV but causes a lower fatality of 0-75% but can affect younger kittens. [7]. It can partially overcome any immunity to RHDV requiring a new vaccination.
The transmission means is like those of RHDV as well as symptoms which will include loss of appetite, congested membranes around the eyes, unexplained bruising or bleeding, fever, weight loss and so on.
Diagnosis of the rabbit hemorrhagic disease type 2 is by postmortem examination. An extra vaccination is necessary to help prevent this virus in areas with viral hemorrhagic disease 2 epidemics.
Like RHD, this viral infection has no cure and the below preventive measures can help for both the two strains of viruses.
Prevention – prophylaxis
This RHD virus has a high morbidity and mortality rate with over 90% deaths in affected rabbitries or where it was introduced [8] with the new variant RHD2 having a slightly lower mortality rate.
Means to prevent its spread include the following:
- Restriction of meat, fur or rabbit importation from affected areas
- Strict quarantine, surveillance, and stamping in case there is already an outbreak. You should also ensure your house rabbit does not get infected from wild ones in case of a breakout in wild populations.
- Quarantine and disinfection of fomites (anything that can transmit the disease) as well as control of insects and predators as they can spread the virus.
- For disinfection, use household bleach, sodium hydroxide both at 10% or 1-2% formalin, benzalkonium chloride disinfectant (Ark-Klens), Anigene HLD4V dilution 1:50 can help wipe out the rhd2 virus.
- Sanitize clothing and shoes if you visit a rabbitry as well as any tools and your hands
- Vaccination
RHD and RVHD2 vaccine
Since its outbreak, several vaccines have been developed to help boost immunity against this deadly virus both homologous and heterologous. Note that vaccinations are not available in all countries including the US, Canada, and Australia.
Initially, rabbits needed one vaccine for myxomatosis and RHD such as Nobivac Myxomatosis-RHD in the UK given to kits aged over 5 weeks. However, right now you now need to go for a second annual vaccine to protect your animals against RHD2 as the first vaccine does not offer protection against RHD2.
RHD can also be vaccinated by Cunivak® RHD among other vaccines developed in various countries.
The RVHD2 vaccine (such as Eravac in the UK) can be given after 30 days and after every after 6-12 months to ensure your furry friend is protected. It must be given at least two weeks after the Myxomatosis-RHD vaccine and not at the same time.
Some side effects of these vaccinations include local skin reaction at the point of injection, some rabbits may be very quiet for about a day, among others.
The RHD and RVHD2 vaccine cost will slightly vary depending on the service charge your vet may require as well as the specific brand use and your geolocation. For instance, if you are in the UK, expect to spend anything from £26 - £100 annually.
Finally, discuss your vet at the right time to vaccinate your animal as he will assess its condition and advise you accordingly.
Conclusion
Both the RHD and RHD2 in rabbits do not cause any threat to both human beings as well as other animals. Put in place preventive measures and report an outbreak to avoid epidemics.
Leave a Reply
You must be logged in to post a comment.