VHD: what every rabbit owner in America needs to know

Last updated 27th August 2005

What is VHD?

Viral Haemorrhagic Disease of rabbits is an acute and deadly disease affecting European rabbits (Oryctolagus cuniculus), the same species as the domestic rabbits kept as pets.

Also known as RHVD or RCD, the USA saw its first outbreak of VHD in 2000. However, rabbit owners in other countries have faced this disease for two decades.

When did VHD appear in the US? Where did it come from?

So far there have been four officially confirmed outbreaks in the US:

The source of infection in all these outbreaks is not known. However, these probably aren’t the only outbreaks to have happened in the past - and they won’t be the last. It seems possible that VHD may have been present in the USA for some time, with small outbreaks going unrecognised and/or unreported.

Furthermore, DNA sequencing of virus samples taken from the first two US outbreaks suggests that the viral strain from the Iowa outbreak was different from that in Utah, implying at least two different sources for the USA outbreaks to date.

VHD first appeared in China in 1984 and subsequently spread across Asia. It reached Mexico in frozen rabbit meat in 1988, but was later eradicated after a massive culling campaign. Continental Europe has been affected since the late 1980s; the UK since 1992; and Cuba since 1993.

You may have heard of VHD in connection with wild rabbits in Australia. The virus escaped from Wardang Island, where it was being tested to see if it could be used as a biological control agent to kill wild rabbits. Once loose on the Australian mainland, it killed 10 million rabbits in 8 weeks.

Can humans or any other animals catch VHD?

No. As far as current knowledge stands, only rabbits get VHD, although European Brown Hares can get a similar disease. American Cottontails and Jack rabbits are not susceptible to VHD.

What happens to rabbits if they catch VHD?

When a rabbit catches VHD, the virus heads for the liver where it causes massive inflammation and deranged blood clotting. Internal bleeding then occurs. It's basically a viral haemorrhagic fever and has been nicknamed "rabbit Ebola" for very good reason.

VHD usually kills so quickly that no treatment is possible. Death rates of over 90% are quoted.

Baby rabbits, under about 8 weeks of age, typically don’t show any signs of illness. However the disease is usually fatal in rabbits over 8 weeks of age. Infected rabbits may just die very suddenly, with no outward sign of anything being wrong. Or they may get very ill before dying, have difficulty breathing, go off their food, have a high temperature and bleed from the nose and bottom. A small percentage of rabbits develop a more chronic form of the illness and may die of liver failure after 1-2 weeks.

VHD usually kills so quickly that no treatment is possible. Death rates of over 90% are often quoted. However, it's important to note that fatality rates can vary a great deal. In some outbreaks in Europe - particularly in the UK - only a small number of rabbits from a herd died. This is another reason why all rabbit owners should be alert to sudden deaths, even if only a few rabbits are affected.

How is VHD spread? Could my houserabbit catch it?

Rabbits can pick up the virus in lots of ways, from contact with infected rabbits to including indirect vectors such as birds, insects, people and equipment. Other rabbits may pose a risk - especially rabbit shows or other rabbit gatherings.

The problem with VHD is that the virus itself is incredibly tough. It lasts a long time in the environment (at least 225 days at 4 degrees centigrade; 105 days at room temperature dried on cloth; and 2 days at 60 degrees centigrade), is difficult to inactivate with disinfectants and remarkably easy to catch.

It all sounds very alarming, and it is. But take a moment to put the risk in perspective.

First of all, in most other countries affected by VHD, there's a wild population of the European rabbit, Oryctolagus cuniculus, acting as a reservoir and helping to spread the virus. This just isn't going to happen in most areas of the United States (where the local rabbit species is the cottontail, which is not at risk from VHD) which immediately reduces to the risk to your rabbits, because in most of the USA the only rabbits able to act as "virus factories" are other domestic rabbits. Having said that, there are localised wild/feral populations of European rabbits in some areas - Seattle in Washington State being one example - and rabbit owners in such areas need to be particularly alert.

Secondly, most houserabbits rarely mix with rabbits outside their home or come into contact with birds or insects. Obviously, this does not necessarily apply to rabbits kept outdoors. Rabbit owners whose pets live outdoors may want to review their rabbits' living conditions, especially in the event that VHD occurs in your region.

All rabbit owners and caretakers need to be aware of VHD, but as things stand at the moment most rabbits in the USA are not facing any immediate risk. So far, you have only had four confirmed outbreaks in five years, and each of which appears to have been rapidly contained. Even so, there are some common sense precautions you can take.

• Stop and think before allowing people to handle your rabbits.

• If you hear of someone who loses more than one rabbit for no apparent reason, don't visit them or handle any of their rabbits. Urge them to ask their vet to perform a post mortem examination on the animals.

• Decide for yourself on the risks you are prepared to take, especially if VHD appears in your state. For example, some show rabbit breeders have cancelled attending shows until the position becomes clearer; and those involved in rabbit rescue will need to re-think the risk/benefit ratio of adoption events and fostering arrangements if VHD pops up in the vicinity. The HRS website contains information pertinent to rabbit rescuers and those with companion rabbits: http://www.rabbit.org/care/vhd-guidelines.html

What you really should do is beef up on the politics of VHD, because in the event that VHD should become more widespread in the USA, or occurs in your locality, then it will pose more of a threat.

How did other countries tackle VHD?

Most countries with VHD also have wild European rabbits, making eradication of the disease impossible (wild rabbits act as a reservoir of infection) so they have mostly opted for vaccination as the preferred control measure.

In the UK, VHD first appeared in domestic rabbits. Eradication was attempted initially, but failed once the disease became established in the wild rabbit population.

Mexico - like the USA - does not have any wild reservoir for the VHD virus. When VHD arrived, the Mexican authorities chose to eradicate the disease by imposing "ring slaughter" measures. All rabbits living within a certain radius of a confirmed case of VHD were killed. VHD arrived in Mexico in December 1988 and by September 1989, 65,000 rabbits had died from VHD and a further 95,000 destroyed to halt the spread of the disease.

What about vaccines?

Other countries have been using VHD vaccines for years and they are widely regarded as safe and effective. In the event of VHD becoming widespread in the USA (which seems increasingly unlikely given the paucity of outbreaks so far) then vaccination would be the only way for the rabbit world to continue the way is does now.

However, the USA is unlikely to look at using vaccines against VHD any time soon. There are several reasons for this.

Firstly, only four, apparently isolated, outbreaks of VHD have been confirmed in the USA. There isn't really any need for a vaccine at the moment.

Secondly, in the event of further outbreaks, USDA/APHIS may decide to blood test rabbits nearby to see if they have been exposed to the virus. The screening tests used for surveillance purposes can't differentiate between a rabbit who has been vaccinated and one who has survived the disease itself.

There is a possible problem with this strategy: what if American domestic rabbits come up positive on these screening tests despite having been nowhere near the VHD virus? This is exactly what happened in the UK a few years ago. Some laboratory rabbits (from closed colonies, who had definitely never been vaccinated or in contact with VHD) were found to possess antibodies in their blood capable of cross-reacting with the VHD testing kits in use at that time. Researchers eventually concluded that the antibodies possessed by these rabbits was due to natural exposure to a harmless, related calicivirus (possibly the ancestor of the killer strain of VHD).

As far as we are aware, nobody yet knows whether American domestic rabbits may possess similar cross-reacting antibodies. We can only hope that someone plans to undertake a study to try and obtain an answer to this very important question.

Thirdly, no VHD vaccine is currently licensed for use in the USA.

Some rabbit lovers are also concerned by the way VHD vaccines are made. Although synthetic, recombinant vaccines are being developed, the commercially available vaccines in Europe and elsewhere are made from liver extract taken from laboratory rabbits. This may seem terrible, but the sacrifice of one rabbit (which is euthanised before it actually becomes unwell) will protect nearly 6000 others. If Mexico had chosen to vaccinate rather than eradicate, 10 or 11 rabbits would have died to protect the 65,000 who succumbed to VHD and there would have been no need to kill 95, 000 healthy animals.

What would happen if my rabbits caught VHD?

Sadly, if the disease didn't kill them then almost certainly they would be euthanised as part of the measures to control to the spread of the disease - premises are described as being "depopulated and decontaminated".

Rabbits are not classified as agricultural animals in the USA, so USDA/APHIS could not automatically impose a ring slaughter the way the Mexican authorities did. Each outbreak would be handled on a state by state basis.

Anyone who suspects their rabbit may have died from VHD should contact their own and the state veterinarian.

Where can I keep up to date?

VHD has succeeded in bringing together all the different rabbit-owning communities in the USA. Owners of pet, show and meat rabbits all have a vested interest in preventing VHD getting established in the USA.

VHD Info is an electronic mailing list which carries information to rabbit owners as soon as USDA/APHIS release it to the public. Members of the group keep rabbits for all purposes, from houserabbit owners to meat rabbit breeders and a degree of tolerance is expected. To join the list, send a blank email to: vhdinfo-subscribe@yahoogroups.com

Important information

This article is based upon "VHD - what every rabbit owner needs to know", an information sheet produced for British rabbit owners by the Rabbit Welfare Association & Rabbit Welfare Fund. This version, adapted for American rabbit owners, was written in 2001 and updated in August 2005 to include the June 2005 Indiana outbreak.

American rabbit owners are advised to make every effort to stay informed as the VHD situation in the USA develops over the next few months or years. Somewhat inevitably, this article has been written from a British perspective (!) and as knowledge of VHD becomes more widespread amongst the rabbit-owning groups in the USA, you will find a more local perspective helpful. The regulatory bodies overseeing matters pertaining to VHD in the USA are APHIS and USDA and you may want to make contact with their local office.

And don’t forget – the RWA is delighted to welcome international members! For £27.50 a year you too can enjoy "Rabbiting On", our fabulous quarterly magazine packed with health, behaviour and care advice to help you build a wonderful relationship with your bunny - whether s/he lives indoors or out.

You can even join online!

And a word from the RWA...

We try very hard to bring you up-to-date information on rabbit health issues, but there is no substitute for consulting your own, rabbit-friendly, vet. If you think your rabbit is unwell, you should seek veterinary help immediately. We cannot accept any responsibility for any loss or harm suffered as a result of information given on this web site.

Although we make every effort to keep the information on our web site free of errors, we are only human, so please tell us if you spot a glitch! We welcome feedback - both from rabbit owners and veterinary professionals. So, if you spot an error; would like to comment on something you have read; have a suggestion for a topic you would like us to cover; or have spotted something that is out of date, please contact us.

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Copyright © Dr Linda Dykes/RWA 2005