Many rabbit owners are understandingly growing concerned about Rabbit Hemorrhagic Disease Virus (RHDV) in the United States. Here are six things rabbit owners need to know about RHDV:
1. What is Rabbit Hemorrhagic Disease Virus?
There was a recent outbreak in the Southwestern United States of Rabbit Hemorrhagic Disease Virus (RHDV). RHDV is resistant to disinfection, stays infectious in the environment for months, and survives heat and freezing temperatures well.
The original virus, RHDV (lagovirus europaeus GI.1.), was first reported in China in 1984. There was a rapid spread throughout most of the world. Mostly, it only affected the European rabbit, Oryctolagus cuniculus, meaning pet rabbits. Wild rabbits (hares and cottontails) were resistant to this genotype.
The genotype that is cropping up in the United States and across the world more recently is RHDV-2, also known as lagovirus europaeus GI.2. Vaccine for the original virus is ineffective against RHDV-2. RHDV-2 spread rapidly throughout Europe, UK, Asia, Australasia, Melanesia, Micronesia and Polynesia, and is able to infect pet rabbits as well as hares and cottontails. RHDV-2 is now the predominant genotype.
RHDV-2 has been reported in British Columbia, Washington, New York City, Ohio, Arizona, New Mexico, Texas and Colorado. Outbreaks affected pet rabbits, black-tailed jackrabbits (hares), and desert cottontails (which are the same genus as Eastern cottontails.) Mexico has also confirmed RHDV but has not done genotyping to determine RHDV or RHDV-2.
2. How is RHDV transmitted?
The virus is transmitted via contact with bodily secretions such as urine, feces, saliva, and oculonasal secretions, as well as hair, and direct contact with infected animals. In addition, insects may act as mechanical vectors (such as a fly landing on an infected rabbit, touching eye secretions, then landing on another rabbit), and predators can excrete intact virus in their feces. Some related small mammals may also become infected and play a role in transmission (i.e. shrews).
The incubation period for RHDV-2 is three to five days, so rabbits may shed the virus before they become symptomatic. Both genotypes are highly contagious. Mortality rates for RHDV-2 vary widely from 5-70%. Historically, 20% was average, but mortality has been on the rise.
Transmission to pet rabbits in Minnesota would probably come from eastern cottontails via pet rabbits spending time in the yard or virus on shoes that is tracked inside. Precautions for rabbit owners would likely include not allowing outdoor time , changing clothing after gardening and changing shoes after walking outside prior to handling a pet rabbit. If you currently travel to a state where the virus is present, upon your return home, it is recommended that you wash clothes, disinfect your shoes, and shower prior to handling your rabbit.
3. What does RHDV do to the rabbit’s body?
RHDV causes acute death of liver tissue. The liver helps make clotting proteins, so the body loses its ability to clot and hemorrhage results in many different tissues. Bronchopneumonia, pulmonary hemorrhage or edema can also be seen. The spleen can become enlarged due to hemorrhage or the body’s response to blood loss, and heart muscle cells can die as well.
The most common symptoms include lethargy and fever. As liver damage ensues, the skin of the ears or the whites of the eyes may turn yellow. A heart murmur or heart arrhythmia may be heard, and the rabbit may display neurologic signs such as unsteadiness on its feet, staring up at the ceiling, or tremors. The rabbit may have nosebleeds as hemorrhage worsens, and sudden death can occur at any time, with or without other symptoms. Diagnosis has been confirmed in two cases by certain elevated liver values combined with clinical signs.
4. How is RHDV treated in infected pet rabbits?
Treatment is largely supportive care like IV fluids and handfeeding. Sometimes plasma transfusion is indicated to help increase clotting factors. Recovered animals may shed virus for months; however, the virus doesn’t cause a chronic long-term infection and does clear the body completely after several months.
To disinfect the rabbit’s environment, a 1:10 dilution of bleach to water is recommended. Many other disinfectants are ineffective.
5. Will pet rabbit owners in Minnesota get a vaccine to protect their rabbits?
It is unknown at this time whether or not we will get a vaccine. The USDA does grant import permits for vaccine to specific businesses and specific veterinarians in the face of an outbreak. Veterinarians will be lobbying hard to get a vaccine in the United States to protect pet bunnies.
In wild rabbits, watch for groups of dead rabbits. If you see a group of dead rabbits, don’t touch them or go near them or let your pets go near them. Wash your clothes and disinfect your shoes with 1:10 bleach when you get home, then take a shower before handling pet bunnies. Members of the general public can call the local Department of Natural Resources offices to report suspected wild bunny deaths due to RHDV. Wild populations are often euthanized in the area of the outbreak to prevent the spread.
This is a reportable, foreign animal disease, so veterinarians must notify the state veterinarian and the USDA if RHDV is suspected in a patient. If they agree, the USDA will send a diagnostician to collect samples for further testing. In Minnesota, vets with suspected patients should contact their state veterinarian (Dr. Greg Suskovic is contact point for the state vet at firstname.lastname@example.org) and the USDA in their state (Mary.l.Donahue@usda.gov).
Infected pet rabbits must be strictly quarantined, and owners must observe hygiene requirements (i.e. keeping the rabbit enclosed in its own room, changing clothes after rabbit handling) Other rabbit owners should not visit the home for several months. It’s possible that the USDA would have some say in how disease prevention is handled.
If you have any questions or concerns, you can contact your family veterinarian or Dr. Bean, MPH, DABVP (Exotic Companion Mammal Practice), the head of Animal Emergency & Referral Center of Minnesota’s Avian & Exotic Medicine service.