Animal health matters: Foreign rabbit disease enters South Dakota borders
You may not have realized it, but last month a foreign animal disease was diagnosed in South Dakota.
In recent years, some foreign animal diseases haven’t been so “foreign” after all. Consider Porcine Epidemic Diarrhea (PED) virus in pigs, Highly Pathogenic Avian Influenza in turkeys and chickens, and West Nile Virus in horses. When I was in vet school, all of these were obscure, exotic footnotes to an infectious disease course — not something I’d ever expect to see in South Dakota.
This time, it’s a disease affecting rabbits.
Rabbit Hemorrhagic Disease (RHD) was identified in the Black Hills during the third week in May. It wasn’t a total surprise. The vets at our Animal Industry Board had sounded the alarm bells back in the summer of 2020 as they watched the disease hop northward from an initial outbreak in New Mexico.
South Dakota is the most recent of 13 states to identify cases within their borders. It’s not clear where it came from, but northern Mexico has had recent outbreaks.
This is a tricky disease. Rabbit Hemorrhagic Disease is caused by a virus that’s easily transmitted between rabbits through any of the animal’s secretions, including saliva, feces and respiratory fluids. Susceptible rabbits ingest or breathe in the virus.
Three to five days after infection, disease signs appear and progress rapidly. Affected rabbits spike fevers, become lethargic and die. Some animals show signs true to the name of the disease, such as bleeding from the nose. The virus spreads through rabbit populations rapidly: in one Arizona instance, 1,000 rabbits died. In some locales in the southwest, it’s estimated to have killed 50% of the cottontails and jackrabbits.
Those of you with newly emerging gardens might not be too concerned with a disease that results in fewer rabbits around. What real danger does RHD pose?
The virus type causing the current RHD outbreak doesn’t just affect wild cottontails and jackrabbits – it also affects domestic rabbits raised for show, meat or just as pets. People raising those rabbits should be very worried about RHD. The real risk for these domestic rabbits is the possibility for contact with wild rabbits. Biosecurity — housing that excludes wild cottontails and jackrabbits — becomes critical.
Another troublesome aspect of the RHD virus is that — unlike some viruses — it’s adapted itself to survive a long time outside the animal. The virus stays infectious in carcasses for weeks — maybe months — after the rabbit has died. Any contact with that carcass, even the fur, can result in virus transmission. Flies, birds and other animals, while not affected themselves, can carry the virus from one place to another.
This creates another biosecurity concern for people raising domestic rabbits. Say a person goes hiking and steps in some rabbit droppings containing the virus. They could track the virus home on their shoes and walk it into their rabbits’ pens. This is one good reason to restrict visitors from rabbit housing areas.
While I stated above that rabbits generally die soon after they’re infected, some can survive for a while and carry the RHD virus — making it important for rabbit raisers to isolate any new arrivals before introducing them to the group. Producers shouldn’t borrow equipment from others, because of this prolonged virus survival.
Other animal species and people are not known to be affected by Rabbit Hemorrhagic Disease, thankfully. Still, it’s best to avoid any dead rabbits you encounter: tularemia is another disease that kills rabbits but does pose a human health risk. Game Fish and Parks should be alerted to any unusual losses of wild rabbits you come across. Sickness and death losses in domestically raised rabbits should be reported to your veterinarian and the Animal Industry Board.
Rabbit Hemorrhagic Disease serves as a reminder of the potential for foreign animal diseases to cross our borders. As livestock producers, we might consider our animals to be insulated from such incursions, particularly from a wildlife-borne disease such as RHD. However, one only has to recall the emergence of PED, avian influenza or West Nile virus for examples of exotic diseases that can become established in our domestic animals. Doing what we can to prevent these diseases from entering the country — and being prepared for that possibility — is more important than ever.
Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at firstname.lastname@example.org at 605-688-5171.