Virus May Threaten Cottontails in Northeast

(The following is excerpted from ecoRI by Todd McLeish)

It hasn’t yet reached Rhode Island, but local scientists are on the lookout for a disease that rapidly kills wild and domestic rabbits before it wipes out the rarest rabbit in the Northeast, the New England cottontail.

Rabbit hemorrhagic disease causes what Roger Williams Park Zoo veterinarian Kimberlee Wojick called “very sudden death” in rabbits by attacking internal tissues and causing acute bleeding. The animals seldom show symptoms of the virus and instead are simply found dead with blood coming from their noses.

Biologist holding New England cottontail

Scientists who handle New England cottontails in the wild and in captivity take precautions to protect the animals from disease.

The disease can be traced to Europe and Asia, but outbreaks have been reported this year in nine states, resulting in the death of several species of wild cottontails, hares and jackrabbits, mostly in the Southwest.

“We don’t know how it got to the U.S., but it’s having widespread effects on wildlife,” Wojick said. “The virus can survive for a long time in the environment outside of the rabbit — it’s shed through their urine and blood, it’s in carcasses and can contaminate food sources — so even though an infected rabbit may have died and been removed from the land, the virus could still be there when a new rabbit moves through.”

Both species of wild rabbit in Rhode Island, the eastern cottontail and New England cottontail, are highly susceptible to the disease.

“The eastern cottontail population is large and thriving, so while they may take an overall hit, they won’t be decimated because their population is so high,” Wojick said. “What we are really worried about is the New England cottontail.”

New England cottontails are the only rabbit native to New England, and they have declined precipitously in recent decades because of habitat loss and competition with eastern cottontails. Efforts are underway to breed the species in captivity at Roger Williams Park Zoo, maintain a breeding colony on Patience Island in Narragansett Bay, and release them into the wild at targeted locations throughout the region.

“If the disease gets here fast and furious, we could lose the entire remaining New England cottontail population,” said Lou Perrotti, director of conservation at Roger Williams Park Zoo, who is responsible for the captive breeding effort. “It’s that contagious.”

Conservationists in the region are making plans for how to respond if the disease approaches the area. Much of the planning involves the development of biosecurity protocols so the biologists working with New England cottontails don’t inadvertently move the disease around.

“There’s a lot of on-the-ground conservation of the species going on, lots of field monitoring of existing populations, biologists trapping rabbits and collecting fecal samples,” Perrotti said.

“We’re going to have to do things like disinfect the tires on our trucks, change our clothes, disinfect our traps and bags and anything that holds rabbits. Whenever moving from population to population, we have to be conscious of what we’re bringing and be diligent about proper disinfection methods.”

The New England cottontail conservation team is in close contact with counterparts in California who are similarly trying to protect the endangered riparian brush rabbit.

“Their first reaction was to contact us about how to hold a safe, captive population in a bio-secure location,” Perrotti said. “We’re also getting information from them about how they’re dealing with the disease, because that’s a state where it’s already reared its ugly head.”

The potential saving grace is that a vaccine is available in Europe, though it’s not yet licensed for use in the United States. To get it, conservationists must apply through the U.S. Department of Agriculture (USDA), work through an import broker, and ensure it gets through U.S. Customs while remaining refrigerated. The USDA will not approve applications for the vaccine from states not already affected by the disease, however.

“We need a positive case in the area before they’d even think about giving us the vaccine,” Perrotti said. “But in an area as small as Rhode Island, if we find a case it’s going to be too late.”

New England cottontail in transport cage

New England cottontails reared in captivity are released in the wild to bolster local populations and to create free-ranging populations in secure areas such as Patience Island in Narragansett Bay./M. Racey

Assuming the vaccine can be acquired, Perrotti and the cottontail conservation team are developing a plan for how best to administer it. Captive animals will likely be vaccinated first, followed by as many in the free-ranging Patience Island breeding colony as can possibly be captured.

“And then we’d opportunistically vaccinate any other rabbit we get our hands on,” he said. “Can we get them all? No. Can we target all populations? No. But we’d prioritize the vital populations that are especially important.”

According to Wojick, the vaccine only provides immunity to the disease for about one year, and immunity is not transmitted to their offspring. But since the rabbits typically only live for one or two years, a one-year immunity may be sufficient.

While the arrival of the disease in southern New England isn’t necessarily imminent, it could easily make the leap from the Southwest to Rhode Island by someone transporting an infected domestic rabbit to the area.

“What we’re most afraid of is some dude that moves East with his domestic rabbits. If they’re infected and he puts them in a hutch outside, wild rabbits will be drawn to the smell of the hay and food and there will be an interaction,” Perrotti said. “That’s all it’s going to take.”

He noted that Rhode Island doesn’t have large-scale breeding of domestic rabbits for game dinners or laboratory use, as some other states do. And domestic rabbit shows are also not big business in the state.

“The pet industry is quite large, though, so the risk of getting the disease here is not low,” said Dylan Ferreira, a wildlife biologist at the Rhode Island Department of Environmental Management (DEM). “That being said, COVID has canceled a lot of rabbit shows, and that has helped us mitigate the potential spread.”

DEM has a fact sheet with detailed recommendations for rabbit breeders and wildlife rehabilitators on biosecurity practices to prevent the spread of the disease. Those who observe unusual rabbit mortalities or other suspicious cases should report them to Ferreira at 401-789-0281 or Scott Marshall, the state veterinarian, at 401-222-2781.

Rhode Island resident and author Todd McLeish runs a wildlife blog.