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Fatal virus that affects rabbits detected in New York state, sparks innovative vaccine initiative

Bunny sits on a windowsill at home.
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A highly infectious disease that has spread internationally was detected in New York state late last year, and it has ignited a movement for widespread vaccination — of rabbits.

Kim Dalheim is a serial rabbit rescuer.

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provided by Kim Dalheim
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The Rabbit Resource
Kim Dalheim works with The Rabbit Resource, a regional chapter of The House Rabbit Society

Through her work with The Rabbit Resource, a regional chapter of the House Rabbit Society, she's saved countless house rabbits that were discarded to the outdoors – an almost certain death sentence for the domestic animals that would otherwise typically live 10 years or longer.

In one of her latest rescue missions, she helped save a pregnant mother that gave birth to kits just hours after reaching a foster home. Other times, she’s cared for severely injured bunnies.

It’s not for the faint of heart, but she said it can be rewarding.

“You get them healed, and they're just the most loving creatures,” Dalheim said. “All they want to do is sit on your lap and drool happily as a puddle of rabbit fur and live the rest of their life in peace.”

But Dalheim's work may soon get more complicated.

A highly infectious disease that has spread internationally was detected in New York state late last year, and it has ignited a movement for widespread vaccination — of rabbits.

RHDV2 — Rabbit Hemorrhagic Disease Virus 2

Back in November, a house rabbit died abruptly near Albany. The cause: RHDV2, a strain of the highly contagious and deadly rabbit hemorrhagic disease virus that affects both domestic and wild rabbits.

Death is often sudden with no warning signs. If there are symptoms, fever, lethargy, seizures, and hemorrhaging have been reported. The virus causes lesions on rabbits’ internal organs, notably the lungs, liver, and heart, which leads to bleeding out internally.

Similar to wasting disease in deer, it spreads directly from rabbit to rabbit, and through excrement. It can live on surfaces, like bedding and hay and the deceased body of an infected rabbit. It can be passed by insects, and through contaminated materials like clothing — which means humans can spread it, even though they cannot contract it.

Ways to prevent the spread include cleaning, changing clothes before and after interacting with rabbits, and quarantining new arrivals to limit the risk of contamination to other rabbits.

Another way is by vaccination.

Last September, the USDA approved a vaccine made by Medgene Labs for emergency use authorization. The vaccine requires two doses 21 days apart, similar to Pfizer’s COVID-19 vaccine.

Infectious disease makes world tour

RHDV2 first appeared in France in 2020. It’s since spread to Australia and Canada, and starting in 2018, it was mostly sequestered in the western part of the United States.

Then in 2020, it jumped from domesticated rabbits to the wild rabbit population in that region. That same year, a group of wildlife veterinarians used vaccines made in the European Union on endangered species of wild rabbits in an effort to prevent their extinction.

In New York state, the threat was much less imminent. That same year, while there was a cluster of cases in New York City at a vet clinic, in that instance, the virus was quickly contained and eradicated.

A rabbit sits in a home.
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So far, any cases that have popped up in New York state have only affected domestic rabbits, but that doesn’t diminish the risk to wild rabbits here.

“The biggest worry is that someone who has a domesticated rabbit with that virus, (if they) let their domesticated rabbits go, or let them play around outside ... it could transfer to the cottontails,” said Joanne Iavoli, a wildlife rehabilitator in Mendon who specializes in wild rabbits.

If the virus were to rip through the wild rabbit population here as it has done out west, it wouldn’t only affect lagomorphs. Animals like hawks, wolves and other predators rely on wild rabbits like the cottontail for food. The New York state Department of Environmental Conservation warns that it could be impossible to control and devastating for the larger ecosystem.

Iavoli can’t help but liken RHDV2 to another virus that spreads rapidly: “It's very dangerous to have exploded just like COVID hit here, you know, something you just do not want in the population.”

Technological advances in vaccine development could provide relief

Until recently, there was no vaccine authorized for use in the United States. Then in late September, the USDA granted emergency-use authorization to Medgene’s vaccine. The biotechnology company in South Dakota had been working on a solution since the 2020 outbreak.

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Jason Melby
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Medgene Labs
Medgene Labs Research and Development Lab

The innovations behind this vaccine are a bit like the mRNA methods for COVID-19 vaccines, which use genetically modified cells that are then injected into the body so that the body creates the proteins.

But Jason Melby, marketing director with Medgene Labs, said this technology goes even further.

“We're growing those proteins in the lab,” Melby said.

The process involved the USDA, which had tested rabbits who had died of RHDV2. The USDA sent the sequencing of those rabbits’ DNA samples to Medgene by email, Melby said. Using virus cells from insects, scientists are able to manipulate those cells to replicate proteins that an animal’s body would need to protect against infection.

"At our lab, we never have any animals, and we never have any live virus on hand that could leak out or ... go out and infect something else,” Melby said.

In an efficacy study, no rabbits that were given the vaccine died, whereas 70% of rabbits that were not given the vaccine died. The company has already identified more than 100 protein constructs that could be used for vaccines with this system, Melby said.

While the vaccine is not authorized in some states, the New York Department of Agriculture and Markets’ division of animal industry affirms that the vaccine is approved for sale to licensed veterinarians in all areas of New York state.

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Jason Melby
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Medgene Labs
Medgene Labs Research and Development Lab

Getting shots into rabbits

For house rabbits, Dalheim and her colleagues are leading an initiative to coordinate vaccine clinics with veterinarians around the state.

James Morrissey, a Cornell University professor and veterinarian who has worked with rabbits for 30 years, said his clinic recently received a shipment of a limited supply of vaccines. Morrissey said the first clinic could be up and running this month, but getting them administered may be a struggle.

“COVID-19 has made veterinary practices just insane. We're down people and the caseload has increased,” Morrissey said. “So, adding a vaccine clinic to an already overworked bunch of people is challenging.”

Morrissey said, though, that if the clinic goes well, they’ll likely keep doing them.

According to the New York Department of Environmental Conservation, RHDV2 is a reportable disease in the state, so any sick or dead domestic rabbits should be reported to the state Agriculture and Market’s division of animal industry at 518-457-3502, or to the USDA at 866-536-7593.

Multiple wild rabbits found dead, or wild rabbits with blood-stained noses should be reported to the New York State Department of Environmental Conservation’s Wildlife Health Unit at 518-478-2203.