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Researcher collects insect samples off of a deer.

Vaccine for virus lethal to deer shows promise

A viral disease that impacts deer around the country can be devastating, but a vaccine shows promise for the $8 billion per year deer farming industry.

The disease, epizootic hemorrhagic disease virus, or EHDV, is the leading cause of herd losses for deer farmers. In some cases, 15,000-20,000 deer can die in one season from EHDV, according to Samantha Wisely, professor and director of the UF/IFAS Cervidae Health Research Initiative (CHeRI). Typically, the disease is managed with pesticides that reduce the midge population that causes the disease, but this is not guaranteed to eradicate the disease.

“The vaccine has changed how we look at this disease,” Wisely said. “We finished vaccine testing here in Florida last year and found it to be efficacious. Another vaccine is in development to be released next year and we look forward to both of these vaccines becoming licensed for use in farmed deer. These are complicated pathogens and having more researchers working on resources to prevent outbreaks will help us manage EHDV and ultimately really help the industry.”

“We are very excited about the new EHDV vaccine because of the promising results during the field trials,” said Juan Campus Krauer, UF/IFAS research and extension veterinarian. “This new vaccine gives deer farmers the long-waited possibility to prevent outbreaks of the disease in their herds. We are sure that this vaccine will be a game-changer in the deer farming industry with the potential of saving thousands of deer susceptible to this disease.”

EHDV is an insect-borne disease carried by “no see ums” or midges. In Florida, the impacts of the disease are seen seasonally with the greatest caseload occurring between early-August and late-November. It a member of a virus family that includes bluetongue virus, and symptomatically it can be difficult to tell the difference between the two. There are six additional hemorrhagic disease viruses that may cause similar symptoms and kill deer, so diagnosis and treatment can be difficult, she said.

At CHeRI, diagnostic testing for Florida deer farmers with deer suspected to have EHDV or bluetongue is free, confidential and assists Wisely and the team in developing new and better vaccines for HD viruses. Testing is available for those outside Florida for a fee.

Florida ranks fourth for deer farming in the country. Between 2016 and 2018, the industry grew by 50 farms and now exists in 65 of 67 the Florida counties, according to Florida Fish and Wildlife Commission records.

“Like other agricultural industries, deer farming is concentrated in rural counties serving as an economic boost for the area,” Wisely said. “Keeping deer healthy is important for the farmers and the communities in which they operate. We’ve seen farmers that lose 50% of their population and it can be economically devastating for them.”

In Florida, EHDV is primarily a concern for farmed deer but the virus does exist in wild populations. Occasionally a build-up of the disease in wild populations will cause a small loss, but our focus is on managing EHDV in farmed populations, she said. The disease is very episodic – some years many farms are impacted, others it isn’t so bad.

“While we understand that midges and weather patterns impact EHDV, we don’t exactly understand the climate relationship,” said Wisely. “We know that the disease is slowly moving north with the first case ever seen in Canada in 2018, so it likely has to do with rising temperatures. Our dream is to better understand these patterns so that someday we could help farmers predict when it may be a tough year.”

Now that CHeRI has determined that the vaccine is effective, the next step is to determine the best way for farmers to administer vaccines, time of year to administer, age of deer best suited for vaccination and more.

“We don’t want to give guidance to farmers that is impractical for them to implement,” Wisely said. “We have opened up the opportunity for farmers to provide feedback to ensure the guidance we provide is helpful while also effective at mitigating the disease.”

“Due to the way deer are raised, we must still find the most effective way to administer the vaccine so that all animals can be immunized,” Campos said. “On the other hand, we need to continue monitoring the disease to increase our understanding of the prevalence and distribution of the different serotypes of EHDV in Florida.”

For more information on EHDV and additional research updates, visit the CHeRI website.

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