May 13, 2020 419 PM
TRI-COUNTY — Readers who have felt anxious about coronavirus can take comfort in one fact: at least they’re not rabbits.
As coronavirus spreads across the United States, humans aren’t the only ones facing a deadly new disease outbreak, according to the Texas Parks & Wildlife Department.
Since March, the agency says it’s recorded the first cases of a new strain of RHD, or rabbit hemorrhagic disease, in Texas. The illness “appears to only affect” rabbit species and not humans or other animals, the agency said.
Like COVID-19 (the disease caused by the SARS-CoV-2 coronavirus) this strain of rabbit hemorrhagic disease is caused by a virus, and is relatively new to the United States. It mostly affects adult rabbits and comes with scary-sounding acronyms like RHDV2 (short for “rabbit hemorrhagic disease virus 2”). But unlike COVID-19, which has an estimated fatality rate in the range of three or four percent, RHDV2 is “nearly always fatal” in adult rabbits, TPWD said.
There’s no sign that the disease can sicken other creatures besides rabbits. But if the disease gets out of control, it could still affect wildlife in other ways — especially in Far West Texas.
“The loss of this prey species can affect big game populations as well as other populations like rodents, due to a shift in what predators will go after,” John Silovsky, the deputy director for TPWD’s Wildlife Division, said in a statement. “That’s especially true in fragile areas like the Trans Pecos.”
The origins of rabbit hemorrhagic disease are murky. The first known outbreak occurred in China in 1984, where it killed 14 million domesticated rabbits before spreading across the globe, according to the Center for Food Security & Public Health at Iowa State University.
That first strain — RHD or RHDV1 — was “extremely contagious” and killed “most or all” infected rabbits, according to the center. There were soon regular outbreaks of the disease in much of the world — but, in good news for North American rabbits, many or all rabbit species here weren’t affected, and the disease didn’t quite catch hold.
That isn’t true for RHDV2 — the latest strain that has descended on Texas.
While the strain first cropped up in Europe in 2010, it’s much newer to North America, first appearing in British Columbia around 2018 and Ohio in 2019. In recent months, it’s spread like wildfire through the desert Southwest — with cases recently confirmed in Texas, New Mexico, Arizona, Colorado and Mexico.
And like coronavirus, the disease appears to have stayed a step ahead of scientists. So far, researchers have found “no epidemiological link to the other areas where RHD has been found in North America,” said Megan Radke, a TPWD spokesperson.
The Texas Animal Health Commission reported the first Texas cases of RHDV2 in early April — around six or seven domestic rabbits living in Hockley County near Lubbock.
“Vaccines are not available or approved for use in Texas at this time,” Dr. Andy Schwartz, the state veterinarian, warned. In a statement, he urged rabbit owners to “practice strong biosecurity” to “mitigate the risk of disease in their rabbit herds.”
A few days later, the Texas Parks & Wildlife Department announced bad news: some more Texas rabbits had been tested, and their results were also positive.
A wild black-tailed jackrabbit in Lubbock County had the disease, as did a wild cottontail rabbit in Hudspeth County. They were the first known cases of RHD in wild rabbits in Texas.
So far, the disease has killed rabbits across the Far West Texas region, including in El Paso, Hudspeth, Brewster, Terrell, Lubbock and Pecos counties.
While symptoms can include seizures and a lack of appetite, some rabbit-handlers may not even know their herds have it.
“Often,” the TPWD said, “the only clinical sign is sudden death.”
Rabbits can reduce the spread of rabbit hemorrhagic disease by practicing good hygiene and social distancing. Cages should be cleaned regularly, the TPWD advises, and pet rabbits should be kept away from other rabbits.
In a phone interview on Tuesday, Bob Dittmar, wildlife veterinarian for TPWD, said RHD has continued to spread. The agency has heard reports of RHD-like symptoms throughout Far West Texas and the Texas Panhandle — though results haven’t confirmed it yet. A dead rabbit in Presidio County had trademarks of the disease, but its test came back negative.
“The numbers that are tested are very small,” Dittmar said. Typically, veterinarians submit results from affected rabbits — though the disease’s appearance in wild rabbit populations has complicated that image.
To estimate the number of Texas RHD tests, Dittmar suggested people “count the number of counties that are positive and multiply by one, possibly two” — a tongue-in-cheek way of noting that each county had, at most, two rabbits tested. But with such low testing rates, Dittmar stressed that infected rabbits are almost certainly hiding in the general rabbit public.
Asked if he sees parallels to coronavirus, Dittmar said yes and no. In a sense, all disease outbreaks are “very similar” because they involve factors like contact and population density, he said.
But he cautioned against drawing too many parallels between RHD and coronavirus, noting there are many questions about RHD that researchers still “don’t really have an answer for.”
“How did it get here?” he asked. “What caused it to pop up at this point in time?”