The United States is currently experiencing a multistate outbreak of a highly contagious and deadly disease affecting rabbits. But what is this disease and how did it spread throughout the country?
rabbit hemorrhagic diseaseas it is known, is caused by a form of viral hepatitis that can infect rabbits and rabbits – in other words, animals belonging to a group called lagomorphs.
According to Andrew DeSalvo, a wildlife veterinarian with the Pennsylvania Game Commission, the viruses that cause rabbit hemorrhagic disease (RHD) currently fall into three distinct pathogen groups: RHDV, also referred to as classic RHDV or RHDVa; RHDV1, a subtype of RHDV; and RHDV2, sometimes referred to as RHDVb.
“While North American lagomorphs do not appear to be susceptible to infection with other groups of viruses, they and lagomorphs of European lineage—most rabbits kept as pets or livestock fall into this category—are highly susceptible to RHDV2 infection,” de Salvo said. NEWSWEEK.
The virus was first documented in France in 2010 and has since spread throughout Europe, parts of the Mediterranean, the Middle East, Asia, New Zealand, Australia and the United States.
RHDV2 was initially detected in the United States in pet rabbits in 2018 in Ohio, according to William Wepsala, a public affairs specialist with the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service. A few sporadic outbreaks in wild and wild rabbits followed in 2019 and early 2020 in Washington and New York.
In April 2020, the virus was found in wild lagomorphs in the southwestern United States, including New Mexico, which was the starting point for the current multistate outbreak. There are now a total of 28 states, primarily in the Southwest and West, with RHDV2 discoveries amid the outbreak, affecting native, feral and wild lagomorphs. Additional cases of RHDV2 were recently detected in Ontario and Alberta in Canada.
“The source or means of emergence of the disease in the current multistate outbreak is unknown,” Wipsala said. NEWSWEEK.
According to de Salvo, RHDV2 is “highly durable” – very resistant to temperature extremes and can survive long periods in the environment – as well as being “highly contagious”. Infected rabbits or rabbits can excrete the virus in their secretions (respiratory and salivary tracts, for example) and secretions (such as feces and urine).
“The disease can spread between rabbits and rabbits via many paths that include direct contact with a live or dead rabbit or rabbit; ingestion of contaminated food or water; inhalation; contact with contaminated equipment, tools and attachments; Viral movement by flies, birds, biting insects, predators, litter, and humans; and contact with urine, feces, and respiratory secretions from the infected.”
“The virus can live on clothing, shoes, plant materials or other items that could be accidentally transmitted from an endemic area.”
While RHDV2 does not affect human health, recent discoveries of the virus show the role that people play in spreading the disease, according to de Salvo. For example, humans can spread the virus indirectly by carrying it on their clothes and shoes.
“Because of its highly contagious nature and many routes of transmission, RHD can spread very quickly,” de Salvo said. “In addition to being highly contagious, RHDV2 has mortality rates after infection often in excess of 70 percent. It is very concerning.”
Often the only symptoms of the disease are sudden death and a bloody nose from internal bleeding, although affected animals may also develop a fever, hesitate to eat, or show respiratory or nervous signs.
Early in the current outbreak, the disease spread outward from affected areas in a contiguous pattern, according to Basala. But recently, the disease has made a geographical jump in pet rabbits away from known infected areas. This points to some not fully understood risk pathways.
“For this reason, strict biosecurity measures are necessary to prevent the virus from entering new areas including sanitation and disinfection, maintenance of closed colonies or isolation of new rabbits entering rabbits, and attention to feed sources that may be contaminated,” he said. .
“Early in the outbreak, the spread was rapid. In 2022, the spread was more sporadic and marked by geographic leaps into new areas,” said Wipsala.
The ease with which the virus can spread and the fact that it can persist for months in the environment makes eradicating the disease in the wild after introduction is inherently difficult, according to de Salvo.
“Cleaning and disinfection is not possible in the wild environment, so often wild lagomorph populations must naturally develop immunity before populations can recover,” he said.
“Any disturbance in wild lagomorph populations can have significant environmental impacts, so we are working hard to educate the public about the threat the RHD poses not only to the Pennsylvania snowshoe rabbit, Appalachian cottontail and eastern cottontail rabbit, but to all wildebeest and wild habitats within the Commonwealth.” .
Aside from being highly contagious, lethal and highly tolerant, Wepsala said RHDV2 is of concern as an emerging disease because it has a wide host range, which includes both domestic and wild animals. rabbits. In addition, there is no treatment for infected rabbits.
“In areas where the disease is present in wild populations, there are a number of threatened and endangered wild rabbits,” said Wipsala.
Compounding the problem until last year was the fact that readily available tools to fight the disease were out of reach.
At the beginning of the current outbreak, the US Department of Agriculture’s Center for Veterinary Biology (CVB) allowed the import of RHDV2 vaccines licensed in Europe. But importing these vaccines was costly and logistically difficult. Then in September 2021, a US-based company received emergency use authorization for the RHDV2 vaccine.
“This vaccine has varying levels of approval for use in 45 states and has made an important prevention tool much more available to rabbit owners,” said Wipsala. “The company is working with CVB to obtain a conditional license.”
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