Rabbit Hemorrhagic Disease Virus (RHDV)
In early 2020, a new variant of rabbit hemorrhagic disease virus (RHDV) entered the United States. This variant is common in wild rabbits in Europe, Asia, and Australia. Since its first discovery in the US, it has spread to multiple states in the US, with Kansas being the most recent state affected.
What Is Rabbit Hemorrhagic Disease Virus (RHDV)?
Rabbit Hemorrhagic Disease Virus is a member of the calicivirus family. There are other viruses in this family, but they do not cause issues in rabbits. Common diseases in this family include norovirus in humans that causes vomiting and diarrhea, and feline calicivirus that results in respiratory signs.
Both wild and domestic species of rabbits can become infected with the virus; however, it does not infect people or other animals. Once a rabbit becomes infected, the virus travels through the blood stream resulting in rapid damage to the cells of the liver. Subsequently, liver failure and clotting issues occur, resulting in death of the rabbit. Due to the massive damage to the liver, infected rabbits often have evidence of liver dysfunction that can be seen as jaundice (yellow coloration of the skin and whites of the eyes), as well as blood from the nose, mouth, eyes, and in the urine. Affected rabbits may also appear lethargic with a decreased appetite, as well as decreased urination and defecation. An increased temperature is a consistent feature of RHDV infection. Other rabbits may present with nervous system signs (seizures, wobbly gait, paralysis, rigid neck extension, or paddling behaviors). Respiratory signs have also been described including increased respiratory effort, and frothy to bloody nasal discharge.
The incubation period of RHDV is short, around 1-5 days, and death of rabbits occurs rapidly within 12-26 hours.
How Does RHDV Spread?
RHDV can survive in the environment for months, which means when an infected wild rabbit sheds the virus outdoors, the virus can then be brought into a household via clothing or shoes. The result is introduction of the virus to pet rabbits in the house. The virus can be shed in the blood, urine, or feces of an infected rabbit and resultantly expose an uninfected rabbit. The virus can also be introduced via fomites (shoes or other objects that the virus is on), insects that feed on either rabbit carcasses or live rabbit blood, or even in the feces of scavenger animals such as foxes or crows.
There are important considerations that rabbit owners should put in place to reduce the risk of spreading RHDV to their own rabbit.
1. Domestic rabbits should not be allowed to graze outdoors in areas where wild rabbits are known to frequent commonly.
2. Any outdoor clothing or shoes should not be worn in the household, especially in areas where a pet rabbit can access.
3. Domestic rabbits should not be fed outdoor plants, grasses, weeds, or flowers, especially if they are taken from areas that are frequently visited by wild rabbits.
4. Ensure good hygiene and always wash hands after being outside and prior to handling any rabbit.
Treatment of RHDV
There is no specific treatment for rabbits with RHDV. The majority of rabbits infected with RHDV die rapidly. Generalized supportive care including fluids, syringe feeding, and warmth can be instituted in rabbits that survive infection. Any infected rabbits should be strictly quarantined, as they are highly infectious to other rabbits.
Vaccination Against RHDV
There is a vaccine available for our pet rabbits, now more readily available in the US. The vaccine is not fully licensed by the USDA but has been given Emergency Use Authorization. This means preliminary safety and efficacy data of the vaccine has been demonstrated and further studies continue to be underway.
Overall, the side effects of the vaccine have been mild, but may include mild swelling at the injection site and mild fever or lethargy for a few days after administration. To be effective, the vaccine requires two doses administered at least three weeks apart, and six month to one year boosters thereafter.
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