Rabbit Hemorrhagic Disease Virus (RHD) In Pennsylvania

Rabbit Hemorrhagic Disease (RHD) is a highly fatal disease that attacks the liver and causes internal bleeding in wild and domesticated rabbits and hares— a group of animals known as lagomorphs. Other symptoms of RHD infection include lethargy, lack of coordination, difficulty breathing, convulsions, and bleeding from the nose or mouth. The disease progresses quickly; infected animals may die within days, and some even die before they show visible signs of infection. While not all infected animals will die from the virus, the mortality rate can be as high as 80%.

The disease is highly contagious and is very difficult to eradicate once it is present in an area. The virus spreads through body fluids and waste, such as saliva, blood, and feces (Figure One).  Additionally, the virus can be transported to new areas by predators, scavengers, and biting insects that feed on infected animals. RHD is particularly dangerous because the virus can remain active and capable of infecting lagomorphs in fluids that have been dried out—even after several months. While there is no cure for RHD, there is a vaccine for domestic rabbits.

Figure 1: Common pathways of RHD spread (Source: rhdv2.org)

What is RHDV2?

Rabbit Hemorrhagic Disease Virus (RHDV) is the virus that causes RHD. It was first discovered in Europe in the 1970s, where it affected both domestic and wild rabbits. Shortly after the discovery, it rapidly spread across the world. Until recently, RHD was not a major threat to North American wild rabbits and hares, as they are immune to the original virus. Unfortunately, a new strain of RHD-causing virus—Rabbit Hemorrhagic Disease Virus Serotype 2 (RHDV2)—has surfaced that can infect North American lagomorphs. This new virus was first discovered in France in 2010, and in 2020 it was detected in the United States.

RHDV2 is a new virus so little is known about how it will impact wild rabbit and hare species in North America, but research is ongoing to determine how this new disease will affect wild lagomorphs.

As of August 2023, RHDV2 has been detected in 29 states—13 have reported cases among wild lagomorphs and 16 only reported cases among domestic rabbits (Figure 2). No wild cases have yet been found in the eastern United States. RHDV2 was detected in Pennsylvania in August 2022 in a domestic rabbit facility in Fayette County.

Figure 2: Domestic and wild cases of RHDV2 by state, as of August 2023. (Source: rhdv2.org)

How will RDHV2 affect Pennsylvania?

In Pennsylvania, there are three species of rabbits and hares: eastern cottontail rabbit (Sylvilagus floridanus), Appalachian cottontail rabbit (Sylvilagus obscurus), and snowshoe hare (Lepus americanus). Eastern cottontail rabbits are common and found across the state, while the other two species are imperiled. Appalachian cottontails are considered to be of "greatest conservation concern" due to habitat loss, and snowshoe hare populations have been declining from habitat loss, climate change, and other factors. While it is possible for all species of lagomorphs found in Pennsylvania to get RHDV2, as of August 2023 no cases have been found in wild animals in the state.

Figure 3: A snowshoe hare in Montana (Photo credit: L. Scott Mills Research Lab, University of Montana)

If RHDV2 becomes established in Pennsylvania's wild lagomorphs, the consequences would be severe. An escape of RHDV2 from captivity would likely start with eastern cottontails and then spread rapidly across the state. Eastern cottontails can be found in the same habitat as other lagomorphs, so they could transmit the virus to Appalachian cottontail and snowshoe hare populations. It is not yet known how high the mortality rates could be for these species. Snowshoe hares and Appalachian cottontails are habitat specialists, so they are only found in limited areas with specific climate and vegetation. RHDV2 could greatly reduce or wipe out these small, but important populations, which would be devastating to these imperiled species.

Rabbits and hares are important prey species for many carnivores, so any losses of these species due to RHD would affect entire ecosystems. They are also culturally and culinarily important to Pennsylvanians, as rabbits and hares have been an important source of protein for thousands of years. Losses caused by RHDV2 would make hunting more difficult and may result in restrictions or additional regulations on harvests. RHDV2 negatively impacts PGC's ability to monitor populations through hunter harvest, which is the longest running monitoring method for these species in the state.

How is Pennsylvania Responding to RHDV2?

The main risk of the introduction of RHDV2 to Pennsylvania is from humans moving rabbits/hares, their parts, and products. The Pennsylvania Department of Agriculture has imposed new regulations on the importation of domestic rabbits, rabbit parts, and related equipment from areas that have had RHDV2 cases. The Pennsylvania Game Commission (PGC), which manages wild lagomorphs, has issued a ban on the importation of wild rabbits and hares from states with RHDV2 cases.

The Pennsylvania Game Commission adopted an RHD Management Plan to prevent RHDV2 from becoming established in the state. The Plan includes:

• Guidelines for monitoring for the disease
• Responses to any new confirmed cases
• Allocating resources for better diagnostic methods and increased testing capacity
• Setting up Rabbit Hemorrhagic Disease Management Areas (RHD-DMAs) around positive RHDV2 cases, where it is illegal to remove wild rabbit and hare parts from inside the RHD-DMA to outside the RHD-DMA

To be sure RHDV2 has not escaped captivity, PGC is testing samples from any mortality event in which two or more lagomorphs die with no known cause. Currently, there is one RHD-DMA, which is in Fayette County around the domestic rabbit facility that had the first positive cases (if no cases are found in the future, this RHD-DMA may be discontinued). For the most recent information about Disease Management Areas, see this Pennsylvania Game Commission website.

What can I do about RHDV2?

To prevent the spread RHDV2, people should:

• Vaccinate all domestic rabbits
• Be sure to always wash hands, clothing, and equipment after handling lagomorphs
• Use a 1:10 solution of bleach and water to sanitize hard surfaces and equipment that lagomorphs or RHDV2 may have encountered
• Disinfect shoes before and after interacting with lagomorphs (both wild and domestic) or when visiting areas where RHD occurs
• Keep domestic rabbits indoors and away from contact with wild lagomorphs
• Do not give rabbits outdoor-grown food/bedding from areas with RHDV2

If a domestic rabbit becomes sick or dies for no apparent reason, contact a veterinarian immediately. RHD can kill rabbits without showing visible symptoms, so diagnostic testing is needed.

Members of the public should not handle or transport wild rabbits and hares; if you are concerned about the welfare of a live wild rabbit or hare, call a licensed rehabilitator. Rehabilitating wild rabbits and hares in RHD Disease Management Areas is prohibited to prevent the spread of RHDV2. Outside of RHD-DMAs rehabilitators should also employ biosecurity practices. If you encounter dead rabbits or hares in the wild, especially if there is more than one dead individual and no identifiable cause, call the PGC at 1-833-PGC-WILD or 1-833-PGC-HUNT to report it. Visibly sick wild rabbits or hares can also be reported to these numbers. When reporting suspected cases, always try to provide GPS coordinates, take pictures of the site, do not touch dead rabbits or hares, and sanitize shoes with a bleach/water solution after leaving the site.

Rabbit and hare hunters should follow the below biosecurity measures:

• Wear disposable gloves while handling a rabbit or hare carcass
• Carcasses should be processed on surfaces that can be discarded, such as plastic sheeting, or that can be disinfected with a 1:10 solution of bleach and water
• All knives and other equipment that come into contact with the carcass should be disinfected after use with a 1:10 solution of bleach and water or disposed of in a lined landfill
• Any remains should be placed in a sealed plastic bag and sent to a lined landfill, completely incinerated, or buried several feet underground (to ensure that scavengers will not reach them)

When hunting with animals (e.g. dogs or hawks), hunters need to take the following steps:

• Limit the amount of contact that animals have with rabbit and hare carcasses
• Do not store carcasses in animal transport areas such as dog crates
• Any equipment used in hunting should be disinfected
• The talons of a bird that has come into contact with a rabbit or hare must be cleaned with a 1:10 bleach-water solution or a bleach wipe
• Do not transport or release lagomorphs to train dogs and birds

Although RHD poses no threat to human health, rabbits and hares may be infected with other diseases and parasites. It is recommended to always cook meat to at least 165 degrees Fahrenheit before consumption.

Where can I learn more?

For the most up-to-date information and the management plan visit the  Pennsylvania Game Commission website. For information about RHDV2 and national maps of spread see Rhdv.org.

Sources

Boyd, E. 2022. Snowshoe hare/Cottontail rabbit report 2022. Pennsylvania Game Commission, Harrisburg, PA.

Pennsylvania Department of Agriculture. 2022. Interstate/International Quarantine Order; Rabbit Hemorrhagic Disease. Pennsylvania Bulletin 50:39(5272-5273).

Pennsylvania Game Commission. 2022. Pennsylvania Rabbit Hemorrhagic Disease Management Plan. Pennsylvania Game Commission, Harrisburg, PA.

Pennsylvania Game Commission. 2023. Rabbit Hemorrhagic Disease. Accessed 4/26/2023.

Rhdv2.org. 2023. Accessed 4/26/2023.