What is ‘bunny ebola?’ All you need to know about the deadly and contagious virus that's killing rabbits in US
Known as the rabbit hemorrhagic disease virus serotype 2 (RHDV2), it is a fatal disease in rabbits. RHDV2 does not impact human health
As the US struggles to bring the coronavirus pandemic under control, another deadly disease nicknamed “bunny ebola” is killing the country's rabbits. The disease was first detected in February 2020 by animal health officials in a domestic rabbit in New York City and since then has spread to multiple states across the Southwest US. The US rabbit industry is estimated to be worth between $2.2 billion and $2.3 billion, of which 80% to 90% are represented by the value of pet supplies and care of over 6.7 million pet rabbits (primarily domestic European rabbits) in approximately 2.9 million households.
What is the disease?
Known as the rabbit hemorrhagic disease virus serotype 2 (RHDV2), it is a fatal disease in rabbits and is considered a foreign animal disease in the US. It was detected in February this year for the third time in the US since 2018. RHDV2 does not impact human health, according to the United States Department of Agriculture (USDA). It is also not known to affect livestock or pets other than rabbits. “We refer to it as ‘bunny ebola,” Dr Amanda Jones, a veterinarian based in Killeen, Texas, told The Cut. While it is “not related in any way, shape, or form” to Ebola -- a disease that is marked by severe bleeding (hemorrhage), organ failure and, in many cases, death in humans -- Jones said RHDV2 ravages the bodies of rabbits in a similar way.
After the first detection this year, the virus was quickly identified, isolated, and eradicated. But the disease was later confirmed in a rabbit in New Mexico in March 2020. Since then, RHDV2 has continued to spread in New Mexico and across multiple states, including Arizona, California, Colorado, Nevada, and Texas. This disease is caused by several virus strains. RHDV2 is a highly contagious strain and, unlike other rabbit hemorrhagic disease viruses, it affects both domestic and wild rabbits, including jackrabbits and cottontails. Many times, the only signs of the disease are sudden death and blood stained noses caused by internal bleeding. Infected rabbits may also develop a fever, be hesitant to eat, or show respiratory or nervous signs. Rabbits can become infected with RHD at any age, but young rabbits (less than 50 days old) experience only ‘sub-clinical’ disease.
“As of May 12, 2020, RHDV2 has been confirmed in 9 US states since 2018 (Ohio, Washington, New York, New Mexico, Arizona, Texas, Colorado, Nevada, and California). Since March 2020, RHDV2 has been confirmed in four wild species: black-tailed jackrabbit, desert cottontail, antelope jackrabbit, and mountain cottontail. Detections of RHDV2 have also been confirmed in domestic rabbits and feral domestic rabbits,” says the USDA.
Health officials caution that the risk of additional RHDV2 outbreaks is high in the US as a result of the potential for additional introductions from Canada as well as further spread in Washington, New York, and New Mexico. The incubation period for RHDV2 is 3 to 9 days, and death typically occurs in 1-3 days. The death rate of rabbits exposed to this virus is very high. It is estimated to be between 40-100% for RHDV1 and 5-70%-plus for RHDV2, according to the House Rabbit Society, a non-profit. “In the 2020 Southwest US and Mexico outbreak, officials are reporting a death rate from RHDV2 of about 90%,” it says.
How does it spread?
The virus can be spread through direct contact or exposure to an infected rabbit’s excretions or blood. The virus can also survive and spread from carcasses, food, water, and any contaminated materials. People can spread the virus indirectly by carrying it on their clothing and shoes. The RHDV2 virus is very resistant to extreme temperatures. It can persist in the environment for a very long time, making disease control efforts extremely challenging once it is in wild rabbit populations. For example, viable virus has been detected for as long as 105 days in its dried state on a fomite (cloth) at room temperature.
The virus is transmitted between rabbits through contact with other infected rabbits or carcasses, their meat or their fur, contaminated food or water, or materials coming into contact with them. People can also inadvertently spread the virus to new areas. The virus can persist in the environment for a very long time, making disease control efforts extremely challenging once it is in wild rabbit populations. “Transmission routes include direct contact with live or dead infected rabbits, meat, or fur; mechanical vectors (such as wild carnivores and raptors); or by contaminated fomites (for example, chilled or frozen meat, food, bedding, and water) through oral, respiratory, or conjunctival routes and skin trauma. The virus is present in all secretions and excretions,” say experts.
They add, “Viable virus has been found in decaying tissue after 90 days outdoors, potentially serving as a reservoir.” Officials warn that exposures may occur in animal shelters, wildlife rescue centers, and in the wild if releases happen. “Any of these transmission routes may be a possible pathway for disease introduction to and spread in the US,” they explain.
Is there a treatment?
There is currently no cure for rabbits infected with RHDV2 or any of the fatal RHDV viruses. Sick rabbits should be isolated immediately to prevent contact with other rabbits, say experts. State Animal Health Officials (SAHO) and the USDA are working together to respond to and conduct epidemiological investigations. Activities include conducting trace-ins and trace-outs, testing, quarantines, and ensuring appropriate cleaning and disinfection.
No vaccine for RHDV2 is currently licensed in the US. But due to the recent outbreak, vaccines licensed in the European Union (EU) have been allowed on a limited emergency basis in affected states. However, USDA-Animal and Plant Health Inspection Service (APHIS) has no information on the efficacy of the two vaccines. “There are 2 killed vaccines for RHDV2 licensed in the EU which may be used in the US under special permit. If your state has confirmed cases, contact your regular veterinarian, who can request permission to use the vaccine from the state veterinarian. Special permit applications for importation will only be considered with the approval of the state veterinarian,” says USDA.
What measures can be taken?
According to officials, it is up to owners to protect their rabbits through simple steps such as not allowing other rabbits (pet or wild) to have contact with the rabbit, excluding visitors from rabbitries, fencing out wild rabbits, not introducing new rabbits from unknown or untrusted sources, and washing hands with warm soapy water before entering the rabbit area, after removing protective clothing and before leaving the rabbit area. If an outside rabbit is brought to a facility or home, experts suggest keeping them separated from existing rabbits for at least 30 days. Sanitizing all equipment and cages moved on or off-premises before they are returned to the rabbitry -- by disinfecting them with 10% bleach or 10% sodium hydroxide mixed with water -- is another suggestion.
“Anyone working with rabbits should always practice good biosecurity. This includes basic steps like washing your hands before and after working with rabbits and not sharing equipment with other owners. The virus is hardy and you need to be careful about how you dispose of a rabbit that has died. A carcass could be a means of spread of the virus. Contact your veterinarian or state or federal animal health officials for guidance. Establish a working relationship with a veterinarian to review biosecurity practices for identification and closure of possible gap,” recommends USDA.