Rabbit hemorrhagic disease



Rabbit viral haemorrhagic disease (VHD) is a highly contagious disease that mainly affects rabbits of the Oryctolagus cuniculus species but has also been confirmed to affect various species of cottontails (Sylvilagus spp.) and hares (Lepus spp.). VHD is also known as rabbit haemorrhagic disease (RHD), rabbit calicivirus disease (RCD), rabbit calici-virus disease (RCVD), and viral hemorrhagic disease of rabbits (VHDR).

It is caused by the rabbit haemorrhagic disease virus (RHDV), also known as rabbit calicivirus (RCV).



How is RHD transmitted?
The RHD virus is spread by oral, nasal, and other parenteral transmission. It is present in urine and feces from infected rabbits. The virus can survive for 10-19 months at room temperature outside the host.

Specifically, research has shown that the virus can survive the following situations:


 * Viable virus has been detected as long as 105 days on cloth at room temperature.
 * Viable virus has been found in decaying tissue after 90 days outdoors.
 * The virus can survive 1 hour at 50C (122F).
 * The virus can remain viable for 22-35 days at 22C (72F).
 * The virus remains viable for 3-7 days at 37C (99F).
 * It can survive freeze/thaw cycles.

It is thought that wild birds carried the infection from Europe the the wild rabbits in the UK. The disease is also incubated in wild hares that can carry the virus without clinical effect. :89

RHD may be transmitted directly from contact with wild rabbits and hares or indirectly through footwear and clothing. Contaminated plants picked from areas grazed by infected rabbits can also be a source of infection.

How can RHD be disinfected?
Effective disinfectants for RHD after 10 minutes of exposure include the following:
 * 1% potassium peroxymonosulfate (Virkon-S)
 * 1% sodium hydroxide
 * 1-2% formalin
 * 1.0-1.4% formaldehyde
 * accelerated hydrogen peroxide (Rescue wipes or solution)
 * Parvosol
 * 2% 1-stroke Environ
 * Chlorine dioxide at 10 ppm concentration
 * 0.2-0.5% beta-Propiolactone
 * 1:10 dilution household bleach
 * No-splash & Splash-less versions of bleach will not work, as it does not disinfect. A product meant for disinfection is what fights viruses and bacteria.
 * Once diluted, bleach loses efficacy after 24 hours.

RHDV1
RHDV1 is the original strain of RHD, first discovered in China in 1984. In the UK, this strain seems to have died out and has been replaced by RHDV2.

Baby rabbits can have a natural immunity under 4 weeks of age and develop a life-long immunity if exposed to the disease. They become increasingly susceptible until 6-10 weeks of age.

Two vaccines against RHD are available in the UK:


 * Nobivac Myxo-RHD is the most common vaccine used in the UK that protects rabbits against the original variant of RHD as well as myxomatosis.
 * Filavac is effective against both the original variant of RHD and RHDV2.

RHD has a short incubation period of 1-4 days, and the virus replicates in many tissues including the lung, liver, and spleen. Symptoms will generally manifest in three ways:


 * Peracute: animals will be found dead within a few hours of eating and behaving normally. This is most common.
 * Acute: affected animals will show lethargy and a heightened fever (>40οC) with an increased respiratory rate, usually passing away within 12h.
 * Subacute: rabbits will show mild or subclinical signs from which they recover and become immune to further RHDV.

Non-pathogenic rabbit calicivirus (RCV)
It is believed that non-pathogenic strains of RHD (RCV) can be responsible for protecting rabbits by stimulating antibody production. Investigations in Australia and UK have revealed its presence.

RHDV2
RHDV2 is a new variant of RHD first discovered in a French rabbitry in 2010 and identified in Italy in 2011 and in the UK in 2013. However, retrospective analysis of samples suggests that the infection has been in the British Isles since 2010.

Unlike the original strain of RHD, rabbits under 4 weeks of age have no natural immunity to RHDV2. It also appears to affect hares.

Two vaccines against RHDV2 are available in the UK:


 * Filavac is effective against both the original variant of RHD and RHDV2.
 * Eravac is only effective against RHDV2.

Clinical signs of RHDV2 are the same as RHDV1 except they develop after 3-9 days instead. Subacute or chronic infections are more frequent so more rabbits may survive.

Further reading


 * Le Gall-Reculé, et al. (2013). Emergence of a new lagovirus related to Rabbit Haemorrhagic Disease Virus
 * Marlier, D, et al. (2014). Le nouveau variant du virus de la maladie hémorragique virale (le RHDV2) identifié en Région Wallonne. [PDF in French]

RHDV1-K5: Korean strain
RHDV1-K5 is a variant of RHD that is more lethal than RHDV1 and appears to have less cross-immunity with non-pathogenic strains. It has been deliberately released in Australia to kill wild rabbits. Vaccination against RHDV1 protects pet rabbits from this disease.

European brown hare syndrome virus (EBHSV)
European brown hare syndrome (EBHS) affects wild and farmed hares of the species Lepus europaeus and Lepus timidus. The disease was first reported during the 1980s, and it occurred simultaneously in many European countries.

Further reading


 * Lavazza, A, et al. (1996). Susceptibility of hares and rabbits to the European brown hare syndrome virus (EBHSV) and rabbit haemorrhagic disease virus (RHDV) under experimental conditions.

Europe
All strains of RHD are prevalent throughout Europe.

You can find a map of reported RHD2 cases in the UK at RHD2map UK.

The following are articles with more information about RHD in Europe:


 * Hinde, J. (2016). RVHD2: The UK’s Newest Fatal Rabbit Disease.
 * Pieters, J. (2015). Bunny owners warned of new hemorrhagic disease killing Dutch rabbits
 * Dierenkliniek Wilhelminapark. VHS of RHD: een virusziekte bij het konijn. [in Dutch]
 * Rev. sci. tech. Off. int. Epiz., 1994, 13 (3), 881-891, Control of viral haemorrhagic disease of rabbits in Poland by J. GÓRSKI, B. MIZAK and M. CHROBOCIÑSKA

Australia & New Zealand
Australia also has a number of variants of RHD.

The following are more articles with information about RHD in Australia.


 * The Rabbit Doctor. (2016). Overview on the Calici Virus
 * Australian Veterinary Association. (2017). The facts about the K5 variant of rabbit calicivirus
 * Journal of Virology, Comparative phylodynamics of rabbit haemorrhagic disease virus (RHDV) in Australia and New Zealand

North and South America
The source of infection in past American VHD outbreaks is not known. However, these may not be only outbreaks to have happened in the past.

The current status of RHD in the US can be found here.

RHDV1

 * Late 1980s to 1991 - Endemic in Mexico: The source of the Mexican outbreak was traced to the importation, through the United States, of 18 metric tons of rabbit meat from the People's Republic of China to a supermarket chain outside Mexico City. Over 110,000 rabbits died or were destroyed.


 * 2000 - Iowa (US): began 9 Mar 2000 in a backyard rabbitry of 27 pet Palominos and California White rabbits in west central Iowa. 25 of the 27 rabbits died by Apr 6, the rest euthanized, and the outbreak was contained to the single premise. The origin of the outbreak is unknown, and no new rabbits had been introduced over the last two years. Aug 1999 was the last time the rabbits had left the farm and returned.


 * 2001 - Cuba: an outbreak was reported Jan 15 in Havana and Havana City province in an operation that produced rabbits for private consumption.


 * 2001 - Utah (US): began 17 Aug 2001 in a rabbitry in Utah County, Utah. 65 of 900 rabbits on the premises had died by Aug 20, and the rest were euthanized. The farm had shipped rabbits to three locations: 3 rabbits to another site in Utah, 3 rabbits to a premise in Yellowstone County, Montana, and 72 rabbits to a location in Mercer County, Illinois. No clinical disease was noted in the second Utah premise; however, both premises were depopulated. At the Montana site, the rabbits from Utah were euthanized and buried on the property, and the remaining rabbits were placed under quarantine until final test results from the euthanized Utah rabbits was negative. Two other rabbits (not the Utah origin rabbits) from the Montana premises, while in route to a truck for slaughter, had been co–mingled with rabbits that were on their way to the Montana State Fair. These two Montana rabbits were then placed on a truck carrying 3,600 rabbits in route to California through Idaho; all 3,600 rabbits considered to be contacts were euthanized.


 * 2001 - Illinois (US): an outbreak in Mercer County, Illinois, due to receiving 72 rabbits from infected Utah premises. All rabbits were depopulated (over 3,000 ).


 * 2001 - New York (US): an outbreak was diagnosed Dec 2001 in the Bronx Zoo in New York City. Two rabbits died - one was positive for RHD. Seven other rabbits were euthanized, and the disease was contained.


 * 2004 - Uruguay: an outbreak was reported 28 Dec 2004 among backyard domestic rabbits in suburban areas of the city of Montevideo, and in adjacent areas in the departments of Canelones and San Jose. This was the first report of RHD in Uruguay and South America. 4,689 rabbits were affected on 45 premises, and 2,820 rabbits died. The remaining 1,869 sick rabbits were culled.


 * 2005 - Cuba: an outbreak was reported 21 Jan 2005 in the Havana city and province. 14,450 affected rabbits and 2,362 rabbit deaths were reported by 28 Dec 2004.


 * 2005 - Indiana (US): began 27 May 2005 in a backyard rabbitry in Vanderburgh County, Indiana. Eight of a group of eleven rabbits that were purchased in Kentucky at a flea market died acutely three days later in Indiana following introduction into the herd. The owner had approximately 200 rabbits in total, nearly half of which also subsequently died.


 * 2008 - Maryland (US): Private residence involving 4 mature pet rabbits.


 * 2010 - Minnesota (US): a facility in Pine County, Minnesota, that received donated pet rabbits for use as a food source at a wildlife center reported an outbreak early Feb 2010. 20 died initially, with more rabbits that were brought in quickly dying rapidly without clinical disease as well. 25 rabbits died or were euthanized, and there was no known further spread. The initial source of the disease is unknown.


 * 2011 - Manitoba (CA): A 1-year-old grey and white neutered male 2.6-kg lop-eared rabbit was seen at a clinic 30 Mar 2011 and died after seizing and going into cardiac arrest with unsuccessful CPR. The body was submitted for necropsy 31 Mar 2011 at the Manitoba Veterinary Diagnostic Services Laboratory. The lop was purchased from a local pet store in the spring of 2010 and was surrendered to the store from a previous unknown owner. Two other rabbits living at the premises remained in good health and tested negative after regularly sharing a cage and litter box with the affected rabbit. The origin of the disease is unknown, but it is speculated that it may be related to the 2010 Minnesota outbreak due to geographical proximity.


 * 2018 - Pennsylvania (US): The USDA confirms that rabbit hemorrhagic disease (RHDV1) was found in two "pet rabbits" that died December 7th in Clover Township, Jefferson County. Farm and Dairy reported that "Rabbit owners who have questions about this disease should contact their veterinarians. Veterinarians who suspect RHD cases should immediately contact the department’s Bureau of Animal Health at 717-787-4250."

RHDV2

 * 2016 - Three farms near Rimouski (Mont-Joli & Bas-Saint-La), Quebec (Canada): New rabbits were introduced from one farm into another, "small hobby rabbit farms." Start of the outbreak: Aug 13th, 2016. Virus showed 96.2% identity to RHDVb (or RHDV2) isolate (GenBank: KT000337.1) from São Jorge in Azores Islands. Source


 * 2018 - British Columbia (CA): SPCA was contacted about a group of dead rabbits on 18 Feb 2018. Three rabbits were sent to the Animal Health Centre in Abbotsford and confirmed to have RHD. On 27 Feb 2018, reports about an unusual number (12) of dead rabbits found in the Rotary Bowl in Nanaimo were reported on. On 2 Mar 2018, Victoria News reports that rabbit haemorrhagic disease was the cause for the deaths around the Vancouver Island University area. The British Columbia Gov't officially warns people "to take precautions." CBC News update. On 17 May 2018, Dr. Jaspinder Komal (Deputy Chief Veterinary Officer, Canadian Food Inspection Agency) filed his 4th and last weekly report with OIE-WAHIS. OIE-WAHIS writes about future reporting, "The event cannot be considered resolved, but the situation is sufficiently stable. No more follow-up reports will be sent. Information about this disease will be included in the next six-monthly reports." 25 Oct 2018: The Ministry of Agriculture reported that the last positive case was detected in early May."Since that time, the ministry’s Animal Health Centre has tested 23 rabbits and all have been negative for the disease. No vaccinated animals have contracted the disease, and ministry staff have been hearing that healthy feral European Rabbits have been returning to affected areas. - source"

"The rural household had 5 pet rabbits, not bred or shown. 'Three animals had previously been found dead in the last couple of weeks, and the fourth was taken to an exotics vet for diagnosis. A postmortem was done, and the alert and knowledgeable veterinarian knew that a check for RVHD was in order. Contact was made with the OH State Veterinarian's office and samples were sent to Plum Island's Foreign Animal Disease Diagnostic Laboratory, where testing revealed RHDV2. - Pamela Alley (Admin), North Americans RHDV2 Group. Info from Dr. Summers from the Ohio's Veterinarian's Office (Sep 26th, 2018)." The Ohio Department of Agriculture (ODA) will work with state and federal partners to conduct surveillance of wild rabbits near the location. Plum Island's Foreign Animal Disease Diagnostic Laboratory conducted the PCR and ELISA tests and the RHDV2 virus was isolated, twice with ELISA antigen (Ag) detection. OIE-WAHIS) 29 Sep 2018: Pamela Alley posted [[Media:APHISanswer92918.pdf|a Q & A response from the USDA/APHIS]] by Donna Karlsons (USDA/APHIS Public Affairs Specialist). FADDL (Plum Island) found that "The whole genome sequencing indicated that the virus was very similar to the one detected in Canada." VIN news service reported that the virus found in Ohio was first identified in France in 2010.  12 Oct 2018: Twelve rabbits died at the Fairfield County Fair and initially it was thought that the virus had spread to Lancaster, Ohio (210 miles or 338 km). Over 300 rabbits were put under quarantine. The test result found pneumonia... the 12 rabbits were let to die by not giving them antibiotics.
 * 2018 - Ohio (US): First RHDV2 case reported in USA. The virus was detected in Medina County, Ohio on 19 Sep 2018 and reported by the Ohio DOA and Ohio Veterinary Medical Association on 25 Sep 2018. The rabbits were housed in horse stalls and were at the location for many years with no new rabbits introduced. It's currently not categorized as an outbreak and the farm that had the infected rabbit has been quarantined. Currently the source of the virus is unknown.


 * 2019 - British Columbia (CA): RHD was found again March 2019 on Vancouver Island and lower mainland, with confirmed cased in Saanich, Parksville, Qualicum, north of Nanaimo, and Vancouver.


 * 2019 - Washington (US): The disease was identified in the San Juan Islands in July 2019, on Whidbey Island in November 2019, and Clallam County in December 2019. It is suspected that this outbreak may be connected to the ongoing outbreak in British Columbia, Canada. Three sites on Orcas Island and one site on San Juan Island with owned domestic rabbits have been confirmed with RHD. Feral domestics have been confirmed sick on Whidbey and Lopez Islands. Positive cases were identified in owned domestic rabbits in a single site in Clallam County.


 * 2020 - New York (US): In Feb 2020, two out of 11 recently deceased rabbits at the veterinary clinic The Center of Avian and Exotic Medicine tested positive for RHDV2. The clinic quickly quarantined the one remaining rabbit on the premise and suspended all rabbit intakes at the clinic temporarily. A final total of 13 rabbits died, and no further RHDV deaths associated with the clinic have been reported since 6 Mar 2020. There are no known links from the New York outbreak to outbreak events in Washington.


 * 2020 - New Mexico (US): Since Mar 2020, RHDV2 has been confirmed in domestic rabbits in Chaves, Cibola, Curry, Dona Ana, Eddy, Grant, Lincoln, McKinley, Santa Fe, Torrance, and Valencia Counties. Wild black-tailed jackrabbits (Lepus californicus) and desert cottontails (Sylvilagus audubonii) have also been confirmed to be dying from RHDV2 throughout southern New Mexico in Apr 2020. There are no links from the New Mexico outbreak to outbreak events in Washington and New York.


 * 2020 - Arizona (US): Since Apr 2020, the Arizona Department of Agriculture has confirmed two separate cases of RHDV2 in domestic rabbits in Cochise County and wild jackrabbits and cottontails in Navajo County.


 * 2020 - Texas (US): In Apr 2020, RHDV2 has been confirmed in domestic rabbits in Hockley County, Hockley, Texas.

Novel calicivirus variant

 * 2001 - Michigan (US): acute fatalities of the Michigan rabbit calicivirus (MRCV) began 01 Jan 2001 and continued over a 3-week period at a privately owned New Zealand White rabbitry in Michigan. Before this episode, the farm had operated for 1.5 years without disease. Approximately 200 rabbits were kept in a closed barn, and no new rabbits had been acquired in the past 18 months. 65 rabbits died over about 3 weeks. Because the MRCV genome is unique among the lagoviruses and no later outbreaks were reported nor was it identified again, MRCV could be considered an ‘attempt’ at emergence by a new RHDV-like virus.