Rabbit hemorrhagic disease: Difference between revisions
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{{Merge|Rabbit haemorrhagic disease virus| discuss=Talk:Rabbit haemorrhagic disease virus|date=September 2008}} |
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{{Merge from|Rabbit haemorrhagic disease virus| discuss=Talk:Rabbit haemorrhagic disease virus|date=January 2011}} |
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| familia = ''[[Caliciviridae]]'' |
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| genus = '''''Lagovirus''''' |
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| species = '''''Rabbit haemorrhagic disease virus''''' |
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'''Rabbit haemorrhagic disease''' ('''RHD'''), also known as '''rabbit calicivirus disease''' ('''RCD''') or '''viral haemorrhagic disease''' ('''VHD'''), is a highly infectious and often fatal disease that affects [[rabbits]] of the species ''[[Oryctolagus cuniculus]]''. The infectious agent responsible for the disease is [[rabbit haemorrhagic disease virus]] (RHDV), or [[rabbit calicivirus]] (RCV), genus ''[[Lagovirus]]'' of the family [[Caliciviridae]]. |
'''Rabbit haemorrhagic disease''' ('''RHD'''), also known as '''rabbit calicivirus disease''' ('''RCD''') or '''viral haemorrhagic disease''' ('''VHD'''), is a highly infectious and often fatal disease that affects [[rabbits]] of the species ''[[Oryctolagus cuniculus]]''. The infectious agent responsible for the disease is [[rabbit haemorrhagic disease virus]] (RHDV), or [[rabbit calicivirus]] (RCV), genus ''[[Lagovirus]]'' of the family [[Caliciviridae]]. |
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'''Rabbit haemorrhagic disease virus''' ('''RHDV'''), also known as '''rabbit calicivirus''' ('''RCV'''), is the [[type species]] of the genus ''[[Lagovirus]]'' belonging to ''[[Caliciviridae]]'' family. RHDV is an important [[pathogen]] that causes a highly contagious disease in wild and domestic rabbits, [[rabbit haemorrhagic disease]] (RHD). The virus infects only [[rabbit]]s, and has been used in some countries to control rabbit populations. |
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Two vaccines are available against VHD in the UK. One is named Cylap and made by [[Fort Dodge Animal Health]]. The other is Lapinject and is made by [[CEVA Animal Health Ltd]]. Both last 12 months and contain inactivated strains of VHD. |
Two vaccines are available against VHD in the UK. One is named Cylap and made by [[Fort Dodge Animal Health]]. The other is Lapinject and is made by [[CEVA Animal Health Ltd]]. Both last 12 months and contain inactivated strains of VHD. |
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The first reported case in the United States was in Iowa on March 9, 2000.{{Citation needed|date=July 2008}} The affected population included [[List of rabbit breeds#Palomino rabbit|Palominos]] and [[Californian rabbit|California Whites]]. By April 6, 25 of the 27 affected rabbits had died as a result of RHD. In order to contain the disease, the remaining two rabbits were euthanized. No new introductions of rabbits were placed on the farm for two years after the discovery of RHD and August 1999 was the last time rabbits left and/or returned to the farm. The United States experienced other outbreaks of RHD in 2001 ([[Utah]], [[Illinois]], [[New York]]) and 2005 ([[Indiana]]). |
The first reported case in the United States was in Iowa on March 9, 2000.{{Citation needed|date=July 2008}} The affected population included [[List of rabbit breeds#Palomino rabbit|Palominos]] and [[Californian rabbit|California Whites]]. By April 6, 25 of the 27 affected rabbits had died as a result of RHD. In order to contain the disease, the remaining two rabbits were euthanized. No new introductions of rabbits were placed on the farm for two years after the discovery of RHD and August 1999 was the last time rabbits left and/or returned to the farm. The United States experienced other outbreaks of RHD in 2001 ([[Utah]], [[Illinois]], [[New York]]) and 2005 ([[Indiana]]). |
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==History== |
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Rabbit haemorrhagic disease first appeared in [[China]] during the early 1980s. In 1984 the virus that caused the disease was discovered. The virus spread westward and reached Europe in 1988. The virus has since appeared in [[Mexico]], [[Cuba]], [[Australia]], [[New Zealand]] and the [[USA]].<ref name=Merck>{{cite web | title = Rabbit Calicivirus Disease | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/171330.htm | accessdate = 2007-06-17 }}</ref> |
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== World geographic distribution == |
== World geographic distribution == |
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===Australia/New Zealand=== |
===Australia/New Zealand=== |
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===Australia=== |
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The virus was imported into Australia in 1991 as a potential [[biological control agent]]. Testing of the virus was undertaken on [[Wardang Island]] in [[Spencer Gulf]] off the coast of the [[Yorke Peninsula]], [[South Australia]]. In 1995 the virus escaped from the island. The virus was subsequently released into rabbit populations throughout Australia in an attempt to control rabbit infestations. |
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===New Zealand=== |
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In July 1997, after considering over 800 public submissions, the [[New Zealand Ministry of Health]] decided not to allow RHDV to be imported into New Zealand to control rabbit populations. This was backed up in an early August review of the decision by the Director-General of Agriculture. By late August, it was confirmed that RHDV had been deliberately introduced to the [[Cromwell, New Zealand|Cromwell]] area of the [[South Island]]. |
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An unsuccessful attempt was made by New Zealand officials to control the spread of the disease. It was, however, being intentionally spread, and several farmers (notably in the [[Mackenzie Basin]] area) admitted to processing rabbits that had died from the disease in kitchen blenders for further spreading. |
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Had the disease been introduced at a better time, there would have been a more effective control of the population. Unfortunately, it was released after breeding had commenced for the season, and rabbits under 2 weeks old at the time of the introduction were immune to the disease. These young rabbits were therefore able to continue to grow and breed back up. Ten years on, now rabbit populations (in the [[Mackenzie Basin]] in particular) are beginning again to reach near plague proportions, though have still not quite returned to pre RCD levels. |
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In 1991 the virus that caused RHD was imported to Australia under strict [[quarantine]] conditions to research the safety and usefulness of the virus if it was used as a [[biological control agent]] against Australia and New Zealand's rabbit pest problem. However, in 1995 a laboratory accident in Southern Australia led to the escape of the RHD virus and consequently killed 10 million rabbits within 8 weeks of its exposure.{{Citation needed|date=July 2008}} The disease is currently epidemic throughout Australia and New Zealand. When Calicivirus was first released it wiped out 90% of the rabbits in Australia. |
In 1991 the virus that caused RHD was imported to Australia under strict [[quarantine]] conditions to research the safety and usefulness of the virus if it was used as a [[biological control agent]] against Australia and New Zealand's rabbit pest problem. However, in 1995 a laboratory accident in Southern Australia led to the escape of the RHD virus and consequently killed 10 million rabbits within 8 weeks of its exposure.{{Citation needed|date=July 2008}} The disease is currently epidemic throughout Australia and New Zealand. When Calicivirus was first released it wiped out 90% of the rabbits in Australia. |
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Revision as of 13:37, 31 January 2011
| Rabbit hemorrhagic disease | |
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| Scientific classification | |
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| Genus: | Lagovirus
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| Species: | Rabbit haemorrhagic disease virus
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Rabbit haemorrhagic disease (RHD), also known as rabbit calicivirus disease (RCD) or viral haemorrhagic disease (VHD), is a highly infectious and often fatal disease that affects rabbits of the species Oryctolagus cuniculus. The infectious agent responsible for the disease is rabbit haemorrhagic disease virus (RHDV), or rabbit calicivirus (RCV), genus Lagovirus of the family Caliciviridae.
Rabbit haemorrhagic disease virus (RHDV), also known as rabbit calicivirus (RCV), is the type species of the genus Lagovirus belonging to Caliciviridae family. RHDV is an important pathogen that causes a highly contagious disease in wild and domestic rabbits, rabbit haemorrhagic disease (RHD). The virus infects only rabbits, and has been used in some countries to control rabbit populations.
Two vaccines are available against VHD in the UK. One is named Cylap and made by Fort Dodge Animal Health. The other is Lapinject and is made by CEVA Animal Health Ltd. Both last 12 months and contain inactivated strains of VHD.
History
RHD first appeared in 1984 in the People's Republic of China. Scientists can not pinpoint its exact origins; however, it is believed the disease emerged from a virulent calicivirus spreading asymptomatically in European rabbit populations, particularly in the German Democratic Republic. The Chinese outbreak was spread by the angora rabbit, which had originated in Europe.[citation needed]
In 1992, the United Kingdom reported its first case of RHD in domestic show rabbits.[citation needed] By the late 1990s, RHD stretched to forty countries and had become a serious endemic in wild rabbit populations in Europe, Australia, New Zealand and Cuba. In Europe there was a rapid increase in research into RHD, due to the commercial value of rabbit meat and fur production.
The first reported case in the United States was in Iowa on March 9, 2000.[citation needed] The affected population included Palominos and California Whites. By April 6, 25 of the 27 affected rabbits had died as a result of RHD. In order to contain the disease, the remaining two rabbits were euthanized. No new introductions of rabbits were placed on the farm for two years after the discovery of RHD and August 1999 was the last time rabbits left and/or returned to the farm. The United States experienced other outbreaks of RHD in 2001 (Utah, Illinois, New York) and 2005 (Indiana).
History
Rabbit haemorrhagic disease first appeared in China during the early 1980s. In 1984 the virus that caused the disease was discovered. The virus spread westward and reached Europe in 1988. The virus has since appeared in Mexico, Cuba, Australia, New Zealand and the USA.[1]
World geographic distribution
Asia
Within a few months of RHD being reported in China in 1984, the disease was widely seen in many commercial rabbitries and had reached the Republic of Korea. RHD has also been reported in India and the Middle East.
Americas (North and South)
Since 1993, RHD has been endemic in Cuba; it is also believed to be thriving in Bolivia. From 1988 to 1992 Mexico dealt with an RHD endemic in domestic rabbits.[citation needed]
After outbreaks of RHD in 2000, 2001, and 2005, the United States has eradicated RHD from its rabbit populations.[citation needed]
Australia/New Zealand
Australia
The virus was imported into Australia in 1991 as a potential biological control agent. Testing of the virus was undertaken on Wardang Island in Spencer Gulf off the coast of the Yorke Peninsula, South Australia. In 1995 the virus escaped from the island. The virus was subsequently released into rabbit populations throughout Australia in an attempt to control rabbit infestations.
New Zealand
In July 1997, after considering over 800 public submissions, the New Zealand Ministry of Health decided not to allow RHDV to be imported into New Zealand to control rabbit populations. This was backed up in an early August review of the decision by the Director-General of Agriculture. By late August, it was confirmed that RHDV had been deliberately introduced to the Cromwell area of the South Island.
An unsuccessful attempt was made by New Zealand officials to control the spread of the disease. It was, however, being intentionally spread, and several farmers (notably in the Mackenzie Basin area) admitted to processing rabbits that had died from the disease in kitchen blenders for further spreading.
Had the disease been introduced at a better time, there would have been a more effective control of the population. Unfortunately, it was released after breeding had commenced for the season, and rabbits under 2 weeks old at the time of the introduction were immune to the disease. These young rabbits were therefore able to continue to grow and breed back up. Ten years on, now rabbit populations (in the Mackenzie Basin in particular) are beginning again to reach near plague proportions, though have still not quite returned to pre RCD levels.
In 1991 the virus that caused RHD was imported to Australia under strict quarantine conditions to research the safety and usefulness of the virus if it was used as a biological control agent against Australia and New Zealand's rabbit pest problem. However, in 1995 a laboratory accident in Southern Australia led to the escape of the RHD virus and consequently killed 10 million rabbits within 8 weeks of its exposure.[citation needed] The disease is currently epidemic throughout Australia and New Zealand. When Calicivirus was first released it wiped out 90% of the rabbits in Australia.
Europe
RHD is endemic throughout most of Europe. Italy's first case of RHD was recorded in 1986 and Spain's in 1988.[citation needed] France, Belgium (June) and Scandinavia followed in 1990. Within a few years of RHD's first appearance in Europe it had caused the largest mortality in domestic and wild rabbits in Germany, Austria, Spain and Italy. Spain was the worst affected by RHD.
When the United Kingdom's first case of RHD in 1992 was discovered, the disease was transmitted into the wild by domesticated pet rabbits.[citation needed] Sources vary in the number of confirmed cases of RHD; there were 9 known outbreaks in 1994, 32 cases but some sources believe there were as many as 512 cases of RHD in 1995, and around 30 RHD cases in 1996 throughout Scotland, England and Wales.[citation needed]
Transmission
Transmission of RHD occurs by direct contact with an infected animal and fomites. Rabbits acquire RHD through oral, nasal or conjunctival pathways. Urine, faeces and respiratory secretions may also shed the virus. The virus may also be carried by the wind. Carriers of the virus may remain infectious for up to a month depending on climate conditions; however, the virus has been known to persist for as little as 2 days and as long as 215 days. An infected carcass or hairs from an infected animal may also transmit RHD. Fomites such as clothing, contaminated food, cages, bedding, feeders and water will also harbour the virus. Even though the virus cannot reproduce in other mammals, it is believed[who?] that predators and scavengers such as foxes, ferrets and some birds can excrete the virus through their faeces after ingesting an infected rabbit carcass. Flies, rabbit fleas, and mosquitoes can also spread the virus between rabbits.
Climate appears to play a crucial role in the transmission of RHD.[citation needed] In normal conditions, most outbreaks of RHD occur in winter or spring. High temperatures in late spring and summer will considerably reduce the spreadof the virus. RHD will also be more prevalent in dry and semi-dry areas than in areas that are relatively cool and humid.
Signs
RHD primarily infects only adult rabbits. In fact, research has shown[citation needed] that rabbits younger than 8 weeks of age are resistant to the virus. The incubation period for the RHD virus is between 1 to 3 days, with death following 1 to 2 days after the infection. There is a wide range of RHD symptoms. Most rabbits will show no signs of external symptoms of RHD.
Symptomatic cases of RHD will display fever, squeals, and often coma leading to death within 12 to 36 hours. In less severe cases, rabbits may display uneasiness, excitement, anorexia, swollen eyelids, paralysis, ocular haemorrhages, and paddling. Convulsions may be seen as well. A fatal bloody discharge from the nose as been exhibited along with blood-stained cage floors, though these symptoms may have occurred after death. Rabbits who have recovered from the less severe symptoms usually develop severe jaundice with weight loss and lethargy. Diarrhoea, constipation and abdominal cramping are then exhibited right before death a few weeks later.
Research conducted at the CSIRO Australian Animal Health Laboratory claimed that rabbits did not show any outward signs of pain or suffering as a result of having RHD. The researchers further claimed that most infected rabbits became quieter and died quietly with no pain or suffering. However, the research did not in anyway prove or disprove that the rabbits did not experience severe and prolonged pain, only, that based on the subjective observation of their researchers, that the rabbits CSIRO infected grew quieter before death. It should be noted that CSIRO was actively researching RHD to use as an agent to help exterminate selected rabbit populations in Australia.
RHD causes rapid development of blood clot formation in major organs such as the heart, lungs and kidneys. The clots block blood vessels causing heart and respiratory failure. An infected rabbit that has died from RHD will often have its legs straight out and head over its neck as if trying to catch its breath.[citation needed]
Diagnosis
RHD may be indicated when several animals in the herd die after experiencing a fever and lethargy. Differential diagnosis includes pasteurellosis, myxomatosis, poisoning, heat exhaustion, and E. coli or Clostridium perfringens type E enterotoxemia.
Rabbits that die from RHD are usually in good outward state. However, the most frequent post-mortem lesions are hepatic necrosis and splenomegaly. The liver of RHD rabbits may have a fine reticular pattern of necrosis outline each lobule and maybe yellow, gray or pale in colour. The liver is also usually friable and swollen. The spleen will be black in colour and also swollen with rounded edges, while the kidneys are dark brown in colour. Haemorrhages will also be seen many other organs and tissues. The trachea may present a foamy, bloody mucous. Enteritis of the small intestine and swollen meninges may also occur.
Laboratory tests such as reverse transcription polymerase chain reaction (RT-PCR), Western blotting, negative-staining immunoelectron microscopy and ELISAs may be performed on samples from the liver, blood, spleen or other organs.
Morbidity, mortality, and immunity
RHD is extremely hard to locate in the wild since about 75% of rabbits with RHD will die in their burrows underground. Due to this difficulty, the morbidity and mortality estimates for RHD have a broad range. The morbidity rate ranges from 30% to 100% and the mortality rate from 40% to 100%; however, the typical mortality rate is usually around 90%.[citation needed]
In the wild, outbreaks in rabbits vary depending on the season, breeding cycles and geographical location. Some areas will see a high morbidity and mortality among its rabbit populations followed by calmer outbreaks.
Maternal antibodies such as immunoglobulin G (IgG), which are readily transmitted to the young across the placenta, may explain why very young rabbits are resistant to RHD.[citation needed] Some scientists also believe that the immature immune system of a young rabbit cannot produce the number of chemicals needed to initiate clotting in order to kill.[citation needed] Rabbits may develop immunity against other strains of the RHD virus, while others may endure persistent infections. The immunity does not survive through the next generation, leaving open the possibility of further outbreaks in the population.
A population of rabbits on the San Juan Islands, Washington, USA appears to be immune to RHD. The cottontail rabbit and jackrabbit are not affected by the disease; nor are humans or other mammals.
Control
Countries that are uninfected by RHD may place restrictions on importation from endemic countries. According to the Merck/Merial Manual For Pet Health, Home Edition, 2007, RHD is a reportable disease in the United States. If a diagnosis is made by a veterinarian, a notification of the "appropriate government authorities" must be made.[citation needed]
Because of the highly infectious nature of the disease, it is recommended[who?] that animals be quarantined when outbreaks occur. Depopulation, disinfection, surveillance and quarantines are the only way to properly and effectively eradicate the disease. Good disinfectants include 10% sodium hydroxide, 1-2% formalin, 2% One-Stroke Environ, and 10% household bleach. The RHD virus is resistant to ethers or chloroform. Deceased rabbits must be removed immediately and discarded in a safe manner. Surviving rabbits should be quarantined or humanely euthanized. Test rabbits may be used to monitor the virus on vaccinated farms.
An effective, safe "killed" vaccine (ATCvet code: QI08AA01 (WHO)) has been developed in various countries, particularly Spain, and is believed to give protection for 5 to 15 months[citation needed]; however, vaccine manufacturers recommend a booster be administered annually. The vaccine is also recommended in areas where the disease is widespread and eradication efforts have been made.
Use as biological control agent
The European rabbit is the second most serious pest in New Zealand. Rabbits compete with livestock for grazing pasture, kill trees, shrubs, and have contributed to the extinction of some native plants. Consequently, rabbits contribute to soil erosion by eliminating the protective vegetation and disturb the soil by burrowing.
The estimated combined cost of control and production losses in New Zealand as a result of rabbits is about $23 million annually.[2] This figure is only a small portion of the damage caused by rabbits.
Control measures used against rabbits in New Zealand include poisoning, shooting, ripping, blasting, releasing predators, and fencing.
After the safety of RHD was confirmed by laboratory research, RHD was approved for release as a biological control agent in New Zealand. RHD is safe because it infects rabbits, but not other animals or humans. It is also safe to eat the meat of infected RHD rabbits.[citation needed] Virus mutation is not a concern; many years of research show no evidence that the virus has changed to affect any other species other than European rabbit.
However, it is possible that widespread rabbit deaths might cause predators to prey upon other food sources, such as endangered or rare native species. With proper vaccination plans, the safety of domesticated rabbits should not be a concern.
See also
References
- ^ "Rabbit Calicivirus Disease". The Merck Veterinary Manual. 2006. Retrieved 2007-06-17.
- ^ http://www.maf.govt.nz/mafnet/rural-nz/research-and-development/pest-control/rcd/rcdsonza.htm
- Cooke, B.D. Rabbit Haemorrhagic Disease: Field epidemiology and the management of wild rabbit populations. Common Wealth Scientific and Industrial Research Organisation (CSIRO) Sustainable Ecosystems. http://www.oie.int/eng/publicat/rt/2102/COOKE.pdf. Retrieved on 2008-02-06.
- RCD – Frequently Asked Questions. Rabbit Biocontrol Advisory Group. http://www.maf.govt.ns/mafret/publications/rabbit-biocontrol-advisory-group/rbag0002.htm. Retrieved on 2008-02-06.
- Rabbit Calicivirus Disease. Center for Emerging Issues. http://www.aphis.gov/us/ceah/cei/taf/iw_2000_files/domestic/rabbitcal.htm. Retrieved on 2008-02-06.
- Rabbit Calicivirus Disease. The Merck/Merial Manual For Pet Health 2007 Home Edition. Page 995-996.
- Rabbit Calicivirus Disease. The Merck Veterinary Manual, Eighth Edition (1998). Page 1398–1399.
- RHD – A New Rabbit Disease. The British Association For Shooting and Conservation Ltd. http://www.basc.org.uk/media/rabbits.pdf. Retrieved on 2008-02-06.
- Rabbit Hemorrhagic. Center for Food Security & Public Health Iowa State University College of Veterinary Medicine. http://www.cfsph.iastate.edu/Factsheets/pdfs/rabbit_hemorrhagic_disease.pdf. Retrieved on 2008-02-06.</ref>
- Rabbit Viral Haemorrhagic Disease (RVHD). Scottish Natural Heritage. http://www.snh.org/uk/publications/on-line/advisorynotes/31/31.htm. Retrieved on 2008-02-06.
- NOAH Compendium of Animal Medicines - Lapinject http://www.noahcompendium.co.uk/CEVA_Animal_Health_Ltd/Lapinject_VHD/-42505.html
- NOAH Compendium of Animal Medicines - Cylap http://www.noahcompendium.co.uk/Fort_Dodge_Animal_Health/Cylap/-44932.html