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Rabbit Hemorrhagic Disease - Causes, Symptoms & Treatment

 
By Laura García Ortiz, Veterinarian specialized in feline medicine. April 13, 2021
Rabbit Hemorrhagic Disease - Causes, Symptoms & Treatment

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Rabbit haemorrhagic disease is a highly contagious and potentially fatal viral disease according to the World Organization for Animal Health (OIE). The virus can affect both domestic and wild rabbits of the species Oryctolagus cuniculus (European rabbit). The virus affects the blood vessels after it mobilizes in defensive cells of the rabbit. It can result in various symptoms, but the most characteristic is hemorrhaging which can present in various forms.

In this AnimalWised article, we look closely at rabbit hemorrhagic disease and present its causes, symptoms and treatment. We also explain how we can best prevent our rabbit from developing an infection in the first place.

You may also be interested in: Dog Flu - Symptoms and Treatment

What is rabbit hemorrhagic disease?

Rabbit haemorrhagic disease is a viral infectious process that affects domestic and wild rabbits of the species Oryctolagus cuniculus (European rabbit). It has high mortality and morbidity rates. Furthermore, it is an endemic disease in most of Europe, Asia, Africa, Cuba, New Zealand and Australia.

What virus causes rabbit hemorrhagic disease?

It is an RNA virus (one that contains ribonucleic acid) and a lagovirus of the Caliciviridae family. This means it can infect lagomorphs, its natural host. Aamong rabbits it is a very resistant and highly contagious virus. It has been recorded at surviving prolonged exposure to temperatures as high as 50 ºC and can survivie thaw after being frozen.

Rabbit hemorrhagic disease virus (RHDV) has 6 genogroups and the capsule protein is highly immunogenic. Of these 6, there are three strains which are most important in terms of rabbit infection. They are rabbit hemorrhagic disease virus (RHDV), rabbit hemorrhagic disease virus a (RHDVa) and rabbit hemorrhagic disease virus 2 (RHDV2). They all have the ability to agglutinate human and avian group 0 red blood cells.

How is rabbit hemorrhagic disease spread?

The contagion between rabbits occurs through secretions, dad animal carcasses and excretions. Parthenogenesis can occur in in the forms:

  • Direct: especially through the oronasal route, although also conjunctival, oral and respiratory.
  • Indirect: through people, food, water and fomites.

Fortunately it is not a disease which is spread to humans, nor other animals.

Causes of rabbit hemorrhagic disease

As we said, rabbit haemorrhagic disease of the rabbit has a viral origin. The virus has a predisposition towards the reticuloendothelial system and the phagocytic mononuclear system.

Upon arrival in the body, it passes into the blood via process known as viremia. Since it is present in the blood, it can reach various places with blood cells such as lymphocytes, macrophages and monocytes. The lesions they produce are as a consequence of cell death or necrosis in organs such as the liver. The lesions can appear in the endothelium of the blood vessels, resulting in a dilation that results in hemorrhages and degeneration of the endothelium.

Microthrombi also occur due to the precoagulant substances produced and endothelial degeneration. In turn, this causes bleeding and ischemia (restriction of blood supply) due to consumption of clotting factors and platelets.

Rabbit Hemorrhagic Disease - Causes, Symptoms & Treatment - Causes of rabbit hemorrhagic disease

Symptoms of rabbit hemorrhagic disease

The incubation period for rabbit haemorrhagic disease ranges from several hours to 3 days. The clinical forms can be super-acute, acute and subacute, depending on the severity.

Symptoms of super-acute RHD

This usually occurs in areas that do not normally have the disease, causing mortality rates of more than 90%. In this clinical form, rabbits infected with the virus develop:

  • Fever
  • Opisthotonus
  • Seizures
  • Shrieking
  • Sudden death in 12-36 hours

Symptoms of acute RHD

This clinical form presents a course of 26-48 hours and signs such as:

  • Hyperthermia
  • Depression
  • Anorexia
  • Prostration
  • Eye hemorrhages
  • Dyspnoea
  • Cyanosis
  • Nasal discharge
  • Seizures
  • Ataxia
  • Abdominal distension
  • Epistaxis
  • Death

In some rabbits, the course may be longer, initially appearing to recover, but then developing jaundice, lethargy and weight loss. After this it, is common for them to die within a few weeks. Our article on signs your rabbit is dying will help you to understand further.

Symptoms of subacute RHD

In the subacute clinical form, many rabbits survive and milder signs lasting 2-3 days occur, such as:

  • Hyperthermia
  • Depression
  • Anorexia

Organic lesions of the disease

The lesions that the virus can produce in affected rabbits, especially in severe clinical forms, are the following:

  • Hepatic necrosis
  • Serohemorrhagic pneumonia
  • Pulmonary edema
  • Spleen enlargement
  • Hemorrhages and congestion in the heart and kidney
  • Generalized circulatory dysfunction

If your rabbit has a strange behavior and has any of these symptoms of a sick rabbit, we recommend that you take them to the vet as soon as possible.

Diagnosis of rabbit hemorrhagic disease

Suspicion of this disease should appear when many rabbits on a farm suddenly die after a period of fever with or without any of the aforementioned symptoms. When a necropsy is performed and liver necrosis is seen, it should confirm the diagnosis.

Differential diagnosis

The differential diagnosis of rabbit hemorrhagic disease includes the following common diseases from which lagomorphs can suffer:

  • Atypical myxomatosis
  • Poisoning
  • Hemorrhagic septicemia due to Pasteurella multocida
  • Gestational toxemia
  • Enterotoxemia due to E.coli or Clostridium perfringens type E

Laboratory diagnosis

Laboratory diagnosis is carried out with blood samples or biopsies taken from the liver, spleen or other organs which can suffer necrosis. Test include:

  • Direct tests for the detection of viral antigen: RT-PCR, direct ELISA, direct immunofluorescence, hemagglutination and electron microscopy.
  • Indirect tests for the detection of antibodies: inhibition of hemagglutination and indirect ELISA.
Rabbit Hemorrhagic Disease - Causes, Symptoms & Treatment - Diagnosis of rabbit hemorrhagic disease

Treatment of rabbit hemorrhagic disease

Rabbit haemorrhagic disease has no treatment, but its symptoms can be managed. Although it is very difficult to eradicate in wild rabbits, it is achieved in domestic rabbits with biosecurity measures such as:

  • Hygiene and frequent disinfection of their space.
  • Elimination and extermination of affected rabbits.
  • Strict quarantine when ifnection is confirmed.
  • Vaccination prevention where possible.
  • Good ventilation of their hutch.
  • Protective nets (if they have access to the garden).
  • Prevent the access of rodents or wild rabbits.
  • Epidemiological surveillance with sentinel rabbits.
  • Disinfection, deratization and disinsection program.

Whenever a case or an outbreak is confirmed, the World Organization for Animal Health must be notified as it is a notifiable disease in rabbits. Since diagnosis will require a veterinarian, this is something which will usually be addressed by the clinic, but it shows the importance of reporting certain diseases.

Rabbit haemorrhagic fever vaccination

Although the disease cannot be treated, infection can be prevented with vaccination. The rabbit haemorrhagic disease vaccine can be of sole protection against this disease or administered with the myxomatosis vaccine:

  • Single Immunity Vaccine: The Single Immunity Vaccine Against Hemorrhagic Disease is an inactivated vaccine that includes the immunogenic protein of the virus, the VP60 protein. It is inoculated subcutaneously.
  • Mixed vaccine: on the other hand, the mixed vaccine with myxomatosis is intradermal.

In a domestic rabbit, the primary vaccination is carried out at two months or 10 weeks and it is revaccinated once a year. For more information, check speak to your veterinarian about what vaccinations for rabbits are required in your area and begin a suitable vaccination schedule.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Rabbit Hemorrhagic Disease - Causes, Symptoms & Treatment, we recommend you visit our Viral diseases category.

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