Rabbit haemorrhagic disease is a viral disease highly contagious, deadly and notifiable to the World Organization for Animal He alth (OIE). It is caused by a virus that affects domestic and wild rabbits of the species Oryctolagus cuniculus (European rabbit). The virus affects the blood vessels after its mobilization in defensive cells of the rabbit. This results in lesions such as hemorrhages, microthrombi, ischemia, organic necrosis and cell death. In turn, the disease can give rise to forms from peracute to subacute, depending on the severity. The disease has no treatment, but control is sought with biosafety measures and through a vaccine.
In this article on our site we will address the topic of rabbit hemorrhagic disease, its pathogenesis, symptoms, diagnosis and control.
What is rabbit hemorrhagic disease?
Rabbit hemorrhagic disease is a infectious-contagious process of viral origin that affects domestic and wild rabbits of the species Oryctolagus cuniculus (European rabbit), and which has high mortality and morbidity rates. In addition, it is an endemic disease in most of Europe, Asia, Africa, Cuba, New Zealand and Australia.
What virus causes rabbit hemorrhagic disease?
This is a RNA virus of the family Caliciviridae and the genus Lagovirus. It is a very resistant virus in organic matter and very contagious. It has 6 genogroups and the capsule protein is highly immunogenic and has the ability to agglutinate human and avian group 0 red blood cells.
How is rabbit hemorrhagic disease spread?
Contagion between rabbits occurs through secretions, corpses and excretions, it can be in the form:
- Direct: especially oronasal, but also conjunctival, oral and respiratory.
- Hint: Through people, food, water, and fomites.
Luckily, it is not one of the diseases that rabbits transmit to humans or other animals.
Causes of rabbit hemorrhagic disease
As we said, rabbit haemorrhagic disease has a viral origin. The virus has a predisposition towards the reticuloendothelial system and the mononuclear phagocytic system.
After arrival in the body, it passes into the blood producing viremia, reaching various places with blood cells such as lymphocytes, macrophages and monocytes. The lesions they produce are a consequence of cell death or necrosis in organs such as the liver. In addition, it causes lesions in the endothelium of the blood vessels, which consists of a dilation that results in hemorrhages and degeneration of the endothelium.
Microthrombi are also produced due to the precoagulant substances produced and endothelial degeneration, which cause hemorrhages and ischemia due to the consumption of coagulation factors and platelets.
Symptoms of Rabbit Hemorrhagic Disease
The incubation period for rabbit haemorrhagic disease ranges from several hours to 3 dayss. The clinical forms can be peracute, acute and subacute, depending on the severity.
Symptoms of the overacute form
It usually occurs in areas that do not have the disease, causing mortality rates of more than 90%. In this clinical form, diseased rabbits develop:
- Fever.
- Opisthotonos.
- Seizures.
- Shrieking.
- Sudden death in 12-36 hours.
Symptoms of the acute form
This clinical form presents a course of 26-48 hours and develops signs such as:
- Hyperthermia.
- Depression.
- Anorexy.
- Prostration.
- Eye hemorrhages.
- Dyspnoea.
- Cyanosis.
- Nasal discharge.
- Seizures.
- Ataxia.
- Abdominal distension.
- Epistaxis.
- Death.
In some rabbits, the course may be longer, appearing to recover but developing jaundice, lethargy and weight loss, dying within a few weeks.
Symptoms of the subacute form
In the subacute clinical form many rabbits survive and milder signs of 2-3 days duration occur, such as:
- Hyperthermia.
- Depression.
- Anorexy.
Organic lesions of the disease
The lesions that the virus can cause in affected rabbits, especially in severe clinical forms, are the following:
- Hepatic necrosis.
- Serohemorrhagic pneumonia.
- Pulmonary edema.
- Enlargement of the spleen.
- Hemorrhages and congestion in the heart and kidney.
- Generalized circulatory dysfunction.
If your rabbit is behaving strangely and has any of these Symptoms of a Sick Rabbit, we recommend that you take him to the vet as soon as possible.
Diagnosis of Rabbit Hemorrhagic Disease
Suspicion of this disease should appear due to the appearance of sudden death of many rabbits on the farm after a period of fever with or without symptoms of the aforementioned. When an autopsy is performed and liver necrosis is observed, it would confirm the diagnosis.
Differential Diagnosis
The differential diagnosis of rabbit haemorrhagic disease includes the following diseases that lagomorphs may suffer:
- Atypical myxomatosis.
- Poisoning.
- Hemorrhagic septicemia due to Pasteurella multocida.
- Toxemia of pregnancy.
- Enterotoxemia due to E.coli or Clostridium perfringens type E.
Laboratory diagnosis
Laboratory diagnosis is performed with samples such as blood or liver, spleen or other organs obtained at necropsy, and includes:
- Direct tests for the detection of viral antigen, such as: RT-PCR, direct ELISA, direct immunofluorescence, hemagglutination and electron microscopy.
- Indirect tests for the detection of antibodies, such as: hemagglutination inhibition and indirect ELISA.
Treatment of rabbit hemorrhagic disease
Rabbit haemorrhagic disease has no treatment, but it can be controlled. Although it is very difficult to eradicate in wild rabbits, it can be achieved in domestic rabbits with biosecurity measures such as:
- Frequent hygiene and disinfection of your space.
- Elimination and sacrifice of affected rabbits.
- Strict quarantine.
- Vaccination.
- Good ventilation.
- Protective nets (if you have access to the garden).
- Prevent the access of rodents or wild rabbits.
- Epidemiological surveillance with sentinel rabbits.
- Disinfection, rat extermination and disinsection program.
Whenever a case or outbreak is confirmed must be notified to the World Organization for Animal He alth as it is a notifiable disease in rabbits.
Rabbit haemorrhagic fever vaccination
Although the disease cannot be treated, it can be prevented with vaccination. The rabbit hemorrhagic disease vaccine can be the only protection against this disease or 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, ask your veterinarian about your rabbit's vaccination schedule.
