Seasonal outbreaks of infectious diseases are often observed on farms where rabbits are bred. One of these diseases is hemorrhagic disease of rabbits – a serious infectious disease that significantly affects the internal organs of animals. This disease is also known as necrotic hepatitis or hemorrhagic pneumonia, because it has serious complications in the respiratory organs and the liver. The disease is manifested by a rapid course, a high level of infectivity and, in most cases, causes the death of the entire herd.
Description and history
Rabbit hemorrhagic disease, also known as rabbit necrotizing hepatitis or hemorrhagic pneumonia, is a serious infectious disease that causes damage to internal organs in rabbits. The causative agent of this disease is RNA-lagovirus (Lagovirus) of the genus Caliciviridae.
One of the characteristics of hemorrhagic disease of rabbits is its extreme stability in the external environment. The virus can withstand temperatures from -50 to +60 degrees Celsius for three months. It is also capable of being stored on inventory and in cages for up to two years, sometimes longer. Even after a five-year freeze, it can demonstrate viability. It is noted that the virus is not sensitive to treatment with chlorine or ether, but dies when interacting with lime, carbolite, chlorine and alkalis.
The first cases of hemorrhagic disease of rabbits were recorded in China, in the province of Jiangsu at the beginning of the 20th century. In 1984, this terrible virus penetrated the “Far Eastern” state farm located on the border with China, and all the rabbits died instantly.
After that, the disease quickly spread throughout the country. Since 1986, it has migrated to farms in Europe, and especially in Italy, where infected rabbits were imported from China. For a long time, it was not possible to identify the causative agent of this disease, and it was called “disease X”. However, in the early 2000s, rabbit hemorrhagic disease became widespread throughout the world. Continuous research is being conducted aimed at clarifying the characteristics of this disease and developing measures to prevent its epidemic. It is worth noting that hemorrhagic disease affects only rabbits among all animal fauna.
Paths of disease transmission
Hemorrhagic disease of rabbits can be transmitted in several ways. Rabbits older than 1.5 months can be affected by this disease (however, it is still not clear why rabbits up to 45 days old are resistant and immune to this disease) and weighing more than 3 kg. Rabbits who feed their young at any time, regardless of sex, breed and seasonality, are also at risk of infection.
The source of the causative agent of the disease is sick and sick rabbits.
The main routes of transmission of the virus include:
- Airborne route: contact of a rabbit with an infected relative, especially through inhalation of droplets containing the virus.
- Fecal route: The virus can live up to 30 days in pus, so contact with infected pus can lead to infection.
- Alimentary route: transmission through the consumption of infected food and water, contact with the hands of personnel, as well as through the consumption of infected rabbit meat.
Given these routes of transmission, it is important to pay attention to hygienic measures, including the observance of sanitary standards when handling manure, thorough hand washing after contact with sick rabbits, and avoiding the consumption of infected food.
Continued research and increased awareness of the routes of transmission of rabbit hemorrhagic disease will help to control the disease more effectively and prevent its spread.
Symptoms and forms of hemorrhagic disease
The incubation period of the disease in rabbits usually lasts 2-3 days, but it can last up to 5 days. After the virus enters the rabbit’s body, it begins to multiply actively. First of all, it attacks the liver, which leads to tissue necrosis and hemorrhages. Then the lungs, heart and kidneys are affected. As a result of the disease, blood clots form in the blood vessels, which adds complications to the process.
Symptoms of rabbit hemorrhagic disease may include:
- Loss of appetite and decreased activity.
- General weakness and fatigue.
- Hemorrhagic manifestations, such as bleeding from the mouth, nose, eyes, anus, as well as bloody discharge.
- Diarrhea that may contain blood.
- Skin irritation and redness.
- Difficulty breathing and shortness of breath.
- Instant death of an animal at any stage of the disease.
Hemorrhagic disease of rabbits can have different forms of severity, from mild to severe, depending on the degree of damage to the organs and systems of the rabbit’s body. Understanding the symptoms and forms of the disease is important for quickly identifying and treating sick rabbits and preventing the spread of the disease on farms.
Diagnostics
Diagnosis of rabbit hemorrhagic disease is usually based on several methods to establish a final diagnosis. The main diagnostic methods include:
- Clinical examination and observation: The veterinarian conducts a detailed clinical examination of sick rabbits, observes characteristic symptoms of hemorrhagic disease.
- Laboratory studies: After the death of the rabbit, it is important to take the carcass to the laboratory for analysis. Microscopic examination of organs after dissection helps to reveal characteristic changes, such as tissue necrosis, bleeding and other pathological signs, indicating hemorrhagic disease of rabbits.
- Exclusion of other diseases: The veterinarian must first of all exclude diseases with similar symptoms, such as heat stroke, pasteurellosis, salmonellosis, poisoning. For this purpose, additional laboratory and diagnostic tests may be performed.
An accurate diagnosis of “rabbit hemorrhagic disease” is established after a comprehensive analysis of clinical symptoms, laboratory results and exclusion of other diseases that may have a similar clinical picture.
Clinical signs of the disease
Clinical signs of rabbit hemorrhagic disease can vary depending on the resistance of the rabbit and the strength of the virus strain. The disease has three forms of course, which are characterized by different symptoms:
- Ultra-acute form: This form proceeds without noticeable external signs. However, some symptoms may be observed before death, such as an increase in body temperature to almost 42°C, lethargy, apathy, labored breathing with interruptions, and loose stools.
- Acute form: In this form, rabbits show cyanosis of the mucous membranes, swelling of the eyelids, noisy breathing with interruptions, arching of the back, straining of the paws, possible bloody stools, nosebleeds, accelerated heart rate and fever. It is important to note that even in this form, symptoms may be absent, and before death, the rabbit may suddenly stop chewing and only convulsively flinch several times. Bleeding from the nose, mouth and anus may occur during death.
- Chronic course: In this form, such symptoms as conjunctivitis, ARVI, runny nose, bleeding from the anus, inflammation of the stomach and intestines, paleness or blueness of the mucous membranes, and inflammation of the lungs can be observed. A rabbit can survive a chronic course, but at the same time becomes a lifelong carrier of the virus, and also develops immunity to the disease.
It is important to remember that in some cases the symptoms may be less noticeable or absent at all, but hemorrhagic disease of rabbits can still lead to the death of the animal.
Pathological anatomical changes
During the autopsy of rabbits with hemorrhagic disease, the following signs are observed:
- Clogging of venous vessels and heart with blood clots.
- Marked accumulation of blood in the eyes, throat, nasal cavity and ulcers in the mouth.
- Point lesions in the lungs, which are manifested by swelling and discoloration.
- The liver is enlarged and filled with blood.
- The spleen has increased in size by 2-3 times and has a dark appearance.
- The occurrence of an inflammatory process in the stomach and intestines.
- Destroyed lymph nodes.
These pathological changes indicate serious damage to the internal organs of the rabbit and the presence of hemorrhages. They confirm the severity of the disease and its potentially fatal course.
Features of mortality
Hemorrhagic disease of rabbits differs in that death from it occurs at different times. All animals do not die at the same time. This contagious disease is quickly transmitted from one rabbit to another. However, the peculiarity is that rabbits fall victim to the disease more than once.
First, a few rabbits become ill, and then the disease spreads, gradually affecting adult and pregnant rabbits, as well as breeding rabbits. The mortality rate depends on the resistance of animals, but in any case, mortality is at least 90% of the total number of sick animals.
Can sick rabbits be saved?
Treatment is possible only at early signs of an acute course of the disease. However, with an extremely acute course or in cases where the disease is already quite widespread, it is impossible to save the animal. However, it is important to remember that the most effective measure is to prevent the spread of the disease through the use of preventive measures and vaccination.
Treatment of hemorrhagic disease
To date, it has not been possible to develop an effective treatment for viral hemorrhagic disease of rabbits. In practice, only specific serum immunotherapy is used.
Specific serum immunotherapy:
- It is made from the blood of rabbits that have been vaccinated against hemorrhagic disease. One dose of serum contains 32 antihemagglutinating units of calcivirus, but is completely safe for animals.
- The first dose of serum is administered intramuscularly or subcutaneously at 0.5 ml to all rabbits on the farm, regardless of their weight and age. The procedure is repeated after a day.
- Thanks to the serum, the synthesis of antibodies against the virus is stimulated, which provides passive immunity already 1.5-2 hours after administration and lasts for 1 month.
Experienced rabbit breeders claim that with timely diagnosis (which is the most difficult task due to the almost asymptomatic course of the disease) and the introduction of a specific serum against hemorrhagic disease, most cases of the spread of this terrible disease can be stopped.
Prevention
Hemorrhagic disease of rabbits cannot be completely cured at this time, but its spread can be prevented if the following preventive measures are followed:
- Vaccination: Vaccinate rabbits regularly according to the recommended vaccination schedule. Vaccination can provide immunity against disease and reduce the risk of infection.
- Quarantine: Follow quarantine measures for animals with suspected disease, as well as for newly purchased rabbits. Isolation can prevent the disease from spreading to other rabbits on the farm or holding.
- Sanitation and hygiene rules: Follow all rules of sanitation and hygiene when breeding rabbits. Keeping the premises clean, regularly ventilating them and disposing of waste can help prevent the spread of the virus.
- Disinfection and pest control: Disinfect premises regularly, including cages, utensils and equipment. In addition, ensure deratization (control of rodents) and disinsection (control of insects) to reduce the risk of infestation.
Following these preventive measures will help reduce the risk of rabbit hemorrhagic disease and protect your herd from its spread.
Vaccination
Due to the lack of effective treatment, the main method of prevention of hemorrhagic disease is vaccination of rabbits. Interestingly, rabbits born from vaccinated rabbits have 100% immunity to hemorrhagic disease during the first 30 days of life. However, this immunity gradually decreases until the end of the third month and then disappears completely.
Doses and methods of vaccine administration
There are three methods of vaccination against hemorrhagic disease:
- Administration during pregnancy: Rabbits are vaccinated before birth to pass immunity to their littermates.
- Vaccination of rabbits at the age of 1.5 to 3 months: Young rabbits are vaccinated to develop their own immunity.
- Revaccination of adults according to the schedule: Adult rabbits are subject to revaccination according to the established schedule.
For vaccination, polyvalent formol vaccines or tissue extracts-lyophilisates (type 1, 2 or 3) are used. Vaccinations are carried out intramuscularly (in the thigh of the animal) in the recommended dose according to the instructions for the selected drug.
The list of available vaccines includes:
- Kunipravak-RHD
- Tissue inactivated hydroxyaluminum vaccine
- Rabivak-V
- Dervaximixo
Complex drugs that protect against several diseases at the same time are also used:
- Derkunimix (including myxomatosis)
- Dry-associated vaccine (including myxomatosis)
- Inactivated drug (including pasteurellosis)
Vaccination recommendations:
- Vaccinate only healthy rabbits.
- It is best to inoculate in spring or autumn.
- Before the introduction of the vaccine, animals are given drugs for the prevention of helminths.
- Inspect livestock and quarantine animals suspected of having any disease.
- After vaccination, the farm is quarantined for 14 days (before the vaccination begins).
Following these recommendations will ensure effective vaccination and help protect rabbits from hemorrhagic disease.
Actions in the event of an epizootic
When diagnosing hemorrhagic disease on a rabbit farm, in addition to administration of serum and vaccination, measures aimed at disposal of infected material and disinfection are important.
Action algorithm:
- Movement of healthy animals: Healthy rabbits are moved to another disinfected place of residence, antihemorrhagic serum is applied and vaccination is carried out.
- Cleaning and disinfection of equipment: After moving healthy livestock to a new location, clean and disinfect cages and other equipment that has been in contact with infected animals. Mechanical cleaning is carried out with the help of brushes, brooms, shovels, scrapers, buckets, boxes, sprayers. Then disinfect using hot water with caustic soda.
- Disinfection of the rabbit hutch and equipment: The rabbit hutch and equipment are disinfected with chlorine, formalin, phenol, carbolite, glutex, iodine, verocide, ecocide, slaked lime and laundry. Removable feeders and drinking bowls are soaked in a disinfectant solution (for example, formaldehyde, lime, calcium hypochlorite) for 3-4 hours. It is also desirable to burn the cages with a blowtorch.
- Disposal of contaminated material: In the facility for disposing of corpses of sick animals (Beckari pit), dead livestock, small feeders, litter, leftover food from cages, feces, plastic dishes and small equipment for care, as well as workers’ clothing are burned. The territory where the sick animals were, cesspools and manure are covered with dry lime.
- Disinfection and deratization: Conduct disinfestation and deratization to eliminate insects and rodents that can be carriers of disease.
- Inspection and drying of the premises and cages: After all disinfection measures, it is recommended to wash the premises and cages with soda solution and dry them well.
- Additional measures: If rabbits were transported, all used cars are also disinfected.
It is strictly forbidden to eat the meat of dead rabbits, as well as to use their fur or skins. It is also forbidden to buy rabbit meat without a veterinary and sanitary supervision label.
After disinfection, it is recommended to repeat all disinfection measures after 2 weeks.
Recovery of the economy after illness
After a case of hemorrhagic pathology, a new batch of rabbits can be brought to the farm no earlier than 15 days later. This period is necessary to ensure the recovery of the economy and prevent the further spread of the disease.
Viral hemorrhagic disease of rabbits is a serious disease that can cause irreparable damage to rabbit farms. To prevent the penetration of the causative agent of the disease, it is necessary to pay due attention to preventive measures. In particular, it is important to vaccinate rabbits on time, to carefully monitor their condition, and to properly feed and care for them. Compliance with all sanitary and hygienic norms is also a necessary condition for preserving the health and well-being of animals.
After the disease, it is important to carry out a thorough disinfection of the premises and equipment that were in contact with infected rabbits. Disinfection measures should include cleaning and disinfection of cages, disinfection of equipment and surfaces, and disposal of contaminated material. Only after complete decontamination can you start the process of restoring the farm by importing new rabbits.
It is emphasized that the correct implementation of all prevention and disinfection recommendations is key to preventing the further spread of viral hemorrhagic disease of rabbits and preserving the health of animals.