Rabbit Hemorrhagic Disease: A Highly Contagious and Fatal Threat to Rabbits

Rabbit Plague, also known as Rabbit Viral Hemorrhagic Disease (RHD) or Rabbit Hemorrhagic Fever, is a highly contagious and rapidly spreading viral infection with a broad epidemiological reach. It boasts an alarming mortality rate of 90% to 100%, making it one of the most devastating diseases in the rabbit industry. Postmortem examinations primarily reveal hemorrhages in the respiratory organs and parenchymal tissues.

I. Pathogen
The causative agent is the Rabbit Hemorrhagic Disease Virus (RHDV), which exhibits a spherical morphology with an icosahedral symmetry. It possesses the ability to agglutinate human red blood cells of types O, A, B, and AB. The virus disseminates throughout all tissues and organs of infected rabbits, with the highest viral load concentrated in the liver, followed by the lungs, spleen, kidneys, intestines, and lymph nodes. It is resistant to sulfonamides and antibiotics. Effective disinfectants include 1%–3% sodium hydroxide solution and 20% lime milk.

II. Epidemiology
Transmission occurs via the respiratory tract, digestive tract, wounds, and mucous membranes. The disease spreads through direct contact with infected rabbits, their excretions, secretions, fur, blood, or organs, as well as through exposure to virus-contaminated feed, water, utensils, cages, or carrier rabbits. Rabbits over three months of age and adults are highly susceptible, while nursing young rabbits exhibit partial resistance and lower susceptibility. Although cases can occur year-round, outbreaks are most frequent during winter and spring.

III. Symptoms and Lesions

Peracute Form:
Most common in the early stages of an outbreak, infected rabbits may die suddenly without showing any symptoms. Some emit a sharp cry before death, leap forward, collapse, kick their limbs, extend their necks, and die within minutes. A small number of rabbits may discharge foamy blood from the nostrils.

Acute Form:
Symptoms include depression, reduced or absent appetite, fever (40.5–41.5°C), generalized tremors, gasping breaths, collapse, convulsions, and death. The disease course lasts 0.5 to 2 days.

Chronic Form:
Typically observed in the late stages of an outbreak or in recently weaned young rabbits, symptoms include fever (40–41°C), lethargy, reduced appetite, and rapid weight loss. Those surviving beyond two days often recover but remain contagious, shedding the virus and posing an infection risk to other rabbits.
Lesions include congestion and hemorrhages in the nasal cavity, larynx, and tracheal mucosa, most pronounced in the tracheal rings; pulmonary congestion, edema, and hemorrhage; hepatomegaly with a dark red hue and occasional bleeding; renomegaly ranging from dark purple to blackish-purple with grayish-white or yellow speckles; congestion of cerebral and meningeal blood vessels accompanied by blood clots in the pineal and pituitary glands; and occasional hemorrhages in the uterus and intestinal serosa.

IV. Diagnosis
A preliminary diagnosis can be made based on clinical symptoms and pathological changes. Confirmatory diagnosis requires laboratory testing, commonly using hemagglutination and hemagglutination inhibition assays. Alternative methods include neutralization tests or experimental infection of rabbits to induce the disease.

V. Prevention and Control
Strictly prohibit the introduction of breeding rabbits from epidemic areas and restrict unauthorized access to rabbit housing. In the event of an outbreak, implement quarantine measures, isolation, and disinfection. Dispose of dead rabbits by deep burial or incineration. Emergency vaccination of unaffected rabbits may be necessary when appropriate. Currently, no effective treatment exists for this disease, underscoring the critical importance of prevention as the primary strategy.