Rabbit Hemorrhagic Disease (RHD)

Hemorrhagic rabbit disease (RHD) is a highly lethal viral infection in rabbits caused by rabbit hemorrhagic disease virus (RHDV).

Hemorrhagic rabbit disease (RHD) is a highly lethal viral infection caused by hemorrhagic disease virus (RHDV). RHDV induces hemorrhaging and necrosis of the parenchymal organs in rabbits. RHD mainly poses a threat to juvenile and adult rabbits, with a susceptibility rate and mortality rate above 90%. However, in recent years, the onset tends to be younger, and the disease has become the enemy of the rabbit industry all over the world. With years of research experience, BioVenic is committed to helping customers reduce the losses caused by RHD to the rabbit industry.

Cause

RHDV is a non-enveloped positive-sense RNA virus with a diameter of approximately 35-40 nm, belonging to the Lagovirus genus of the Caliciviridae family.

Fig. 1 Schematic diagram of the structure of RHDV.¹

With the continuous mutation of the virus, there are three types of RHDV, namely RHDV1, RHDV1a, and RHDV2. RHDV1 was first reported in the People's Republic of China in 1984, and RHDV1a is a new naturally occurring RHDV1 variant discovered in 1996. RHDV2 was isolated from an outbreak in France in 2010.

RHD is not a zoonotic disease.

Transmission and Spread

Due to its robust environmental resistance and persistence, RHDV can be transmitted through various routes.

• Direct contact with infected rabbits can result in the transmission of RHD.
• RHD also be transmitted through contact with contaminated materials.
• Indirect transmission of RHD can occur through insect vectors.
• The transmission of disease through contact with individuals who have had contact with infected rabbits.
• Transmission through infected rabbit meat products.

Epidemiological Features

The disease occurs year-round but tends to seasonal outbreaks (breeding season) in wild rabbits. It mainly affects rabbits over 2 months old. Adult rabbits and lactating female rabbits have a high mortality rate, and lactating young rabbits rarely die. The onset of this disease is acute, the case fatality rate is high, and it is often an outbreak that spreads rapidly. Symptoms spread rapidly throughout the entire group within two to three days after onset.

RHD in the US

RHD is a notifiable disease in the United States. RHD was confirmed in Iowa, USA in April 2000, but the source of infection has not been identified. In September 2018, RHDV2 was confirmed in Ohio, USA, and then RHDV2 broke out in several states in the United States.

Signs and Symptoms

RHD is characterized by a variety of clinical symptoms and signs. The course of the disease is divided into the most acute, acute, and chronic.

• The Most Acute Type
  It is more common in non-epidemic areas or the early stages of epidemics. Sick rabbits often die suddenly without obvious symptoms.
• Acute Type
  High fever above 41℃ at the beginning of the disease, followed by a sharp drop in body temperature, anorexia, convulsions, nervous system symptoms, and bleeding. The course of the disease is about 1 to 2 days. After death, the horn arch is opisthotonus, and red foamy liquid flows out of the nostrils.
• Chronic Type
  More common in old epidemic areas or the late epidemic period. The incubation period and the course of the disease are longer, the body temperature rises slightly, the spirit is low, the body becomes thin rapidly, and dies of weakness.

Diagnosis of RHD

With years of rich experience, BioVenic develops comprehensive and accurate diagnostic solutions for customers. Our service capabilities are mainly divided into pathogen detection and immune response detection.

• RHDV Detection
  We help customers develop ELISA, RT-PCR, NGS, and other immunodiagnostics and molecular diagnostics techniques that can be used to detect pathogens in samples.
• Immune Response Detection
  We help customers develop competitive ELISA, isotype ELISA, hemagglutination inhibition, and other immunodiagnostics assays to detect the specific immune response of rabbits to RHDV.

Treatment, Prevention, and Control

There are no effective treatments for RHD. Due to the disease's rapid progression and high mortality rate, the options for supportive care are limited.

Vaccination is considered to be one of the most effective measures to prevent RHD. Vaccines against specific RHDV strains have been developed and are recommended for use in high-risk rabbits. BioVenic has rich experience in vaccine development and is fully capable of developing custom vaccines for RHD for customers.

Biosecurity measures, including proper sanitation, quarantine protocols, and vector control are also critical to preventing the spread of disease. We recommend the following specific measures,

• Monitor rabbits closely for relevant symptoms.
• It is advisable to refrain from any contact between domestic rabbits and wild rabbits.
• Pay attention to disinfestation to prevent insects from spreading RHDV.
• Insist on all in all out when breeding rabbits.
• Foreign personnel and vehicles should not be allowed on the rabbit farm.
• Disinfect the farm and all utensils regularly.
• Hay must be obtained from RHDV-free areas.
• All staff entering and leaving the farm need to be fully disinfected.
• Workers wear special clothes, shoes, etc. on the farm.

RHD poses a major challenge to the global rabbit industry. To help acceptance researchers effectively combat RHD, BioVenic has been working to better understand the virus, develop more precise diagnostics solutions, and more effective vaccines, and improve control strategies. If you are interested in our services, please feel free to contact us.

References

1. Wang, Xue, et al. "Atomic model of rabbit hemorrhagic disease virus by cryo-electron microscopy and crystallography." PLoS pathogens 9.1 (2013): e1003132.
2. Velarde, R., et al. "Spillover Events of Infection of Brown Hares (Lepus europaeus) with Rabbit Haemorrhagic Disease Type 2 Virus (RHDV 2) Caused Sporadic Cases of an European Brown Hare Syndrome-Like Disease in Italy and Spain." Transboundary and emerging diseases 64.6 (2017): 1750-1761.