August 16, 2022

Rabbit Haemorrhagic Disease: A Threat to Wild Rabbits in Borrego Springs, San Diego County

Share

Rabbit haemorrhagic disease (RHD) is a serious and often fatal illness that affects wild rabbits in many parts of the State of California and possibly in Borrego Springs based on the rapidly declining rabbit population seen by locals. The virus responsible for RHD is called Rabbit haemorrhagic disease virus (RHDV) and it was first identified in 1984. RHDV is part of a larger group of viruses called rabbit lagoviruses, which also includes non-pathogenic viruses known as RCVs.

RHDV2 in Wild Rabbits in Borrego Springs

RHDV2 is the strain of RHDV that have been identified throughout California in wild rabbit populations; this strain is highly virulent and can cause higher mortality rates in wild rabbits than other strains. This strain has been spreading rapidly throughout California since it was first identified in 2011, and has replaced other strains in most California wild rabbits population.

Wildlife experts and conservationists need to be aware of the potential threat of RHDV2 and take appropriate measures to protect wild rabbit populations in Borrego Springs and other parts of San Diego County. Biosecurity measures such as avoiding human contact with wild rabbit populations and not feeding them with domestic rabbit food, and promoting research to understand how to prevent the spread of this disease are crucial to protect wild rabbit populations in Borrego Springs and nearby Anza Borrego State Park.

Disease Occurrence

Rabbit haemorrhagic disease (RHD) is a highly contagious and often fatal illness that affects adult wild and domesticated rabbits of the Oryctolagus cuniculus species. Young rabbits, those under 6 to 8 weeks old, may be infected but show no symptoms, however, they may develop a specific humoral response. Unvaccinated animals are particularly vulnerable to severe losses, and on intensive farms, the death rate can vary depending on the strain of the virus.

RHDV/RHDVa, the classic strain, can be particularly deadly with a mortality rate of 80-90%. However, the newer strain RHDV2 can have a more variable mortality rate, ranging from 5 to 70%. This disease can also devastate wild rabbit populations in San Diego County, particularly when it is first introduced. RHDV is highly contagious and can spread very easily.

Note: EBHSV is a virus that can also cause a disease similar to RHD in cottontails (Sylvilagus floridanus)

Hosts

RHD affects wild and domesticated members of Oryctolagus cuniculus , the European rabbit.

List of Oryctolagus cuniculus (Rabbits)

  • Domestic rabbit European rabbit Wild European rabbit
  • Common rabbit
  • Domestic hare
  • European hare
  • Belgian hare
  • Flemish giant
  • French lop
  • Giant papillon
  • Giant rex
  • Hotot
  • Holland lop
  • Jersey wooly
  • Lop-eared rabbit
  • Mini lop
  • Netherland dwarf
  • Polish rabbit
  • Satin rabbit
  • Silver marten
  • Tan rabbit
  • Thrianta

It’s worth noting that Oryctolagus cuniculus is the scientific name for the European rabbit, which is the most common domesticated rabbit and also exists in the wild. Many breeds of domestic rabbits are derived from European rabbits.

While rabbits of all ages can get infected, young rabbits under 6-8 weeks old usually do not show symptoms if infected with the classical strain RHDV/RHDVa. However, if infected with RHDV2, young rabbits as young as 15-20 days old can become ill and die.

RHDV/RHDV has not been found to infect other animals, including animals that eat rabbits. Scientists have also tried giving the virus to 28 different animals, but it did not cause any illness, and the virus did not multiply in their bodies.

Transmission

  • Direct contact with infected animals through the oral, nasal or conjunctival routes.
  • Exposure to an infected carcass or hair from an infected animal.
  • By means of fomites, including contaminated food, bedding and water.
  • Experimental transmission by oral, nasal, subcutaneous, intramuscular, or intravenous routes.
  • Importation of infected rabbit meat. This could be one of the main means of transmission of RHD to a new area. Meat contains high levels of virus-infected blood, which survives freezing well.
  • Mechanical transmission. Flies and other insects are very efficient mechanical vectors; only a few virions are needed to infect a rabbit by the conjunctival route. Wild animals can transmit the virus mechanically. Although virus replication does not seem to occur in predators or scavengers, these animals (dogs, foxes, etc.) can excrete RHDV in faeces after eating infected rabbits.
  • How long rabbits that have recovered from RHD may remain infectious remains unknown. A low level of serum antibodies is sufficient to protect rabbits from the disease, but infection at the intestinal level could occur with shedding of the virus in the faeces. High sensitivity PCR demonstrated a long-term persistence (up to 2 months) of the viral RNA in recovered or vaccinated and then infected rabbits. Whether this is due to real and active persistent or latent RHDV infections is still to be demonstrated.

Sources of virus

  • The liver has the highest virus titre, followed by the spleen and serum.
  • Most or all excretions, including urine, faeces and respiratory secretions, are thought to contain virus.
  • Rabbit meat contains virus by virtue of its high blood supply.

Control Measures

Additionally, monitoring wild rabbit populations for signs of RHD and reporting any suspicious cases to the appropriate authorities can also help to control the spread of the disease.

It is also important to note that wild rabbits in Borrego Springs may be exposed to other strains of RHDV that are circulating in domestic rabbit populations.

In addition to RHDV, other diseases and parasites may also affect wild rabbits in Borrego Springs. Wildlife experts and conservationists need to be aware of these potential threats and take appropriate measures to protect wild rabbit populations.

Protecting wild rabbit populations in Borrego Springs from RHD and other diseases is crucial for preserving these animals and their ecosystem. It is the shared responsibility of wildlife experts, conservationists, rabbit farmers, and the public to take appropriate measures to protect wild rabbit populations and ensure their survival.

Animal and Plant
Health Inspection
Service
June 2020

June 14, 2026
June 2026 Skywatching Highlights
By Sunbelt Publications June 9, 2026
A Sunbelt Spotlight with Diana Lindsay  For 17 years, Marshal South and his family lived on Ghost Mountain, a remote, waterless mountaintop in Blair Valley, now part of Anza-Borrego Desert State Park. Their life of isolation, creativity, and survival became one of the desert’s most talked-about stories. Life on Ghost Mountain From 1930 to 1947, the South family lived in a handmade home on Ghost Mountain. Marshal South wrote about their primitive lifestyle in monthly articles for Desert Magazine, drawing thousands of readers into the family’s unusual desert experiment. A Writer, Poet, and Desert Storyteller South wrote poems, novels, essays, short stories, and more than 100 pieces for Desert Magazine. His writing celebrated the silence, beauty, natural history, and healthful qualities of the desert. The Story Behind the Legend Diana Lindsay, editor of Marshal South and the Ghost Mountain Chronicles, shares the history behind the South family’s life, the questions surrounding their years on Ghost Mountain, and why the story continues to fascinate readers today. About Diana Lindsay Diana Lindsay is an award-winning author, historian, editor, and president of Sunbelt Publications. Her work has helped preserve and share the history of Anza-Borrego and the remarkable story of Marshal South. .
By Dennis Mammana June 9, 2026
By Dennis Mammana Week of June 14-20, 2026  The universe is a colorful place, but stargazers are often frustrated when they cannot see the glorious colors that appear in celestial photographs. These are all quite real, so why are we unable to see them? One reason is that the color receptors of the human eye (the cones) don't respond well under faint light. They need a significant amount of energy falling on them to become active. You can prove this to yourself by trying to see colors around you in a dark movie theater. Sure, those on the screen are vibrant — that's some pretty bright light hitting your eyes — but colors throughout the dim theater appear completely muted. The second reason that astronomical photographs show beautiful colors is that camera detectors are not affected by human physiology. They can "see" colors from even the faintest of light. This is important because these colors tell us a lot about the physical and chemical properties of celestial objects. This doesn't mean you can't see color in the night sky; it just means that you'll need to find bright stars to improve your chances. One of the brightest shines high in the eastern sky after dark this week: Arcturus. Follow the handle of the Big Dipper away from its bowl, and you'll soon encounter this star. If you have good color vision, you may notice that Arcturus shines with a yellow-orange light that indicates a temperature of about 7,200 F. Now look lower toward the northeastern sky. There you'll find Vega, a nearly white star that burns considerably hotter than Arcturus — about 17,000 F. Very low in the southeast after dark, you'll find a star even more orange than Arcturus. This is Antares, the brightest in the constellation of Scorpius, glowing with a temperature of "only" 6,100 F. Aim binoculars or a small telescope toward these stars, and their colors will appear to pop. This is because the optics gather much more light than your eyes, and this helps to stimulate your color receptors. Now if you'd like to see an intensely red star, you'll need to cast your gaze high overhead. Here you'll find a star that astronomers know as Y Canum Venaticorum. Most stargazers just call it La Superba (the magnificent), so named by the mid-19th century astronomer Father Angelo Secchi. To locate it, you'll need to start at the Big Dipper; just above it appear the two most prominent stars of Canes Venatici, the hunting dogs. About two-thirds of the way between the bend of the Dipper's handle (Mizar) and the westernmost star of Canes Venatici (Chara) lies a very faint star — one you may not be able to spot with your eyes alone from near the lights of a city. What makes this star unique is that it's what astronomers call a carbon star, one of the few visible to the unaided eye. Yes, it's a giant star like Arcturus, and it's also nearing its death, but, unlike "normal" such aging stars, La Superba has accumulated more carbon compounds in its outer atmosphere. Find this faint star and aim binoculars or a small telescope toward it. I promise you'll be delighted by what you see. Visit Dennis Mammana at dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com. Learn More About Borrego Springs
By East County News Service June 8, 2026
Photo via San Diego County News Service
By Andrea McKenna June 8, 2026
A Day of Discovery at Anza-Borrego Desert State Park
By Andrea McKenna June 8, 2026
Jeff Sloan, Christmas Circle Community Park Board President
Show More

Share This Post