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Be Aware: There's a Deadly Virus on the Loose Striking These Pets


Story at-a-glance -

  • Myxomatosis is a virus in domestic rabbits, usually caused by insects such as fleas and mosquitoes. It is almost always fatal but does not affect humans
  • Symptoms come on quickly, evidenced by swollen, pink-tinged eyes, lips, face and genitals. A high temperature and seizures follow
  • In the U.S., the virus is found in a strip from Oregon to California and south through Baja California, Mexico, where the wild brush rabbit is the “reservoir” of the disease, but is not affected by it.
  • Indoor rabbits have a much better chance of survival than those left outside. If pet rabbits must be outdoors, they should be in a pen with sides, a top, floor and a very secure door

By Dr. Becker

There’s a deadly virus going around that is striking pet rabbits, and the outcome is nearly always fatal.

Myxomatosis is a pox disease transmitted by fleas, mosquitoes, fur mites, black flies and other insects that can bite. Dr. Hilary Stern, a veterinarian in the San Lorenzo Valley area of California, said there’s no treatment and no vaccine for this virus, and she’s never seen an infected rabbit survive.

In fact, only 1 percent of rabbits with the virus outlast it. Symptoms come on quickly, evidenced by swollen, pink-tinged eyes and genitals, and if you look closer, around the rabbit’s face and lips.

The first signs can be noted within three days of infection, according to MediRabbit.1 At later stages of the disease, the rabbit goes blind.

As the virus progresses, infected rabbits are lethargic, have a high fever with difficulty breathing and often have seizures. The disease is usually fatal between days eight to 15 after infection with the virus. The Santa Cruz Sentinel reported the experience of one pet rabbit owner:

“Paisley Frost lost both her pets to the disease. She and her husband were making dinner on a Saturday night, their two bunnies hopping around the kitchen as usual.

But she noticed Princess Peach’s eyes were swollen so she rubbed them with coconut oil, and hoped the 2-year-old rabbit would be better in the morning. Instead, she was worse, and her 3-year-old companion, Zuko, was showing signs of sickness as well.”2

Frost said when she realized something was wrong with her bunnies, who lived both indoors and outdoors, she spent the day searching for a rabbit specialist who could see her pets immediately.

Frost ended up taking Zuko and Princess Peach to an emergency veterinary clinic, where Dr. Jessica Kurek broke the sad news and advised euthanizing the pets so they wouldn’t suffer any longer.

Frost’s pets weren’t the only rabbits to succumb to myxomatosis that day. Another was euthanized at around the same time. Bunbunz was a stray domestic rabbit taken in by a family who had kept him outdoors with their chickens.

“So many illnesses we can at least try to do something,” Kurek said. “It’s heartbreaking for owners.”

The virus had a previous run in Santa Cruz County two years prior to the current outbreak. Myxomatosis shows up sporadically along a narrow strip of western coastline running from Oregon to California and south through Baja California, Mexico, according to House Rabbit Society.3

The Baja coast is the territory where the wild brush rabbit (Sylvilagus bachmani) is the “reservoir” of this disease. However, the last known outbreak in that area was in 1993.4 There have been no reports of myxomatosis outbreaks in the state of Washington.

Myxomatosis Around the World

Myxomatosis was first discovered in 1896 in Uruguay. It has since spread to areas of Chile, Europe and Australia, according to MediRabbit.

“In the 1950s, the myxomatosis virus was introduced and spread among wild rabbits in Australia, in order to reduce its population. This operation decimated almost all the wild rabbit population, except a few individuals that seemed resistant to this virus.

“The surviving rabbits started to reproduce offspring and colonized the country anew. In Europe, the virus spread rapidly and has now become endemic in some regions, which are populated by the European rabbit.”5

While this disease has been detected in a relatively small area of the U.S., myxomatosis has also decimated pet and wild rabbit populations alike in the southeast Australian province of Victoria.

In fact, the government’s website6 reports that 2015 was a particularly hard year due to high amounts of rain, which expanded the mosquito population.

Australia in the late 1800s was being virtually overtaken by 600 million rabbits, and the population was growing fast. First, Louis Pasteur sent a team from Paris in 1888 to introduce chicken cholera. It didn’t work. Authorities then introduced myxomatosis in a state of desperation.

When the first infected bunny was released, the virus spread so fast that within a few months, scientists couldn’t keep up with the mortality rates. Within a year, the rabbit population decreased to around 100 million, according to The Monthly.7

The virus was also introduced in Belgium in 1953 to curtail the rabbit population. In a similar scenario the same year, it killed 99 percent of Britain's wild rabbits.8 There are different strains, but the one on the west coast of the U.S. seems to be the most virulent, scientists say.

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How Myxomatosis Spreads and How to Help Prevent It

The only thing owners of healthy pet rabbits can do to help prevent infection with the virus is to bring them inside, Dr. Stern said.

Ironically, while native cottontail rabbits are the species that carry myxomatosis, they’re not infected by it. But when they are in the same proximity of pet rabbits, say, in an outside cage, they can bite the domestic rabbits and give them the virus. Pet rabbits come from a different European genus.

Other ways the virus can spread to healthy animals is when they’re housed with or in direct contact with infected pet rabbits or handled by someone who’s been in direct contact with one that’s sick. Keeping your rabbits indoors and putting screens in your windows are among the best ways to protect your pet from infection.

Other Health Threats to Domestic Rabbits

Indoor rabbits have a much better chance of survival than those left outside. Some of the most common problems facing pet rabbits who spend a lot of time outdoors include:

  • Predators, the most common threat
  • Weather such as cold, rain or wind
  • Moldy or toxic plants
  • Toxic fertilizers or pesticides
  • Bacteria in dirt

Some people are bemused to find that even in a locked, outdoor hutch, their pet rabbit has died. What they often don’t realize is that:

“With her acute vision, hearing and smell, a rabbit can sense the presence of a predator such as a raccoon even in your neighbor’s yard. She may panic and injure herself, or she may die of shock. Many raccoons can open hutches. Other predators include coyotes, owls, hawks, possums, cats and dogs.”9

While it’s best for your rabbit to live indoors, he should get outside when possible for sunshine and vitamin D. But when Thumper is outside, his pen should have a top and bottom, as well as sides, because rabbits can dig their way free. For bunnies who must spend some of their time out of doors, protection against mosquitoes is the next best remedy against myxomatosis. You may want to cover rabbit play areas with mosquito netting.  

Tularemia, also called rabbit fever, also can be transmitted through insects like ticks, deer flies or fleas, via ingestion of or exposure to an infected animal such as a rabbit or rodent, or contaminated soil or water. However, tularemia can also affect humans. Seen most often in cats, dogs, fish, birds, pigs, horses and sheep can also acquire it.