Myxomatosis in the US

Jul 18, 2019

Myxomatosis in the US
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What is Myxomatosis?

Myxomatosis is a virus.  Wild rabbits can carry Myxomatosis, but do not become sick.  Myxomatosis is fatal to domestic (pet) rabbits with a 99% mortality rate, and there is no treatment.  Symptoms include swollen eyelids, lips, and genitals, a high fever, lethargy, and progresses to difficulty breathing, and death, within 2 weeks.

How is Myxomatosis spread?

Mosquitoes, fleas, black flies, or fur mites bite a wild rabbit with Myxomatosis and then bite a domestic rabbit.  Myxomatosis can also be spread by direct contact between infected rabbits, or indirect contact through handling a sick rabbit, then handling a healthy rabbit.

Where is Myxomatosis in North America?

Myxomatosis

Photo by Jessica Kurek, DVM

Myxomatosis cases in pet rabbits are reported in the coastal areas of Oregon, California, and Baja California, Mexico, in the territory of the brush rabbit (Sylvilagus bachmani) who is a reservoir of this disease.

When are Myxomatosis cases seen?

So far, cases have been reported June-September, with one October case report.

Western Oregon

2016

2015 Polk County: June
2010 Western Oregon
2004 Linn & Benton counties: July
2003 Linn & Benton counties: July

Northern California

2019

  • Santa Cruz County: July (Santa Cruz, Boulder Creek), August (Bonny Doon, Watsonville)
  • San Luis Obispo County: July
  • Santa Barbara County: July (Buelton & Santa Barbara)

2018

  • Sonoma County: September (reported by CDFA)

2017

  • Monterey County/San Benito County: August (Aromas, reported by Dr. Hilary Stern at Animal Hospital of Soquel)
  • Santa Clara County: June (Los Gatos, reported by guardian & Dr. Curt Nakamura Adobe Animal Hospital)
  • Santa Barbara County: June, July, August, August

2016

  • San Luis Obispo: Sept
  • Santa Cruz County: July & Sept
  • Santa Barbara County: (reported by CDFA) July & July & August

2015

  • Monterey County: Sept
  • Santa Cruz County: Sept

2014 Santa Cruz County: August
2013 Sonoma County: October (Sebastopol – reported by guardian & Dr. Pfann, Brandner Vet)
2012 Monterey County (reported by AFRP’s Rescue Rabbits Rock)

Southern California
2019 Ventura County: July (reported by CDFA)
2017 Ventura County: August (reported by CDFA)
2010 San Gabriel Valley (near Los Angeles): July

Baja California (Mexico)
1993 Ensenada: Sept-Oct

House Rabbit Society is collecting reports of cases of Myxomatosis to add to this list.  If you are a vet with a patient with Myxomatosis, or a rabbit guardian whose rabbit has been diagnosed with Myxomatosis, please email us at hq@rabbit.org to have the case added.

If you are a vet in California, please submit deceased rabbits suspected of Myxomatosis for necropsy with a CAHFS state lab (fee $135) or report confirmed Myxomatosis cases to the California Department of Food and Agriculture (CDFA): evet@cdfa.ca.gov.

There have been no cases of Myxomatosis reported to the Washington State Department of Agriculture from 2011-2016.

Photo by Hilary Stern, DVM

Photo by Hilary Stern, DVM

What are other diseases that might look like Myxomatosis?

Take your rabbit to the vet immediately if you are concerned your rabbit might have Myxomatosis, and separate them from any other rabbits in your home.  Your vet can determine whether your rabbit might instead have rabbit syphilis, an upper respiratory infection, or an eye infection, all of which are treatable conditions.

How can I protect my rabbit from Myxomatosis?

House your rabbits indoors with window screens.  Rabbits live longer, healthier lives when indoors. Because myxomatosis is just one of many concerns facing rabbits who live outdoors, House Rabbit Society recommends indoor homes for rabbits as the primary preventative, along with adequate screening on doors and windows.

If you live in an area with reported Myxomatosis cases, treat your rabbits monthly with Revolution, to prevent fleas and fur mites.  Revolution is a prescription medication, available through your veterinarian.  Or, treat with over-the-counter Advantage, which provides protection from fleas (but not from mosquitoes or fur mites).  Be sure to give your cats and dogs flea treatment, too.  Don’t let your rabbit play outside if you live in an area with currently reported Myxomatosis cases.

Vectra 3D is a flea/tick/mosquito/mite/fly/lice repellent for dogs – using it on a rabbit is “off-label” use and could be harmful to your rabbit at the wrong dose. Santa Barbara rescue Bunnies Urgently Needing Shelter use this medication as just one of their tools to try to keep rabbits safe. Please consult with your vet before using and get bunny-sized dosing information from them.

For rabbits who must live or spend some of their time outside, protection against mosquitoes is next best bet, protecting the rabbit’s play area with mosquito netting or some other barrier.  Read more on the hazards facing outdoor rabbits.

Why isn’t the vaccine in Europe/the UK available in the US?

The Myxomatosis vaccine available in Europe and in the UK has not been approved by the USDA’s Animal and Plant Health Inspection Service’s (APHIS) Center for Veterinary Biologics. There is no vaccine available in the United States, and it is not legal to import the vaccine from other countries.

Hilary Stern, DVM of Santa Cruz, CA has repeatedly tried to import the European vaccine and failed. Dr. Stern said, “The FDA won’t allow it because it is a live vaccine. I am not aware of any killed vaccines that are effective.

The European vaccine is for a different strain of Myxomatosis. The California (US) strain of Myxomatosis is more virulent, and it is unknown if the European vaccine would be effective against the CA strain.

More info on Myxomatosis:
https://en.wikipedia.org/wiki/Myxomatosis

By Anne Martin, PhD
Executive Director, House Rabbit Society
&
Margo DeMello, PhD
Board Member, House Rabbit Society

Updated 8/27/19