Sarcocystis study – A new neurological disease in rabbits?

Mar 15, 2018

Sarcocystis study – A new neurological disease in rabbits?
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Sarcocystis – A new neurological disease in rabbits?  If you have a rabbit with neurological symptoms, you may be able to participate in a House Rabbit Society study.

In the last few years at House Rabbit Society headquarters in Richmond, CA, we have seen a number of rabbits with neurological symptoms that are different than what we would expect with E. cuniculi.  From 2016-2018, we have found 34 rabbits with neurological symptoms who have tested positive for a parasite called Sarcocystis, using a PCR blood test.  Two rabbits with neurological symptoms passed away and on necropsy were found to have Sarcocystis in their brain tissue or spinal fluid, using a PCR test, and unidentified organisms were seen in brain tissue upon histopathology.  Most of these rabbits have tested negative for E. cuniculi.

These rabbits have come from at least 6 counties in Northern California (Alameda, Contra Costa, San Francisco, San Mateo, Santa Clara, and Sacramento), Ventura County in Southern California, Chicago, IL, Pittsburgh, PA, and Huntington, NY.

House Rabbit Society is seeking to enroll 30 rabbits with similar symptoms in this study.  These rabbits can be in a rescue/shelter, or in a private home.

What is Sarcocystis?

Sarcocystis is a genus of single-celled parasites that have a two-host lifecycle.  The definitive host is generally a wildlife predator species, and a prey animal contracts the parasite by eating feces-contaminated grass or plants.  The infected prey animal must be eaten by a predator to transmit the parasite, and the predator’s feces can then contaminate plants.

There are many different species of Sarcocystsis that affect different animals. S. neurona causes neurological symptoms in horses and sea mammals, while S. falcatula causes neurological symptoms in birds of prey.  House Rabbit Society is doing DNA sequencing to try to determine which species of Sarcocystis is being found in rabbits.  At this point, we know the species affecting rabbits is not S. neurona or S. falcatula, but there are many species of Sarcocystis, and it’s possible this could even be a closely related Apicomplexa.

What are the symptoms of Sarcocystis?

The most common symptom of rabbits who have tested positive for Sarcocystis is ataxia.  The rabbits have a “drunken” appearance and are wobbly when they hop, often have intention tremors where the wobbling is worse when they’re trying to move towards something, and might fall over.  They might also have weakness in a hind-limb, and the weakness, ataxia, and falling over may get progressively worse. Other symptoms have included: seizures, turning in circles, head tilt, rolling, and stargazing.

Here are videos of rabbits who are positive for Sarcocystis.

House Rabbit Society has tested some healthy rabbits who tested positive for Sarcocystis, but those rabbits have not developed neurological symptoms. At this point, it appears that not all rabbits who have been exposed to the parasite will develop neurological symptoms.

How can I prevent my rabbit from getting Sarcocystis?

Rabbits cannot catch Sarcocystis from each other. Housing your rabbit indoors will prevent your rabbit from coming into contact with wildlife or predator feces. If you live in an area where you see wildlife like opossums or skunks, or in an area where there have been other rabbits diagnosed with Sarcocystis, you may want to restrict outdoor playtime for your rabbit or put down a clean blanket/rug outside covering the exercise area before providing supervised outdoor playtime.

Is there treatment for Sarcocystis?

House Rabbit Society has been treating rabbits who have tested positive with Ponazuril and/or ReBalance.  Both of these drugs were developed to treat S. neurona in horses.  While these drugs seem to help stabilize some of the affected rabbits, others have had progressively worsening neurological symptoms or have died.  As we learn more about Sarcocystis in rabbits, we hope to be able to help find new treatments.

Who can participate in this study?

House Rabbit Society is looking for 50 rabbits who have similar symptoms to what is described above to enroll in our study. Rabbits can be in a rescue/shelter or in a private home.

Rabbits will have blood drawn for an E. cuniculi and Sarcocystis blood test, and the results will be shared with you. If you are in the SF Bay Area, we may ask you to come to House Rabbit Society or a partnering vet office for a blood draw. If you are elsewhere in the country, we may ask your rabbit-savvy veterinarian to help draw and submit the blood to the labs on our account.  There is little risk to your rabbit for participating in the study; there can be temporary bruising at the site of the blood draw.  If your rabbit tests positive for one or both parasites, we recommend following up with your primary veterinarian to discuss treatment, and we may follow up with you in the future to inquire about your rabbit’s health and to share any new information that might be helpful.

There is no cost for your rabbit to participate in the study. The value of the blood tests is approximately $150.  If you choose to make a donation to House Rabbit Society of any amount, we can test additional rabbits.

The findings from this study will help House Rabbit Society learn more about rabbits who are positive for Sarcocystis, and may help us to improve diagnosis and treatment of neurological conditions in rabbits.  We will post our findings to rabbit.org and presented our findings at the fall 2018 Exoticscon exotic veterinary conference and will present at future veterinary conferences.

If you are interested in your rabbit participating, please email us with your city/state and a short video or two of your rabbit’s neurological symptoms.  If you are a veterinarian and would like to learn more, you are also welcome to email us.

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