seizures / previous question

Question
Dr. Krempels, I asked you a couple of questions last month regarding my netherland dwarf 7 year old female rabbit.  She has been having seizures related to Ecuniculi (sp?) since August.  

I had her on a 30 day regimen of Panacur and she did not have any seizures during the medication cycle.  Approx 3 weeks after we stopped the cycle the seizures have come back.  We have put her back on the panacur.  We are wondering what your opinion would be on a cycle of the panacur that would be effective in keeping the seizures at bay. We don't really want to keep her on the medication non-stop, but feel that it would be effective if she wasn't off more than 3 weeks.  Is it safe to keep her on the panacur this way, in your opinion.

Thank you, Brian Menzer

Answer
Dear Brian,

This is a tough call.  I've heard of other bunnies having recurrence of signs upon stopping fenbendazole (Panacur), but it doesn't always happen.  Makes me suspect that it merely suppresses the parasites effects on the host, but doesn't always kill the parasites.  No one really knows for sure.

I might ask the vet about combining Panacur with ponazuril, or switching to ponazuril completely.  This new drug (expensive!) was developed to treat EPM (equine protozoal meningitis), which is caused by a microsporidian parasite similar to E. cuniculi.  We've used it against coccidia with excellent results, but it's so new that no controlled studies on rabbits/E. cuniculi have been done yet.

It might be worth a try, though you'll probably have to buy an entire horse tube and dilute it.  If you decide to do that, I can help.  Just let me know.

I do know some people who have had their bunnies on Panacur long term.  There are possible risks, such as aplastic anemia.  But these have not been confirmed in rabbits (fenbendazole is known to be toxic to birds in this way; it's a radiomimetic toxin that can damage the bone marrow).  

I can't really make a decision for you, but I hope this information will help you make the right choice for your bunny.

Good luck!

Dana