E-Cuniculi drugs

Question
We have a 6 1/2 year old bunny who has tested as a high positive for e-cuniculi.  He had previously had head tilt a few years back and some back leg paresis, so that's what led to him being tested in the first place.  Anyway, he's previously been on Panacur (the horse paste, as I like to call it) about 4 or 5 times over the last couple of years, with pretty good success, at least initially.  Basically, when his legs seem to get weaker and more splayed, we would call the vet, get a supply of Panacur and he would show improvement, usually within the first couple of days.  This would last about 3 or 4 months, until the weakness and "splaydness" would start to return.  Recently, that weakness has returned again and it's been about 4 months since he had a round of Panacur.  I called the vet to get another supply of Panacur and this time, they decided to give us Valbazen, which I don't know much about.  Is this drug safe?  I only really know about the Panacur (Febendazole) and I've seen where you have recommended Ponazuril, in the past.  I've brought up Ponazuril with my vet, but he said has never heard of it before.  I'm very reluctant to switch drugs, especially one I don't know, since the other drug seemed to work fine, albeit with not very long lasting effects.  I'm just not sure what to do here.  Should I try the Valbazen or just try and obtain some more Panacur from somewhere else?  We'd do anything to help our little guy and our usual plan seemed to be working fairly well.  Perhaps there are some long-term effects to using the Panacur, I don't know, but I don't want to risk hurting him in any way, just to try something more aggressive.  Thoughts?

Thanks in advance, Dana!

Answer
Dear Paul,

Valbazen is the brand name for albendazole, and I would definitely NOT switch to this.  The earliest tries at treating E. cuniculi with the benzamidazole drugs were done with albendazole, and the reason that many vets switched to oxibendazole or fenbendazole were that (1) those drugs worked better than albendazole and (2) albendazole has a relatively high toxicity.

We had this discussion on one of the rabbit veterinary lists recently, and *all* the experienced rabbit vets who weighed in said they would no longer use albendazole because of its toxic effects.  One vet (from Switzerland) cited a study in which several rabbits died from acute toxicity of the albendazole.

So long story short:  No, I do not think albendazole is as safe as fenbendazole.  Not all rabbits have problems with it, but in my opinion ONE is too many.  

Please insist on the Panacur, or ask more about Ponazuril.  The vet you're seeing might want to get on VIN or Exotic DVM (two large veterinary listserves) and ask about ponazuril, which some vets are using with good success.  It was developed to treat a similar microsporidian parasite in horses.  (It's *fantastic* for treating coccidia.)

If your vet won't budge, then I would try to find another vet for a second opinion:

www.rabbit.org/vets

But I would not, under any circumstances, use albendazole.

I hope this helps.

Dana