Bunny death

Question
I just lost my 2 year old Mini Rex on Saturday and am still researching to try to figure out what went wrong.  I have a 3 year old Mini Rex and am concerned about his well being.  My 2 year old was taken into the vet a week ago and diagnosed with an ear infection (eventual scans showed an overgrowth of the normal bacteria which we were treating with Tri Otic every other day)  He had been scratching his ears throughout the week before the vet visit which is what prompted us to go.  Thinking back the only symptoms that could barely be noticed were slight decline in activity after he had seen the vet, a week before he passed.  During that week he also had a urination episode that included a large amount in many places in a very short amount of time(1 minute.) He also seemed more alert (wary) than usual.  We blamed that on the medication application since my fiancee and I had to hold him to administer the cream in his ears.  On the day of his passing he was eating and drinking, but suddenly had a backward head tilt (agonal phase?) with his mouth partially parted.  He was not necessarily breathing hard, but I now assume the mouth might have been open to allow for more air.  He was trying to find a dark spot to hide.  Within 2 minutes he coughed a few times, lost the use of his hind legs, and died.  After researching I am now concerned about VHD.  My vet has suggested a neural toxin, botulism, or even valley fever.  I opted to not do the necropsy in part due to funding.  We are very upset and going through the normal stages of grief, but am still watching my other bunny carefully although there were minimal signs with my other bunny.  Is there any information you could provide based on what I am able to recall about this situation.  I am looking for some peace of mind, but most importantly for it to never happen again.  I appreciate your time.  Sincerely, Amber

Answer
Dear Amber,

I am so sorry about the terrible loss of your friend.

Sadly, there is absolutely no way to confidently ascertain a cause of death without a post-mortem exam, preferably including histopathology of major organ tissues.  The signs you describe are very vague, and could have been due to any of dozens of different things.  It is quite possible that a toxic event was responsible, as this could cause renal failure (symptoms would include copious urination and excessive drinking), and neurological signs in the final stages.

If you noticed any other particular signs of unusual behavior before he died, then please read:

www.bio.miami.edu/hare/sickbun.html

which might give some clues.  But unless you can provide a lot more specific information, this is the best I can offer.  

If the body has been kept very cold (not frozen), and it has been less than 24 hours since death, a necropsy may still be possible, if you feel that would give you closure and peace of mind.  You can find an experienced rabbit vet here:

www.rabbit.org/vets

to call and find out what your options might be.

I am very sorry for your loss.

Sincerely,

Dana