Sudden Death in 2 Rabbits

Question
Dear Ms Krempels,
Vet thought it might have been VHD due to the massive seizures both Rabbits had just before death. There were no visible signs though.
Wether here had been quite hot although rabbits were in a non sunny area, kept very cool by surrounding walls, fences etc.
The rabbit that died last, when we got him to the vet, she did comment that his temperate was  on the low side ~ is that a side effect of heat stroke ?
The coincidence of both dying within 24 hours of each other is really bothering me.
many thanks
Steve

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Followup To

Question -
I'm writing from the UK.
3 weeks ago one of my English Giant Rabbits became very lethargic late in the afternoon. I kept him separate in the house overnight, checking on him every couple of hours. At about 4:00am he started thrashing around screaming and struggling. He died a few minutes later. Later the next day the other English Giant started behaving in the same way ~ we rushed him to the emergency vet, who gave him some pain relief and said that it looked like VHD and therfore we should be prepared for the worst. He died later that night in the same way. Both bodies went off for a post mortem, which has revealed absolutely nothing untowards, histology and toxolgy was also no result. The vet thinks that they may have eaten something poisonous. The only thing I can find in their runnning area are some japanese flowering cherry (prunus amanogawa )shoots coming up from a tree about 100 metres away. Some sites say these are poisonous ~ others don't mention them. If this was the cause of death, how quckly would this happen ? The vet says that there were no traces in their intestines, but, there may have been no signs on post mortem. Have you any ideas please ?
Steve

Answer -
Dear Stephen,

What made the vet think it was VHD?  Were the rabbits hemorrhaging from the eyes/nose/mouth, etc?  VHD can cause death without externally visible hemorrhage, but post mortem exam would likely have revealed internal hemorrhage.

I wonder how hot it is where you are.  If it's above 80 Farenheit, then the rabbits (especially being large) might have been subject to heat stroke. Rabbits do not tolerate heat well, and can rapidly overheat when the weather is hot.

I could not find much on the toxicity of Prunus "Amanogawa" either, and doubt that this would be the cause.  The main toxin in most species of Prunus is cyanide, and it is concentrated primarily in the seed--far less so (if present at all) in the vegetative parts of the plant.

Did anyone spray pesticide in the area?  

I, too, am at a loss.  If post-mortem exam and toxicology showed nothing, I certainly can't do better than guess.

I am very sorry for your loss.  I wish I could be of more help.

Dana

Answer
Dear Steve,

If the rabbits were hypothermic, then they did not likely die from heat stroke, which would be characterized by hyperthermia.  Abnormally low body temperature is a sign of shock, which could be a result of poisoning, systemic infection, or any number of things, including VHD.  But if there was no sign of hemorrhage, then it's not likely this was VHD.

I'm sorry I don't have any answers for this terrible mystery, and I still am very sorry about the loss of your bunnies.

Take care,
Dana