Sudden & totally unexpected death of Two Rabbits

Question
Hi Randy,
I would really appreciate your input - thanks for your time.
I have kept rabbits here in the UK for 6+years, and currently have a Netherland Dwarf doe who is 3 years 1 month old.  Until yesterday I also had a Dwarf Lop doe of 4.5 yrs, and a Mini Lop buck (my pride and joy, friendly, outgoing, full-of-personality boy xx) who was nearly 2 years old.
Yesterday morning around 10h30 I fed all the rabbits as usual - burgess excell dwarf pellets, hay, spring-greens and half a carrot each and refilled water bottles.  I noticed nothing unusual, and they all greedily started eating immediately as usual.
It has been very cold here recently, around 1-5 degrees Celsius, so I left the cover flap down on the female's hutch (but not fastened, just down loose) and the buck as usual had the run of the front garden with access to three straw filled retreats - a small open hutch with food, water & 'bedroom' that he often uses, an off the ground kennel which he likes to explore, and the garden shed housing his 'base hutch' also with food and water where he gets closed in whenever necessary eg if the gate is going to be open for any length of time, or if I've spotted foxes about.
When I went to collect my son from school shortly before 3pm I chatted to the buns as I passed, as usual, and was surprised that Fudge (male) didn't come bounding out to me as usual, so I looked for him but couldn't find him. Very strange.  Whilst searching I checked the females, and at first didn't realise that Noodge wasn't just relaxing.... she looked totally normal lying on her side the way she likes to, paws daintily crossed, carrot half eaten. Then she didn't move in response to my talking, so I opened her hutch door and was SHOCKED to realise she was dead.  ???!!!.  I can't express how stunned I was - I still can't believe it!  Her eyes were open and looked normal, still moist; she looked totally relaxed, but was going stiff (sob) and was cold.  The 'under' side of her, i.e. the side on the straw, was still soft.
As if this was not bad enough, further searching revealed Fudge - and here's the part I'd really like your opinion on please - lying in EXACTLY the same position on his side, eyes open, seemingly relaxed... tucked behind the garden bin.  His location was slightly unusual, but not hectically so - for all I know he may have spent lots of time there but usually he came running over whenever I was around so I wasn't used to seeing him lying there.  He, too, had eaten apparently normally, and had no signs of injury / blood / distress / foaming mouth / ANYTHING untoward.  He, too, was cold on 'top' and still soft and slightly warm on the underside lying on not straw here but paving stone. His back feet were muddy, but that was totally normal for him.
???
TWO rabbits dying suddenly at the same time???
They could not have both eaten something poisonous because they were in different locations;
Nothing happened to cause shock / trauma that I am aware of,
The other rabbit, who lives in the bottom part of the same double hutch the female lived in the top part of, is fine.
They were all eating and drinking normally.

My hypothesis is that maybe they got too cold ??  Are lop-eared buns more susceptible to the cold than uppy-eared buns? Would that explain why Tikki is still fine?
Or:  they had some mystery illness I haven't spotted, but I can't see how - I handle my buns all the time and they were behaving normally.

We did have a new bathroom fitted last week, which involved some hammering and domestic disruption, but that was Mon-Fri last week and I can't really see how it would affect the buns in a delayed way like this.  Other that that I am stumped.  And sad.

Any opinions or advice you could offer would be most gratefully received.  I've decided I've been very lucky with my rabbits to date, because I've been scouring the internet looking for similar situations and reading everything I can find on rabbit illnesses and have read more disturbing and scary rabbit-health stuff tonight than ever!  Who knew so much could go wrong for little buns!  But none of it seems to fit what happened to mine.  I keep going over and over what I might have done differently if I'd known there was a problem, but I really didn't.  There was no warning at all.

Thanks in anticipation,
Yours sincerely,
Denise

Answer
Hi Denise,

I am so sorry about the unexplained loss of your rabbits.  This is truly a mystery and I have read your questions numerous times and even charted them out to see if I could see something.  But there are just too many possibiities.  I really doubt the cold was the cause since rabbits deal with cold much better than heat.  And here in my part of the US, many people have outdoor rabbits and our temps have been in that range, and a little lower on some nights, for several weeks with no problems.

When I have multiple rabbits that have medical issues at once, I normally look for the common denominator and in most cases it's the food.  And just because your other rabbits didn't get sick even if they were on the same food doesn't mean it wasn't the food.  In many natural products, and most rabbit products contain hay and in some cases corn, and that makes them prone to mold and their by products, mycotoxins.  Mycotoxins can be toxic in parts per billion.  Many times it can't be seen or detected by odor.  Mycotoxins are usually "spot toxins" and there might be only one small area of pellets or hay that is affected.

Since these appears to outside rabbits...is it possible that something like a spider or some venomous creature entered their housing?  With some of my breeder friends that have outside rabbits....they have lost rabbits due to predator attacks (their rabbits were never actually touched by the predator....just literally scared to death), spider bites, rodent bites (rats), snakes (unlikely in your situation due to the temperature) and we have seen people lose rabbits when their rabbits ate a mouse that had been poisoned (and yes rabbits will eat meat....they shouldn't but the will).

At this point, without a necropsy, you will never know what happened and even with a necropsy, the real cause may not be revealed.  But I will keep considering your situation and see if I can come up with something.  This is really unusual.

As far as what you read on the internet....take that with a "grain of salt".  There is so much information out there that is ridiculous.  I have worked very sick rabbits for many years.  I live near a major vet school with quite a few "exotics focus" vets and all of them support my domestic and my wildlife rescue....and that gives me access to tons of clinical information.  I have even developed treatment protocols that many vets are using.  The stuff I see on the internet many times is based on old and unproven information from breeders.  No flaming of breeders intended but back when this information came about, very few vets would treat rabbits and the few that did treated them like cats...they are really treated more like horses.  The breeders were desperate to help their rabbits when they were sick....and I have to admire that.  But they had no way to clinically work a protocol to test it's effectiveness or problems.  Unfortunately a lot of that old school stuff is still out there...and in some cases, vets are stuck on it too.  An example is E Cuniculi...so much wrong info out there.  I am working a new treatment for that using a horse drug called Ponazuril.  I would suggest you join one of both of these fantastic rabbit forums that are open to the public.  I don't have the addressed right now, but a Google search will easily find them.  first is Etherbun.  This forum is headed up by Dr. Dana Krempels...she is head of the biology department at the University of Miami (in Florida in the US).  I am a moderator in the infirmary of Rabbits Online.  I share a lot of my medical research in that forum to assist both rabbits and vets.  There are very talented people on these forums and I suggest you join at least one of them.