Mice dying

Question
I purchased 10 female mice (not fancy, just ,mice)about 2 months ago.  I put them in a 50 gallon aquarium that I had thoroughly cleaned and disinfected with animal safe disinfectant a few days before getting the mice.  They are on aspen bedding, which is changed weekly.  (I've heard that pine and cedar are bad for them.)   They have clean water at all times.  The water bottle is cleaned and disinfected each time it is filled.  They are being fed rat/mouse blocks I get at Petco.  Over the weekend, all but 3 of my mice have died.  It seemed quite sudden that they became very thin and were hanging out under the water bottle.  There was no sneezing/coughing, etc.   Any ideas?  Thanks!

Answer
Hi Deborah,

Take a look at their waste - are any of them having diarrhea?  Is their poo normally colored?  It's possible you may have a gastrointestinal bug going around in the colony, especially considering the sudden weight loss.  The most important thing is to keep the remaining mice as hydrated as possible and to make sure they are all eating well.  Even if a tummy problem isn't the culprit, severe discomfort will cause mice to stop eating, making things much worse.  Supplement with treats high in protein, such scrambled eggs made without milk or with kitten milk replacement, or with dry cat or dog food.  This will make every calorie they consume count.  You're spot on with the aspen bedding, but it wouldn't cause any health issues.  Check the temperature in case inside the cage becomes too hot or cold; you want to aim somewhere between 65 and 85 degrees F.  Check the sipper on the bottle and make sure it drips readily, too, because sometimes they can get stuck and the mice will become dehydrated very quickly.  Lastly, make sure that you are completely rinsing away any disinfectants you use, as even when evaporated most cleaning chemicals will leave a toxic residue unless rinsed away thoroughly with water.

Since I'm not a vet, I can only guess at what is causing the problem, and if you can take the survivors by a professional vet they will be able to give you a definitive solution and help you treat it.  It may be that the survivors need antibiotics, but without knowing the real problem, I can't guess at how to correct it.  Problems could have come in on bedding or food, as sometimes wild rodents get into supplies while in warehouses or stores, or perhaps you have some rodent visitors in your home who could have transmitted a disease.  Since it's so sudden and so long after you purchased them, I wouldn't think any issues could have came from the pet store.  All I can do is guess, though, so definitely swing by a vet if you can, because losing so many pets so quickly is definitely not good!

Remember to wait three weeks symptom-free before getting them new buddies, if you decide to bring home new friends to replace the ones they lost.  Let me know if you have any more questions, and I hope the other three stay healthy!

-Tam