Mice Mysteriously Lethargic

Why did some mice suddenly become ill after a new mouse arrived?

Q: I have owned four mice for about six months and, except for the one I bought a few weeks ago, the other three are quite big.

This morning, I found my two favorite mice (both a male and female) to be barely moving, lying on their sides. I’m not sure if they are just cold because it’s the middle of winter here. I put a hot water bottle in the bottom of their enclosure and wrapped the mice in a towel above it, and I separated the baby mouse and the other healthy mouse.

The two mice seem to be a bit brighter but not much. They have plenty of water, food, and fresh fruit and veggies available to them.

What could be wrong with my mice? How do I make them well again? I don’t live anywhere near a veterinarian, which is about two hours away.

A: It is impossible to say what is wrong with your two sick mice without any more of a description of the problems. Keeping them warm and making sure there is food and water, as you did, is the best you can do.

Here’s my guess. Your three older mice seemed to be doing well as you said they were quite big. You bought another mouse a few weeks ago. All of a sudden, two of your healthy mice seem very sick. This is very suspicious; an infectious disease might have been brought into your colony through the new young mouse.

Many times, carriers of disease do not appear sick. They may have immunity to the disease. If they come in contact with mice that have never been exposed to the disease, those previously unexposed mice (they are called naïve mice) will get very sick and may die.

The timeframe of a few weeks fits perfectly with a viral disease. If that is the case, there is not much you can do other than what you are doing, providing warmth, fluids and food.

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Critters · Mice and Rats