Question about older mice

At one time I had a thriving mouse colony of 5 females (plus additions and
subtractions), but sadly illness, age and time took their toll and I lost
all but two. These two girls were never great friends, but get along fine
now because they only have each other. They have been alone together now
about 4 months, and are doing fine, although both are showing their age.
They are 1.5 years and 1 year old, both very shy and don't want too much to
do with humans.

I have not gotten more mice because all the illnesses and losses got to me
and I decided to "get out of mice". Now I'm not so sure I can do it. I
love mice. Plus, when one dies, and the other doesn't, I can't live with
myself leaving one alone.

Ok, so here's the question. Will adding 1 or 2 new female mice (preferrably
young) in with these two older ladies stress them massively? Kill them?
Introduce germs that will stress their immune systems?

Meghan

I think older girls like having littler ones to be more important than.
Make sure to check the mouse thouroughly for any signs of illness. Make
sure to look for mites too. They usually require very sharp eyes. I
adopted a boy recently from PetCo, and found mites when I got him home.
I short bath with *majorly* diluted flea & tick cat shampoo and a
q-tip, and one night of quarintine, and my boy was right as rain.
Always quarentine if you have any suspicions about a new mouse, untill
she's passed inspection.

Good tricks for introducing mice-
1)Clean everything so that nothing (not even the cage, or house) smells
like any mouse. Then put all mice in at the same time. Then everyone
loses confidence, and is less likely to try and defend their home.
2)Put a dab of vanilla extract on each mouse. Mice usually know each
other by scent, so if all the mice smell odd (even an old friend), they
usually seem to be more inquisitive than hostile.

But ALWAYS watch them for the first few minutes, and don't go out of
earshot for too long. You may see them all run into the house together,
and you may think this means they're all getting along, but this just
means they're all confused or scared. Once you leave them alone they
may start working out the pecking order. But as long as there's no boys
involved, everything should soon mellow down.

As far as all your mice dying, are you using a wood substrate, or
newspaper?