Baby mouse suddenly fighting older mouse

Question
QUESTION: Hey, Sorry  I know you don't do health questions, actually this is about My mouse Anna, Her sister passed away last friday, so she was left alone. Anna is about 1 year 3 months. We got her two new little friends to hang out with Sophie and Betty. Everything seemed to be going well, all of them sleeping together, and hanging out... We did the whole bleaching the cage, vanilla extract, putting into a neutral environment deal so it all went really good!  But I notice how Betty gets over excited and seems to twitch or hop like crazy. Tonight Betty and Anna got into a big fight, i had to put my hand in to separate them twice, second time I noticed that Anna, my older mouse had a little blood above her right eye (which she is blind in) She is acting normal, seemed pissed off though. Anyway, should i be worried about infection for Anna's  little cut and is their a reason for Betty's crazy aggressive behavior?

ANSWER: Dear Wendy,
thank you for your question.
From what you describe, I would guess that the mice have mites or other parasites. The twitching and sudden jumping is fairly typical for that. It's also possible that Anna hasn't been hurt in the fight but scratched herself bloody. I recommend seeing a rodent vet with them to find out what exactly is wrong and to get the right treatment for the mites, if they have any (over the counter antiparasitic meds are either useless or dangerous plus you need to find out the type of parasite to treat it effectifely).
Parasites are very stressful for mice and this may be the cause for the fight as well.
You can find good rodent vets here:
http://gerbilforum.proboards.com/index.cgi?board=vet
http://www.gerbils.pwp.blueyonder.co.uk/gerbils/vets.htm
http://www.rmca.org/Vets/
I hope I was of some help to you
Jennifer

---------- FOLLOW-UP ----------

QUESTION: Really? Mites? Anna didn't have the cut above her eye right before the fight, and I witnessed it. They were both standing on their back legs with their arms up at each other. Anna's sister Winnie that passed away used to get excited and hop and kinda twitch around before. Someone else told me that is excitement.  Is there any treatment for mites that I could buy at they pet store? We clean their cage once every week.
I just thought this was a dominance issue?

Answer
I can only guess of course without having seen the mice, but it is definitely a possibility. I would strongly advise against store bought mite treatments, those are either useless or even dangerous, plus you need to find out which species of parasites the mites have, if they have any, to treat them correctly.

Dominance issue are rare with properly introduces mice. But if you have ruled out parasites, then I would recommend introducing them again to prevent the fights from getting more serious. Mice fighting like this is unusual (it's more gerbil style), but sometimes even female mice suddenly decide that that they don't like each other any more. It's also possible that the introduction of another mouse will quiet things down, but there's no guarantee for that.