Disease??

[BulkMice]

When in doubt sterilize everything thoroughly. It may not be MCP but there's a good chance another Mycoplasma caused an infection...

[Freakie_frog]

Sounds like the ear infections we get from time to time in the colony. It is treatable if cause early enough, keep an eye on the rest of them. Like was said before I'd clean and sterilize everything really good just to make sure.