Oh no! You said diarhea!

This can be caused be a few factors. First, if the rat has been fed too many fruits or vegetables, it could lead to diarhea.

Second... she could have SDA, which in case the other rat would have it too. SDA itself is relatively harmless. However it lowers the immune system allowing other types of infections, such as MYCO to invade the body causing rapid death. It has wiped out breeding colonies in less than a week. I had a case of SDA a few months ago and lost two rats. One last an eye. SDA is very highly contagious and spreds through the air. Petstore rats are very susceptible to SDA and MYCO because they are constanlty handled by new people and caged with other rats.

Signs of SDA nclude the following. Weight loss, dehydration from diahrea, swelling of the lympnodes (chipmunk cheeks) and throat, loss of appetite, and corneal cysts. The eyes will appear dry and porethyrin stained (looks like blood). Because they eyes are so dry the rat constantly rubs them. This causes corneal abrasions and nasty infections. You will need to use Terramycin ointment three times a day to prevent the loss of an eye.

Your rats problem can also be due to stress. All new rats shouldbe quarantined for a MINIMUM of three weeks before being introduced into an existing colony. SDA is airborn and clings to the hands and clothes. If possible keep the babies seperated from the others until their quarantine period is up. If your new rat has something and you have touched the others consider them now infected also. Most rats from petstores are sick. That is why it is safe to go to a breeder.

You need to make sure your rat recieves plenty of fluid. If you can buy some pedialyte or lactated ringer solution (your parents will know what this is) and give one teasespoon full every six hours that will insure your rat will not get dehydrated. Be prepared for the worst. Most rats who suffer from diahrea do not make it. Keep your other rats safe and do not introduce them yet! Wait til quarantine is up.