My Rats are Dying..Why?

Question
I bought my first rat - a common black and white one - from my local pet store a little over a month ago for a zoology project at school. She was a little over two weeks old, just barely weened. She was very sweet and energetic. She was loveable and would fall asleep in your hands or pocket. I kept her at the school during the week and home on the weekends.
Two weeks or so after I bought her, I woke up one morning and went to take her out of her cage. When I held her she felt cold to the touch. She had a normal amount of food and water and I had cleaned her cage the day before, so I dismissed it as being nothing. But when I put her away, I noticed she stumbled and fell. I wondered if the food I was giving her was making her sick and I called my mom to tell her to bring home some rat pellets after work. When I came in to check on her about four hours later, she was dead. She looked as though she had fallen asleep.

I had to buy another rat for the project, so I went out and got one two days later. I used the same cage and bedding, but different food. She was from the same pet store, same age as the first one was when I bought her, even the same color. She was also very, very sweet, though she was not as energetic. She slept a lot, but still moved around quite a bit. She seemed completely healthy until just this morning - I checked her fur and there were little brown bugs all over it, which I think were lice. She was also ditier than usual, as though she had neglected to clean herself, and slightly cold. I called the vet immediatley, who told me that the bedding she was using may have given her the lice and that I should buy some powder for her to kill them. I left to get some and by the time I got back, she was dead as well. She had lasted the same amount of time as my first rat.

I am extremely confused as to what was killing the poor things - I don't know if the lice killed her somehow or if it was some other type of illness. It makes sense that it may have been the same thing both times, but I don't have any idea what that thing may be. I need to find out so I know if I will be able to buy another one without it dying as well.

Some other notes: The second rat had the red discharge stuff around her nose before she died. They were both using pine bedding, which I was not aware was toxic until today - however, I don't think that could kill them within two weeks. None of the other rats in either of their broods had health problems. The cage, food, and bedding were all new when I put the first rat in them.

Please help..I'm worried for the safety of the next rat I'm going to have to buy.

Answer
Using pine shavings for bedding in rats causes not only respiratory issues, but also can cause what you saw and that is bugs. It is highly not recommended for rodents to use this or cedar bedding. What I recommend care-fresh which is a fluffy bedding that is very absorbent and soft on the feet. I also would try to go with a little older of a pet or maybe trying another pet store. I hope that this helps you and here are some websites that are going to give further details :)


http://exoticpets.about.com/cs/guineapigs/a/woodshavings.htm

http://exoticpets.about.com/od/guineapigs/tp/tpbedding.htm

http://hubpages.com/hub/Signs_of_Illness_In_Your_Rat