Prevention
If you want to prevent your Sims from getting the disease the easiest way is to make sure you keep the guinea pig cage clean. The Guinea Pig Disease is contracted when a Sim is bitten while playing with the guinea pig.
The Cure
There are three ways to cure the Guinea Pig Disease. The easiest way is to buy the Guinea Pig painting. The second is to give a Sim lots of food and rest. The third way requires a little luck. In the "Living Large" expansion pack there is a chemistry set. Have your Sim use this to develop a white potion.
Remember, next time, make sure the guinea pig cage is clean before you play with it.

