Learn more about GPD This animal is classified as GPD class 1 and might spread the Guinea Pig Disease GPD. The GPD virus can infect Sims and may lead to sickness and death for the Sims if you do not follow daily hygiene rules.
The SimCity Veterinarian Department

WIth the introduction of the first Guinea Pigs to Sim City early 2000 the Guinea Pig Disease [GPD] has also been introduced to the town. Since then Sim City scientists were working hard to get this disease under control but until now no 100 % cure has been found yet.
The bad thing is that most pets seem to be resistent to the virus but Sims can easily get infected and may even die. The statistics shows that with the increase of pets in Sim City since mid 2000 the number of Sims with pets died more likely than Sims without any pets. So pets can cause sicknesses and diseases that even can lead to death.

This is not a reason to panic or to give away your pet. You can prevent getting infected by simply following daily hygiene rules. Wash your hands after you played with your pet or after you have fed your pet.

First Aid Medicine Cabinet Chemistry Set UPDATE:
KILLERSIMS introduced the First Aid GPDX Beta sets recently! Or just mix your own cure sickness potion with our chemistry sets. If you already got infected by the GPD please see our drugstore in the second floor for a first aid kit. Otherwise get a day off work or school, stay in bed, drink a lot of coffee or soda and take care or your hygiene. You may also try to cure yourself by viewing the some of the paintings available in our 4th floor.

Always keep in mind Pets are not toys. You need to take care of them otherwise you should not buy them.

The following animals are classified GPD Class 1:
- Beach Crabs
- Bunnies
- Cats (Teli Kitty)
- Cows (Jersey Cow)
- Dogs (all except Sparkey)
- Dinosaurs
- Ducks (Duck and her brood)
- Elephants
- Geese
- Giraffes
- Guinea Pigs
- Hamsters
- Horses (Diablo and Sea Biscuit)
- Jaguars
- Lambs
- Mice
- Monkeys (Ground Monkeys)
- Pigs
- Polarbears
- Rabbits
- Rats
- Roosters
- Tigers
- Tribbles
- Zebras

The following animals are classified GPD Class 1 but it's very hard to get infected, unless you jump into the aquarium
- Fishes (Tropical)

If nothing helps, use cheatcode MOVE_OBJECTS ON and delete the Sim in BUILD mode. You can get him back after clicking the character with all green levels.