Hello and thanks for researching this very important question!
Guinea Pigs can develop respiratory symptoms for a variety of reasons. Cedar bedding has fallen into disuse with Pocket Pet owners for a few good reasons: 1) Allergic problems (sneezing, coughing, itching, hair loss); 2) Toxicity (the chemicals that cause the sweet smell are very harmful when close contact is maintained for a long time). Fatalities are frequently seen after long exposure.
Pine shavings can have a similar effect in sensitive animals. New bedding types, such as recycled paper and aspen shavings, are more frequently seen on the market. They are somewhat less absorbent and should be changed more often. There is no substitute for good hygienic practices.
Guinea pigs are susceptible to a number of cold viruses and can become ill quickly from eating a diet that is lacking in vitamin C. Packaged pellets are a good source of protein, fiber and other nutrients, but Vitamin C is very fragile and decays quickly under warehouse conditions.
Many dog-and-cat medications are toxic to GPs, and can make them sicker (ex: amoxicillin).
What to do at home:
In addition to changing the bedding to a less toxic paper or aspen type, please go to the pharmacy right away tonight and get a pediatric vitamin C supplement (liquid)...give 25mg tonight and 20mg for the next 7 days (thereafter give 15mg every day).
Avoid feeding too many "wet" veggies (celery, lettuce, tomato) as these can cause diarrhea and digestive imbalance in general.
Make sure your house is warm enough for a GP...raise the room temperature to 78F degrees while he is sick, then you can keep it at around 73F degrees.
Also get some jars of baby food fruits and veggies so that you have some soft foods to feed with a dropper to keep energy and nutrition high, especially if he goes off his food. You can also mix his regular pellet food with warm water to give with a spoon or dropper.
Guinea Pigs can get fungal (yeast) infections in their respiratory tract and lungs...a dietary supplement such as Bene-Bac or Probiocin (found at better pet stores, Online, or at veterinary offices) can help combat this type of microbe, or prevent it from getting a hold in an already ailing pet.
***If this little one does not show any significant improvement by tomorrow, or gets any worse, please seek veterinary help right away...GPs are very fragile once they become sick.***
These links will help you find medical assistance (not all medicines are safe to use in GPs, so you want to have your new friend examined by doctors who know how to treat exotic pets):
http://www.cavyinfo.com/html/vet.htm http://www.aracnet.com/cgi-usr/seagull/vetfinder.cgi http://cavyspirit.com/vets.htm
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Retired Veterinary Technician
Dog, Guinea Pig, Hamster, Gerbil breeder / Reptile Keeper / Bunny-Ferret-Exotic Specialist