Hello and thanks for researching this very important question!
Thanks for the updated info...I'll list all the reasons that might be involved in this kind of situation, then make some suggestions for actions to take today.
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, and high ammonia content in wet bedding can lead to irritation and illness of the sinuses and lungs as well.
The Guinea Pig immune system is quite fragile...eating the wrong foods, or not eating proper portions of the right foods can damage their ability to fight off infection on a daily basis.
If the teeth are not meeting properly, ingestion of foods and absorption of nutrients will be critically reduced.
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:
1) Please go to the pharmacy right away today and get a pediatric vitamin C supplement (liquid)...give 40mg tonight and 20mg for the next 7 days (thereafter give 15mg every day to maintain proper immune function).
2) Make sure your house is warm enough for a GP...raise the room temperature to 80F degrees while he/she is sick, then you can keep it at around 75F degrees after recovery.
3) 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. You can also mix the regular pellet food with warm water to give with a spoon or dropper if you don't see chewing.
4) 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 today, or gets any worse, please seek veterinary help right away...GPs are very fragile once they become sick and stop eating. They can look fine one minute, then perish seemingly "in an instant".
These links will help you find qualified medical assistance (not all medicines are safe to use in GPs, so you want to have your tiny 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