Guinea pigs are very sensitive to infections of the upper respiratory tract and lungs.  A seemingly minor sniffle or sneezing episode may be an early sign of a much more serious disease.  A guinea pig may appear normal one day, have a nasal discharge and sneeze the next day, and develop labored breathing (their abdomen moves instead of their chest) and have pneumonia and even die within 48 hrs of the first signs of a problem.  Some other signs of a respiratory tract infection are poor appetite, weight loss, ruffled fur, and crusty eyes.  Due to the speed at which a guinea pig can go from healthy to critically ill, we recommend a health consultation at the first sign of a respiratory infection.

There are many different kinds of microorganisms that can cause respiratory illness in guinea pigs.  The bacteria Bordetella bronchiseptica (the same bacteria that causes "kennel cough" in dogs) and Streptococcus pneumoniae are among the more common infections.  Some guinea pigs may live for a long time with these bacteria in the respiratory tract without showing signs of disease but any stress, such as a change in routine, pregnancy, or introduction of a new cagemate may trigger an outbreak of respiratory problems.

Streptococcus is apparently mainly passed from us to our guinea pigs.  Bordetella is often found in apparently healthy rabbits (and dogs) and can be passed from the rabbits (and dogs) to any guinea pigs that have close contact.  If you have other pets in the house, it is always a good idea to thoroughly wash your hands with warm soapy water before playing with your guinea pig.

Antibiotics and other medications need to be started early to give your guinea pig the best possible chance of recovery.  Unfortunately, some guinea pigs still die despite treatment for reasons we do not fully understand.

Many guinea pigs that develop respiratory disease are deficient in vitamin C either because their guinea pig pellets are too old and the vitamin C has wasted away or they get vitamin C in their water but do not drink enough water.  It is critical to make sure your guinea pig gets at least 50 mg of vitamin C a day when sick and about 15 mg a day to stay in good health.