http://www.angelfire.com/ky3/kyratwl/Links.html
There are several symptoms of a guinea pig becoming ill. The main ones/most serious are not eating/drinking, diarrhea, discharge from eyes and/or nose, hair loss, weight loss, not moving (listless), hunched position or their nose near the corner of the cage. Eating their feces is not a concern. Guinea pigs do this because it is full of nutrients and proteins that is essential for them, so don't think there's a problem if you notice this!
I noticed Zilch sitting in his cage in the corner and not moving much when I realized he was very sick. And, Domino I noticed a big loss in weight, but only after I knew he was having problems with his teeth. He wasn't eating enough. Rueben was sick and he was scratching a lot. From what I was told it could be a skin infection, mites, an allergic reaction to something, or just itchy skin. He was given Griseofluvin and then Ivermectin (for mites). There are many medicines that are toxic to a guinea pig. Check out the sites below for lists of them. No medicine should be given without consulting a vet beforehand!
Some of the illnesses my guinea pigs have had
Zilch
Zilch had Pododermatitis (Bumblefoot). This is a very gross looking infection in the foot that vets think is caused by wire cages. This link says it's painful but Zilch never showed any sign that it hurt him one bit! Guinea Lynx-feet and foot problems
Domino
Domino had mites shortly after I got him. I took him to the vet and she gave him a shot of Ivermectin and it seemed to clear them up FAST! I didn't even have to take him in for a second shot. He also had a problem with his teeth. I thought he had caught the cold I had had for about a week. I hadn't been spending much time with him because I didn't want him to get the cold because they can be deadly to guinea pigs. I took him to the vet after I noticed he was loosing weight and not seeming to eat much. I got Rueben for him, they do better in pairs. Domino continued not to eat and just lay around. Some days he would eat some yogurt from a spoon for me and some baby food off of a little plate but he wouldn't eat any solid food. I took him to the vet and she said that he had a problem with his teeth, they weren't wearing down like they should be. She said it can be caused by maybe that he hurt his mouth chewing on the cage, which I had noticed he did sometimes or it could be a hereditary disease. The vet said his teeth needed to be trimmed down or else he would not be able to eat and would eventually kill himself. I felt so bad and didn't have the money for the surgery. I also figured that I'd be spending $50 to put him under to even do the surgery and with him being so weak and small I didn't figure that he'd wake up so I went ahead and put him to sleep.
Rueben
Rueben also had mites. I took him into the vet and she said it was ringworm at first but it ended up that the medicine didn't work for it at all and after a month he was still scratching like crazy! I took him into the vet again and another vet gave him an Ivermectin shot and he stopped scratching for the most part, so after 10 days I had to take him back in again for the second shot and since then he's been okay!
For a time, when Spot would use the bathroom, she was squeal. She was taken to the vet, but nothing was found. She suggested to return, if the squealing became worse. She said it may be bladder stones or a UTI. So far, we've not had to return. Her appetite was fine and nothing out of the ordinary.
Baby doesn't really have an illness but it's a disease called Polydactyl. It's basically that she has an extra toe on one of her back feet. Guinea pigs generally have 3 toes on their back feet but Baby has 4 on one foot and 3 on the other. This didn't seem to bother her one bit so I never took her in to get it removed.
Mohave became ill about three days ago. I noticed a weight loss and her not eating as much. I separated her for the night and the next day, she seemed fine. I watched her, but put her back with her daughters. The next day, I noticed her laying in her cage and was not responsive. I ran her to the Emergency Vet and they gave her some Baytril. She was put in an oxygen tank for a few as well. Her temp was low, so they wanted to warm her up. We returned home. I kept her on a heating pad and noticed later, she was not walking on her back feet. The vet advised us to return, so we did. He gave her some pain medicine and we again returned home. We saw Mohave's normal vet the next morning. She gave her some critical care from Oxbow Hay. She seems to be doing some better, but still somewhat weak. We are keeping our fingers crossed that she will recover. Unfortunately, about a week later, she became ill with the same symptoms again. I called the vet and asked to get her in asap. They could get her in in about 45 min. I raced across town and at the vet's office, she started to twitch really bad and her heart was beating irregularly. She was in the process of passing on. To speed the process I asked for her to be put to sleep. This is a hard decision but one I felt best again for her, to keep her from suffering.
Last night, I noticed Drostan was chewing kind of funny and looked at her teeth. She has lost her top teeth and her bottom ones have grown very long. I had gone out of town for a few days, and not noticed anything out of the ordinary from her. She's been eating and drinking fine. I felt absolutely terrible. Thankfully, the teeth were able to be trimmed down by our vet and she's doing fine so far. Hopefully everything will be okay w/her.
Guinea Lynx
PetsHub.com I like this site, even though it does say you can put Vitamin C in water...most other places say NO