Sick Foster Kitten - PLEASE HELP!!

[Kate345]

I have a foster kitten who has recently become very sick. She is 6-8 weeks old and is the only one showing these symptoms out of a litter of 4. About 6 days ago she began vomiting her dry food immediately after she ate. She also seems to get very mucus-y and congested after eating any dry food (currently eating Royal K9 - baby-Cat). She seems to dry heave and have a difficult time breathing. This lasts for a few minutes, and she eventually vomits up the few kibbles she managed to eat. It looks like she still has an appetite, and is drinking water and using the litter box, although she is rapidly losing weight. Her energy level is very low, mainly rests, and doesn't interact with her siblings. So far we have tried a high calorie supplement and kitten formula, which she doesn't seem to like. Does anyone know what this could be? Or more importantly how to get her better? If I take her back to the humane society, I'm afraid they'll just put her down. Any help would be appreciated greatly!

[Justine Lee, D.V.M., DACVECC]

I'd definitely recommend bringing your kitten to the vet for an exam. While upper respiratory infections (URI) can cause some congestion, pus from the eyes and nose, and poor appetite, it shouldn't be to the degree that your kitten is losing so much weight. A high calorie diet may help, but it's important that she be brought to a vet, especially since she is having difficulty breathing!