8 weeks: eats and passes food within minutes

*Sorry in advance for the lengthy post* Hi Vets, Background: We picked this two babies up from the shelter on Friday - they were found as a litter of 9 in a shed with no Mum and have been hand reared by the shelter for the past few weeks. They are 8 weeks old and we’re fleaed and wormed before we collected them - but we’re covered in poo and sharing a couple of litter boxes between the 9 of them. Saturday/Sunday: both experienced diarrhea which was yellow in colour, absolutely stunk and had slight sickness. Monday: vets couldn’t diagnose because they were too young (?) gave them anti-sickness injections and more worming liquid. Told us to keep an eye on them over the next 10-14 days. Same symptoms as above. Today: Our tabby has perked up loads and is now having almost solid poos and no sickness. Her sister, however, is going to the toilet with diarrhea almost instantly after eating (can’t even make it to her litter tray) and is very lethargic, but still alert. She’s lost lots of weight too and only approximately 450g. We do have a vets appointment tomorrow morning for her as I don’t think she’d see the next 10 days if she was to carry on like this. Has anybody ever experienced anything like this? I’m hoping it could be parasites or something and not anything more sinister 🥺 Thank you in advance!

Hello and Im sorry to hear about your poorly kittens.  It sounds as though they may have some kind of infection or other underlying disease.  It could be that your male kitten was the stronger of the two, but it also sounds as though your little girl may be losing fluid / water in the poo faster than she can replace it, leaving her dehydrated and lethargic.   Such a case should be seen as an emergency if at all possible, as she might need an IV drip.  Please do update us as to how she gets on.