I was in much the same position as you, a foster mum for the SPCA. I was fostering a very pregnant girl (Maisie) who was about to give birth. When Maisie had her three kittens, all torties and all girls, it was apparent from the start that there was something different about the middle kitten. I later discovered that an elderly and over-enthusiastic volunteer had somehow persuaded the vet (who has since retired) to give Maisie a shot against panleukopenia when she came in. The panleukopenia vaccine is a live but weakened vaccine (what they call ‘attenuated’) so this was a really, really bad idea as it exposed the kittens in the womb to the panleukopenia virus (which is why you do not give it to pregnant cats). Of course, the mum may have been infected in the wild but the timing is suspicious. Anyway, Maddie and Milo, the oldest and youngest kittens, developed more or less usually — they were perhaps a little clumsier than other kittens but if you hadn’t been told that they were, you would never have noticed. In New Zealand, the SPCA cannot find enough homes for healthy kittens so if I hadn’t taken Millie, she would have been put down. I had only heard of CH because another TDKer, a very experienced and knowledgeable foster mum in the US, had rescued two kittens which she eventually realised had CH. When Millie couldn’t seem to manage to learn to walk properly, I realised I probably had another CH kitten on my hands. CH is not generally known about in NZ, except for among vets. Millie’s is a pretty severe case, I imagine she got the full dose of vaccine into her and saved her siblings from harm. ALl you can do right now is keep an eye on her, give her any extra help and loving she seems to need, and watch her development. If she has CH, it will become apparent as she gets older, especially in relation to her siblings’ development. It never gets any better or any worse but cats learn to adapt to it. CH kittens are otherwise perfectly happy and healthy, they are not in any pain (they are more accident-prone so need a careful eye kept on them), their cat intellects are not affected, they are entirely normal except that their fine motor function doesn’t work very well. It is the feline equivalent of human cerebral palsy. Millie is determined, stubborn, brave and triumphant when she manages something, she is a brilliant climber (their front legs often become very strong to make up for their back legs not working) and she has a huge personality. She is demanding but she is also the snuggliest and most loving cat I’ve ever had. Toilet training can be an issue, depending on the degree of affectedness — but we can deal with that when your kitten gets to it. It is not likely that the vet will be able to diagnose it for sure until she is about three or four months old but there is no treatment. People often say that they have ‘taught their CH kitten to walk properly’ but Millie’s is so severe that that she has never been able to walk properly (although she is much better outside on earth) and I suspect what happens is that their CH kitten is just adapting naturally to its condition as it gets older so though I felt guilty for a while that I couldn’t seem to help to teach Millie to walk, I now think that it’s not possible to improve their condition — as the books say, it doesn’t get worse, it doesn’t get better, but kitten adapts. The more time Millie spent outside, where she finds it easier to walk and run, the stronger her back legs became and the better she became at walking. But she will always have trouble with falling over, especially inside.
(That is not to say that gently massaging and exercising kitten’s back legs won’t help as it may well do, especially if her problem is not actually CH. I massaged and exercised Millie’s back legs when she was a kitten and made her practise putting her weight on them. Anything that can help strengthen their back leg muscles will help kitten adapt.)
If you are in the US, then probably you can arrange some sort of trolley or cart for kitten. There are DIY videos on youtube on constructing carts for CH kitties. Here in NZ, where the condition is almost unknown, there is no such thing and unfortunately I am no handyman, but Millie has a good life and if she has special needs, she also rewards me by being an extra-loving, snuggly and cuddly kitty who, at three years old, loves to snuggle me all night and all day if possible. Luckily she is small and not heavy so that’s not usually a problem.