Hi! Please help!

I have two new Kittens. One of them has diarrhea.

I've had them both for ten days, and when I first got them their poo was fine.

But for a week now my boy has had diarrhea... He's making a real mess of the litter tray, tracking poo over the floor, he has a dirty bum most of the time, and whats worst, I'm worried he's developing a bit of a complex about the toilet [he tries to get behind my bookcase to poo].

I'd say he uses the toilet 'the usual' number of times per day. His poo is not watery, just loose [sorry for gross details!].

Everything else is fine - he's eating well, playing lots, happy and putting on weight.

The sellers [who were a pet store] recommended giving him some human anti-diarreha medicine, usually an injection, administered orally. I did that, but no change].

Both the cats eat the same, dry purina kitten biscuits, [which they aren't crazy about] and the 'single serve' whiskas kitten pouches [which they are crazy about]. [No other food available in my part of China].

When I search google it makes kitten diarrhea sound quite serious, and attributes it to lots of nasty things, and says it can cause dehydration. He is not dehydrated, and there are no symptoms of any worms or disease.

I can't take him to a vet easily because I live in China and cats are not comon pets here, I think the vet won't know what's going on.

Should I be worried? Maybe it's normal for a kitten after moving to a new home? What can I do? How long will this last?

Thanks so much!