Yes, there are pockets of wealth everywhere. Even in a place like Chad, in East Africa.
But is there a Chadian Autism Society?
Awareness is low in these places. Lots of times, they can't even get something like Tylenol, no less an autism diagnosis. It's really tough nuggies on anybody who is autistic, as far as these nations are concerned. And tough nuggies for people with many other diseases/disorder, unless their image is affected, like when Ebola swept through West Africa.
I would say the incidence of autism is probably lower, over all, in the Third World, but it does exist. Many people with low-functioning autism get sent to institutions, or they might, if they are lucky, be the beneficiaries of a church charity. If you're Aspergian, it's tough nuggies, too; you have to make a living somehow!
Obviously, to dismiss these people because they can't obtain a diagnosis is ridiculous.