3 week old kitten has severe diarrhea with bowel incontinence. already dewormed.

I live in a third world country where there is little veterinary care beyond euthanization and castration, although many over the counter medications are available for cats.

We found this kitten abandoned with his brother in a box. The other died several days ago after severe dirrhea that somehow infected his legs and area around anus, causing an "eaten" look. We had given them both dewormer, but the one still died. After that, we gave more dewormer to the surviving kitten after hearing they should have had a higher dosage.

We are giving him only water with sugar and salt. Rice and pumpkin didn't work.

symptoms:
severe diarrhea (complete liquid, basically poops out his water)
incontinence of bowel movements
abdominal discomfort
red, swollen anus and tail area near anus after bowel movements

No other symptoms! No vomitting, coughing, etc.

Please, please help with any suggestions for what it may be and what we can do. He may not survive through the night. I am desperate and, like I said, have NO other options right now.

[Piparskeggr]

One thing we did when our Kessie was having her trouble, if kitten is still able to be helped, find an anti-diarrheal that is made with kaolin and pectin.  Give kitten 1/4 teaspoon a couple of times a day.

A kitten this young needs momma cat's milk to build up the immune system, but try goat's milk.