A thin young Chihuahua has diarrhoea for 7 days

"He likes to eat anything on the floor?" I asked.
"Yes, yes," the lady said."Newspapers and even the cotton bud I dropped accidentally!"
Diarrhoea for 7 days as many as 6 times yesterday and 5 times today. No vomiting. Still eats.




The active dog whimpered when I palpated her back half of the abdomen which was filled with gas. The front half was full like a big bag of clothes. 

What's the cause of diarrhoea and what's the solution? 

James Herriot in one of his stories in "Vets In Harness" mentioned about the use of sedatives and tranquilisers to let the dog suffering from long periods of diarrhoea sleep and recover. He used Nembutal in one poodle successfully.