Dog hasn't eaten in 3 and a half days what could be wrong?

[MayH]

Hello, i have a chihuahua mix fox terrier and he has refused his food for 3 and a half days now. He has gone around a day without eating before but never to this extent. He was doing fine on the instinct chicken kibble and recently i changed it to instinct with raw bits,but still chicken flavored. He got through like 1/4 of the bag no problem until now. He still drinks water and his activity levels have remained the same. He also does not look ad if he had lost weight. He does urinate, however his stools are few and runny. Also, i did spray some flea spray on him around a week ago but since then i assume it has gotten washed out with the rain. The bottle did say natural and i made sure it was safe. Could there be a possibility that this was the cause? One more thing, he is not neutered and has been whining for the same amount of time he hasn't been eating. Ive heard that male dogs sometimes will refuse to eat if a female is in heat nearby. Im trying to rule out everything. This morning i bought him some wet food toppings to mix in with his kibble, he only ate some of it but i kind of had to force him and ignored the kibble completely. Im really worried and any hints and advice is much appreciated.

[marthaah000]

This exact same thing happened to my GSD puppy he stopped eating for a bit then he stopped drinking water. He also lost weight and wanted to sleep most of the time. Turns out he had parvo, a deadly virus if left untreated. The thing that saved him was when he wasn't eating we gave him water with electrolytes. There's no "cure" but what the doctors do is help them with the symptoms. Maybe you should get him checked for that, I hope I helped.