A pustular lesion was noted on the abdominal wall which ruptured spontaneous a few days ago. Since last Sunday, he has developed seizure for a few times. He also got a bad pneumonia. My vet has set a ivi drip for him and given antibiotic and Vit B12 for him. Concerning the bowel motion, he had no more diarrhoea in the last 2 days but resumed to diarrhoea with blood and mucus again.
Fever still persist.
It does sound like you are describing the symptoms of a puppy infected with distemper virus. With treatment some puppies survive distemper and some do not. There is no good way to determine in an individual puppy how virulent the strain of distemper they have is. Some puppies who do not seem to have severe disease die and some puppies have serious clinical signs but live through them. We will usually try very hard to save puppies since this is the case.