I am so sorry Bruce is not felling well.
It sounds like he has Colitis:
Of course protozoan parasites cannot be over ruled:
Purina EN isgood but lets try him on the Canine colitis diet:
Purina DCO - has a fiber content between maintenance foods and w/d - it is around 7% fiber (w/d is around 15%)
---Eukanuba Optimum weight control
Here are a few other web pages with useful information:
Omce he is better try a small amount of boiled chicken with all fat drained off, chop meat , or baby food with no onion, beef, turkey, etc add cooked white rice or infant rice cereal.] @ two tablespoons per meal. This is to rest his GI tract.
Dogs get dehydrated and hypoglycemic very easily from diarrhea.
Add unflavored pedialyte to his water 50/50 to hydrate him and balance his electrolytes.
Put a drop of pancake syrup on his tongue to raise his blood sugar in case he is a bit hypoglycemic. That should perk him up.
Do not allow him to drink a lot at a time If he throws up water, he can lick ice
Keep him on that very light diet of boiled chicken or baby food with rice cereal for 48 hours after the stool is normal.
Also give him one teaspoon a day of plain yogurt to keep "good" bacteria in his system.
If he develops any abdominal pain, bloating, constipation or cannot keep anything down he needs to be reseen by a vet.
Please let me know how he is doing. I will always be here for you
I hope your boy feels better very soon..