dog green diarrhea

Question
I have a 5 year old lab abd border collie mix.  Lately he has been having diarrhea which normally wouldnt make me worry so much but its been about 4x in the last week and the diarrhea is green.  When I first brought diarrhea up to our vet he said that its the food he eats so I changed his diet to a natural food source called holistic health extension but ne still seems to be getting it.  My major concern now is that its green and the only thing I could find about green diarrhea is a parasite known as Giardia.  If you have any insite on this situation please contact me.   
thank you
Daniela

Answer
Hi Daniela,

Hope your lab/collie mix is doing okay. You are correct about the giardia. It is likely that it could be the cause of the diarrhea; however, the diarrhea would likely be more frequent (several times a day and would only get worse and worse unless treated, it wouldn't go away for a few days and then come back unless the dog is getting re-infected by the giardia). Giardia is transmitted from host (dogs, cats, humans, etc...) to host via a cyst stage (an immature stage like an egg). It can withstand chlorinated water and high temperatures. It is possible, but not proven, to be transmitted from animals to humans. Basically the giardia cyst is eaten or ingested in water (giardia naturally occurs in streams, rivers, ponds, etc...). The cyst then invaginates (hatches) to form an adult that attaches to the intestines and this takes about 6-8 days. During times of diarrhea adults can be found in the stool (can only be seen by a microscope) and during times of normal stools cysts are passed. The prevelance of giardia in dogs in the U.S. is about 36% and is greater in more humid wetter climates (such as in the south). Please note that giardia infections are usually only seen in young animals they are hardly ever seen in animals over 1 year of age, yet it is possible for an older animal to have them. The feces caused by giardia infection is usually greasy, watery (but not too soft) light-colored, and mixed with mucus (like thick spit). Your vet can preform a fecal exam to determine if this is the cause. Due to the age of the animal I wold lean toward the diet causing the problem. Your vet should be able to prescribe a medicated food to help with the problem. If you have anymore questions or would like more infromation please feel free to ask. Hope all turns out well.