Giardia is a parasite that can live in the intestines of mammals, birds, and amphibians. Not all dogs show signs of this parasite, but when they do, it is unpleasant. The most common symptom is diarrhea.

Lyme disease is one of the most common tick-transmitted diseases in the world but only causes symptoms in a small percentage of the dogs that are affected. Bacteria called Borrelia burgdorferi are transmitted through the bite of the Ixodes tick (deer tick).