Giardiasis
Giardia are single-celled organisms called protozoa.  They cause an intestinal disease called giardiasis that is infectious to dogs and humans.  The most common symptom in humans and dogs is usually diarrhea.

After the giardia organism attacks the digestive tract of an infected dog, it is passed as cysts in the dog’s waste.  From here, it can be accidentally ingested by other dogs or humans (especially as the result of improper hand washing). This pathogen can also be found in swimming pools, ponds, rivers, and lakes that have been contaminated with feces.  Studies show that giardiasis is one of the most common waterborne diseases in the United Sates.