Morphological and physiological characteristics of a virulent and zoonotic assemblage A Giardia duodenalis canine strain.

Giardiasis is an intestinal parasitosis that affects millions of people worldwide and is considered a zoonotic disease. Frequently in contact with humans, dogs are the main host involved in this zoonotic transmission. Here, we compared some aspects of Giardia duodenalis biology between two strains: a recently isolated dog strain (BHFC1) and a human reference strain (Portland-1). Growth curve analysis revealed that BHFC1 trophozoites multiply faster than the human isolate Portland-1 in axenic culture, but has a lower rate of cysts formation. Scanning electron microscopy revealed that BHFC1 trophozoites have the same conventional shape and morphological structures expected for G. duodenalis trophozoites, but presented a more prominent flange. For the best of our knowledge, this work is the first description of morphological aspects and encystation process of a G. duodenalis strain isolated from a dog. Since BHFC1 and Portland-1 have been maintained in axenic cultures for different periods of time, differences observed in growth, encystation rates and flange size may be attributed to adaptation of Portland-1 to axenic culture and lack of the environmental pressures. BHFC1 can be useful as tool for better understanding of Giardia duodenalis biology.