Within the group of protozoa the genus Giardia is included in the phylum Sarcomastigophora. In this genus different species are admitted, however, according to the arrangement of the microtubular structures present in the bodies means, three groups of species are admitted: Giardia agilis, Giardia muris and Giardia intestinalis (duodenalis or lamblia). This flagellated protozoan colonizes the intestine of humans and animals, producing a disease called Giardiosis that can be asymptomatic, acute or chronic, with diarrheal symptoms of varying intensity that can lead to malabsorption syndrome. G. duodenalis has high levels of genetic diversity, having differentiated 7 genotypes called A, B, C, D, E, F and G. Among the assemblies of G. duodenalis, assemblies A and B have the broadest specificity of host, as it has been found to infect humans and other mammals. Set A is frequently found in cattle (cattle, water buffalo, sheep, goats, alpacas and pigs) and pets (dogs, cats and horses). G. Duodenalis A and F are more frequent in cats and rodents.