Giardia can also be detected microscopically (service 234 Blood Parasites – microscopic).
Giardia is a flagellate that can be found in the intestine of mammals, birds, reptiles, amphibians and humans. There are some well-differentiated species, such as G. intestinalis (lamblia, duodenalis). Giardia is ingested orally (food, water) or through smear infection as cysts, excystates in the intestine and attaches as trophozoites to the intestinal wall where it replicates. Damage to and detachment of the intestinal epithelium cause chronic intermittent catarrhal to mucous-bloody diarrhoea. The cysts that are excreted with the faeces remain infectious for many months in cold water and a humid environment.
Except for Giardia in birds and amphibians, Giardia is partially of zoonotic nature. Seven variants have been identified through genetic characterisation of which variants (assemblages) A and B mainly occur in humans, variants C and D are primarily detected in dogs and variant F can mostly be found in cats.
Across species, however, isolates of different subtypes of A as well as those of B can be detected in different animal species, so that a transmission from humans to animals and from animals to humans cannot be excluded. In dogs and cats, Giardia is the predominant type of intestinal parasites. In our own examinations, Giardia infections were detected in 15% of cats; 3.5% of these animals contained the human-pathogenic assemblage A.