Giardia & Giardiosis: Yesterday, today and tomorrow

The ancient question is about the role of Giardia in the disease development: is the finding of the protozoa a cause or a consequence of the clinical signs? This question is still open and unsolved. In the past, due to the frequency of isolation and to identification problems, almost all animal species had their Giardia sp. Now three major morphological groups have been identified: G. muris from mice, G.agilis, from amphibians and a third group from various warm–blooded animals. Within this last group, G.duodenalis is a species complex infecting humans and domestic animals, that is further differentiated molecularly. There are seven recognized genotypes or Assemblages named A–G. Dogs are infected primarily with Assemblages C and D, cats with F and humans only with Assemblages A and B. The potential zoonotic role of dogs and cats arises from recent genotyping studies that described Assemblages A and, occasionally B, in these pets. Our data about giardiosis in Italy, collected from the different regions, allowed us to define a strange picture of the national situation. Where vets became aware of the supposed problem from industries (drugs or diagnostic kit producers), we obtained data that show that Giardia can be frequently found in dogs and cats. The identification of Assemblages, realized in specific research institutes, agrees with data published in international literature. Where this mechanism is less active, the parasite seems to be even absent. The final understanding of the potential zoonotic risk of Giardia from either pets must rely on comprehensive studies that incorporate biological, molecular and epidemiological tools, testing samples from pets and humans of the same household. Under the banner of “one medicine”, we are working in this direction.