Epidemiology and Zoonotic Potential of Giardia Infections

Determining the source of infection is central to an understanding of the epidemiology of giardiasis. In this respect, the role of zoonotic transmission has been a matter of controversy for many years. This has been complicated by the fact that the causative agent of giardiasis, Giardia duodenalis, is a common parasite of people, domestic animals and wildlife. The development and application of molecular epidemiological tools has now made it possible to directly genotype Giardia isolated from animals and environmental samples. These studies have shown that many species of mammals are susceptible to infection with zoonotic and host-adapted genotypes of G. duodenalis and that they are often present in the same endemic foci. Recent studies have also demonstrated that zoonotic transmission does occur in nature. However, available data suggests that zoonotic transmission does not appear to play a major role in waterborne outbreaks of giardiasis. More studies are required on the molecular epidemiology of Giardia infections in order to more accurately determine the frequency of zoonotic transmission in localised endemic foci and in outbreak situations.