2011/07/01 by Richard C. Thompson · 1 citation
Immunology and Microbiology · Medicine · #Parasitic Infections and Diagnostics #Giardia #Outbreak #Diarrheal disease #Biology #Medicine #Virology #Diarrhea #Pathology #Microbiology
paper · doi:10.1093/med/9780198570028.003.0052
openalex publication_date 2011/07/01 · openalex created_date 2022/05/12 · openalex updated_date 2026/06/16
<italic>Giardia</italic> is a ubiquitous intestinal protozoan parasite of vertebrates and the most common intestinal pathogen of humans and domestic animals with a worldwide distribution including both temperate and tropical regions. <italic>Giardia</italic> was first observed in 1681 by Antony van Leeuwenhoek in his own faeces (Dobell 1920), and the organism has intrigued biologists and clinicians ever since. However, the first detailed description of the parasite was not given until two centuries later by Lambl (1859). Koch’s postulation was proven by Rendtorff in 1954 when he successfully transmitted symptomatic <italic>Giardia</italic> infection to human volunteers following orally administered cysts. The first symptoms of clinical giardiasis were reported in the early 1920s, although the significance of <italic>Giardia</italic> as a cause of diarrhoeal disease was controversial for many years (see Farthing 1994; Cox 1998), and it is only recently that the significance of <italic>Giardia</italic> as a cause of chronic disease in children and its association with failure to thrive, wasting and malabsorption syndromes has been fully realised (reviewed in Farthing 1994; Hall 1994; Gracey 1994; Rabbani and Islam 1994; Hesham <italic>et al.</italic> 2005; Savioli <italic>et al.</italic> 2006; Thompson 2008). The question of <italic>Giardia</italic> ’s role as a source of zoonotically transmitted disease again has been controversial. The World Health Organization (WHO) recommended that <italic>Giardia</italic> should be considered as a zoonotic agent in 1979 (Anon. 1979). Since that time, increasing circumstantial epidemiological evidence from waterborne outbreaks, the results of some cross-infection experiments and molecular characterization studies of <italic>Giardia</italic> isolates from humans and other animals has led most authorities to conclude that <italic>Giardia</italic> should be considered a zoonotic parasite (Acha and Szyfres 2003; Savioli <italic>et al.</italic> 2006; and reviewed in Thompson 2004). However, as discussed below, the frequency of zoonotic transmission is uncertain.