A scoping review of risk factors and transmission routes associated with human giardiasis outbreaks in high-income settings

Sarah Krumrie; Paul Capewell; Alison Smith-Palmer; Dominic Mellor; Willie Weir; Claire L Alexander

doi:10.1016/j.crpvbd.2022.100084

A scoping review of risk factors and transmission routes associated with human giardiasis outbreaks in high-income settings

Curr Res Parasitol Vector Borne Dis. 2022 Feb 21:2:100084. doi: 10.1016/j.crpvbd.2022.100084. eCollection 2022.

Authors

Sarah Krumrie¹, Paul Capewell^{1

2}, Alison Smith-Palmer³, Dominic Mellor^{1

3}, Willie Weir¹, Claire L Alexander⁴

Affiliations

¹ University of Glasgow School of Veterinary Medicine, 464 Bearsden Road, Glasgow, G61 1QH, UK.
² BioClavis Ltd, Queen Elizabeth Teaching and Learning Centre, 1345 Govan Road, Glasgow, G51 4TF, UK.
³ Gastrointestinal and Zoonoses Team, Public Health Scotland, Meridian Court, 5 Cadogan Street, Glasgow, G2 6QE, UK.
⁴ Scottish Microbiology Reference Laboratories, New Lister Building, 10-16 Alexandria Parade, Glasgow Royal Infirmary, Glasgow, G31 2ER, UK.

Abstract

The flagellated pathogen Giardia duodenalis is one of the leading causes of parasitic gastrointestinal illness worldwide. In many higher income countries, such as the United Kingdom, the disease is often perceived as being travel-related, likely leading to the under-reporting of sporadic cases and outbreaks. A summary of the literature describing outbreaks and risk factors in higher income countries is necessary to improve our understanding of this pathogen and identify existing knowledge gaps. Initial literature searches were carried out in September 2016 and updated at regular intervals until November 2021, using appropriate search terms in Medline, Embase and PubMed databases. A total of 75 papers met the inclusion criteria, revealing that the consumption of contaminated water and contact with young children of diaper-wearing age were the most common transmission routes leading to outbreaks of giardiasis. Of the ten studies where food was primarily associated with outbreaks, food handlers accounted for eight of these. Another reported transmission route was direct contact with fecal material, which was reported in six studies as the primary transmission route. Travel-associated giardiasis was considered the sole transmission route in two studies, whereas multiple transmission routes contributed to giardiasis outbreaks in eleven studies. The evidence around zoonotic transmission was less clear and hampered by the lack of robust and regularly applied parasite molecular typing techniques. This literature review summarizes the findings of Giardia outbreak investigations and epidemiological studies in high-income countries. Transmission routes are identified and discussed to highlight the associated risk factors. These data also indicate gaps in our current knowledge that include the need for robust, in-depth molecular studies and have underscored the importance of water as a transmission route for Giardia cysts. These future molecular studies will improve our understanding of Giardia epidemiology and transmission pathways in higher income countries to prevent spread of this significantly under-reported pathogen.

Keywords: Epidemiology; Giardia; Giardiasis; Outbreaks; Zoonoses.

Publication types

Review