The controversies surrounding Giardia intestinalis assemblages A and B

• Published in: Current research in parasitology & vector-borne diseases Vol. 1; p. 100055
• Main Authors: Zajaczkowski, Patricia, Lee, Rogan, Fletcher-Lartey, Stephanie M., Alexander, Kate, Mahimbo, Abela, Stark, Damien, Ellis, John T.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2021; Elsevier
• Subjects: Assemblages; genotype; genotyping; Giardia lamblia; Giardiasis; humans; loci; Molecular biology; parasitology; public health; Review; Typing; Zoonotic potential; Zoonotic potential; Assemblages; Typing; Molecular biology; Giardiasis
• ISSN: 2667-114X; 2667-114X
• DOI: 10.1016/j.crpvbd.2021.100055

Giardiaintestinalis continues to be one of the most encountered parasitic diseases around the world. Although more frequently detected in developing countries, Giardia infections nonetheless pose significant public health problems in developed countries as well. Molecular characterisation of Giardia isolates from humans and animals reveals that there are two genetically different assemblages (known as assemblage A and B) that cause human infections. However, the current molecular assays used to genotype G. intestinalis isolates are quite controversial. This is in part due to a complex phenomenon where assemblages are incorrectly typed and underreported depending on which targeted locus is sequenced. In this review, we outline current knowledge based on molecular epidemiological studies and raise questions as to the reliability of current genotyping assays and a lack of a globally accepted method. Additionally, we discuss the clinical symptoms caused by G. intestinalis infection and how these symptoms vary depending on the assemblage infecting an individual. We also introduce the host-parasite factors that play a role in the subsequent clinical presentation of an infected person, and explore which assemblages are most seen globally. [Display omitted] •A review of the epidemiology and molecular characteristics of Giardia intestinalis assemblages A and B.•Both assemblages have been found in humans and animals suggesting zoonotic potential.•Currently there is no clear correlation between assemblages and specific symptoms.•Using single-locus typing for genotyping G. intestinalis is unreliable.•A MLST system targeting tpi and IGS regions is encouraged when typing G. intestinalis.