Pathogenetic features of Giardia lamblia, achievements and prospects for genotyping the protozoan

Giardiasis does not lose its relevance, despite the active development of such areas of medicine as diagnosis, treatment and prevention. There are 8 genetic groups of the protozoan Giardia lamblia from A to H. Genetic complexes A and B have long been associated with the occurrence of invasion in humans, when others - from C to H - were detected only in specific animal hosts. Recent data indicate that this distribution is conditional and the circulation of G. lamblia genetic assemblies is a more complex and multifactorial process. In turn, phenotypically indistinguishable groups A and B also have significant genetic differences and are divided into subgroups AI, AII and AIII, as well as BIII and BIV. In many scientific studies, the main method to establish the belonging of G. lamblia to a particular assembly, along with partial or full genome sequencing, is multilocus determination of restriction fragment length polymorphisms using «traditional» genes, such as beta-giardin (bg), triosephosphate isomerase (tpi) and glutamate dehydrogenase (gdh). Intensive searches are conducted to identify new targets suitable for identifying genetic groups.

Due to the lack of standardized approaches to molecular genotyping of the causative agent of giardiasis, the stage of accumulating knowledge about its genetic diversity continues. This information is important for understanding the relationships between genetic complexes of G. lamblia and clinical manifestations, as well as long-term consequences of the disease; pathogenesis and interaction between pathogens during co-infection with different genetic assemblies, and also assessment of the contribution of each of them to the infectious process, as well as the potential for the accumulation of genetic recombination mutations and their level of prevalence in age groups or territories. The review presents latest data on the current state of knowledge about the genetic diversity of the causative agent of giardiasis and its pathogenetic features, and also evaluates the prospects for improving genotyping of G. lamblia.

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