Abstract
Giardia duodenalis is one of the most common causes of diarrhea in humans with about 250–300 million cases per year. It is considered to be a species complex comprising of eight genetic assemblages (A to H), with assemblages A and B being the major causes of human infections. In this study we carried out genotypic characterization of G. duodenalis isolates detected in asymptomatic school-going children aged 3–16 years. Between May and September 2017, a total of 329 fecal samples were collected from school-going children from Chawama compound of Lusaka City and were screened for Giardia by microscopic examination. All microscopically positive fecal samples were analyzed by semi-nested polymerase chain reaction (PCR) targeting the glutamate dehydrogenase (gdh) gene. Genotyping of amplified PCR products was conducted by restriction fragment length polymorphism (RFLP) and DNA sequence analysis. Microscopically, Giardia was found in 10% (33/329) of fecal samples. The PCR-RFLP analysis of the gdh gene revealed assemblages A and B in 27.3% (9/33) and 72.7% (24/33), respectively. Furthermore, analysis with restriction enzymes identified sub-assemblages AII (27.3%, 9/33), BIII (12.1%, 4/33), BIV (51.5%, 17/33) and mixed infections of BIII and BIV (9.1%, 3/33). Phylogenetic analysis showed the clustering of 27.6% (8/29) and 72.4% (21/29) of Zambian Giardia gdh gene sequences into assemblages A and B, respectively. This study has revealed the presence of both assemblage A and B and that spread of G. duodenalis in school-going children appears to be mostly through anthroponotic transmission. To our knowledge, this is the first report of genotypic characterization of G. duodenalis identified in Zambia.
Highlights
Giardia duodenalis is a protozoan parasite which is responsible for 250–300 million symptomatic human infections annually, with less developed communities being the most afflicted (Einarsson et al, 2016)
G. duodenalis assemblages can be distinguished based on single nucleotide polymorphism and/or genotypic analysis of the ssu – rRNAbeta, (β)-giardin, triose phosphate isomerase and glutamate dehydrogenase genes (Caccio and Ryan, 2008)
Children who had not had diarrhea in the month preceding the date of sample collection were considered in this study, whilst those who had at least one bout of diarrhea in the same period were excluded from the study
Summary
Giardia duodenalis is a protozoan parasite which is responsible for 250–300 million symptomatic human infections annually, with less developed communities being the most afflicted (Einarsson et al, 2016). The infection can manifest as acute diarrhea, which may become chronic if not treated, with majority of infections being asymptomatic (Certad et al, 2017). Chronic infection is associated with malabsorption which can lead to subsequent weight loss and wasting in children (Squire and Ryan, 2017). G. duodenalis is reported to be associated with cognitive impairment in school-age children (Berkman et al, 2002). There have been recent reports of humans being infected with assemblages E and F (AbdelMoein and Saeed, 2016; Fantinatti et al, 2016; Gelanew et al, 2007; Zahedi et al, 2017). G. duodenalis assemblages can be distinguished based on single nucleotide polymorphism and/or genotypic analysis of the ssu – rRNAbeta, (β)-giardin (bg), triose phosphate isomerase (tpi) and glutamate dehydrogenase (gdh) genes (Caccio and Ryan, 2008)
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