Molecular Characterization of Giardia duodenalis in Children in Kenya

Abstract

Background: Giardia duodenalis is an important intestinal protozoan in humans worldwide with high infection rates occurring in densely populated and low resource settings. The parasite has been recorded to cause diarrhea in children. This study was carried out to identify G. duodenalis assemblages and sub-assemblages in children presenting with diarrhea in Kenya.

Methods: A total of 2112 faecal samples were collected from children aged ≤ 5 years and screened for the presence of Giardia cysts using microscopy. A total of 96 (4.5%) samples were identified as Giardia positive samples and were genotyped using glutamate dehydrogenase (gdh), triose phosphate isomerase (tpi) and β-giardin loci.

Results: The three markers successfully genotyped 72 isolates and grouped 2 (1.4) isolates as Assemblage A, 64 (88.9) as Assemblage B and 7 (9.7%) consisted of mixed infections with assemblage A and B. A further analysis of 50 isolates using GDH Polymerase Chain Reaction and Restriction Fragment Length Polymorphism (PCR-RFLP) categorized 2 assemblage A isolates as sub-assemblage AII while 6 and 14 assemblage B isolates were categorized into sub-assemblage BIII and BIV respectively. A mixed infection with sub-assemblage BIII and BIV was recorded in 28 isolates. Over half (55.6%) of Giardia infections were recorded among the children between 13 to 48 months old.

Conclusion: This paper reports the first data on the assemblages and sub-assemblages of Giardia duodenalis in children representing with diarrhea in Kenya.

Keywords: Children; Genotyping; Giardia; Informal settlements; Kenya; Subtyping.

Fig. 1

Evolutionary relationships of G. duodenalis isolated from selected test samples. The evolutionary history was inferred using the Neighbor-Joining method [44]. The optimal tree with the sum of branch length = 1.10022 is shown. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (2000 replicates) are shown next to the branches (Felsenstein et al., 1985). The evolutionary distances were computed using the p-distance method (Nei M et al., 2000) and are in the units of the number of base differences per site. The analysis involved 50 nucleotide sequences. All positions containing gaps and missing data were eliminated. There were a total of 289 positions in the final dataset. Evolutionary analyses were conducted in MEGA5 [20]. The samples are coded according to where they were recruited from and patient number. M1070 refers to Mukuru patient (outpatient) number 1070, MB108 refers to Mbagathi patient (inpatient) number 108