Prevalence and genotypic characterization of giardia duodenalis isolates and associated risk factors of infection from asymptomatic school-going children in Chawama, Lusaka district, Zambia.

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Tembo, Shadreck
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The University of Zambia
Giardia duodenalis (synonyms: G. lamblia, G. intestinalis) is a mammalian infective protozoan flagellate which infects humans. The genus Giardia consists of six species, namely G. agilis, G. ardeae, G. psittaci, G. microti, G. muris and G. duodenalis. Among these species, only G. duodenalis is known to infect several hosts, including humans. G. duodenalis is said to be a species complex comprising of eight genetic assemblages (A to H) and infection in humans being mainly caused by assemblages A and B. The purpose of this study was to determine prevalence and genotypic characterization of Giardia duodenalis isolates and associated risk factors of infection from asymptomatic school-going children in Chawama, Lusaka, Zambia. A cross-sectional study was conducted between May and September 2017. A total of 329 faecal samples were collected from school-going children in Chawama within Lusaka City. G. duodenalis isolates were detected in asymptomatic school-going children aged three to sixteen years. All microscopically positive faecal samples were analyzed by semi-nested polymerase chain reaction (PCR) targeting the glutamate dehydrogenase (gdh) gene. Genotyping of amplified PCR products were further analyzed by restriction fragment length polymorphism (RFLP) and DNA sequence analysis. The microscopic examination of faecal samples showed 10% (33/329; 95% CI = [0.07 – 0.13]) prevalence of G. duodenalis infection. The infection amongst girls was 12% (22/183; 95% CI = 5 – 61) and 7.5% (11/146; 95% CI = [0.39 – 0.49]) amongst boys. Giardia infections were more observed in children enrolled in public schools (15.4%, 19/123; 95% CI = [0.32 – 0.43]) than those in community schools (6.8%, 14/206; 95% CI = [0.57 – 0.68]) and infection was significantly (p = 0.011) associated with the type of school. The PCR-RFLP analysis revealed assemblages A and B in 27.3% (9/33; 95% CI = [0.14 – 0.46]) and 72.7% (24/33; 95% CI = [0.54 – 0.86), respectively. Furthermore, analysis with restriction enzymes identified sub-assemblages AII (27.3%, 9/33; 95% CI = [0.14 – 0.46]), BIII (12.1%, 4/33; 95% CI = [0.04 – 0.29), BIV (51.5%, 17/33; 95% CI= [0.34 – 0.69) and mixed BIII/BIV (9.1%, 3/33; 95% CI = [0.03 – 0.26]) infections. Assemblage B and sub-assemblage BIV infection was predominant in this study. However, no statistical significance (p > 0.05) was found between G.duodenalis assemblages/sub-assemblages and sex or age. The phylogenetic analysis showed the clustering of 27.6% (8/29; CI = [0.14 – 0.48]) and 72.4% (21/29; CI = [0.52 – 0.86]) of Zambian Giardia gdh gene sequences into assemblages A and B, respectively. This study provides the first report on genotypic characterization of G. duodenalis infection in children in Chawama, Lusaka District, Zambia. The study revealed the circulation of assemblages A and B infection, which were further split into sub-assemblages AII, BIII and BIV. Mixed infections were observed between BIII/BIV. The assemblages detected could suggest anthroponotic transmission. The prevalence of Giardia infection was lower compared to previous surveys done in Zambia. Giardia infection was significantly associated with the type of school that children attended. Therefore, control measures aimed at improving hygiene in schools and the communities, along with education campaigns could help in curbing giardiasis.
Thesis of Master of Science in Medical Parasitology.