Nested PCR targeting intergenic spacer (IGS) in genotyping of Giardia duodenalis isolated from symptomatic and asymptomatic infected Egyptian school children

Abstract

Distinct sequences of Giardia duodenalis assemblages raised the hypothesis that certain assemblages may contribute to its clinical outcome. However, sequences analysis is time consuming, expensive, and needs many manual operations. Nested PCR targeting intergenic spacer (IGS) region was applied successfully to genotype G. duodenalis. This study aimed to identify the prevalence of G. duodenalis assemblages among giardiasis school children and its relation to the presence of symptoms using nested IGS/PCR. Of 65 microscopically confirmed Giardia-positive samples, 65 samples were genotyped proving high sensitivity (92.3%) of IGS/PCR. Negative IGS/PCR samples were also negative for β-giardin gene. Subassemblage AI was the commonest with 66.6% (20/30) among asymptomatic children compared to 53.3% (16/30) of symptomatic, while assemblage B was found in 40% (12/30) of symptomatic compared to 20% (6/30) of asymptomatic. The difference was significant. AII was only found in asymptomatic with 13.4% (4/30), while mixed infections (AI&B) were recorded only in 6.6% (2/30) of symptomatic group. A significant relation was found between younger children susceptibility for AI and B infections as presented in 77.7 (12/16) and 83.3% (10/12) of symptomatic, respectively, and 80 (16/80) and 33.4% (2/4) of asymptomatic, respectively. Significant relations were found between AI with intermittent diarrhea and B with chronic. A significant relation was found between assemblage distributions and heavy infection intensity. In conclusion, higher incidence of assemblage B among symptomatic children compared to asymptomatic could denote its possible pathogenic potential.

A Comprehensive Review of Common Bacterial, Parasitic and Viral Zoonoses at the Human-Animal Interface in Egypt

“…In humans, between 2001 and 2017, Giardiasis has been reported in different localities of Egypt and the prevalence rates ranged between 10% and 75% [ 152 , 192 , 204 , 206 , 209 , 210 , 211 , 212 , 213 , 214 , 215 , 216 ]. The most prevalent G. duodenalis genotypes were assemblage A and B and to lesser extent assemblage E among diarrheic patients in Egypt [ 204 , 205 , 206 , 209 , 214 , 215 , 217 , 218 , 219 , 220 ]. The prevalence of G. duodenalis was high in rural areas more than in urban areas which was attributed to the higher exposure to multiple risk factors such as poor water supply, poor sanitation, and presence of animals [ 204 ].…”

Giardia duodenalisin the UK: current knowledge of risk factors and public health implications

“…Asymptomatic individuals with the disease show no signs of infection however will still shed the parasite in their feces. Differences in the symptomology are now suspected to be due to assemblage variance, with assemblage B of the parasite thought to result more commonly in symptomatic infection, compared with assemblage A, which appears to do this less so (Hussein et al ., 2017; Puebla et al ., 2017). Host factors such as age, immune status and gut fauna are thought to be involved in the development of the infection.…”

“…The lack of complete homologies existing to date further highlights common doubts which appear when attempting to sub-genotype Giardia assemblages using these methods (Bonhomme et al ., 2011). Past and current approaches using intergenic spacer regions have proved successful recently, allowing both assemblage and sub-assemblage typing (Hussein et al ., 2017). The identification of novel target genes suitable for genotyping would be advantageous, along with more reliable methodologies when using tpi, β -giardin or gdh genotyping.…”

Asymptomatic protozoa community infections in humans from southwestern China

“…The presence and proportion of assemblages seems to presents spatiotemporal variations [40,41] although socio-economic factors have been also suggested as potential drivers for G.lamblia assemblage distribution [22]. Interestingly, assemblage's variance seems to be involved in clinical presentation and only assemblages A and B have been described as causative agents of human infection, with assemblage B resulting more frequently in symptomatic infection in endemic settings [21,42]. Regarding assemblage A, AI has been one of the commonest sub-assemblage reported in the literature although AII is considered the most pathogenic sub-assemblage in humans [17,43,44].…”