Abstract
It is estimated that faecal-orally transmitted diseases are common in Afghanistan, as a consequence of poor hygienic standards of life and widespread contamination of water and food with both human and animal faeces. However, there is little information in the literature concerning infections caused by intestinal parasites in the Afghan population. In this study, we report the occurrence of Giardia intestinalis assemblages (A and B) in formalin-fixed stool samples collected from 245 Afghan schoolchildren living in Ghazni Province in eastern Afghanistan. Detection of the parasite’s DNA and genotyping was performed using real-time PCR, specific to the β-giardin gene of G. intestinalis. Positive results were recorded in 52 (21.2%) samples. Genotyping was successful in 39 faecal samples and showed the predominance of assemblage B of G. intestinalis in this population (15 assemblage A and 24 assemblage B). Co-infection with both genotypes A and B was detected in four samples. Additionally, we evaluated the effect of 10% buffered formalin fixative on the detection of G. intestinalis DNA using real-time PCR and nested PCR characterised by different lengths of PCR products (74 and 479 bp, respectively). The human faeces containing the Giardia cysts were tested for 16 weeks. Amplification of G. intestinalis DNA with real-time PCR was possible up to 6 weeks of preservation of stool sample in formalin, compared to only 2 weeks with nested PCR. This suggests that real-time PCR is a more suitable tool in cases where stool samples have to be kept in formalin for longer periods of time.
Highlights
Giardia intestinalis is a protozoan parasite belonging to the Giardia genus which causes gastrointestinal diseases in humans and animals worldwide (Karanis and Ey 1998; Smith et al 2007; Reynolds et al 2008; Ryan and Cacciò 2013)
Prior to the investigations of Giardia strains in the Afghan schoolchildren, we evaluated the effect of 10% buffered formalin fixative on the detection of G. intestinalis DNA using real-time PCR and nested PCR
Among 245 faecal samples collected from Afghan children, DNA of G. intestinalis was detected in 52 (21.2%) samples using real-time PCR (Table 2, Fig. 3)
Summary
Giardia intestinalis is a protozoan parasite belonging to the Giardia genus which causes gastrointestinal diseases in humans and animals worldwide (Karanis and Ey 1998; Smith et al 2007; Reynolds et al 2008; Ryan and Cacciò 2013). It is a species complex consisting of eight genetically distinct genotypes (assemblages A–H) which differ in terms of host specificity, of which two (A and B) have been commonly reported to be associated with human infections (Homan 1992; Mayrhofer 1995; Nash 1995; Andrews et al 1998; Karanis and Ey 1998; Thompson 2000). At least 913 outbreaks associated with the waterborne transmission of protozoan parasites have been reported, of which G. intestinalis has been responsible for at least 340 (37.2%) (Karanis et al 2007; Baldursson and Karanis 2011; Efstratiou et al 2017)
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