الفهرس 
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Abstract
Giardia duodenalis is a flagellated protozoan that colonizes the upper small bowel and adheres to the apical surface of the epithelium. Giardiasis is acquired through ingestion of cysts by the faeco-oral route either directly or indirectly. It represents a public health problem in the developing world where inadequately treated water is consumed by the majority of people. Giardia cysts can survive in aquatic environments for as long as 2–3 months with gradual temperature-dependent inactivation. They are more resistant than enteric bacteria to oxidative disinfectants such as chlorine. Transmission through ingestion of cysts in contaminated water plays an important role in dissemination of infection. Despite efforts directed to water quality management, water related outbreaks of giardiasis have been repeatedly reported from different countries (Pons et al., 2015; Efstratiou et al., 2017b). Understanding the impact of water contamination on transmission of G. duodenalis in a locality is needed to set priorities for control.
The aim of the present work to investigate the role of water supply in transmission of Giardia infection through detection and genotyping of G. duodenalis in diarrheic children and water sources in two villages of El-Behira Governorate (Egypt).
A total of 100 diarrheic children (50 children from each village) attending the local health units were included in the study during the period from February 2018 to September 2018. Data on potential risk factors for Giardia infection were recorded and a single stool sample was collected and examined parasitologically. Thirty drinking water samples were collected from the domestic water taps of the two villages (15 samples in each village) and examined microscopically for protozoal contamination. Besides, ten raw water samples were collected from canals passing through the villages. Microscopically positive stool samples and all water samples were examined by two different PCR protocols for amplification of Giardia gdh and tpi genes and genotyping of the isolates.
In village A; 32 % of the studied children were < 5 years old, while 68 % were ≥ 5 years. In village B; 44 % of the studied children were < 5 years, and 56 % were ≥ 5 years. Regarding gender of participating children, 66 % of the sample in village A, and 60 % in village B were males. The study revealed that 49 out of 100 children had intestinal parasitic infection. The rate of parasitic infection was significantly higher among children in village B (64%) compared to children in village A (34 %). Among the 50 participating children in village A, G. duodenalis was the most prevalent among all protozoa (14%), followed by Blastocystis spp. and E. histolytica / E. dispar complex (6% each). The non-pathogenic protozoa, Entamoeba coli were detected in 2% of children. As regards intestinal helminthes, Hymenolepis nana was found in 4% of children while Ancylostoma spp. was found in 2%. Among the 50 participating children in village B; again G. duodenalis was the most prevalent (34 %), followed by Blastocystis spp. (18%). The E. histolytica / E.dispar complex was found in 12% and the non-pathogenic Entamoeba coli were found in 4%. Regarding helminthes, Enterobius vermicularis and Schistosoma mansoni were detected in equal percentages (4% each) while A. lumbricoides and H.nana were found in lower percentages (2% each). A statistically significant difference was observed between Giardia infection rates in village A (14%) and village B (34%). No significant difference was observed for the other parasites. In village B, eight children had mixed parasitic infection.
Out of 30 drinking water samples (including direct tap water and filtered water), protozoal contaminants were detected microscopically in 4 samples (13.3 %). Protozoa were not detected in water samples filtered by domestic filters (n=3) while 14.8 % of tap water samples (4 out of 27 samples) showed protozoal contamination. In village A, E.histolytica/ E.dispar was detected in one of 15 collected drinking water samples (6.7%). In village B, E.histolytica/ E.dispar complex, Entamoeba coli and Blastocystis spp, were detected (each in one sample). There was no statistically significant difference between the two villages regarding the detection rate of different protozoa in water samples.
Abdominal Pain was the most frequently reported symptom among infected and non-infected children (95.8 % and 82.9 % respectively). Moreover, 45.8 % of infected children and 36.8 % of non-infected children suffered from nausea. Vomiting: was present in 4.2 % of infected children compared to 14.5 % of non-infected children. The difference was not statistically significant. On the other hand, loss of appetites was more common among infected compared to non-infected children (70.8 versus 56.6 %). Fever was present in 20.8 % of infected and 13.2 % of non-infected children. The duration of diarrhea ranged in both Giardia-infected and non-infected children from 1 to 7 days.
The rate of Giardia infection among diarrheic children <5 years was 18.4 % while the corresponding rate in older children was 27.4 %. It was found that the age had no statistically significant effect on Giardia infection among children. As regards gender, 25.4 % of males and 21.6 % of females had Giardia infection; the difference was not statistically significant.
Children in village B had 3 times higher risk of Giardia infection compared to children in village A. It was found that the place of residence had statistically significant effect on Giardia infection.
The rate of Giardia infection was lower in children who usually wash their hands before eating (18.5%) compared to those who don’t (30.4%). However, the difference was not statistically significant.
Contact with animals, exposure to canal water, and attending day daycare centers were not associated with higher risk of Giardia infection.
Among the study participants, 81 children were using tap water for drinking while 19 children used water filtered by domestic filters. The rates of Giardia infection among these two groups were 25.9 % and 15.8 % respectively. Drinking water source had no statistically significant effect on Giardia infection.
PCR amplification of G. duodenalis gdh was successful in 16 out of 24 (66.6%) microscopically positive stool samples and in all raw water samples. NlaIV digestion of gdh PCR product obtained from the stool and raw water samples generated a pattern corresponding to sub-assemblage AII (bands at 70, 80, 90 and 120 bp). In all drinking water samples, amplification of gdh yielded negative results.
In all microscopically positive stool samples and all raw water samples, the tpi gene of assemblage A was successfully amplified using TPIA-PCR but tpi of assemblage B was not detected. Digestion of the TPIA-PCR product with Rsa I produced the characteristic diagnostic pattern of sub-assemblage AII with bands at 235 and 202 bp in all PCR positive samples. In all drinking water samples (including tap water and filtered water), no amplification was observed for tpi genes (tpi A and tpi B).