الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Water contains numerous pathogenic microorganisms as bacteria, viruses, fungi and protozoan parasites. Cryptosporidium spp., G. intestinalis, E. histolytica, B. hominis, and FLA such as Acanthamoeba spp. and N. foweleri are the most prevalent water-borne pathogenic protozoan parasites. Our current study is based on both microscopy and molecular approach (PCR and sequencing). A total of 190 pooled water samples (25 L each sample) were collected from different water sources as follow flowing water, wastewater, ground water, water tank and tap water from 5 different districts; Mansoura, Sandoub, Gedella, Mit-Mazah and Aga in Dakahlia governorate during the period extended from October 2019 to October 2021.Water samples were processed by flocculation using alumnium sulphate (Al2(SO4)3) and the parasites in water samples were concentrated using the modified Wisconsin sucrose flotation method. The concentrated samples were examined under light microscopy (X10 and X40). The harvested protozoan parasite positive samples (n=62) were subjected to DNA extraction by QIAGEN DNeasy® Plant Mini Kit (Qiagen Valencia, USA), after that PCR reaction using specific primers for the protozoan parasites Cryptosporidium spp., G. intestinalis , B. hominis (SSU rDNA gene at 479 bp), Acanthamoeba spp. (18S rDNA gene at 423-551 bp) , Naegleria spp. and N. foweleri from various water sources as well as the sharp bands were undergone to sequencing reaction to know genotypes and / or subtypes of those protozoan parasites. The obtained sequences were subjected to data analysis to compare with other sequences to know their identity percent and submitted to GenBank to take accession numbers and phylogenetic trees and networks to study their relationship. Microscopic examination revealed a parasite prevalence of 32.6% (62/190) in pooled water samples; additionally, the frequency of parasites in variety of water sources were detected in flowing water and wastewater samples (50% for each) followed by ground water (40%) and finally water tank and tap water (10% for each). The highest infection rate of waterborne parasites was detected in Mit-Mazah district (23/48, 60.5%) followed by Gedella (17/38, 44.7%), then Sandoub (13/38, 34.2%), Aga (5/38, 13.1%) and lastly Mansoura (4/38, 10.5%) in Dakahlia governorate.Cryptosporidium spp. (4.7%), Giardia spp. (1.5%), Blastocystis spp. (2.1%), Acanthamoeba spp. (12.6%), E. histolytica (0.5%), Eimeria spp. (13.1%), Isospora spp. (4.2%) based upon microscopy.Regarding seasonal variations, A gradual rise in a waterborne parasites infection was noticed in autumn season (19 /47, 40.4%), then reached at its peak in winter season (25 / 48, 52%), then the infection rate began to decrease gradually in spring season (10 / 47, 21.2%) and the lowest DROP in the infection in summer season (8 / 48, 16.6%). Overall occurrence of the three protozoa (Acanthamoeba, Naegleria and Blastocystis) in various water sources from Egypt, Acanthamoeba had the highest statistically significant (p-value = 0.0035) with a mean prevalence of 43.03% approximately double that of Naegleria (23.79%), while Blastocystis exhibited the lowest occurrence (2.01%). The majority of samples tested in the previous surveys took mostly from tap water, River Nile, swimming pools and drinking water treatment plants (WTP). These four water sources had high prevalence of Acanthamoeba ranging from 37.97 to 60.71% with no significant variations. The mean Acanthamoeba prevalence for raw water was 60.71%, while finished water was 22.62% significant variation (p-value = 0.00043) was detected; nonetheless, the effectiveness of water filtration for Acanthamoeba occurrence in WTPs in Egypt was estimated in 60.34%. A high Acanthamoeba mean prevalence (51.42%) was found from water tank. the mean prevalence of Naegleria was the highest in River Nile samples (26.69%), which varied significantly (p-value = 0.01593) from that estimated for tap water samples (12.88%), but not significantly differed (p-value = 0.06162) from that detected for swimming pool samples (20.10%).Molecular analysis of 62 harvested pooled water samples documented the presence of Acanthamoeba spp. (38.7%) followed by Cryptosporidium spp. (14.5%), Naegleria spp. (9.6%), then B. hominis (6.4%), G. intestinalis (4.8%) and N. foweleri (3.2%). Sequencing reactions (20 samples for Acanthamoeba spp. and one sample for B. hominis) were subjected to data analysis to compare with other sequences, The obtained data revealed that 20 isolates (7 haplotypes) belong to Acanthamoeba spp. (T3 isolated from 18 samples) and (T4 found in 2 samples) but only one strain of B. hominis belonging to Blastocystis subtype 2 has been found (ST2), then submitted to GenBank to take their accession numbers.