الفهرس 
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Abstract
Vegetables are essential for good health, and they form a major component of human diet in every family, however ingestion of raw vegetables represent an important mean of transmission for several parasitic infectious diseases. There has been an increase in the number of reported cases of food-borne illness linked to fresh vegetables. The transmission of intestinal parasitic infection is caused by the frequent use of untreated human or animal dung as manure in cultivation.
The aim of this study was to determine the extent of parasitic contamination of raw vegetables distributed in markets of Benha city, Qalyubia Governorate, Egypt and the effect of disinfection on these parasites.
(530) vegetable samples were collected from Benha city markets, included five types of green vegetables, the vegetable samples were: parsley (102) samples, lettuce (101) samples, leek (108) samples, green onion (103) samples and watercress (116) samples along the period of study (September 2012 to August 2013). Each vegetable sample was washed in one liter of physiological saline solution then each washing solution was examined using flotation concentration technique, direct smear, iodine stained smear and Modified Ziehl Neelsen stain to detect eggs, larvae, cysts, oocysts and spores.
To study the effect of disinfection on the detected parasites, two disinfectants were used: acetic acid 5% and potassium permanganate 24mg/L for 20 and 30 minutes. The effect of disinfection on parasites was examined by 0.2% trypan blue stain to detect the viability of different parasites and by light and Scanning Electron Microscopy examination; to detect the morphological changes of different parasites due to the effect of disinfection. To study the effect of disinfection on physical properties of some raw vegetables, samples of vegetable were soaked separately in acetic acid 5% and potassium permanganate 24mg/L for 20 and 30 minutes.
Results revealed that out of (530) vegetable samples, (157) vegetable samples were found to be contaminated with different types of the parasites.The detected parasites included: Giardia lamblia cysts, Entamoeba spp. cysts, Enterobius vermicularis eggs, Hymenolepis nana eggs, Hymenolepis diminuta eggs, Ascaris lumbricoides eggs and helminth larvae. The prevalence rate of vegetable samples contaminated with different parasites was (29.6%).
Contamination of vegetable samples by protozoa was (15.6%), helminth eggs (10.4%) and helminth larvae (3.6%) of total examined vegetable samples. It was found that Giardia lamblia cysts considered the highest prevalent parasite detected in raw vegetables (8.8%), followed by Entamoeba spp. cysts (6.8%), Entreobius vermicularis eggs (4.9%), helminth larvae (3.6%), Hymenolepis nana eggs (2.8%), Hymenolepis diminuta eggs (2.1%), Ascaris lumbricoides eggs were the least detected (0.6%) of total examined vegetable samples.
Lettuce was found to have the highest parasitic contamination (45.5%), followed by watercress (41.3%), parsley (34.3%), green onion (16.5%), whereas leek showed the least parasitic contamination (10.2%). Contamination by Giardia lamblia cysts was highest on lettuce (15.8%) and lowest in leek (1.9%), while Entamoeba spp. cysts was highest in lettuce samples (13.9%) and lowest in green onion (1.9%). Enterobius vermicularis eggs were highest in watercress (9.4%) and lowest in leek (0.9%). Hymenolepis nana eggs were highest in watercress (6%) and lowest in lettuce (0.9%). There were no leek samples contaminated with Hymenolepis nana eggs. Hymenolepis diminuta eggs were found to be highest in lettuce (3.9%), and lowest in leek samples which were (0.92%). Ascaris lumbricoides eggs were highest in lettuce (1.9%), followed by watercress (0.9%), while it were not detected in parsley, green onion or leek samples.
The highest rate of parasitic contamination in vegetable samples in different seasons was found in summer (49%); followed by autumn (27.8%), spring (26.9%). The least contamination rate was found in winter (10.8%).
Highest rates of contamination by Giardia lamblia, Entamoeba spp. cysts, Helminth larvae, Enterobius vermicularis eggs were detected in summer (44.6%), (50%), (47.3%) and (42.3%) respectively while the lowest contamination rates by the same parasites were detected in winter (8.5%), (8.3%), (5.2%) and (15.3%) respectively. Hymenolepis nana eggs were highest in summer (53.3%), but it were not detected in winter. The highest rate of contamination by Hymenolepis diminuta eggs was in summer (54.5%), and the lowest contamination rate was in spring (9%). Ascaris lumbricoides eggs were detected only in summer (100%) and were not detected in other seasons.
According to seasonal variability, the contamination rate of lettuce with Giardia lamblia cysts was highest in spring (44.4%), and there was no contamination in winter, also contamination rate of watercress with Giardia lamblia cysts was highest in winter (50%) and was lowest in spring (23.1%). Contamination rate of parsley with Giardia lamblia cysts was highest in winter (66.7%) and lowest in autumn (28.6%). Contamination rate of green onion samples with Enterobius vermicularis eggs was highest in winter (100%), while Giardia lamblia cysts were highest in spring (66.7%). Contamination rate of leek samples with helminth larvae was highest in autumn (100%), followed by summer (37.5%). There were no helminth larvae contaminate leek samples in winter nor spring.
After exposure to acetic acid 5% for 20 and 30 minutes the percentage of viable eggs of Hymenolepis diminuta was (60.8%) and (47.8%) respectively. While in the corresponding non-treated parasite control it was (97.8%). Percentage reduction in viability was (37.8%) at 20 minutes and (51.1%) at 30 minutes.
As regards Hymenolepis nana eggs, after exposure to acetic acid 5% for 20 and 30 minutes, the percentage of viable eggs was (58.1%) and (54.8%) respectively. While in the corresponding non-treated parasite control it was (93.5%). Percentage reduction in viability was (37.9%) at 20 minutes and (41.4%) at 30 minutes.
As regards Giardia lamblia cysts, after exposure to acetic acid 5% for 20 and 30 minutes, the percentage of viable cysts was (72.2%) and (66.7%) respectively, while in the corresponding non treated parasite control it was (96.3%). Percentage reduction in viability was (25%) at 20 minutes and (30.8%) at 30 minutes.
The percentage of viable cysts of Entamoeba spp. cysts was (71.6%) and (70.1%) at 20 and 30 minutes exposure to acetic acid 5% respectively. While in the corresponding non-treated parasite control it was (95.5%). Percentage reduction in viability was (25%) at 20 minutes and (26.6%) at 30 minutes.
Enterobius vermicularis eggs treated with acetic acid 5% showed decrease in their viability as the percentage of viable eggs was (91.9%) which was equall at both times of exposure (20 and 30 minutes) compared with the viability in the corresponding non-treated parasite control (100%). Percentage reduction in viability was (8.1%) at 20 minutes and 30 minutes.
After exposure to potassium permanganate 24mg/L for 20 and 30 minutes, the percentage of viable eggs of Hymenolepis diminuta was (54.3%) and (41.3%) respectively. While in the corresponding non-treated parasite control it was (97.8%). Percentage reduction in viability was (44.4%) at 20 minutes and (57.8%) at 30 minutes.
As regards Hymenolepis nana eggs, after exposure to potassium permanganate 24mg/L for 20 and 30 minutes, the percentage of viable eggs was (67.7%) and (61.3%) respectively. While in the corresponding non-treated parasite control it was (93.5%). Percentage reduction in viability was (27.6%) at 20 minutes and (34.5%) at 30 minutes.
The percentage of viable cysts of Entamoeba spp. cysts was (76.1%) and (73.1%) after 20 and 30 minutes exposure to potassium permanganate 24mg/L respectively. While in the corresponding non-treated parasite control it was (95.5%). Percentage reduction in viability was (20.3%) at 20 minutes and (23.4%) at 30 minutes.
As regards Enterobius vermicularis eggs treated with potassium permanganate 24mg/L for 20 and 30 minutes showed decrease in their viability as the percentage of viable eggs was (81.1%) and (78.4%) respectively compared with 100% in the corresponding non-treated parasite control. Percentage reduction in viability was (18.9%) at 20 minutes and (21.6%) at 30 minutes.
As regards Giardia lamblia cysts, after exposure to potassium permanganate 24mg/L for 20 and 30 minutes, the percentage of viable cysts was (85.2%) and (75.9%), while in the corresponding non treated parasite control it was (96.3%). Percentage reduction in viability was (11.5%) at 20 minutes and (21.2%) at 30 minutes.
Percentage reduction in viability of some parasites after exposure to acetic acid 5% and potassium permanganate 24mg/L for 20 and 30 minutes (R1&R2) have no significant statistical difference (P value < 0.05).
There were some morphological changes due to exposure to acetic acid 5% and potassium permanganate 24mg/L detected by light and Scanning Electron Microscopy including irregularities or shrunkage of the cyst wall and deformity of the egg shell.
Exposure of raw green vegetables (parsley, lettuce, leek, green onion and watercress) to both acetic acid 5% and potassium permanganate 24mg/L for (20 and 30 minutes) show normal taste, smell, consistency with no color changes except slightly vinegar smell in case of acetic acid which is accepted as vinegar is used with different food like salad.