Investigation of parasitic contamination of salad vegetables sold by street vendors in city markets in Damascus, Syria

Abstract

Monitoring parasitic contamination in raw vegetables used in salads is an important measure in controlling the occurrence of gastroenterological diseases, which may be life-threatening. This study aimed to inspect the parasitological contamination of some raw vegetables used in salads. Eight commonly consumed vegetable types were purchased from street vendors in the city markets. Vegetables were washed and the sediments were obtained for microscopic examination. Genomic DNA was isolated from contaminated samples. Our result showed that 34.4% of the studied samples were contaminated with one or more species of parasites. Lettuce was the most commonly contaminated vegetable type (29.5%), while tarragon leaves showed the lowest level of contamination (2.3%). The risk of contamination was significantly higher in lettuce samples in comparison with the other samples studied. Giardia duodenalis was the most prevalent parasite detected (38.6%) and was abundantly found in lettuce isolates (23.5%). Molecular typing revealed that all Giardia samples found in the contaminated specimens belonged to Assemblage B. Blastocystis spp. were the second most prevalent parasite in samples (29.5%), they were frequently detected in lettuce leaves (30.8%). Other parasites were found in low frequencies. The high level of parasitic contamination found in our study indicates an urgent need to identify the sources of contamination and to monitor irrigation water and ensure its cleanliness.

Keywords: Contamination; Damascus; Giardia; Intestinal parasites; Vegetables.

Fig. 1

Iodine stained parasites found in this survey. a. Giardia cysts (arrows); b. Entamoeba spp. cysts (arrows); c. Ascaris lumbricoides ova; d. Strongiloides spp. larvae. Original magnification: 400×.

Fig. 2

Agarose gel electrophoresis of the PCR products after HaeIII enzyme digestion. Lane 1 uncut β-giardin PCR product, lane 2 represent assemblage B (our study sample) (150, 117–113, 84, 26–24 bp). Lanes 3–5: positive controls [lane 3: assemblage B, lane 4: assemblage A (200, 150, 117–113, 50 bp), lane 5 assemblage (A + B) as mixed control]. M: Molecular marker.