The Prevalence of Parasitic Contamination of Vegetables Consumed in Malayer City, West of Iran, in 2014

Khadije Rahmati; Mohammad Fallah; Amir Hossein Maghsood; Tayebeh Shamsi-Ehsan; Mohammad Matini

doi:10.5812/ajcmi.42380

The Prevalence of Parasitic Contamination of Vegetables Consumed in Malayer City, West of Iran, in 2014

Khadije Rahmati ^{1 , 2} , Mohammad Fallah ² , Amir Hossein Maghsood ² , Tayebeh Shamsi-Ehsan ^{1 , 2} and Mohammad Matini ^{2 , *}

Authors Information

¹ Students Research Center, Hamadan University of Medical Sciences, Hamadan, IR Iran

² Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, IR Iran

Article information

Avicenna Journal of Clinical Microbiology and Infection: May 2017, 4 (2); e42380
Published Online: May 6, 2017
Article Type: Research Article
Received: September 18, 2016
Revised: December 6, 2016
Accepted: February 18, 2017
DOI: 10.5812/ajcmi.42380

To Cite: Rahmati K, Fallah M, Maghsood A H, Shamsi-Ehsan T, Matini M. et al. The Prevalence of Parasitic Contamination of Vegetables Consumed in Malayer City, West of Iran, in 2014, Avicenna J Clin Microb Infec. 2017 ;4(2):e42380. doi: 10.5812/ajcmi.42380.

Abstract

Results: The results showed that 14.6% of the vegetable samples were contaminated with various pathogenic (5.2%) and non-pathogenic (9.4%) parasites including protozoan cyst (3.7%), worm eggs (3.9%), and free-living larvae (7%). Giardia intestinalis (1.3%) and Entamoeba coli (2.3%) were the only protozoa that were detected in the samples. Frequencies of worm egg contamination were 1.6% for Taenia/Echinococcus spp., 0.5% for Dicrocoelium dendriticum, 0.8% for Toxocara spp., 0.5% for Hymenolepis nana, 0.3% for Trichostrongylus spp., and 0.3% for Fasciola spp. Leek was the most contaminated vegetable (31.7%), although there was no contamination in tarragon (P < 0.001). Significant relationships were observed between parasitic contamination and fertilizer (P = 0.018) and water consumption (P < 0.001) used in the farm vegetables.

Copyright © 2017, Hamadan University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

1. Background

Many societies, especially developing countries, consider intestinal parasitic infections as one of the major public health problems. These infections can cause serious medical and public health concerns, such as malnutrition and growth retardation of children, which can lead to a significant number of morbidity and mortality annually (1, 2). Millions of people suffer from parasitic infections in developing countries because of a shortage of personal health services and poor sanitation (3, 4). The prevalence of intestinal parasites is associated with the consumption of raw vegetables in these countries (5, 6). Food- and water-borne diseases are a major health issue in developing and even developed world (7). Fresh vegetables and fruits are an important source of nutrients and bioactive non-nutrient plant compounds, including vitamins, minerals, phytochemicals, especially antioxidants, and dietary fibers (8, 9). Daily use of fruits and vegetables can reduce the risk of chronic diseases, such as diabetes, cardiovascular disease, cancer, age-related decrease, and improve the function of the digestive system. Thus, nutritionists recommend eating fresh fruits and vegetables in daily diet (10). In order to preserve the flavor and nutrients of vegetables, they are usually consumed raw, which can increase the risk of infectious microbial diseases (3, 11). Consumption of raw vegetables is the most important way of transmission of intestinal parasites and is often considered as a major concern of public health. Protozoan cysts and worm eggs and larvae survive and develop in moist soil and environments of farm vegetables. These conditions are necessary for continuation of soil-transmitted parasite life cycle (7, 12). Vegetables can become contaminated mainly through irrigation and fertilization with untreated sewage water and animal manure, respectively, and may also occur during unsanitary post-harvest processing and marketing (3, 6, 13, 14).

2. Objectives

3. Methods

3.1. The Study Area

This cross-sectional study was performed from July to October 2014 in Malayer, the second largest city of a province with a population of over 287,982 (15) and an area of 3210 square kilometers. The study area lies between 48° 49' longitude east and 34° 17' latitude north with 1725 meters of altitude above sea level. The mean temperature and annual precipitation of the region are 13.2°C and 300 millimeters with about 50 freezing degree days per year (Available on site: http://www.iranhydrology.net/meteo.asp).

3.2. Sampling and Sample Preparation Procedure

Thirty-eight out of 197 farm vegetables were selected and a total of 383 samples were collected accidentally for parasitic contamination analysis. The samples comprised of ten types of vegetables, including leek, parsley, basil, tarragon, savory, coriander, mint, spring onion, cress, and radish. Each sample was gathered separately in a clean nylon bag and, after labeling and recording its characteristics, it was transferred to the parasitology research laboratory of Hamadan University of Medical Sciences. After cleaning and removing soil and coarse particles of the sample, 250 g of each individual sample was immersed in 1 L of normal saline solution containing detergent (1% sodium dodecyl sulfate and 1% Tween 80), followed by continuous shaking for 1 hour. The vegetable samples were removed and the remaining wash water was left to sediment about 12 hours. The supernatant water was discarded and the sediment was passed through sieve No 40 (425 μm), in order to eliminate large particles and detect larvae and free-living nematodes; the final 50-mL volume was then centrifuged at 500 g for 15 minutes (16). Finally, the sediment was examined by direct wet mount and zinc sulphate flotation method, according to the following procedure, after preparation of direct smear, the samples were scanned by a light microscope using low (100 ×) and high (400 ×) magnifications. The test was repeated several times for each sample and the remaining sediment was flooded with zinc sulphate solution centrifuged at 250 g for 5 minutes. After centrifugation, convex meniscus on the top of the tube was created by adding flotation solution and covered by a clean coverslip. After 30 minutes, the coverslip was cautiously removed and subjected to direct wet mount examination, as described above (3). Protozoan cysts identified by Lugol’s iodine and trichrome staining and also morphological characteristics were applied to differentiate larvae and eggs of helminths.

3.3. Data Analysis

Chi-squared (χ²) and Fisher’s exact test were used to evaluate the relationship between parasitic contamination and epidemiological factors studied with a probability (P) value of < 0.05, by using the SPSS statistical software, version 16.

4. Results

Out of 383 vegetable samples, 56 (14.6%) were contaminated with various pathogenic and non-pathogenic parasites including protozoan cysts (3.7%), worm eggs (3.9%), and free-living larvae (7%). The frequencies of pathogenic and non-pathogenic parasitic agents were 5.2% and 9.4%, respectively. The highest pollution of vegetables was associated with free-living larvae (7%) and the lowest belonged to Fasciola spp. (0.3%) and Trichostrongylus spp. (0.3%).

Frequency of parasitic contamination in different types of vegetables is indicated in Table 1. The highest prevalence of parasitic contamination was detected in leek (31.7%), while no contamination was observed in tarragon (P < 0.001).

Table 1. Distribution of Protozoan Cysts, Larvae, and Eggs of Helminths in Vegetables Used for Raw Consumption in Malayer City, Iran^a

Type	Vegetables Number	Pathogenic Parasites						Non-Pathogenic Parasites
		G. intestinalis spp.	D. dendriticum spp.	Toxocara spp.	H. nana spp.	Taenia spp.	Trichostrongylus spp.	Fasciola spp.	E. coli	FL	Total
Radish	38	2 (5.3)	1 (2.6)	0 (0)	1 (2.6)	0 (0)	0 (0)	0 (0)	1 (2.6)	3 (7.9)	8 (21.1)
Cress	38	1 (2.6)	0 (0)	0 (0)	0 (0)	1 (2.6)	0 (0)	0 (0)	1 (2.6)	6 (15.8)	9 (23.7)
Spring onion	38	1 (2.6)	0 (0)	2 (5.3)	1 (2.6)	1 (2.6)	0 (0)	0 (0)	0 (0)	4 (10.5)	10 (26.3)
Savory	38	1 (2.6)	0 (0)	0 (0)	0 (0)	1 (2.6)	0 (0)	0 (0)	0 (0)	0 (0)	1 (2.6)
Mint	38	0 (0)	0 (0)	1 (2.6)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	2 (5.3)	3 (7.9)
Basil	38	0 (0)	0 (0)	0 (0)	0 (0)	1 (2.6)	0 (0)	0 (0)	1 (2.6)	2 (5.3)	4 (10.5)
Parsley	38	0 (0)	1 (2.6)	0 (0)	0 (0)	1 (2.6)	0 (0)	0 (0)	2 (5.3)	0 (0)	4 (10.5)
Tarragon	38	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
Coriander	38	1 (2.6)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	3 (7.9)	4 (10.5)
Leek	41	0 (0)	0 (0)	0 (0)	0 (0)	1 (2.4)	1 (2.4)	1 (2.4)	3 (7.3)	7 (17.1)	13 (31.7)
Total	383	5 (1.3)	2 (0.5)	3 (0.8)	2 (0.5)	6 (1.6)	1 (0.3)	1 (0.3)	9 (2.3)	27 (7)	56 (14.6)

Abbrerviation: FL, free-living larvae.

^aValues are expressed as No. (%).

In this study, 28 of the vegetable farms were irrigated with well water and 10 of them were irrigated with surface or waste-water. Animal and chemical manure were used to fertilize 33 and 5 of the considered agricultural lands, respectively.

Table 2 shows distribution of the parasitic contamination of vegetables, based on type of water and fertilizer used in agricultural farms. Nearly all of the contaminated vegetables (96.4%) belonged to the farmlands that are fertilized with animal manure. There were significant correlations between parasitic contamination and fertilizer (P = 0.018) and water consumption (P < 0.001) used for growing vegetables.

Table 2. Distribution of Parasitic Contaminations in Vegetables Grown in Farms With Different Types of Water and Fertilizer Consumption in Malayer City, Iran^a

Water and Fertilizer Consumption	Parasitic Contamination
	Positive	Negative	Total
Well water	23 (8.2)	259 (91.8)	282 (100)
Surface and waste water	33 (32.7)	68 (67.3)	101 (100)
Animal manure	54 (16.2)	279 (83.8)	333 (100)
Chemical manure	2 (4)	48 (96)	50 (100)

^aValues are expressed as No. (%).

5. Discussion

Recommendation to use fresh fruit and vegetables is one effective way to promote health in the society (10). Vegetables may be contaminated with various enteric pathogens, including bacteria, viruses, and parasites during the cultivation and marketing process (3, 6, 13, 14). Recovery of parasitic agents from raw vegetables can be considered as a health indicator in the community and indicate the link between public health and agricultural policies and programs.

The present study showed that 14.6% of green leafy vegetables collected from Malayer city lands were contaminated with parasites. In comparison with other studies, the 14.6% prevalence of parasitic infestation is relatively moderate. There are different reports about the prevalence of parasitic contamination of raw consumed vegetables in Iran and other regions of the world such as Kenya (65.5%) (17), Libya (58%) (6), Egypt (31.7%) (14), Nigeria (3.5%) (5), Iraq (49.79%) (18), and Turkey (6.3%) (19). Klapec and Borecka reported that the rate of geohelminths eggs on vegetables and fruits from conventional and organic farms was 34.7% and 18.9%, respectively, in south-eastern Poland (20). The other reports from different areas of Iran are 52.7% in Khorramabad (16), 46.5% in Amol (7), 43.7% in southern Iran (21), and 71% in Ardebil (22). The various prevalence rates of contamination may be due to date of studies, the application of different examination methods, and different epidemiological factors such as geographical and climatic conditions of the region, type of water and fertilizer used for growing vegetables, contamination after harvest, and other influential factors.

In this study, the highest prevalence of contamination belonged to free-living larvae (7%), because of the presence of free-living and plant-parasitic nematodes in the terrestrial environment. This finding is in accordance with the study of parasitic contamination of consumed vegetables in Khorramabad and Amol reported by Ezatpour et al. (16) and Siyadatpanah et al. (7). Leek with 31.7% contamination was the most infested vegetable in the present study that agreed with some previous repots (15, 18, 23). High contamination in leek seems to be due to direct contact of its leaves with soil.

Considerably, Ascaris lumbricoides and other human intestinal nematode eggs were not detected in this study. However until a decade ago, human intestinal nematodes, especially Ascaris lumbricoides, were prevalent parasites in Hamadan province. Fallah et al. reported prevalence and moderate intensity of ascariasis as 19.5 and 59.3%, respectively, in Hamadan city, during year 2003 (24). Recently, some conducted studies in the area showed significant reduction in the parasites prevalence such as human intestinal parasitic survey in Hamadan province and among rural inhabitants of Hamadan city, as indicated by the studies of Fallah et al. in 2014 (unpublished data) and Jafari et al. (25) in 2012, respectively. A similar study was simultaneously conducted on farm vegetables of Asadabad, one of the cities of Hamadan province. The findings of this study were close to those of the present study. The parasitic contaminants of vegetables were Entamoeba coli (2.6%), Giardia intestinalis (1.6%), Toxocara spp. (0.8%), Fasciola spp. (0.5%), Dicrocoelium dendriticum (0.3%), and Taenia/Echinococcus spp. (0.3%) (in press). Improvements in public health conditions and implementation of control measures against intestinal nematodes, particularly mass chemotherapy (26), caused high reduction in intestinal parasites, especially intestinal worms, in this area.

Giardia intestinalis cyst was observed in 1.3% of the vegetable samples, which is lower than other reports from Khorramabad (1.1% in winter and 5.8% in spring) (16), Ardabil (10% in imported and 18% in native vegetables) (22), Amol (22.5%) (7), Zahedan (8.1%) (12), and southern Iran (11%) (21). Cyst of Entamoeba coli, non-pathogenic intestinal protozoa, was the second prevalent parasite with a frequency of 2.3%. Detection of E. coli cysts in the samples can be considered as an indicator of fecal contamination of the vegetables.

Eggs of Taenia saginata, T. solium, and Echinococcus granulosus are morphologically indistinguishable from each other using microscopic or other parasitological techniques. In this survey, Taenia/Echinococcus spp. eggs were found in 1.6% of the samples tested for detection of parasite agents. In a few studies conducted by Ezatpour et al. in Khorramabad (16) and Siyadatpanah et al. (7) in Amol, contamination of vegetable samples with Taenia spp. was not reported, whereas other studies in Iran reported contamination with Taenia spp. in examined vegetables (12, 13, 21-23). In the present study, the suspected cestode eggs probably related to Echinococcus granulosus because prevalence of human taeniasis is rare and instead prevalence of echinococcosis in stray dogs and livestock hydatidosis are relatively common in the study area (27, 28), although animal taeniasis should not go unnoticed. Hydatidosis is one of the serious zoonotic parasitic diseases that involves human and farm animals. In Iran, it is estimated that cost of human hydatidosis is annually US $93.39 million with 1295 cases of surgical hydatidosis and an estimated 635 232 asymptomatic individuals (29). The eggs were dispersed in the environment by dogs or other wild canids, as definitive hosts. Infection of human, as an accidental intermediate host, frequently occurs through ingestion of the eggs during eating and drinking of contaminated foods and water. Consumption of infested vegetables by taeniid eggs increases the risk of human cystic echinococcosis and it is a great concern to consumers.

Ingestion of Toxocara spp. eggs can cause toxocariasis, visceral, and ocular larva migrans, in young children. Dogs, cats, and other wild canids and felids are responsible for the spreading of eggs in the environment (21). The results showed 0.8% contamination with Toxocara spp. eggs in the vegetable samples. This report was in accordance with some previous reports (6, 7, 12, 13, 20, 21) and in contrary to some others (16-18, 22). High frequency of Toxocara spp. (48.3%) was reported by Maikai et al. from Nigeria (3).

A few zoonotic intestinal helminths, including Dicrocoelium dendriticum, Fasciola and Trichostrongylus spp. were detected in this study. Prevalence of the parasites in the environment chiefly depends on the rate of the infection in livestock and use of animal fertilizer in farm vegetables.

In conclusion, although this study and other evidences show that the prevalence of human intestinal parasitic infection is decreasing in the Hamadan province, yet the findings indicate that vegetable consumers in Malayer city are at risk of infection with parasitic protozoa and zoonotic helminth parasites. Thus, it is essential for some hygiene measures to be considered, including proper washing and disinfection of raw vegetables before consumption, implementation of sanitation practices, agricultural reform, and other health interventions that can be effective in the control of intestinal infections and public health promotion.

Acknowledgements

Footnotes

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