1. Background
Geohelminth infections are major intestinal pathogens, which affect underprivileged communities with incomplete admission to innocent water and appropriate health facilities. Soil Transmitted Helminth (STH) such as Ascaris lumbricoides, Trichuris trichiura and hookworms are among the most important geohelminths, which have been estimated to infect approximately two billion humans all over the world (1). Infection with geohelminths effect feeding, growth and fitness and also cause chronic infections in the population of endemic areas (1, 2). Soil provides appropriate conditions for conversion of the eggs to the infective stage. Also presence of eggs in the superficial layers of the soil can be considered as a factor affecting their transition to humans in each region (3). One of the main pathways for human infection is ingestion of infective eggs by consumption of raw vegetables and fruits contaminated with soil containing eggs (2, 4). Thus, it seems that soil is the main resource for human infection and can be a direct indicator for the risk of infection among human populations, especially children. Evidences indicate that STH infections affect children in developing and developed countries and are directly associated with growth retardation, physical activity reduction and disorders in learning abilities (5, 6).
Basically, the endemicity of geohelminth depends on the presence of infected individuals, continuous contamination of the soil with feces and suitable soil condition and frequent contact between the soil and healthy individuals. Therefore, geohelminth infection rate is affected by both natural and cultural factors (3, 6, 7). Due to limited resources in most developing countries, prioretising the control of such infections seems very difficult and it could be an important reason for the presence of the infection in these countries. These kinds of infections are considered as neglected diseases, which in case of suitable conditions can cause serious problems (4, 8).
2. Objectives
The present study aimed to determine the prevalence of soil contamination by geohelminth eggs in schools and play areas of Kermanshah city, West of Iran.
3. Materials and Methods
3.1. Study Area
Kermanshah city is located in the center of Kermanshah province in the West of Iran, and the city is divided to six regions. Its’ population is estimated around 850000, where most of its population are engaged in agricultural activities. Kermanshah is one of the western agricultural centers of Iran that produces grain, rice, vegetable, fruits and oilseeds. Kermanshah has cold winters and usually has rainfalls in fall and spring.
3.2. Sample Collection
During the period from September to December 2014, a total of 192 soil samples were collected from 24 primary school and 24 play areas in Kermanshah city. In each of the six regions, the samples were collected from four play areas and four primary schools. The samples were collected from four different parts of each area, including northern, eastern, western and southern part. Samples were collected from loose soil, mainly from flowerbeds. Approximately 200 grams of soil was obtained from an approximate depth of 3 cm, and all samples were then placed in plastic containers, labeled with a number and were exposed to air to dry.
3.3. Parasitological Procedures
Two grams of each sample was isolated using 150 μm mesh sieves and transferred into the test tubes. Next 10-mL Tween-80 with 0.05% concentration was added to the mixture and shook vigorously. The tubes were centrifuged at 1500 rpm for five minutes. In the next step, the supernatants were discarded and the tubes containing the sediments were filled with approximately 1 cm from the top with sucrose solution (1.2 g/cm3) and the sediments were suspended. The tubes were then centrifuged for 15 minutes at 1500 rpm. Finally, the tubes were filled with sucrose solution and a cover slip was placed on each tube and left stationary for 30 minutes and then the cover slips were placed on the microscopic slides and examined under a light microscope using 10X and 40X objectives.
4. Results
A total of 192 soil samples were examined and low rate of geohelminth egg contamination was observed. Although, the prevalence of free-living nematodes was considerably high in the studied areas (Table 1), Trichuris spp. eggs were not observed in any of the studied schools, but were found in three play areas (3.12%). Additionally, no Ascaris eggs were found in the examined soil samples.
Table 1. Soil Contamination With Geohelminth Eggs in Different Parts of Kermanshaha
| Region | Collected Soil Samples | Free Living Nematodes | Trichuris Spp. | Hook Worms | ||||
|---|---|---|---|---|---|---|---|---|
| School | Play Areas | School | Play Areas | School | Play Areas | School | Play Areas | |
| 1 | 16 | 16 | 2 (12.5) | 13 (81.25) | 0 | 0 | 0 | 1 (6.25) |
| 2 | 16 | 16 | 0 | 14 (87.5) | 0 | 1 (6.25) | 0 | 0 |
| 3 | 16 | 16 | 2 (12.5) | 9 (56.25) | 0 | 0 | 0 | 1 (6.25) |
| 4 | 16 | 16 | 3 (18.75) | 14 (87.5) | 0 | 0 | 0 | 0 |
| 5 | 16 | 16 | 3 (18.75) | 8 (50) | 0 | 0 | 0 | 0 |
| 6 | 16 | 16 | 7 (43.75) | 6 (37.5) | 0 | 2 (12.5) | 0 | 0 |
| Total | 96 | 96 | 17 (17.7) | 64 (66.6) | 0 | 3 (3.12) | 0 | 2 (2.1) |
aValues are expressed as No. (%).
5. Discussion
Public sites such as schools and play areas are considered an important source for human infection, especially for children. The places where children play are important for public health (9). In many studies, it has been demonstrated that parasitic infections have a considerable negative influence on health factors such as weight and height (10, 11).
Recent studies evaluated STH prevalence in the soil from parks, playgrounds, schools, etc. (12, 13). Reports of soil contamination with geohelminth eggs have been published in Iran and other countries, as summarized in Table 2. According to the results of the present study, soil contamination with geohelminth eggs (2.6%) is low in Kermanshah compared to the other studied areas in Iran and other countries. Environmental factors such as soil type, pre-processing sieving, suspension of sediment, washing and flotation and specific gravity of flotation solution seem to influence the recovery of geohelminth eggs in the soil (14, 15). Furhtermore, some factors like climate, herbage and presence of animals could affect soil contamination (16). Increase in the number of stray dogs and cats plays an important role in soil contamination with hook worm eggs, one of the main causes of cutaneous larva migrans in humans, which were found in two play areas in separate regions of Kermanshah. The eggs are excreted by infected host to the soil and develop to third stage larva (L3), which is infective and can infect children by direct contact with contaminated soil in schools and play areas (17). During childhood, infection with hookworms plays an important role in moderate to severe anemia in preschool and school-aged children (18-20).
Table 2. Reports of Soil Contamination With Geohelminth Eggs Have Been Published in Iran and Other Countries
| Country/city | Location of Study | Sample. No. (%) |
|---|---|---|
| Poland/Lodz | Park playground | 168 (7.7) |
| School sports fields | 216 (15.7) | |
| Poland/Lublin | Beach | 215 (18.6) |
| Egypt/Sharkyia | Rural and urban areas | 120 (28.3) |
| Philippines/Barangay Bayog | Rural areas | 120 (54) |
| India/Titagarh | Soil of wastewater-irrigated areas | 35 (68.6) |
| Nigeria/Abuja | Public parks | 764 (67.5) |
| Iran/Tehran | Public places | 150 (6.7) |
| Iran/shiraz | Public places | 112 (10.7) |
| Iran/Kermanshah | School/play areas | 192 (2.6) |
Trichuris spp. is another STH, which were found in another region in Kermanshah. Human infections with this parasite are associated with some clinical disorders, which are similar to that of inflammatory bowel disease, such as chronic abdominal pain, diarrhea and other disorders such as impaired growth, anemia and finger clubbing (21).
The results of the present cross-sectional study indicate that the current status of contamination of soil with soil transmitted helminth is fairly good, but some preventive measures such as controlling stray dogs and cats and preventing their entry into public places to keep schools and play areas and other public places uncontaminated seems necessary.
