Prevalence of Blastocystis hominis in Lorestan Province, West of Iran, 2010

MATERIALS AND METHODS

This cross-sectional, descriptive study was carried out on 2838 stool samples taken from people living in Lorestan province (west of Iran) via a multiphase cluster sampling to determine the prevalence of gastrointestinal parasites, particularly Blastocystis hominis. The stools were tested using the wet or direct method (Lugol-Normal Saline) and the concentration method (Formalin-Ether).

The researchers went to towns and cities of the province based on a time schedule. Then they provided the involved health officials with necessary education and facilities. The studied individuals were randomly selected based on a list of available families in health centers via a randomized cluster sampling method. Considering the capacity of the libraries, the health officials went to selected houses, collected the samples and coded the containers. A two-part questionnaire was completed for each person. The first part contained 13 epidemiologic-demographic items including gender, age, place of living, family population, employment, education, water supply, hygienic condition of living place, way of washing vegetables, presence of soap and way of using soap in lavatories. The second part of the questionnaire consisted of the results of laboratory tests such as qualitative results including presence or absence of parasites and quantitative results of each method including the mean of number of parasites in ten microscopic fields in positive cases.

The collected samples were sent to laboratories the following morning and were examined using the direct and concentration methods. The results were recorded in the lower part of the questionnaire both qualitatively and quantitatively. The samples containing Blastocystis hominis were kept in a freezer for molecular examinations and the questionnaires were delivered to the Statistics Unit for statistical analyses.

RESULTS AND DISCUSSION

Out of the 2,838 stool samples collected, the parasite Blastocystis hominis was found to be the second most prevalent parasite in the province with 139 positive cases (5%) after Giardia lamblia with 186 cases (6.7%). Forty two percent of the individuals infected with Blastocystis hominis were living in urban areas and 58% in rural areas. Moreover, 35% and 65% of the infected people were males and females respectively, showing a statistically significant difference. No significant relationship was found in terms of using or not using soap.

Most of the obtained data including the percentage of contamination in terms of age, occupation and prevalence in different areas of the province are presented in the Table 1-3.

This study investigated the prevalence of gastrointestinal parasites, particularly Blastocystis hominis as an unknown protozoan, in Lorestan province (west of Iran) in 2010 for the first time. The prevalence was found to be 5% and this intestinal parasite was found to be the second most prevalent parasite after Giardia lamblia with 6.7%. Present result was not consistent with the result of a study carried out in Tehran in which Blastocystis hominis was reported as the most prevalent parasite with a prevalence of 12.8% (Akhlaghi et al., 2009).

In addition to its exceptional characteristics in morphology, methods of reproduction and life cycles, the parasite possesses many other unique and unknown characteristics. For example, contrary to other parasites which have a fecal-oral transmission route (Dagei et al., 2008), the parasite is more prevalent in elderly individuals (Hussein et al., 2008; Stenzel and Boreham, 1996) and few negative effects of the parasite have been reported on growth indices in children (Ertug et al., 2007). In this study, as presented in Table 1, the highest (8.3%) and lowest (2.4%) rates were reported for the 70-79 age group and the under-10 age group respectively. This result is similar to the results in other areas of the world including a study in China, in which the highest rate was reported for the 60-year-old people and then those in the 10-17 age group (Li et al., 2007).

On the other hand, we know that Blastocystis hominis is a zoonotic protozoan parasite that is transmitted directly. Therefore, as proven in some studies (Rhongbutsri, 2005; Li et al., 2007), it is expected that the prevalence will be the highest in those who handle animals.

Table 1:	Percentage of Blastocystis hominis infection in terms of age groups

Table 2:	Percentage of Blastocystis hominis infection in terms of occupation

Table 3:	Percentage of Blastocystis hominis infection in cities of lorestan province

In our study, the prevalence was the highest (8.3%) in ranchers compared with other occupations despite the lower number of the ranchers (Table 2) and it shows the zoonotic feature of the parasite

The prevalence of the parasite varies in different countries, even in different communities of a countries and different seasons (Rhongbutsri, 2005; Li et al., 2007; Su et al., 2009). It is known to be the resident of tropical and subtropical areas (Stenzel and Boreham, 1996). In this study, as presented in Table 3, the rates ranged from 0 to 20%. In addition, contrary to expectations, the lowest rate was reported for Poldokhtar as the hottest area of the province and the highest rate for Boroujerd as a relatively cold area in the province. Differences in prevalence rates in different countries and even communities depend on diverse factors including culture, health facilities, communications with other humans and animals, etc. However, it seems that the most important factor among epidemiological indicators in these cases is diagnosis and this issue relatively affected the results in our study. The reason is that the parasite is highly polymorphic with diverse forms and sizes and the majority of therapeutic and health centers and even diagnostic centers, in Iran ignore this parasite with proven pathogenesis. Therefore, the parasite has remained unknown. If necessary reforms happen, higher prevalence rates can be expected. It is recommended that positive steps should be taken to have the exact diagnosis of the parasite via applying experts and utilizing more sensitive diagnostic methods such as staining, culturing and molecular diagnosis, since the parasite may be the unknown pathogen of many diseases.

ACKNOWLEDGMENTS

We hereby thank Tarbiat Modarres University of Tehran for the financial support of the present study. We also appreciate the sincere help of Mr. Mokhayeri, Mr. Barkhordari and Mr. Sharafi from the Deputy for Health, Lorestan university of Medical sciences.