Intestinal parasitic infections are amongst the most common infections worldwide. It is estimated that some 3.5 billion people are affected, and that 450 million are ill as a result of these infections, the majority being children. These infections are regarded as serious public health problem, as they can cause iron deficiency anemia, growth retardation in children, and other physical and mental health problems [1,2].

In public imagine Karaj city is commemorated as small Iran and this point completely shows the status of our city in Iran and thus the condition of this area is a symbol of all part of our country and results of every epidemiologic research that performed in Karaj almost shows the status of the whole parts of the country. Epidemiological research carried out in different countries has shown that the social and economical situation of the individuals is an important cause in the prevalence of intestinal parasites. In addition, poor sanitary and environmental conditions are known to be relevant in the propagations of these infectious agents [3,4]. Geographical conditions and poor nutritional and socioeconomic status contribute to making the Islamic Republic of Iran favorable area for parasitic infections. The prevalence of intestinal parasitic infections has been found to vary in different parts of the Iran, with 47.2% in Kerman [5], 22.4% in Shahrekord [6], 21.9% in Mazandaran [7], 65.5% in Amol [8] and 32.2% in Tabas [9]. A review of 300 cases of intestinal parasitic infection in Kerman, a city in south east of Iran, showed that Ascaris lumbricoides was the most common nematode and Giardia intestinalis and Entamoeba histolytica the most common unicellular microorganisms causing intestinal parasitic infections [5]. In addition, many refugees from different provinces of Iran come to this city to work and living, so we performed present research in this place.

The aim of our study was to describe the occurrence of intestinal parasitic infections in our area, considering all people, including hospitalized, outpatients, and healthy people, with the suspect of intestinal parasitosis whose fecal samples were sent to our laboratory during the years 2006-2008.

Among 13,915 persons referred to laboratories for performing stool examinations, 5,304 samples (38.1%) were male and 8,611 (61.8%) were female. Among these numbers, 649 (4.7%) were positive for parasitic infections, that included 13 (0.09%) worm and 636 (4.6%) protozoan infections. At all, 5 cases had co-infection with more than 1 species of parasites. Eleven species of parasites were found in the population studied; maximum infections belonged to Giardia intestinalis int 534 (3.8%) of persons had that infection (Table 1). The next prevalent species were Entamoeba coli (0.39%) and Trichomonas hominis (0.1%). Maximum numbers of referred people to laboratories were in July and the maximum percentage of infections was in August. Analytical results of 2 years were similar, with a point that all 5 Strongyloides stercoralis infections pertained to 2008. Distribution of infection with intestinal parasites in the population according to sex, age, and month are illustrated in Tables 2-4.

Intestinal parasitosis represents a relevant clinical problem, especially in developing countries, where they are responsible for morbidity and mortality in adults and children and many epidemiological data are available for these areas [22]. The prevalence in the communities may be altered because of changes in social behavior and life styles during years. Different epidemiological studies of such infections will provide better understanding of the health status of these countries. In recent years, several researches have been conducted in different parts of Iran to reveal the status of prevalence of intestinal parasitic infections. All these studies indicated that there is a sharp decline in the prevalence of intestinal parasites compared to those studies of previous 3 decades or before that [10-14]. The structure of Karaj city has been founded less than 50 years and made by immigration from different parts of the country with continuing immigration from endemic regions. Therefore, screening for intestinal parasitic infections has remained an important priority in Karaj. Many studies on the prevalence of intestinal parasitic infections have been performed in all continents due to their wide diffusion in human communities.

In our study, the cumulative positive infection rate for all species was 649 (4.7%), and like other researches in Iran, G. intestinalis (3.8%) was the most common species among protozoa and S. stercoralis larvae (0.03%) was the most common among worms that were detected in people. E. coli was the next common intestinal protozoa among the study population. G. intestinalis and E. coli can be transmitted orally by drinking infected water and both are environmental contaminants of the water supply. The water supply is really an important risk factor, for giardiasis, and several large outbreaks of giardiasis have resulted from contamination of municipal water supplies with human waste [19]. In Mexico city, up to 18% of acute diarrhea and dysentery in children requiring hospitalization were found to be associated with G. intestinalis, as well as 10% with E. histolytica and 7% with Blastocystis hominis [19]. In 1983, in the US, G.intestinalis was identified as the cause of 68% of waterborne outbreaks of diarrhea [20].

In our study, the prevalence of intestinal parasitic infections was slightly higher in males than in females, which is in agreement with the findings of a study in Nigeria [17] and previous studies in local regions of the Islamic Republic of Iran, in Tabas [9], Kerman [8], and Shahrekord [6]. However, population studies of the northern part of the Islamic Republic of Iran in Nour, Beshehr [18], and Amol [8], and a research in the Philippines [2] showed a higher prevalence of infection in females than in males. This may be explained by environmental factors as more women are occupied in farming in these areas compared with other parts. In some months of the year, we saw the effects of social behaviors on patterns of parasite distribution because we found that in months with religious (Ramezan in October) or national (Norooz in March) ceremonies in Iran the rate of referring people and also the number of infected people during the 2 years of our research were obviously decreased.

In conclusion, intestinal parasitic infections are still important public health problems in our region, and screening and treatment of infected people, as well as improving sanitary conditions and interventions, including health education on personal hygiene to the students and to the parents, especially to mothers, will help health authorities in strategy of control programs for intestinal parasites. At all it seems that a multisectoral control approach is needed and should be used in Iran.