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Introduction: Alimentary  parasitic  infections  are  still  one  of  the  main  problem  in  developing  countries, and  their  relation  with  environmental  factors  are  important.  Since  children  are  more  vulnerable  to  these  infections, in  basic  researchers  this  group  is  more  targeted.
Materials  and  Methods:  This  descriptive-analytical  cross-sectional  study  was  carried  out  on  1-13  years  children  who  were  living  in  Shahrak-e-Valiasr  Arak.  Simple  random  sampling  was  used  for  selecting  385  children.  Three  days  collected  feces  samples  from  each  person  were  examined  using  formaline-ether  concentration  technique. Data  were  analyzed  by  Chi  square  method.
Results:  The  results  showed  a  prevalence  of  42.3%  of  intestinal  parasitic  infections  in the  children. From  these, 17.4%  were  pathogen  parasits. The  highest  prevalence  was  reported  for  Giardia  lambia  (16.6%).  Girls  were  more  infected  than  boys.  The  level  of  infection  was  significantly  increased  by  age. The  prevalence  of  the  infection  was  more  in  orphans  or  in  children  who  had  uneducated  parents.
Conclusion:  Since  date  indicated  of  a  high  prevalence  of  intestinal  parasitic  infections  in  the  children. It  is  suggested  to  use  washed  and  clean  vagetables   and  fruits  and  also  emphasize  on  personal  and  environmental  hygiene.

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Introduction: There is difference between susceptibility or resistance to infectious diseases such as cystic and alveolar Eclinococcosis in human and animals, that is due to the difference between individual host factors and immunologic responses. This study is done to investigate the resistance and susceptibility markers (HLA) in Hydatid patients and healthy persons. Materials and Methods: This analythical (case-control) study is carried out on 60 patients with confirmed cystic echinococcosis and 30 healthy individuals living in Arak. Blood samples were gathered and tested by microlymphocytotoxicity method. At first diagnostic kits with specific antiserusms for each antigen (28 antigens) were provided and then lymphocytes were separated. After dye and stabling with formalin and based on cells morphology, results were seen by invert microscope. Data was analyzed using Odds Ratio, Relative Risk, Preventive Fraction, Aetiologic Fraction and Chi square test. Results: Results showed that HLA-A1 was significantly higher in patients (p<0.05), and people having this antigen are more susceptible for the infection. In spite, HLA-A10 was higher is healthy individuals (p<0.05) and have a preventive effect in disease involvement. Other investigated antigens had no signigicant difference in the two groups. For more accurate results molecular investigation is needed. Conclusion: In individuals having HLA-A1 there is more chance for cyst growth in confronting hydatosis and this individuals are more susceptible to the disease. But in individuals having HLA- A10 there is less chance for cyst growth in confronting hydatosis and this antigen have a preventive effect against hydatid cyst.

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Background: The purpose of this study was to identify the effect of health education according to health belief model (HBM) on the adoption of preventive behaviors of infection with giardia lamblia by primary school students in Arak. Materials and Methods: In a randomized quasi-experimental case study, 1200 students were randomly divided into two equal groups of test (instruction) and control (non-instruction). The sample size for giardiosis identification tests included 300 students, who had been equally and randomly selected from the control and test groups. Health education was according to HBM and its impact on the students' lifestyle-related patterns of behavior was considered. Results: Paring nails in the test group, significantly increased after education while it decreased significantly in the control group. The number of students who carried a glass for drinking slightly increased, but it remarkably decreased in the control group. The number of students who applied soap after using the restrooms remarkably increased in both the test and control groups. The relationship between not paring nails and infection with giardia lamblia was statistically significant. Additionally, after education, the ratio of reduction of infection with giardia lamblia in the test group to its increase in the control group was statistically significant. Conclusion: Preventive behaviors significantly improved and appeared influential in the reduction of infection with giardia lamblia. Thus, using a HBM in prevention of parasitic infections along with instructing the parents are suggested for prevention of parasitic infections.