Introduction
Hydatid cyst disease (hydatidosis or echinococcosis) is an important chronic disease in many parts of the world, including Iran, caused by the larval stage of parasites belonging to the genus Echinococcus [1]. Infection occurs through direct contact with infected final hosts (i.e., carnivores such as dogs, foxes, coyotes, and wolves) or by eating the parasite’s embryonic eggs in contaminated food, water, or soil [2]. Seventy percent of cysts are found in the liver. Some parasite eggs pass through the liver parenchyma and appear in the lungs and enter the systemic circulation. Therefore, the main organs affected are the liver and lungs [3]. This disease is common in domestic animals and humans as intermediate hosts in Iran, including in Kermanshah Province [2, 5, 6]. Therefore, the present study was performed to evaluate the frequency of hydatid cyst disease in patients admitted to Imam Reza, Imam Hossein, and Bisotoon hospitals in Kermanshah city from 2014 to 2018.
Materials and Methods
In this descriptive study, we studied all patients referred to Imam Reza, Imam Hossein, and Bisotoon hospitals in Kermanshah City, Iran. They underwent surgery and medication with a probable diagnosis of a hydatid cyst from 2014 to 2018. For this purpose, a questionnaire was prepared that includes age, gender, occupation, location, and involved organs. The information was extracted from patient files in the archive. The information obtained from the patients’ files was entered in information tables and forms and was statistically analyzed using SPSS v. 16.
Results
A total of 350 patients with hydatid cysts underwent surgery and received medication from 2014 to 2018. Table 1 shows that out of 350 patients, 207 (59.1%) lived in rural areas and 143 (40.9%) in urban areas.


Their Mean±SD age was 43.2±19.7 in women and 43.3±20.7 years in men. The highest and lowest frequency of hydatid cysts were seen in the age groups of 41-50 (n=58, 16.5%) and 1-10 years (n=17, 4.8%), respectively. According to Table 1 , 42.8% of patients were homemakers, 22.8% were ranchers, and 8.5% were farmers. Regarding the location of cysts or the degree of infection of different organs in 350 patients with hydatid cysts, 241 cases (68.8%) were observed in the liver, 55 (15.7%) in the lungs, 24 (6.8%) in the brain and 29 (8.2%) in the spleen, heart, and bone.
Discussion
In the present study, the prevalence of hydatid cysts in women was higher than in men, and 59.1% of cases lived in rural areas. Because of the low level of personal and public health, the working conditions, and the close association between dogs and humans, hydatid cyst infection was more common in rural areas. Based on a systematic review, the highest disease prevalence in Iran is related to rural areas and females. The results of this study are consistent with the present study [10]. Regarding the higher prevalence of hydatid cysts in women, some reasons such as genetic differences, cleaning and eating raw vegetables, soil eating or geophagy in pregnancy, close contact with domestic animals, and cleaning their living space have been discussed [11, 12]. Regarding the location of cysts or the degree of infection of different body organs in 350 patients with hydatid cysts, 241 cases (68.8%) were observed in the liver and 55 (15.7%) in the lungs. One study found that hydatid cysts in humans were reported in the liver in 50%-70% of cases, in the lungs in 20%-30%, and in the spleen, heart, bone, and other organs to a lesser extent, which is consistent with the results of the present study [13]. This finding is also consistent with global epidemiological data in which the liver is the most common organ affected by hydatid cysts (approximately three-quarters of cases) [14].
Given the importance of hydatidosis in humans, its endemicity, and significant economic and health losses, health officials must take all necessary measures to prevent and control this disease. The need for education to better understand the disease among people, especially homemakers, and to identify infected dogs and treat them to control the disease is necessary to take basic measures.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Kermanshah University of Medical Sciences (Code: IR.KUMS.REC.1398.366). 

Funding
This study is a part of Ms. Nadia Fakhri Mosoob's thesis in the Department of Parasitology, Faculty of Medicine, Kermanshah University of Medical Sciences. This research has not received any funding from funding organizations in the public, commercial or non-profit sectors.

Authors' contributions
All authors contributed equally in preparing all parts of the research.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
We thank the Department of Medical Parasitology and Mycology, Kermanshah University of Medical Sciences. 

References

1. Moro P, Schantz PM. Echinococcosis: A review. Int J Infect Dis. 2009; 13(2):125-33. [DOI:10.1016/j.ijid.2008.03.037] [PMID]
2. Mahmoudi S, Mamishi S, Banar M, Pourakbari B, Keshavarz H. Epidemiology of echinococcosis in Iran: A systematic review and meta-analysis. BMC Infect Dis. 2019; 19(1):1-19. [DOI:10.1186/s12879-019-4458-5] [PMID] [PMCID]
3. Hong S-T, Jin Y, Anvarov K, Khadjibaev A, Hong S, Ahmedov Y, et al. Infection status of hydatid cysts in humans and sheep in Uzbekistan. Korean J Parasitol. 2013; 51(3):383-5. [DOI:10.3347/kjp.2013.51.3.383] [PMID] [PMCID]
4. Zibaei M, Azargoon A, Ataie-Khorasgani M, Ghanadi K, Sadjjadi S. The serological study of cystic echinococcosis and assessment of surgical cases during 5 years (2007-2011) in Khorram Abad, Iran. Niger J Clin Pract. 2013; 16(2):221-5. [DOI:10.4103/1119-3077.110156] [PMID]
5. Chalechale A, Hashemnia M, Rezaei F, Sayadpour M. Echinococcus granulosus in humans associated with disease incidence in domestic animals in Kermanshah, west of Iran. J Parasit Dis. 2016; 40(4):1322-9. [DOI:10.1007/s12639-015-0681-1] [PMID] [PMCID]
6. Vejdani M, Vejdani S, Lotfi S, Najafi F, Nazari N, Hamzavi Y. Study of operated primary and secondary [recurrence] hydatidosis in hospitals of Kermanshah, west of Islamic Republic of Iran. East Mediterr Health J. 2013; 19(7):671-5. [DOI:10.26719/2013.19.7.671] [PMID]
7. Hamzavi Y, Vejdani M, Nazari N, Mikaeili A. The trend of hydatidosis in Kermanshah province, western Iran (1986-2008). Iranian J Parasitol. 2011; 6(4):33-40. [PMID] [PMCID]
8. Youngster I, Hoida G, Craig P, Sneir R, El-On J. Prevalence of cystic echinococcosis among Muslim and Jewish populations in southern Israel. Acta Tropica. 2002; 82(3):369-75. [DOI:10.1016/S0001-706X(02)00026-8]
9. Abdulhameed MF, Habib I, Al-Azizz SA, Robertson I. A retrospective study of human cystic echinococcosis in Basrah province, Iraq. Acta Trop. 2018; 178:130-3. [DOI:10.1016/j.actatropica.2017.11.011] [PMID]
10. Khalkhali H, Foroutan M, Khademvatan S, Majidiani H, Aryamand S, Khezri P, et al. Prevalence of cystic echinococcosis in Iran: A systematic review and meta-analysis. J Helminthol. 2018; 92(3):260-8. [DOI:10.1017/S0022149X17000463] [PMID]
11. Budke CM, Carabin H, Ndimubanzi PC, Nguyen H, Rainwater E, Dickey M, et al. A systematic review of the literature on cystic echinococcosis frequency worldwide and its associated clinical manifestations. Am J Trop Med Hyg. 2013; 88(6):1011-27. [DOI:10.4269/ajtmh.12-0692] [PMID] [PMCID]
12. Mehrabani NG, Kousha A, Khalili M, Oskouei MM, Mohammadzadeh M, Alizadeh S, et al. Hydatid cyst surgeries in patients referred to hospitals in East Azerbaijan province during 2009-2011. Iran J Parasitol. 2014; 9(2):233-8. [PMID] [PMCID]
13. MacPherson CNL, Milner R. Performance characteristics and quality control of community based ultrasound surveys for cystic and alveolar echinococcosis. Acta Trop. 2003; 85:203-9. [DOI:10.1016/S0001-706X(02)00224-3]
14. Tuxun T, Zhang J-h, Zhao J-m, Tai Q-w, Abudurexti M, Ma H-Z, et al. World review of laparoscopic treatment of liver cystic echinococcosis-914 patients. Int J Infect Dis. 2014; 24:43-50. [DOI:10.1016/j.ijid.2014.01.012] [PMID]
15. Dadashi A, Babamahmoodi F, Fakhar M, Ziaei Hezarjaribi H, Amin N, Rahimi B, et al. [Clinical and laboratory study of patients with operated hydatid cysts (Persian)]. J Mazandaran Univ Med Sci. 2018; 27(157):242-6. [Link]