Prevalence of Cystic Echinococcosis Genotypes in Iranian Animals: A Systematic Review and Meta-Analysis

Background Cystic echinococcosis is considered a public health problem that if left untreated can have dangerous consequences for the person. The disease is caused by Echinococcus granulosus sensu lato larvae. The main risk factors for this parasitic infection are habitat, direct contact with dogs, use of raw vegetables, and use of unwashed vegetables. The most important factors affecting the prevalence of HCD are economic, occupational, agricultural, educational, and factors related to public health and cultural habits of the general public in that geographical area. Objectives The purpose of this study was to investigate the prevalence of the types of cystic echinococcosis genotypes (E. granulosus sensu stricto (G1-G3) and E. Canadensis (G6 and G7)) in livestock in Iran. Method This systematic review was conducted, using Medline/PubMed, Scopus, Web of Sciences, and Google Scholar databases, to identify studies of cystic echinococcosis in animals published from 2010 to April 14, 2021. Finally, 28 studies were selected for meta-analysis, which was analyzed using Stata software version 14. The cystic echinococcosis prevalence with 95% confidence intervals of animals was synthesized using the random effect model. Heterogeneity was evaluated and in cases where the I2 index was higher than 75%, subgroup analysis was performed according to the types of animals. Result The highest prevalence of cystic echinococcosis infection was related to G1 genotype (P = 0.91 (95% CI = 0.84, 0.97)) and the prevalence was related to G2 genotype (P = 0.07(95% CI = 0.00, 0.18)). The results of the subgroup analysis showed that in the G1 genotype the highest prevalence was observed in Goats and Buffaloes with P = 1 (95% CI = 0.96, 1) and P = 1 (95% CI = 0.97, 1), in the G3 and G6 genotypes the highest prevalence was observed in camels with P = 0.50 (95% CI = 0.31, 0.69), and P = 0.45 (95% CI = 0.22, 0.69), respectively. Conclusion The cystic echinococcosis genotypes vary from region to region or from country to country and also from host to host, and according to the results, it should always be stopped in areas where the prevalence of such genomes suitable for livestock as well as human food sources to prevent infection of livestock and thus human exposure to cystic echinococcosis.


Introduction
Cystic echinococcosis (CE) is a common parasitic infection of humans and animals caused by the larva of 9pt?>Echinococcus granulosus sensu lato and cystic echinococcosis is a widespread zoonotic disease of global concern This disease has been reported in humans from all parts of Iran [1][2][3], and Cystic echinococcosis is considered an endemic chronic disease that is seen in many countries of the world [4].      Journal of Parasitology Research Eurasia, Africa, Australia, and South America, obscenity is prevalent. E. multilocularis is also distributed in the Northern Hemisphere, including native areas of Central Europe, most of northern and central Eurasia, parts of North America, and North Africa (Tunisia). Epidemiology and control of hydatidosis are often done and since this disease can be known as a disease of livestock, control, and screening of livestock from this infection should be done [9].
Hydatidosis has a global distribution with an annual global incidence rate of 1 to 200 per 100,000. In Iran, hydatidosis is actively transmitted and its annual incidence is estimated at 0.61 per 100,000 [10].
Annual cystic echinococcosis infection causes a lot of economic damage to countries around the world. Infection of livestock with hydatidosis usually leads to a significant reduction in livestock products (meat, milk, and wool) and causes the seizure of infected organs during slaughter. The prevalence of cystic echinococcosis in slaughtered animals in different provinces of Iran is 1.5 to 7. Percentage reported. This cyst can grow in different parts of the animal's body, the most important organs being the liver and lungs. It is worth mentioning that infection with this disease has been mentioned in different parts of Iran, but accurate and comprehensive information on the prevalence of this parasite in livestock and humans is not available at the same time [10].
In a cross-sectional study, a total of 5,381 animals were slaughtered in western Iran, a total of 928 cows, 243 buffaloes, 3,765 sheep, and 445 goats were slaughtered, which were examined macroscopically for cystic echinococcosis. The presence of this parasite was recorded in cows, buffaloes, sheep, and goats with prevalence rates of 38.3%, 11.9%, 74.4%, and 20%, respectively. Prevalence was higher in females than males, but a significant difference (P < 0:001) was observed only in sheep and cattle. The majority of convicted cases were observed in sheep lungs (13.4), indicating that sheep are the most important intermediate hosts for Echinococcus granulosus sensu lato in this region [11]. Since the general prevalence of this parasite in different types of animals native to Iran is not known, therefore, the aim of this study was to investigate the prevalence of cystic echinococcosis genotypes (E. granulosus sensu stricto (G 1 (sheep strain), G 2 (Tasmanian sheep strain), and G 3 (buffalo strain)), E. Canadensis (G 6 (camel strain) and G 7 (pig strains)) [12][13][14] in Iranian livestock.

Materials and Methods
2.1. Research Question. The purpose of this study was to investigate the prevalence of types of cystic echinococcosis genotypes in livestock in Iran.

Research
Strategy. This systematic review was conducted, using Medline/PubMed, Scopus, Web of Sciences, and Google Scholar databases, to identify studies published on hydatid cysts (cystic echinococcosis) in an animal. The keywords used to search the studies were: hydatid cyst, cystic echinococcosis, Echinococcus granulosus sensu lato, Animal, Prevalence, Frequency, and Incidence. All relevant keywords were used to search the databases. In order to perform a more comprehensive search, using "and/or", the above terms were combined.

Inclusion and Exclusion
Criteria. The inclusion criteria of the present research consisted of all original articles reporting the prevalence or frequency of cystic echinococcosis (hydatid cysts), either in English or Persian language and published from 2010 to April 14, 2021. Studies were excluded with incomplete information, from other countries, studies that were about human contamination, review articles, opinions, and letters.

Data Extraction and Quality
Assessment. The studies were entered into the EndNote Software for assessment, then, the extraction of data was conducted. The results were reviewed by two authors (conventional double screening), the abstracts were screened, and related studies were selected. All disagreements were resolved through discussion with a third party. Finally, the full texts of the selected studies were reviewed and 28 publications were selected for the meta-analysis ( Figure 1). The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) was used to determine the quality of the studies [13]: (i) inclusion and exclusion criteria, (ii) methods of selection of participants, (iii) definition of the outcome, (iv) definition of exposure, and (v) calculation of the sample size. Studies with five-star items were considered high-quality studies, and those with four star-items or less were considered lowquality studies.
Finally, a checklist was prepared by the research team to extract the variables of sample size, type of animal, study location, infection prevalence, and type of genotype for meta-analysis and also subgroup analysis.

Statistical
Analyses. The current meta-analysis was executed using Stata software version 14 (StataCorp. 2015, Stata Statistical Software: Release 14, College Station, TX). The cystic echinococcosis with the prevalence of animals was synthesized using the random effect model. Heterogeneity was evaluated with the Q test and the I 2 index. Studies with an I 2 index of <25%, 25-75%, and>75% fell into the category of low, moderate, and high heterogeneity, respectively. In cases where the I 2 index was higher than 75%, subgroup analysis was performed according to the types of animals studied. Forest plots were used to visualize the prevalence in each study and the incorporated estimated with 95% confidence intervals (95% CI), both in the main analysis and the subgroup analysis.

Result
A total of 152 records were identified in databases, during the initial search. We identified 57 papers on Medline/PubMed, 6 papers from Scopus, 4 Papers from Web of Sciences, and 85 papers from Google Scholar. After removing duplicates and applying our exclusion criteria, a title and abstract analysis were performed for 125 papers. Only 28 papers included  Based on the drawn GIS map, it was found that the frequency of different types of cystic echinococcosis genotypes is higher in the western and northwestern regions of Iran, which is a mountainous region and livestock farming is more prevalent (Figure 2).
Based on the drawn bar chart, regardless of the weight of the studies in the meta-analysis, G 1 genotype had the highest prevalence and G 3 genotype had the lowest prevalence ( Figure 3).

Journal of Parasitology Research
The data obtained from all the studies that entered the analysis phase showed that 2579 animals were examined, of which the most studied animals in different studies were sheep (37.6%), and the lowest sample size belonged to Jackal and Donkey (0.05). %) ( Table 2).

Subgroup Analysis.
To reduce heterogeneity in the pooled estimation of the relative frequency percentage of cystic echinococcosis, in G 1 , G 3 , and G 6 genotypes, subgroup analysis was performed based on the type of animal under study. The results showed that in G 1 genotype the highest relative frequency percentage was in Goat and Buffalo with P = 1 (95% CI = 0:96, 1) and P = 1 (95% CI = 0:97, 1), respectively, in G 3 and G 6 genotype. In camels, it was obtained with P = 0:50 (95% CI = 0:31, 0:69) and P = 0:45  (Table 4 and Figures 9-11).

Discussion
The distribution of cystic echinococcosis livestock genotypes in Iran is different from each region to another region, as well as from host to host. Depending on the type of climate and vegetation in Iran, different domestic animals are kept as livestock by the people, since livestock and animal husbandry are traditionally practiced in most parts of Iran. The traditional method of care exposes livestock to parasitic infections, including cystic echinococcosis; therefore, despite initial studies, the prevalence of genotypes of this parasite, especially by animal type, remained unclear. This systematic review and meta-analysis study was performed to investigate the prevalence of hydatid cyst in livestock in Iran. Preliminary study data published from 2010 to April 14, 2021, were collected and analyzed. Finally, 28 studies had the eligibility criteria of the present study and their information was extracted based on the type of animal under study and their cystic echinococcosis genotype. The most studied animal species were sheep and then goats and the most abundant genotype found was G 1 .
The results of the meta-analysis of our study showed that the most common genotypes of cystic echinococcosis in animals in Iran, were Echinococcus granulosus sensu lato (sheep genotype or G 1 ) and E. Canadensis group (camel genotype or G 6 ), respectively. Canadensis group (Pig genotype or G 7 ) were E. The results of the study of Tiemin Zhang et al. showed that the most abundant genotype of cystic echinococcosis in animals of China is G 1 and then G 6 [42], also genotype G 1 is the most abundant type of cystic echinococcosis in different hosts in Ethiopia [43], Tunisia [44], Palestine [45], India [46], China [47], Mongolia [48], and Turkey [49] which is consistent with the results of the present study, in the study of Kheirandish et al., in Lorestan province [40], and the study of Asma A. Latif et al., in Pakistan [50] showed that after G 1 was identified as the most abundant cystic echinococcosis genotype of G 3 . However, in the study of Said Amer et al., in Egypt [51], the most abundant genotype extracted was G 6 . Also, the study of Shahnazi et al., in Isfahan province [16] and the study of Sharbatkhori et al., in central Iran [34] in isolated samples of camels was the most abundant G 3 9 Journal of Parasitology Research genotype, which can be due to different studies in different geographical areas. Cystic echinococcosis may be present during sampling and testing, as well as differences in tissue.
The results of subgroup analysis showed that the highest infection in the G 1 genotype was related to Goat sam-ples (P = 1, 95% CI = 0:96, 1) and Buffalo (P = 1, 95% CI = 0:97, 1); the results of the Pezeshki et al., study in Ardabil province in northern Iran [32], showed that more than 90% of the infections in Goat and Sheep were of G 1 genotype, which is almost similar to our study and in the    [33], the results showed that 100% of the samples isolated from Goat were infected with the G 1 genotype. The results of our study subgroup analysis showed that the highest infection with G 3 genotype was seen in cysts isolated from Camel with P = 0:50 (95% CI = 0:31, 0:69). In the study of Abd El Baki et al., in Golestan province in northern Iran [52], the frequency of G 3 genotype in cysts isolated from Camel was 66.7%, and in the study of Sharbatkhori et al., in central Iran [34] the relative frequency percentage of G 3 genotype in cysts Camel was 42.1%. While the results of a study by Abd El Baki et al., [52] showed that the most common genotype in Camel was the G 1 genotype with a 90% relative frequency percentage, the reason for this discrepancy could be the existence of the sheep breeding industry in Egypt. The use of Camels as a means of public transportation in desert areas and close contact between the two, which eventually led to the predominance of the genotype.
In the study of Sharbatkhori et al., in central Iran [34] in cysts isolated from Camel, 31.6% infection was seen in the G 6 genotype, and in the study of Shahnazi et al., in Isfahan province [16] 65.36% of the samples isolated from Camel, genotype G 6 , while the results of our subgroup analysis showed that the highest percentage of infection with G 6 genotype was seen in cysts isolated from Camel with P = 0:45 (95% CI = 0:22, 0:69); however, in the study of Said Amer et al. [51], the highest percentage of G 6 genotype infection was observed in camels with 0.92%, which was much higher than the percentage of infection in our study. The reason for the mismatch could be camel meat as a rich source of Protein in Egypt, which has led to the high relative frequency percentage of Camel genotype in recent years in this region.

Conclusion
The results of our article showed that the distribution and prevalence of Echinococcus genotypes varies from region to region, or from country to country, and also from host to host, and in Iran due to climate and vegetation, its prevalence in different species. The most studied animal species were sheep and then goats and the most abundant genotype was G 1 . The results showed that the most common genotypes of cystic echinococcosis in Iranian animals were sheep, camel, and pig genotypes, respectively, which according to the results, should it seem that in the areas where the CA method is high, the necessary steps should be taken regarding the identification and timely treatment of livestock in order to prevent the spread of this disease in animals and ultimately humans.