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

Authors: Sahar Khodashenas; Mehran Akbari; Reza Beiranvand; Mojtaba Didehdar; Mohammad Shabani; Parnia Iravani; Behnam Abedi
Journal: Journal of Parasitology Research
 (2022)

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## Abstract

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.


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## Body

## 1. Introduction

Cystic echinococcosis (CE) is a common parasitic infection of humans and animals caused by the larva of9pt?>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 [1–3], and Cystic echinococcosis is considered an endemic chronic disease that is seen in many countries of the world [4].Cystic echinococcosis is considered a deadly disease that if left untreated can have dangerous consequences for the person. The disease is caused by Echinococcus granulosus larvae [5, 6].Echinococcus granulosus is a broad hermaphroditic worm with three growth stages. The structure of a cyst usually consists of three components, which include the pericyst, made of the host’s inflammatory tissue, the exocyst, and the endocyst, where the scolex and the prologue membrane are produced [5, 7].The annual global infection rate is 1.2 million people, the annual mortality rate is about 2.2%, and an estimated 3.6 million disability-adjusted life years (DALYs) are lost annually due to the disease [8].Echinococcosis/hydatidosis has a global geographical distribution and is observed in all countries. In parts of 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 (G1 (sheep strain), G2 (Tasmanian sheep strain), and G3 (buffalo strain)), E. Canadensis (G6 (camel strain) and G7 (pig strains)) [12–14] in Iranian livestock.


## 2. 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.


### 2.2. 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.


### 2.3. 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.


### 2.4. 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 (Figure1). 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 low-quality studies.Figure 1
PRISMA flow diagram of the literature search and study selection.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.


### 2.5. 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 theI2 index. Studies with an I2 index of <25%, 25–75%, and>75% fell into the category of low, moderate, and high heterogeneity, respectively. In cases where the I2 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.


## 2.1. Research Question

The purpose of this study was to investigate the prevalence of types of cystic echinococcosis genotypes in livestock in Iran.


## 2.2. 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.


## 2.3. 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.


## 2.4. 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 (Figure1). 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 low-quality studies.Figure 1
PRISMA flow diagram of the literature search and study selection.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.


## 2.5. 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 theI2 index. Studies with an I2 index of <25%, 25–75%, and>75% fell into the category of low, moderate, and high heterogeneity, respectively. In cases where the I2 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.


## 3. 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 the relative frequency percentage of cystic echinococcosis in animals. The 28 papers underwent the quality assessment and were included in our meta-analysis (Figure1).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 (Figure2).Figure 2
Distribution of different types of cystic echinococcosis genotypes in Iran.Based on the drawn bar chart, regardless of the weight of the studies in the meta-analysis, G1 genotype had the highest prevalence and G3 genotype had the lowest prevalence (Figure 3).Figure 3
Overall prevalence of different types of cystic echinococcosis genotypes in Iran (Regardless of their weight in meta-analysis).


### 3.1. Baseline Characteristics of Studies

Table1 shows the final information of the studies included in the meta-analysis. To have a well-defined outcome and the ability to perform a meta-analysis, analysis was performed in the genotype groups G1, G2, G3, G6, and G7. Also, the type of animal under study (Camel, Sheep, Cattle, Goat, Buffalo, Dog, Red Fox, Jackal, and Donkey) and the sample size of each animal in each study were extracted.Table 1
Baseline characteristics of the 28 studies included in the meta-analysis of cystic echinococcosis relative frequency percentage in animals.
Geographical regionType of animalsSample sizeCystic echinococcosis genotype [1]ReferencesG1(sheep strain)G2(Tasmanian sheep strain)G3(buffalo strain)G6(camel strain)G7(pig strain)1Lolerestan (2011)Sheep88100%[15]Cattle27100%Goat25100%2Esfahan (2011)Camel2634.61%65.39%[16]Cattle1464.28%35.71%Sheep34100%Goat10100%3Western Azerbaijan (2011)Sheep270100%[17]Goat185100%Cattle197100%Buffalo129100%Dog8100%4Urmia, Tabriz, Ardabil, Rasht, Ahvaz (2012)Buffalo25100%[18]5Esfahan (2012)Goat2085%15%[19]6Yasuj (2012)Sheep31100%[20]Goat56100%Cattle6100%7Ardebil (2013)Dog14100%[21]Red fox10100%Jackal1100%8Mazandaran (2013)Goat120100%[22]9Tehran (2014)Donkey1100%[23]10East Azarbaijan (2016)Sheep1989.47%10.52%[24]11Tabriz (2015)Dog1681.259.37%9.37%[25]12Northwest (2015)Sheep4996%4.00%[26]Cattle2892.85%7.15%13Mazandaran (2019)Sheep5100%[27]Cattle1100%14Golestan (2016)Camel966.70%66.70%66.70%33.30%33.30%[28]Sheep1889.21%3.07%16.92%Cattle4089.21%3.07%16.92%Buffalo2100%50%Goat1100%100%15Northwest, North, and Southeast (2017)—11580%0.86%9.6%12.17%[29]16Northeast (2015)Sheep50100%[30]Goat3080%20%17Esfahan (2014)Sheep5163.00%25.00%12%[31]Goat877%21%2%Cattle772%28%18Ardebil (2013)Sheep1995%5%[32]Goat4100%Cattle2199.95%4.76%19Kerman (2012)—3775.67%13.51%10.81%[33]20Central of Iran (2011)Camel1926.30%42.10%31.60%[34]21West Azerbaijan, East Azerbaijan, Ardabil, Gilan, Khuzestan (2011)Buffalo2592%8%[35]22Northwest (2016)—2294.50%5.70%[36]23Kerman (2013)—28070.763%36.5%[37]24Rasht, Gilan (2021)—5794.20%5.80%[38]25Esfahan (2010)Sheep37100%[39]Cattle4100%Camel1866.66%33.33%Goat8100%Tehran (2010)Sheep27100%Golestan (2010)Sheep10100%Cattle5100%Mazandaran (2010)Sheep3100%26Markazi province (2019)—4961%2%37%[6]27Lorestan (2018)Sheep18100%[40]Cattle1888.90%11.10%28Khorasan Razavi (2019)Dog7175%10%15%[41]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). %) (Table2).Table 2
Type of animals percent in 28 studies included in the meta-analysis.
Type of animalsNumberValid percent (%)Camel723.72Sheep72937.62Cattle36919.04Goat46624.05Buffalo1819.34Dog1095.62Red fox100.51Jackal10.05Donkey10.05Not defined638—Total2576—


### 3.2. Main Analysis

The highest relative frequency percentage of infection with cystic echinococcosis in animals was related to G1 genotype with P=0.91 (95% CI=0.84,0.97) and the lowest relative frequency percentage was related to G2 genotype with P=0.07 (95% CI=0.00,0.18). Pooled estimates of infection relative frequency percentage were also statistically significant in G3, G6, and G7 genotypes (Tables 3 and Figures 4–8).Table 3
The pooled estimate of cystic echinococcosis genotypes prevalence in animals of Iran.
Type of genotypeNumber of studies in which each genotype was evaluatedNumber of participantsRandom pooled ES (95% CI)P value for test (ES=0)I2 (%)TheP value for the heterogeneity testEstimate of between-study variance (Tau2)G12723170.91 (0.84,0.97)<0.00195.40%<0.0010.25G25170.07 (0.00, 0.18)0.0286.31%<0.0010.11G3171220.12 (0.07, 0.18)<0.00180.65%<0.0010.07G67740.19 (0.08, 0.33)<0.00187.42<0.0010.15G731560.19 (0.04, 0.42)<0.00196.31%<0.0010.20Figure 4
Forest plot of 27 studies on cystic echinococcosis G1 genotype prevalence in animals.Figure 5
Forest plot of 5 studies on cystic echinococcosis G2 genotype prevalence in animals.Figure 6
Forest plot of 17 studies on cystic echinococcosis G3 genotype prevalence in animals.Figure 7
Forest plot of 7 studies on cystic echinococcosis G6 genotype prevalence in animals.Figure 8
Forest plot of 3 studies on cystic echinococcosis G7 genotype prevalence in animals.


### 3.3. Subgroup Analysis

To reduce heterogeneity in the pooled estimation of the relative frequency percentage of cystic echinococcosis, in G1, G3, and G6 genotypes, subgroup analysis was performed based on the type of animal under study. The results showed that in G1 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 G3 and G6 genotype. In camels, it was obtained with P=0.50 (95% CI=0.31,0.69) and P=0.45 (95% CI=0.22,0.69), respectively. Subgroup analysis was not possible in G2 and G7 genotypes due to the low sample size (Table 4 and Figures 9–11).Table 4
Subgroup analysis of cystic echinococcosis genotypes prevalence by animal types.
Type of genotypeNumber of studies in which each genotype was evaluatedRandom pooled ES (95% CI)P value for test (ES=0)I2 (%)TheP value for the heterogeneity testType of animalsG1Sheep120.98 (0.92, 1)<0.00187.07<0.001Cattle100.95 (0.86, 1)<0.00179.34<0.001Goat111 (0.96, 1)<0.00173.82<0.001Camel40.46 (0.26, 0.67)<0.00164.940.04Buffalo41 (0.97, 1)<0.00155.130.08Dog40.90 (0.73, 1)<0.00171.390.01Red fox11 (0.69, 1)<0.001——Jackal11 (0.03, 1)0.05——Donkey11 (0.03, 1)0.05——Overall480.97 (0.92, 0.99)<0.00187.51<0.001G3Sheep50.12 (0.04, 0.22)<0.00163.270.03Cattle60.04 (0.00, 0.14)0.0637.460.16Goat20.30 (0.00, 0.74)0.04—Camel20.50 (0.31, 0.69)<0.001—Buffalo20.05 (0.00, 0.21)0.22—Dog20.14 (0.07, 0.23)<0.001—Overall190.12 (0.06, 0.20)<0.00162.48<0.001G6Sheep20.13 (0.05, 0.22)<0.001——Cattle20.21 (0.11, 0.34)<0.001——Goat20.14 (0.02, 0.30)<0.001——Camel30.45 (0.22, 0.69)<0.001——Dog10.13 (0.02, 0.38)0.03——Overall100.24 (0.14, 0.36)<0.00169.19<0.001Figure 9
Forest plot of subgroup analysis of studies on cystic echinococcosis G1 genotype prevalence by animal types.Figure 10
Forest plot of subgroup analysis of studies on cystic echinococcosis G3 prevalence by animal types.Figure 11
Forest plot of subgroup analysis of studies on cystic echinococcosis G6 genotype prevalence by animal types.


## 3.1. Baseline Characteristics of Studies

Table1 shows the final information of the studies included in the meta-analysis. To have a well-defined outcome and the ability to perform a meta-analysis, analysis was performed in the genotype groups G1, G2, G3, G6, and G7. Also, the type of animal under study (Camel, Sheep, Cattle, Goat, Buffalo, Dog, Red Fox, Jackal, and Donkey) and the sample size of each animal in each study were extracted.Table 1
Baseline characteristics of the 28 studies included in the meta-analysis of cystic echinococcosis relative frequency percentage in animals.
Geographical regionType of animalsSample sizeCystic echinococcosis genotype [1]ReferencesG1(sheep strain)G2(Tasmanian sheep strain)G3(buffalo strain)G6(camel strain)G7(pig strain)1Lolerestan (2011)Sheep88100%[15]Cattle27100%Goat25100%2Esfahan (2011)Camel2634.61%65.39%[16]Cattle1464.28%35.71%Sheep34100%Goat10100%3Western Azerbaijan (2011)Sheep270100%[17]Goat185100%Cattle197100%Buffalo129100%Dog8100%4Urmia, Tabriz, Ardabil, Rasht, Ahvaz (2012)Buffalo25100%[18]5Esfahan (2012)Goat2085%15%[19]6Yasuj (2012)Sheep31100%[20]Goat56100%Cattle6100%7Ardebil (2013)Dog14100%[21]Red fox10100%Jackal1100%8Mazandaran (2013)Goat120100%[22]9Tehran (2014)Donkey1100%[23]10East Azarbaijan (2016)Sheep1989.47%10.52%[24]11Tabriz (2015)Dog1681.259.37%9.37%[25]12Northwest (2015)Sheep4996%4.00%[26]Cattle2892.85%7.15%13Mazandaran (2019)Sheep5100%[27]Cattle1100%14Golestan (2016)Camel966.70%66.70%66.70%33.30%33.30%[28]Sheep1889.21%3.07%16.92%Cattle4089.21%3.07%16.92%Buffalo2100%50%Goat1100%100%15Northwest, North, and Southeast (2017)—11580%0.86%9.6%12.17%[29]16Northeast (2015)Sheep50100%[30]Goat3080%20%17Esfahan (2014)Sheep5163.00%25.00%12%[31]Goat877%21%2%Cattle772%28%18Ardebil (2013)Sheep1995%5%[32]Goat4100%Cattle2199.95%4.76%19Kerman (2012)—3775.67%13.51%10.81%[33]20Central of Iran (2011)Camel1926.30%42.10%31.60%[34]21West Azerbaijan, East Azerbaijan, Ardabil, Gilan, Khuzestan (2011)Buffalo2592%8%[35]22Northwest (2016)—2294.50%5.70%[36]23Kerman (2013)—28070.763%36.5%[37]24Rasht, Gilan (2021)—5794.20%5.80%[38]25Esfahan (2010)Sheep37100%[39]Cattle4100%Camel1866.66%33.33%Goat8100%Tehran (2010)Sheep27100%Golestan (2010)Sheep10100%Cattle5100%Mazandaran (2010)Sheep3100%26Markazi province (2019)—4961%2%37%[6]27Lorestan (2018)Sheep18100%[40]Cattle1888.90%11.10%28Khorasan Razavi (2019)Dog7175%10%15%[41]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). %) (Table2).Table 2
Type of animals percent in 28 studies included in the meta-analysis.
Type of animalsNumberValid percent (%)Camel723.72Sheep72937.62Cattle36919.04Goat46624.05Buffalo1819.34Dog1095.62Red fox100.51Jackal10.05Donkey10.05Not defined638—Total2576—


## 3.2. Main Analysis

The highest relative frequency percentage of infection with cystic echinococcosis in animals was related to G1 genotype with P=0.91 (95% CI=0.84,0.97) and the lowest relative frequency percentage was related to G2 genotype with P=0.07 (95% CI=0.00,0.18). Pooled estimates of infection relative frequency percentage were also statistically significant in G3, G6, and G7 genotypes (Tables 3 and Figures 4–8).Table 3
The pooled estimate of cystic echinococcosis genotypes prevalence in animals of Iran.
Type of genotypeNumber of studies in which each genotype was evaluatedNumber of participantsRandom pooled ES (95% CI)P value for test (ES=0)I2 (%)TheP value for the heterogeneity testEstimate of between-study variance (Tau2)G12723170.91 (0.84,0.97)<0.00195.40%<0.0010.25G25170.07 (0.00, 0.18)0.0286.31%<0.0010.11G3171220.12 (0.07, 0.18)<0.00180.65%<0.0010.07G67740.19 (0.08, 0.33)<0.00187.42<0.0010.15G731560.19 (0.04, 0.42)<0.00196.31%<0.0010.20Figure 4
Forest plot of 27 studies on cystic echinococcosis G1 genotype prevalence in animals.Figure 5
Forest plot of 5 studies on cystic echinococcosis G2 genotype prevalence in animals.Figure 6
Forest plot of 17 studies on cystic echinococcosis G3 genotype prevalence in animals.Figure 7
Forest plot of 7 studies on cystic echinococcosis G6 genotype prevalence in animals.Figure 8
Forest plot of 3 studies on cystic echinococcosis G7 genotype prevalence in animals.


## 3.3. Subgroup Analysis

To reduce heterogeneity in the pooled estimation of the relative frequency percentage of cystic echinococcosis, in G1, G3, and G6 genotypes, subgroup analysis was performed based on the type of animal under study. The results showed that in G1 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 G3 and G6 genotype. In camels, it was obtained with P=0.50 (95% CI=0.31,0.69) and P=0.45 (95% CI=0.22,0.69), respectively. Subgroup analysis was not possible in G2 and G7 genotypes due to the low sample size (Table 4 and Figures 9–11).Table 4
Subgroup analysis of cystic echinococcosis genotypes prevalence by animal types.
Type of genotypeNumber of studies in which each genotype was evaluatedRandom pooled ES (95% CI)P value for test (ES=0)I2 (%)TheP value for the heterogeneity testType of animalsG1Sheep120.98 (0.92, 1)<0.00187.07<0.001Cattle100.95 (0.86, 1)<0.00179.34<0.001Goat111 (0.96, 1)<0.00173.82<0.001Camel40.46 (0.26, 0.67)<0.00164.940.04Buffalo41 (0.97, 1)<0.00155.130.08Dog40.90 (0.73, 1)<0.00171.390.01Red fox11 (0.69, 1)<0.001——Jackal11 (0.03, 1)0.05——Donkey11 (0.03, 1)0.05——Overall480.97 (0.92, 0.99)<0.00187.51<0.001G3Sheep50.12 (0.04, 0.22)<0.00163.270.03Cattle60.04 (0.00, 0.14)0.0637.460.16Goat20.30 (0.00, 0.74)0.04—Camel20.50 (0.31, 0.69)<0.001—Buffalo20.05 (0.00, 0.21)0.22—Dog20.14 (0.07, 0.23)<0.001—Overall190.12 (0.06, 0.20)<0.00162.48<0.001G6Sheep20.13 (0.05, 0.22)<0.001——Cattle20.21 (0.11, 0.34)<0.001——Goat20.14 (0.02, 0.30)<0.001——Camel30.45 (0.22, 0.69)<0.001——Dog10.13 (0.02, 0.38)0.03——Overall100.24 (0.14, 0.36)<0.00169.19<0.001Figure 9
Forest plot of subgroup analysis of studies on cystic echinococcosis G1 genotype prevalence by animal types.Figure 10
Forest plot of subgroup analysis of studies on cystic echinococcosis G3 prevalence by animal types.Figure 11
Forest plot of subgroup analysis of studies on cystic echinococcosis G6 genotype prevalence by animal types.


## 4. 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 G1.The results of the meta-analysis of our study showed that the most common genotypes of cystic echinococcosis in animals in Iran, wereEchinococcus granulosus sensu lato (sheep genotype or G1) and E. Canadensis group (camel genotype or G6), respectively. Canadensis group (Pig genotype or G7) 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 G1 and then G6 [42], also genotype G1 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 G1 was identified as the most abundant cystic echinococcosis genotype of G3. However, in the study of Said Amer et al., in Egypt [51], the most abundant genotype extracted was G6. 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 G3 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 G1 genotype was related to Goat samples (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 G1 genotype, which is almost similar to our study and in the study of Hajialilo et al., in the southeast of Iran [33], the results showed that 100% of the samples isolated from Goat were infected with the G1 genotype.The results of our study subgroup analysis showed that the highest infection with G3 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 G3 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 G3 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 G1 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 G6 genotype, and in the study of Shahnazi et al., in Isfahan province [16] 65.36% of the samples isolated from Camel, genotype G6, while the results of our subgroup analysis showed that the highest percentage of infection with G6 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 G6 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.


## 5. 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 G1. 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.



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*Source: 8197741-2022-10-19.xml*