Echinococcus granulosus sensu lato Genotypes in Different Hosts Worldwide: A Systematic Review

INTRODUCTION

The aim of this study was to develop a synthesis of the evidence available regarding verified E. granulosus sensu lato (s.l.) genotypes in different species worldwide.

MATERIAL AND METHODS

A systematic review was performed including studies concerning genotypes of E. granulosus s.l. without language or genotyped method restriction, published between 1990 and 2020. A systematic search was carried out in Trip Database, BIREME, SciELO, LILACS, IBECS, PAHO-WHO, EMBASE, PubMed, Scopus, and WoS. Variables of interest were year of publication, country, number of samples, and hosts; genotypes, molecular marker, haplotypes and molecular biology techniques used. Descriptive statistics were applied.

RESULTS

2411 articles were analyzed, however 135 met the selection criteria, representing 8643 liver and lung samples. Of the samples selected 24% were human, the remaining samples pertained to non-human animal hosts; cattle and sheep prevailed with 28.6% and 26.6% of the studied samples, respectively. The reported evidence is mainly from Iran, Turkey, Argentina, China and Chile; with 50, 11, 6, 6 and 5 studies, respectively, published between 1992 and 2020 [most frequently during 2015-2020 (76/135 studies; 56.3%)]. The mitochondrial gene cox1 was generally sequenced and informative (91.8%). Genotypes most frequently identified were E. granulosus sensu stricto (s.s.) (83.2%).

CONCLUSIONS

Based on this overall evidence, it can be concluded that publications related to genotypes of E. granulosus s.l. are heterogeneous. E. granulosus ss accounts for the vast majority of the global burden of E. granulosus s.l. worldwide. Further studies including larger number of cases and adequate internal validity are required to specify the distribution of genotypes in various host species.

TRIAL REGISTRATION

PROSPERO CRD42018099827.

The global status and genetic characterization of hydatidosis in camels (Camelus dromedarius): a systematic literature review with meta-analysis based on published papers

Hydatidosis is a potential zoonotic helminthic disease affecting a broad spectrum of mammals, including humans, worldwide. The current review was conducted to investigate the genotypic status and prevalence of hydatid disease in camels across the world. For the purpose of the study, the articles addressing the worldwide prevalence of hydatidosis in camels were searched in several English language databases. The search process resulted in the inclusion of 122 papers. Based on the data presented in the reviewed articles, the pooled prevalence of hydatid disease in camels across the world was measured at 23.75% (95% CI 20.15-27.55). Moreover, the subgroup analysis demonstrated significant differences in the overall prevalence of hydatidosis among camels based on year, geographic area, climate parameters, camel population, gender, infected organ, fertility rate of the cyst and laboratory diagnostic technique. Furthermore, the Echinococcus granulosus genotypes identified in camels with hydatidosis included G1, G2, G3, G1-G3, G5, G6, G7, G6-G7 and G6-G10, with G6 being the most common genotype throughout the world. The data obtained from the current study are central to the better conceptualization of the biological and epidemiological characteristics of E. granulosus s.l. genotypes around the world, which can be helpful in the planning and adoption of more comprehensive control strategies.

Zoonotic implications of camel diseases in Iran

Approximately 60% of all human pathogens and 75% of emerging infectious diseases are zoonotic (of animal origin). Camel zoonotic diseases can be encountered in all camel-rearing countries. In this article, all studies carried out on camel zoonotic diseases in Iran are reviewed to show the importance of camels for public health in this country. More than 900 published documents were systematically searched to find relevant studies from 1,890 until late 2018. The collected articles were classified according to the aetiological agents. In this study, 19 important zoonotic diseases were reported among Iranian camels including listeriosis, leptospirosis, plague, Q fever, brucellosis, campylobacteriosis, tuberculosis, pasteurellosis, clostridiosis, salmonellosis, Escherichia coli infections, rabies, camelpox, Middle East respiratory syndrome coronavirus, Crimean-Congo haemorrhagic fever, echinococcosis, cryptosporidiosis, toxoplasmosis and dermatophytosis, most of which belong to bacterial, viral, parasitic and fungal pathogens, respectively. Results show that camels are one of the most important sources of infections and diseases in human; therefore, continuous monitoring and inspection programs are necessary to prevent the outbreak of zoonotic diseases caused by this animal in humans.

Echinococcus granulosus genotypes in Iran: a systematic review

Cystic echinococcosis (CE) caused by Echinococcus granulosus sensu lato (s.l.) is a significant zoonosis, especially in developing countries of the Middle East, with many studies focusing on CE genotypes in Iran. We performed a systematic review to determine the exact status of E. granulosus genotypes in the country. We explored English (Pubmed, Scopus, ISI Web of Science and Science Direct) and Persian (Magiran, Iran Medex and Scientific Information Database) databases along with Google Scholar. Our review included 73 studies published prior to the end of 2015. In total, 2952 animal (intermediate and definitive) hosts were examined, and the prevalent genotypes comprised G1 (92.75%) and G6 (4.53%) in sheep, cattle, camels, goats and buffaloes; G3 (2.43%) in five herbivore hosts and dogs; G7 (0.2%) in sheep and goats; and G2 (0.06%) in dogs. G1 was mostly dominant in West Azerbaijan, whereas G3 and G6 were identified most frequently in the provinces of Isfahan and Fars, respectively. Regarding human CE infection, 340 cases were reported from Iran, with the identified genotypes G1 (n = 320), G6 (n = 13) and G3 (n = 7). Most CE-infected humans originated from Isfahan province (168 cases), whereas the lowest number of infected persons was noted in Kerman province (two cases). The information obtained from this systematic review is central to better understanding the biological and epidemiological characteristics of E. granulosus s.l. genotypes in Iran, leading to more comprehensive control strategies.

A rare case of cerebral hydatidosis caused by a G1 genotype of Echinococcus granulosus in a cow from Iran

Hydatidosis is a medically and veterinary important parasitic disease that is endemic in many parts of the world. Unilocular hydatid cysts may develop in almost any part of the body. Up to 70% of hydatid cysts are located in the liver, followed by 25% in the lungs. Cerebral hydatidosis is an uncommon manifestation of the disease, occurring in less than 1/1000 infected hosts, yet diagnosis does pose a problem. We have reported an exceptionally rare case of cerebral hydatidosis in cattle. This is the first report to describe the characteristic pathological features of the cerebral hydatidosis in cattle caused by the G1 genotype of Echinococcus granulosus. Genotypic analysis was performed on a hydatid cyst from a cow originating from southern Iran, based on the sequence analysis of the cox1 mitochondrial gene.

Molecular characterization and sequence analysis of Echinococcus granulosus from sheep isolates in East Azerbaijan province, northwest of Iran

Echinococcus granulosus as an etiologic agent of hydatid cyst is one of the most important zoonotic helminthes in the world that causing enormous economic and health losses. The aim of this study was to evaluate genotype of E. granulosus isolated from sheep using mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and sequencing method in East Azerbaijan province, northwest of Iran. Nineteen sheep hydatid cyst samples were collected. Genomic DNA was extracted from protoscoleces using commercial DNA extraction kit. Mitochondrial cox1 region was amplified by polymerase chain reaction (PCR) and all isolates were sequenced. Afterward, sequences were analyzed for determination of genotypes by related software. G1 (94.73 %) and G3 (5.27 %) genotypes were identified from the isolates which out of 19 hydatid cysts, 17 samples were G1B, 1 sample G1D and the other one had G3 genotype. Results of this study indicate that common sheep strain (G1); especially G1B is the dominant subtype of E. granulosus in East Azerbaijan province.

Epidemiological study of hydatidosis in the dromedaries (Camelus dromedarius) of different regions of Iran

OBJECTIVE

To determine the prevalence of hydatidosis in dromedaries.

METHODS

438 dromedaries were examined in five regions of Iran from 20 March, 2010 to 19 March, 2011. The relationship between host age and the mean number of hydatid cysts, and prevalence and fertility rates was analyzed using chi-square test.

RESULTS

One hundred and thirty five out of 438 (30.82%) camels harboured hydatid cysts of Echinococcus granulosus. Number of cysts was 700 with 72.5% lung cyst. The highest rate of infection was that 54 (40%) of camels was found in the Khorasan Razavi region (in the north-east part of Iran) while the lowest 6 (4.4%) of camels was found in Semnan province. Infection was higher in >15 years age group. The most commonly infected organs were lungs (72.5%) followed by liver (12.6%). Both liver and lungs together constituted 14.8% of infection. A comparison found that hydatid cysts of liver had a higher fertility rate (32.57%) than that of lung (19%); while most of cysts of lung were calcified (24.42%). The mean number of protoscoleces per mL in the lung fertile cysts was higher than that of liver cysts. Fertile or sterile might be due to the different species or genotypes. The mean number of cysts in infected liver and lungs was 1-5 cysts. The intensity of infection increased with age.

CONCLUSIONS

The results of current study can make a background data for implementing hydatid control programs and warrant the importance of camel in public health.

Molecular genotyping of Echinococcus granulosus from dromedaries (Camelus dromedarius) in eastern Iran

With the aim of genotyping Echinococcus granulosus cysts found in Iranian dromedaries (Camelus dromedarius), 50 cysts of E. granulosus were collected from five geographical regions in Iran. Cysts were characterized using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the internal transcribed spacer 1 (ITS1) gene and sequencing fragments of the genes coding for mitochondrial cytochrome c oxidase subunit 1 (cox1). Morphological criteria using rostellar hook dimensions were also undertaken. The present results have shown that 27 out of 50 E. granulosus cysts (54%) were determined as the G1 strain, and the other (46%) were determined as the G6 strain. The molecular analysis of the ITS1 region of ribosomal DNA corresponded with the morphological findings. Because of its recognized infectivity in humans, the G1 genotype is a direct threat to human health and its presence in Iranian dromedaries is of urgent public health importance.

Mitochondrial phylogeny of the genus Echinococcus (Cestoda: Taeniidae) with emphasis on relationships among Echinococcus canadensis genotypes

The mitochondrial genomes of the genus Echinococcus have already been sequenced for most species and genotypes to reconstruct their phylogeny. However, two important taxa, E. felidis and E. canadensis G10 genotype (Fennoscandian cervid strain), were lacking in the published phylogeny. In this study, the phylogeny based on mitochondrial genome sequences was completed with these taxa. The present phylogeny highly supports the previous one, with an additional topology showing sister relationships between E. felidis and E. granulosus sensu stricto and between E. canadensis G10 and E. canadensis G6/G7 (closely related genotypes referred to as camel and pig strains, respectively). The latter relationship has a crucial implication for the species status of E. canadensis. The cervid strain is composed of two genotypes (G8 and G10), but the present phylogeny clearly suggests that they are paraphyletic. The paraphyly was also demonstrated by analysing the complete nucleotide sequences of mitochondrial cytochrome c oxidase subunit 1 (cox1) of E. canadensis genotypes from various localities. A haplotype network analysis using the short cox1 sequences from worldwide isolates clearly showed a close relatedness of G10 to G6/G7. Domestic and sylvatic life cycles based on the host specificity of E. canadensis strains have been important for epidemiological considerations. However, the taxonomic treatment of the strains as separate species or subspecies is invalid from a molecular cladistic viewpoint.

Hydatid cyst formation in male Balb/c mice following the intraperitoneal injection of live protoscoleces and activated oncospheres: a comparative study

This study was designed to evaluate and compare the infection rate and cyst formation in male Balb/c mice following intraperitoneal injection of protoscoleces and activated oncospheres. Protoscoleces were collected aseptically from the liver of naturally infected sheep. The eggs were obtained from three experimentally infected dogs and activated oncospheres were prepared as described by Heath and Smyth (1970) and Kyngdon et al. (2006). A total of 20 Balb/c mice were divided into two groups of ten animals each. The mice of first and second groups were intraperitoneally infected with 1,500 protoescoleces and 1,500 activated oncosphere respectively. After 8 months of infection, all mice were euthanized, necropsied and the hydatid cysts were removed, counted, measured and weighed. The results showed that nine of ten mice of first group were infected. The maximum number of cysts was 551 in one mouse with mean size of 3.78 ± 2.21 mm and total weight of 25.48 g. The minimum number of cysts was 13 in one mouse with mean size of 3.93 ± 2.18 mm and total weight of 0.564 g. In the second group, only one mouse was infected with two cyst with mean size of 11.15 ± 1.94 mm and total weight of 1.193 g. This study showed that the male Balb/c inbred mouse is more permissive to infection with intraperitoneal injection of protoscoleces than activated oncospheres.

Genotyping Echinococcus granulosus from dogs from Western Iran

Cystic echinococcosis is a zoonotic infection caused by the dog tapeworm, Echinococcus granulosus. In the present study, adults of E. granulosus (n=20) were collected from 71 dogs from Western Iran and were genetically characterized using DNA sequencing of the partial mitochondrial cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase 1 (nad1). Consensus sequences were obtained for cox1 (366) and nad1 (471) genes. Phylogenetic analysis of concatenated nad1 and cox1 nucleotide sequence data was performed using Bayesian Inference approach. Overall, the dog isolates indicated nine different sequences in cox1 and seven in nad1 genes. Three genotypes (G1 [75%], G2 [10%] and G3 [15%]) were identified from the isolates. The G2 sequences indicated 100% homology with reference G2 sequence in both cox1 (Genbank accession number M84662) and nad1 (AJ237633) genes. G3 sequences showed 100% homology with G3 reference sequence in nad1 (AJ237633), but displayed two different cox1 profiles, each having 99% homology with reference G3 sequence (M84663). In the phylogenetic tree all of the isolates were grouped into a distinct cluster corresponding to the G1-G3 complex with relevant reference sequences. The presence of G1 genotype (sheep strain) of E. granulosus sensu stricto as dominant genotype in dogs is emphasized. To the best of our knowledge, this study established the first record of E. granulosus sensu stricto, G2 genotype in Iran.

Molecular characterization of livestock and human isolates of Echinococcus granulosus from south-west Iran

Hydatidosis is an important public health problem in several parts of Iran. The aim of this molecular study is to investigate Echinococcus granulosus genotypes as the causative agents of hydatidosis in the south-west of Iran (Khuzestan province). In this study, isolates of 334 hydatid cysts were collected from the liver and lungs of 141 sheep, 104 cattle, 84 goats and 5 human cases. DNA was extracted and examined by nested polymerase chain reaction (PCR) of ribosomal DNA (rDNA) internal transcribed spacer 1 (ITS1) and restriction fragment length polymorphism (RFLP)-PCR. In addition, fragments of genes coding for ITS1 were sequenced. The results of RFLP-PCR analysis revealed the presence of the G1 genotype in all human, cattle, goat and sheep isolates. Furthermore, no camel strain (G6) was detected among all samples in the regions studied. The molecular findings indicate that the predominant genotype involved in E. granulosus transmission in south-west Iran is the common sheep strain (G1 genotype), which occurs in human, cattle, sheep and goat populations. In conclusion, these results may have important implications for hydatid disease control in the areas studied.