The Prevalence of Fasciola (Digenea: Fasciolidae) Species in Livestock and Humans in Iran, A Systematic Review

Document Type : Review Article

Authors

1 Department of pathobiology, Karaj branch, Islamic Azad University, Karaj, Iran

2 Department of Pathobiology, Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran

10.32592/ARI.2025.80.1.263

Abstract

Fasciolosis is a foodborne parasitic disease caused by Fasciola hepatica and Fasciola gigantica. This disease is very important and has been reported in different vertebrate hosts in more than 80 different countries. Compared to Fasciola gigantica, Fasciola hepatica affects a wider range of animals and is often reported from high altitudes and hot and humid areas.
In the present researchstudy, an attempt has been made to update fascioliasis in animal and human hosts in Iran during the years 2019 to 2024. A Systematic systematic search of published articles in English was conducted using electronic databases including Google Scholar, PubMed, Iran Science Direct, SID and Magiran. After a systematic search, a total of 18 articles were selected that met the input criteria for evaluating the prevalence of fascioliasis in humans and animals in Iran. Among the 18 articles analyzed, Fasciola hepatica species were documented in only five articles. In four articles, researchers encountered difficulties in identifying the specific species of Fasciola. Interestingly, the remaining articles reported both F. hepatica and F. gigantica species simultaneously. The results showed that in many cases (61.1%), fascioliasis was identified based on a molecular analysis. The prevalence of human fascioliasis varied from 1.7% to 2.4% in different parts of Iran. The present systematic review showed that limited studies have been conducted in the field of fasciolosis in Iran during the last five years. Therefore, the authors recommend that more studies be conducted on the prevalence of fasciolosis in all provinces. Considering the prevalence of fasciolosis in different provinces, it is recommended to design and inform effective prevention and control strategies for this disease.

Keywords

Main Subjects

1. Introduction

Fasciolosis, a foodborne parasitic disease, is caused by the trematodes Fasciola hepatica and Fasciola gigantica ( 1 ). This disease is of significant concern, having been reported in various vertebrate hosts across more than 80 countries ( 4 ). A comparative analysis reveals that F. hepatica exhibits a broader spectrum of host range, with a propensity to be reported from high altitudes and hot and humid regions, in contrast to the distribution patterns of F. gigantica. The prevalence of human fasciolosis remains uncertain, necessitating further investigation and the collection of additional epidemiological data. Approximately two decades ago, estimations placed the global burden of fasciolosis at approximately 17 million individuals ( 9 - 10 ). It is possible that these figures underrepresent the actual numbers due to a limited understanding of the impact of the disease in numerous African and Asian nations. The life cycle of Fasciola comprises two hosts: gastropods, which function as intermediate hosts, and mammals, which act as final hosts. Following the excretion of eggs by the final host, the miracidium is immediately released into the water. The miracidium, upon entering the skin of a snail from the family Limnidae, undergoes a transformation into a cercaria. Free-floating cercariae can subsequently metamorphose into metacercariae, which attach to aquatic vegetation. Humans and livestock become infected through the ingestion of metacercariae from contaminated water or vegetables. Ingestion of these metacercars leads to their migration through the intestinal wall and liver tissue, reaching the bile ducts and undergoing maturation ( 13 ). In Asia, fasciolosis has been reported principally from Iran and Vietnam. Notably, Iran is among the six countries with the highest annual reports of fasciolosis worldwide ( 16 ). In order to develop effective disease control strategies, it is essential to understand the transmission method and the epidemiological characteristics of the disease ( 4 ). A recent study was conducted to comprehensively assess the prevalence of human and animal fasciolosis in Iran and globally ( 19 - 21 ). However, a comprehensive report on the prevalence of fasciolosis in different hosts during the last five years in Iran is currently not available. The objective of this study is to provide an update on the prevalence of Fasciola in human and animal hosts in Iran from 2019 to 2024.

2. Evidence Acquisition

In this study, the PRISMA method was employed to systematically review and report on standard systematic review studies. A comprehensive search strategy was employed, encompassing English and Persian databases, namely Google Scholar, Science Direct, and PubMed, as well as IranDoc, Magiran, and SID. The search terms included the operators "or" and "and," along with the keywords "fasciola," "fasciolosis," "human," "domestic animals," "diagnosis," "prevalence," and "Iran." The search was limited to articles published between 2019 and 2024. Initially, the titles and abstracts of the selected articles that investigated the prevalence of Fasciola in arthropod hosts in Iran were reviewed. The full texts of the documents were entered into a reference and note management software program, and duplicate studies were removed. The selection of articles meeting the study criteria was conducted by two of the authors separately and according to a predetermined checklist. The extraction and evaluation of studies was conducted using two forms: one form for human studies and one form for animal studies. The two authors then meticulously reviewed the selected studies, and those that met the inclusion criteria were incorporated into the study. Conversely, studies were excluded if they lacked essential information, failed to align their methods with their results and conclusions, centered on treatment, or reported the presence of other trematodes ( Figure 1). The required information was elicited from the selected articles by two independent authors. In the event of inconsistency, the difference between the two was resolved by the other author.

Figure 1. Flowchart of searching and selecting the desired final studies between the years 2019 and 2024.

3. Results

A total of 408 studies were initially identified through database searching, and an additional five articles were appended to this list by examining their reference lists. Subsequent to the removal of duplicate articles (n=40), an initial search of the titles and abstracts of the remaining articles (373 articles) was conducted. The full texts of 68 articles were then evaluated for validation. Following this, 50 articles were excluded from the review due to non-relevance to the subject, the study area being outside of Iran, the presence of parasites other than Fasciola, duplicate results, and lack of full text. Following these exclusions, 18 articles were selected according to the established entry criteria ( 2 , 3 , 5 - 8 , 11 , 12 , 14 , 15 , 17 , 18 , 22 , 23 , 25 , 27 ). Of these, only F. hepatica was reported in five articles, the species of Fasciola was not specified in four articles, and the simultaneous infection of F. hepatica and F. gigantica was reported in other articles. Of the 18 studies conducted on fasciolosis, 11 articles employed molecular tests such as the melting point curve of high-quality genomic material (HRM), standard polymerase chain reaction (PCR), loop-mediated amplification (LAMP), restriction fragment length polymorphism (RFLP), and multiplex PCR. Conversely, serological tests were utilized in only two studies, while morphology tests were employed in five studies. The serological studies that employed commercial kits and natural cathepsin L utilized the aforementioned methods to detect Fasciola (Table 1). A total of seven articles were identified as pertaining to the prevalence of fasciolosis. The prevalence of fasciolosis was most frequently reported in goats, followed by sheep, cattle, and humans (Table 1). This study revealed that fasciolosis has been documented in sheep, cattle, goats, buffalo, and humans in the provinces of Tehran, Ardabil, Fars, Gilan, Khuzestan, Sistan and Baluchestan, Bushehr, Mazandaran, Golestan, Alborz (Karaj), Lorestan, Ilam, West Azerbaijan, East Azerbaijan, Qom, Qazvin, Yazd, Isfahan, Kermanshah, and Razavi Khorasan. The prevalence of fasciolosis in humans has exhibited geographical variation, ranging from 1.7% in Golestan to 2.4% in Sistan and Baluchistan.

aim Provinces Host Diagnostic test Fasciola sp. Finding References
Comparison between molecular and morphological test in identification of Fasciola hepatica in sheep Lorestan Sheep Morphological and molecular F. hepatica The higher sensitivity of molecular tests in the diagnosis of fasciola compared to morphological tests. The prevalence rate was reported as 1.2%. ( 2 )
Serological study of fasciolosis Golestan Human Serology Fasciola sp. The prevalence rate was 1.7% ( 5 )
Genetic diversity and evaluations of different Fasciola hepatica haplotypes in different provinces Elam, West Azerbaijan, East Azerbaijan, Khuzestan, Bushehr, Yazd, Alborz (Karaj), Sistan and Balochistan and Qom. Sheep, goat and cow PCR F. hepatica Among 130 different samples of Fasciola hepatica, 37 different haplotypes were identified based on nad gene ( 7 )
Rapid identification of different Fasciola species using HRM test Gazvin Sheep and Cow HRM F. hepatica and F. gigantica The HRM technique in the present study was found to be a reliable technique for the identification and genetic diversity of liver flukes ( 12 )
Morphological study of Fasciola sp. Golestan Cow and Sheep and Goat ITS1, RFLP and Multiplex PCR F. hepatica and F. gigantica Observation of the first case of Fasciola hybrid in Golestan province ( 15 )
Morphological characterization of Fascila sp. Ardabil, Khuzestan, Isfahan, Tehran, Mazandaran cows, sheep, goats, buffalo PCR F. hepatica and F. gigantica Significant genetic differences between populations of f. gigantica was shown in Asia and Africa, while isolates of f. hepatica from different regions of the world share high similarities. ( 18 )
Molecular characterization of Fascila sp. Lorestan Cow, sheep, goat PCR F. hepatica and F. gigantica Among the mitochondrial genes, the nd1 gene is able to examine the differences and similarities better than the co1 gene. ( 23 )
Serological study of fasciolosis Sistan and Baluchestan Human Serology Fasciola sp. The prevalence of fasciolosis in the samples was 2.4% and a significant relationship between the use of raw vegetables and fasciolosis was reported. ( 25 )
Phylogenetic analysis of fasciolosis from endemic regions Ilam, Lorestan and Khuzestan Cows, Sheep, Goats Multiplex PCR F. hepatica similarity in ITS gene among samples isolated from different hosts is almost similar. The genetic variation in the Cox gene is much higher than that of ITS and NAD ( 27 )
Molecular phylogeny and genetic diversity among Fasciola gigantica Kermanshah cows, sheep, goats. PCR Fasciola gigantica Fasciola gigantica was isolated among 20 samples of 5 different haplotypes based on Nad gene. A statistically significant difference was reported between the genotypes of the present study and other genotypes in the world ( 3 )
Molecular identification of Fasciola Fars cows, sheep, goats PCR F. hepatica and F. gigantica Fasciola gigantica was the dominant species in these areas ( 6 )
Identification and phylogenetic analysis of the isolated species Sistan and Baluchistan, Cow, sheep PCR F. hepatica and F. gigantica Fasciola gigantica was the dominant species in these areas ( 8 )
Prevalence of fasciolosis among Alborz cow morphology Fasciola sp. The prevalence of fasciolosis was reported as 2%. A significant relationship between humidity and fasciolosis was reported. ( 11 )
Investigating the prevalence of fasciolosis in slaughtered animals in Tabriz Tabriz Cows, sheep, goats Morphology Fasciola species The prevalence of Fasciola hepatica in cows, goats and sheep was 3.3, 3.8 and 10% respectively. The prevalence of Fasciola gigantica in cows, goats and sheep was 1.9, 1.8 and 4 percent, respectively. ( 14 )
Investigating the prevalence of fasciolosis in slaughtered cattle Qazvin Cows, sheep, goats Morphology Fasciola species The prevalence of Fasciola in cows, sheep and goats was 1.2, 0.8 and 0.9 percent respectively. ( 17 )
Comparison of molecular methods for the diagnosis of Fasciola hepatica in sheep Lorestan the sheep molecular Fasciola hepatica The prevalence rate of Fasciola was 5.6%. Lamp technique was more efficient than PCR ( 22 )
Investigating the prevalence of fasciolosis in slaughtered animals Fasciola Sabzevar Sheep and cattle morphology Fasciola The prevalence of Fasciola in cattle and sheep was 8.3% and 2.5% respectively. ( 24 )
Investigating the prevalence of fasciolosis in Gilan sheep Morphology Fasciola hepatica The prevalence of Fasciola hepatica in sheep was 3.4 percent. ( 26 )
Table 1.The list of studies that the infection of Fasciola spp. have reported in animals and humans in different provinces of Iran (2019-2024).

4. Conclusion

The present study was conducted with the objective of investigating the various types of human and animal fasciolosis in Iran. Until the conclusion of the 20th century, fasciolosis was acknowledged as a significant veterinary problem due to substantial economic losses. However, with the emergence of human cases worldwide, the World Health Organization (WHO) recognized the need to re-evaluate the significance of this disease. Human fasciolosis has been reported on all five continents, with a surge in cases documented in 51 countries. In some of the reviewed studies, fasciolosis was identified to the genus level due to the use of morphological and serological techniques. However, the challenges associated with accurately identifying parasite species using morphological methods, such as the presence of multiple variations in morphological characteristics, have led to a shift toward the utilization of molecular tests ( 28 ). According to the studies of Khademvatan et al. ( 19 ), the epidemiology of fasciolosis in animals and humans in Iran is still unknown. A review of the literature reveals that only nine studies examined the prevalence of fasciolosis in humans, goats, sheep, and cattle between 2019 and 2024 ( 4 , 5 , 7 , 14 , 17 , 22 , 24 - 26 ). Of these, only two seroprevalence studies were conducted on human fasciolosis. Consequently, it is not feasible to accurately estimate the status of human fasciolosis in recent years in Iran. The prevalence of fasciolosis in various hosts across different time periods ranged from 0.8% to 10%, suggesting a low prevalence of Fasciola in Iran. In a review study by Khadem Vatan et al. ( 19 ), the overall prevalence of fasciolosis in Iran between 1999 and 2019 was reported to be approximately 6%. Recent research suggests a significant drop in prevalence rates of veterinary fascioliasis in Iran, largely attributed to improved collaboration among veterinary organizations in treating livestock and heightened awareness among local farmers ( 29 ). Numerous studies have demonstrated that fasciolosis imposes substantial economic burdens on dairy cattle. The economic repercussions of fasciolosis encompass diminished milk, meat, and wool production; a retarded growth rate; and elevated expenses associated with liver destruction during meat inspection ( 31 ). Notably, a paucity of research addressing the economic ramifications of fasciolosis in Iran has been observed ( 32 - 35 ). The present study revealed that human and animal fasciolosis cases have been documented in twenty Iranian provinces over the past five years. However, when the general population of Iran is taken into consideration, the number of individuals examined for the prevalence of the F. hepatica parasite is minimal. Consequently, in order to obtain a precise estimate of the prevalence of this parasite in Iran, further studies are required throughout the country. Despite the numerous research studies conducted on fascioliasis in regions where the disease is prevalent, many aspects of the condition still require further elucidation ( 36 ). The present systematic review revealed that there has been a paucity of studies conducted in the field of fasciolosis in Iran during the last five years. Consequently, the authors of the present study recommend the implementation of further research focusing on the prevalence of fasciolosis in all provinces. Given the prevalence of fasciolosis in different provinces, it is recommended that effective prevention and control strategies for this disease be designed and disseminated.

Acknowledgment

Not Applicable.

Authors' Contribution

Study concept and design: B H A, N T

Acquisition of data: B H A,Y P,S S Sh

Analysis and interpretation of data: B H A,Y P,S S Sh, NT

Drafting of the manuscript: B H A,Y P,S S Sh, NT

Critical revision of the manuscript for important intellectual content: B H A,Y P,S S Sh, NT

Ethics

We hereby declare all ethical standards have been respected in preparation of the submitted article.

Conflict of Interest

It has been demonstrated that there is an absence of competition of interest.

Data Availability

The data that support the findings of this study are available upon request from the corresponding author.

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Archives of Razi Institute
Volume 80, Issue 1
January and February 2025
Pages 263-269

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