Document Type : Research Paper
Authors
1 Department of Food Hygiene and Aquatic, Faculty of Veterinary Medicine, University of Tabriz, Iran
2 Department of Food Hygiene and Aquatic, Faculty of Veterinary Medicine, University of Tabriz
Abstract
Keywords
Main Subjects
Extended Abstract
Introduction
Cystic echinococcosis (CE), caused by the larval stage of Echinococcus granulosus, is a neglected zoonotic disease with global public health and economic importance. The hydatid cyst develops mainly in the liver and lungs of intermediate hosts, including domestic ruminants and humans. Protoscoleces contained in fertile cysts are of particular epidemiological significance, as ingestion by carnivores enables the continuation of the parasite’s life cycle. Consequently, inactivation of protoscoleces is crucial in controlling disease transmission. Conventional protoscolicidal agents, such as hypertonic saline and ethanol, have shown efficacy but may present toxicity risks and are unsuitable for large-scale applications. Gamma irradiation, a physical method with high penetration capacity and no chemical residues, has been proposed as a promising alternative for parasite inactivation. This study was designed to evaluate the protoscolicidal efficacy of different gamma irradiation doses on hydatid cyst protoscoleces under in vitro conditions.
Materials and Methods
Fertile hydatid cysts were collected from the lungs of naturally infected sheep slaughtered at the Tabriz abattoir between November 2022 and December 2023. Protoscoleces were aspirated aseptically and washed three times with sterile phosphate-buffered saline (PBS). Viability was initially assessed microscopically using 1% eosin staining. Only samples with ≥90% viability were included. Aliquots of approximately 5,000 protoscoleces in 1 mL PBS were transferred into sterile microtubes. Experimental groups were exposed to cobalt-60 gamma irradiation at doses of 0.5, 0.75, 1.0, 1.5, and 2.0 kGy for 1.5 to 5 min using the facilities of the Northwest Research Complex (Bonab, Iran). Positive controls consisted of 5% sodium chloride, while negative controls contained non-irradiated cyst fluid. Following irradiation, samples were incubated at 37 °C for 24 hours, and viability was reassessed using the eosin exclusion test. Data were analyzed by One-way ANOVA followed by Duncan’s multiple range test, with significance set at p < 0.05.
Results
Gamma irradiation induced a dose-dependent reduction in protoscolex viability. The highest mortality rate was observed at 2.0 kGy (98.5%), indicating almost complete inactivation of protoscoleces. Doses of 1.5, 1.0, 0.75, and 0.5 kGy produced mortality rates of 85.38%, 73.61%, 61.73%, and 82.5%, respectively. Interestingly, the 0.5 kGy dose produced higher mortality than 1.0 kGy, which may reflect experimental variability or differential sensitivity of protoscoleces to low-dose radiation. In contrast, the negative control group exhibited minimal mortality, confirming the intrinsic viability of untreated parasites. The positive control (5% NaCl) produced near-complete mortality, consistent with its well-known protoscolicidal properties. Statistical analysis revealed significant differences between irradiated groups and the negative control (p < 0.05), as well as among irradiation doses.
Conclusion
The present study demonstrates that gamma irradiation exerts a strong protoscolicidal effect on hydatid cyst protoscoleces under in vitro conditions, with efficacy increasing in a dose-dependent manner. Doses of 1.5 and 2.0 kGy were particularly effective, achieving mortality rates above 85% and 98%, respectively. These findings suggest that gamma irradiation may serve as a safe, residue-free, and innovative approach for controlling CE by inactivating the larval stage of E. granulosus. The potential application of this method in sterilizing infected organs or animal by-products prior to disposal could significantly reduce transmission risks to definitive hosts and, consequently, to humans. However, further in vivo studies are necessary to validate the safety and practicality of this approach, optimize irradiation doses, and explore its integration into control programs for cystic echinococcosis.
Conceptualization, writing—original draft preparation, writing—review and editing, visualization, supervision, formal analysis, investigation, project administration, Nasser Hajipour; methodology, Elnaz Rahbai.; visualization, supervision, Parviz Hassanzdeh. Authors have read and agreed to the published version of the manuscript..
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Hydatid cyst samples were collected from sheep slaughtered at a licensed abattoir. No live animals were used or harmed specifically for this study. The research procedures were conducted in accordance with institutional and national ethical guidelines.
The author declares no conflict of interest.
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