Five-Year Slaughterhouse-Based Surveillance of Echinococcus granulosus in Sheep from Yili, Northwest Xinjiang, China

TL;DR

A five-year study in Xinjiang, China, found high infection rates of Echinococcus granulosus in sheep, with a dominant strain posing a public health risk.

Contribution

This study provides the first comprehensive five-year surveillance data on Echinococcus granulosus in sheep in Yili Prefecture, China.

Findings

Echinococcus granulosus prevalence in sheep was 22.0% over five years with no significant county-level differences except between Huocheng and Zhaosu.

The G1 genotype was overwhelmingly dominant (95.2%), indicating a zoonotic public health threat.

Network analysis suggested recent population expansion of the parasite, with 14 haplotypes identified.

Abstract

Background: Cystic echinococcosis (CE) remains a significant zoonotic burden in the pastoral regions of China. Yili Prefecture in Xinjiang is a high-risk area, yet comprehensive data are lacking on the prevalence and molecular characteristics of Echinococcus granulosus in its primary intermediate host, sheep. Methods: From 2020 to 2024, a total of 2700 sheep livers were visually inspected for hydatid cysts infection at one randomly selected slaughterhouse in each of the nine counties of Yili Prefecture. Ninety cyst-positive samples were subjected to morphological examination and molecular genotyping by amplifying and sequencing the nad2 gene. Results: The overall prevalence of E. granulosus was 22.0% (594/2700). County-level prevalence ranged from 18.3% (Zhaosu County) to 25.7% (Huocheng County), with no significant differences observed among the counties (p > 0.05) except between Huocheng and Zhaosu. Temporally, the annual prevalence fluctuated between 20.2% and 24.2% without a consistent downward trend. Genotyping revealed that the G1 genotype was overwhelmingly dominant (95.2%, 79/83), with a minor circulation of the G3 genotype (4.8%, 4/83). Fourteen haplotypes were identified; Hap1 was the central and predominant haplotype (47.0%, 39/83), found in all counties. Network analysis suggested a recent population expansion of the parasite. Conclusion: This five-year surveillance study reveals a persistently high prevalence and complex genetic diversity of E. granulosus in sheep in Yili Prefecture. The dominance of the zoonotic G1 genotype indicates a substantial public health threat. Our findings provide crucial data for contributing to the development of local control strategies. However, the specific reasons for the high infection rate in sheep remain unclear, as this study did not include examinations of definitive hosts or environmental samples; this gap should be addressed in future research.

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