Assessment of environmental contamination with Echinococcus spp. through DNA detection in free-roaming canid feces and soil in human echinococcosis hotspots from the Three-River-Source Region of the Qinghai-Tibet Plateau, China

Abstract Background The Three-River-Source Region of the Qinghai-Tibet Plateau is a hyperendemic focus for echinococcosis, with Echinococcus granulosus, E. multilocularis, and E. shiquicus circulating between definitive canid hosts (dogs and foxes) and intermediate hosts (livestock and rodents). However, the extent of environmental contamination by Echinococcus eggs remains understudied and poses significant risks to human and animal health. Methods From 2019 to 2021, we collected 631 canid fecal samples (296 from dogs and 335 from foxes) and 398 adjacent soil samples across endemic counties in the Three-River-Source Region of the Qinghai-Tibet Plateau. Multiplex real-time PCR was employed to detect Echinococcus species DNA in feces and soil samples. Results The overall Echinococcus prevalence in canid feces was 7.13% (45/631), with 3.01% in E. multilocularis (19/631), 2.06% in E. granulosus (13/631), and 2.06% in E. shiquicus (13/631). Foxes presented increased E. multilocularis (3.88%, 13/335) and E. shiquicus (2.69%, 9/335) infections, whereas dogs presented increased E. granulosus prevalence (2.70%, 8/296). Soil contamination with Echinococcus species was detected in 2.51% (10/398) of the samples. The primary contaminants were E. multilocularis and E. shiquicus (1.01% each, 4/398), whereas E. granulosus was less frequent (0.50%, 2/398). Moreover, the soil near fox feces was contaminated with both E. multilocularis and E. shiquicus, whereas the dog-associated soil was contaminated with all three species. Conclusions This study suggests widespread environmental deposition of Echinococcus eggs on the Qinghai-Tibet Plateau, driven by canid defecation. If these eggs remain viable, their persistence in soil would indicate a potential zoonotic transmission risk, highlighting the need for integrated control strategies targeting both domestic and wild canids. Graphical abstract