Prevalence and Molecular Characterization of Enterocytozoon bieneusi in Horses From Northern and Eastern China: Investigation of Associated Risk Factors and Assessment of Zoonotic Potential.
Abstract: Enterocytozoon bieneusi is a zoonotic microsporidian threatening public health, yet epidemiological data on equine infections in China are scarce despite frequent human-horse contact. In this study, 412 fresh horse fecal samples were collected from four Chinese regions covering four rearing systems and were screened for E. bieneusi internal transcribed spacer (ITS) sequences via nested PCR, with risk factor and phylogenetic analyses conducted. The overall infection prevalence reached 15.0% (62/412), varying geographically from 9.7% (Wenzhou) to 29.3% (Qiqihar). Foals <1 year and male horses exhibited significantly higher infection risks, with crude prevalence ratios (PRs) of 4.47 and 2.28, respectively, while prevalence did not differ statistically across rearing modes (p = 0.182). Eighteen genotypes were identified: 11 known (D, horse1, Peru8, Type IV, EbpC, CAF1, GX3, HNR-VI, SHWR5, SYSWR18, SYSWR23) and seven novel (HRBM1, KDM1, KDM2, QQHRM1, QQHRM2, QQHRM3, WZM1). Genotype D was dominant, accounting for 58.1% (36/62) of positive isolates, followed by genotype horse1 at 14.5% (9/62) and genotype EbpC at 3.2% (2/62). The other eight known genotypes and all seven novel genotypes each had one isolate. All seven novel genotypes clustered within zoonotic Group 1 with all the known genotypes except HNR-VI identified here. This study confirms widespread equine E. bieneusi circulation across eastern and northern China, modulated by geography, age, and sex. The predominance of zoonotic genotypes implies horses serve as potential reservoirs for human transmission, supplying baseline epidemiological evidence for equine One Health biosecurity management.
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Objective Summary
This study investigated the prevalence, genetic types, and risk factors of infection by Enterocytozoon bieneusi in horses from northern and eastern China, revealing significant zoonotic potential that highlights horses as a source of human infection.
Introduction and Background
Enterocytozoon bieneusi is a microsporidian parasite known to infect a wide range of hosts, including humans and animals, causing microsporidiosis, mainly affecting the digestive system.
The parasite is considered zoonotic, meaning it can transfer from animals to humans, posing a public health risk.
Previous epidemiological data on E. bieneusi infections in horses, especially in China, are limited despite frequent close human-horse interactions.
Aims of the Study
Determine the prevalence of E. bieneusi in horses from multiple regions in northern and eastern China.
Identify and molecularly characterize the genotypes of E. bieneusi present in these horse populations.
Analyze risk factors associated with infection including geographic location, age, sex, and types of horse rearing systems.
Assess the zoonotic potential of the identified genotypes, particularly whether the strains found are known to infect humans.
Methods
Collected 412 fresh fecal samples from horses across four regions in China, representing four different rearing systems.
Applied nested PCR (Polymerase Chain Reaction) targeting the internal transcribed spacer (ITS) region, a genetic marker used to identify E. bieneusi and differentiate its genotypes.
Performed risk factor analysis to associate infection prevalence with variables such as geographic region, age group, sex, and rearing mode.
Conducted phylogenetic analysis to determine genetic relationships among detected genotypes and to infer their zoonotic potential.
Results
Prevalence: Overall infection rate was 15.0% (62 out of 412 horses), but varied by location:
Lowest in Wenzhou at 9.7%
Highest in Qiqihar at 29.3%
Risk factors:
Foals under 1 year had a significantly higher likelihood of infection with a prevalence ratio (PR) of 4.47 compared to older horses.
Male horses had a higher infection risk (PR = 2.28) than females.
No significant differences in infection rates were found across different rearing systems (p = 0.182), suggesting rearing mode may not majorly influence risk.
Genotypes Identified: Eighteen distinct genotypes were detected:
Eleven known genotypes, including genotype D, horse1, Peru8, Type IV, EbpC, CAF1, GX3, HNR-VI, SHWR5, SYSWR18, SYSWR23.
Seven novel genotypes newly described in this study: HRBM1, KDM1, KDM2, QQHRM1, QQHRM2, QQHRM3, WZM1.
Genotype D was predominant, found in 58.1% of positive samples; horse1 accounted for 14.5%; EbpC for 3.2%; all others appeared in one isolate each.
Phylogenetic and Zoonotic Analysis:
All seven novel genotypes clustered within Group 1, which is known to contain zoonotic genotypes capable of infecting humans.
All known genotypes except HNR-VI also clustered within this zoonotic group.
This clustering strongly indicates that the genotypes circulating in horses have the potential to infect humans, confirming horses as potential reservoirs.
Discussion and Implications
The study reveals important epidemiological patterns, with age and sex influencing infection risk more than rearing system.
The geographic variability signals possible environmental or management-related exposure differences across regions.
The dominance of genotypes from the zoonotic Group 1 supports the idea that horses can transmit E. bieneusi to humans, posing a One Health challenge.
This risk is heightened given frequent human-horse interactions in these areas, particularly for handlers and veterinarians.
The discovery of seven novel genotypes expands the known diversity of E. bieneusi and underscores the need for continued surveillance.
The findings provide baseline data vital for designing biosecurity and infection control measures targeting horses to reduce zoonotic transmission risks.
Conclusion
Equine populations in northern and eastern China harbor a considerable prevalence of E. bieneusi, including multiple zoonotic genotypes.
Age and sex are significant risk factors for infection among horses, but the method of rearing is not.
Given the predominance of zoonotic strains, horses likely serve as reservoirs facilitating transmission to humans.
These insights emphasize the importance of integrated One Health strategies to monitor, control, and prevent E. bieneusi transmission in human and animal populations.
Cite This Article
APA
Peng X, Zhang Z, Yan C, Zhu F, Qin W, Zhao W, Ke J.
(2026).
Prevalence and Molecular Characterization of Enterocytozoon bieneusi in Horses From Northern and Eastern China: Investigation of Associated Risk Factors and Assessment of Zoonotic Potential.
Transbound Emerg Dis, 2026(1), e1144348.
https://doi.org/10.1155/tbed/1144348
Department of Geriatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, Zhejiang, China, wmu.edu.cn.
Zhang, Zhongkai
The First Clinical Medical College of Wenzhou Medical University, Wenzhou 325035, Zhejiang, China.
Yan, Chuhan
Department of Geriatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, Zhejiang, China, wmu.edu.cn.
Zhu, Fanggu
Department of Geriatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, Zhejiang, China, wmu.edu.cn.
Qin, Weimeng
Department of Geriatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, Zhejiang, China, wmu.edu.cn.
Zhao, Wei
School of Basic Medical Sciences, Wenzhou Medical University, Wenzhou 325035, Zhejiang, China, wmu.edu.cn.
Ke, Jiangqiong
Department of Geriatrics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, Zhejiang, China, wmu.edu.cn.
MeSH Terms
Animals
Enterocytozoon / genetics
Enterocytozoon / isolation & purification
Enterocytozoon / classification
Horses
Microsporidiosis / veterinary
Microsporidiosis / epidemiology
Microsporidiosis / microbiology
China / epidemiology
Risk Factors
Horse Diseases / epidemiology
Horse Diseases / microbiology
Prevalence
Zoonoses / epidemiology
Zoonoses / microbiology
Male
Phylogeny
Genotype
Female
Feces / microbiology
Grant Funding
Y2023070 / Basic Scientific Research Project of Wenzhou
Conflict of Interest Statement
The authors declare no conflicts of interest.
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