Background: Fascioliasis is a neglected tropical disease (NTD) with a fluctuating global prevalence, recorded at 14% in 2012 and 4.5% in 2022 across endemic regions such as the Andean highlands, Egypt, and Vietnam. Transmission is primarily driven by the consumption of contaminated water, vegetables, or infected livestock products.
In Mongolia, Fasciola hepatica was first identified in 1967, with indigenous livestock infections confirmed in the Kharaa River basin in 2016. Molecular and morphometric analyses have since confirmed the distribution of F. hepatica among various livestock types across the Kharaa, Yeroo, and Selenge river basins. Studies on intermediate hosts have identified diverse gastropod mollusk species within Mongolia's freshwater ecosystems. Recent serological screenings (ELISA) in livestock across the central region revealed high seroprevalence rates, ranging from 6.22% to 51.02%. Despite the documented prevalence in animals, research on human infection and associated risk factors in these high-risk regions remains limited. Materials and Methods: A descriptive, cross-sectional study was conducted among 273 individuals from 130 herder households across selected soums in Selenge, Darkhan-Uul, Tuv, Khovsgol, and Bulgan provinces. Study areas were selected based on proximity to river basins and previous reports of livestock outbreaks. Data and serum samples were collected to evaluate knowledge, risk factors, and infection status. Fascioliasis was determined by detecting specific IgG antibodies using the Enzyme-Linked Immunosorbent Assay (ELISA) at the National Center for Zoonotic Diseases. Statistical analyses, including Chi-square and Fisher’s exact tests, were performed using SPSS, STATA, and R, while spatial distribution was mapped via QGIS. The study protocol was approved by the Ethics Committee of "Ach" Medical University, and all participants provided written informed consent. Results: Out of 273 participants, the overall seroprevalence of Fasciola-specific IgG antibodies was 11.4%. Geographically, the highest prevalence was recorded in Mandal soum (26.0%) and Bayangol soum (11.5%) of Selenge province. While no significant difference was found across age groups, the 50–59 (14.5%) and 30–39 (12.5%) cohorts showed the highest infection rates. Occupational analysis revealed that herders accounted for 14.7% of positive cases, facing a 1.86 times higher risk of infection compared to other occupations (p=0.05). Ultrasonographic examination of the 273 participants revealed pathological changes in 47 individuals, including increased hepatic and pancreatic echogenicity, renal cysts, and prostatic calcification. When comparing increased echogenicity with fascioliasis infection status, infected individuals were 3.85 times more likely to exhibit increased echogenicity (p < 0.001), indicating a statistically significant difference. Regarding awareness, 52.7% of participants had heard of the disease, though only 41.39% correctly identified contaminated water and vegetables as transmission routes. Knowledge levels varied significantly by province (p < 0.001), with the lowest awareness observed among herders in Selenge province. Conclusion The seroprevalence of fascioliasis was determined to be 11.4% among the population of five soums across Bulgan, Darkhan-Uul, Selenge, and Khuvsgul provinces in the central region. Among these, the highest infection rate was recorded in Mandal soum of Selenge province. While no statistically significant differences were observed regarding age and gender among the overall positive cases, men in Mandal soum of Selenge province were 2.63 times more likely to be infected than women. In terms of occupation, the prevalence of infection was notably higher among herders.
Although the overall awareness of fascioliasis among the study population in the central region was 52.7%, knowledge levels varied significantly across provinces. Regarding risk factors, traditional transmission routes such as the use of untreated river or spring water for drinking and swimming in rivers were not identified as primary drivers of infection. Instead, livestock ownership and the consumption of unwashed raw fruits and vegetables were determined to be the significant risk factors for fascioliasis in this population.

Fascioliasis is caused by two species of parasitic trematodes (Fasciola hepatica, Fasciola gigantica) that mainly affect the liver. It belongs to the group of foodborne trematode infections and is a zoonosis, meaning an animal infection that may be transmitted to humans. Fascioliasis was first included in the World Health Organization report on NTDs (Neglected tropical diseases) in 2010.
Humans become infected by consuming raw plants that have been irrigated or contaminated with Fasciola larvae through exposure to unsafe water sources. Once ingested, the larvae migrate through the liver and bile ducts, causing tissue damage and inflammation.
In 2012, the prevalence of fasciolosis was 14% in 81 countries worldwide, 57.62 but in 2022, the prevalence of fasciolosis among 50 million people in countries around the world decreased to 4.5%.
The spread of fascioliasis is a public health concern. Fascioliasis is not considered a fatal disease, but it is considered a disabling disease. The World Health Organization estimates that fascioliasis causes 90,041 DALYs (Disability-Adjusted Life Years) per year, and causes losses of $3.2 billion in livestock and agricultural production worldwide.