Population genetic evidence of heterogeneous zoonotic transmission of Schistosoma japonicum in endemic communities in the Philippines.

BACKGROUND

Zoonotic schistosomiasis, which is caused by the parasite Schistosoma japonicum, remains a neglected public health concern in Asian countries, including China, the Philippines, and Indonesia. The presence of animal reservoirs poses a significant challenge to controlling the disease. Previous studies in China have found that incorporating measures to control animal reservoirs led to a reduction in human cases. To support control efforts in the Philippines, we conducted a multi-locus genotyping (MLG) analysis using microsatellite markers (STRs) to investigate the transmission dynamics of S. japonicum infections between human and animal hosts in two moderately endemic areas.

METHODS

Stool and faecal samples were collected from human residents and water buffaloes in the provinces of Leyte and Oriental Mindoro. S. japonicum eggs were isolated from positive samples and single-egg genome DNA was extracted for STR/MLG analysis.

RESULTS

STRUCTURE analysis and discriminant analysis of principal components (DAPC) in Leyte showed that the parasite populations in water buffaloes clustered with that in humans, suggesting potential zoonotic transmission. By contrast, STRUCTURE and DAPC analyses revealed distinct parasite populations in water buffaloes and humans in Oriental Mindoro, suggesting limited genetic overlap between parasite populations in humans and water buffaloes in this study area, which may indicate reduced contribution of buffaloes to transmission under the conditions studied.

CONCLUSIONS

Overall, these findings highlight the need to include animal surveillance in guidelines for schistosomiasis elimination. Given the complex life cycle of the parasite, it is crucial to understand infection dynamics across human and animal hosts when designing effective, integrated control strategies.