Uncovering the Pathogenic Landscape of Helminth (Opisthorchis viverrini) Infections: A Cross-Sectional Study on Contributions of Physical and Social Environment and Healthcare Interventions

Abstract

BackgroundHelminth infections have proven recalcitrant to control by chemotherapy in many parts of Southeast Asia and indeed farther afield. This study isolates and examines the influence of different aspects of the physical and social environment, and uneven intervention effort contributing to the pathogenic landscape of human Opisthorchis viverrini infections.MethodologyA cross-sectional survey, involving 632 participants, was conducted in four villages in northeast Thailand to examine the impact on prevalence and parasite burden of the reservoir dam environment, socio-economic, demographic, and behavioral factors, and health center intervention efforts. Formalin-ether concentration technique was used for diagnoses, and multivariate models were used for analyses.Principal FindingsThe importance attributed to O. viverrini infections varied among health centers in the four study villages. Villages where O. viverrini infections were not prioritized by the health centers as the healthcare focus were at a higher risk of infection (prevalence) with odds ratio (risk factor) of 5.73 (3.32–10.27) and p-value < 0.01. Priority of healthcare focus, however, did not appear to influence behavior, as the consumption of raw fish, the main source of O. viverrini infections in the study area, was 11.4% higher in villages that prioritized O. viverrini infections than those that did not (p-value = 0.01). Landscape variation, notably proximity to reservoir, affects vulnerability of local population to infection. Infection intensity was higher in population located closer to the reservoir with risk ratio of 2.09 (1.12–4.02) and p-value < 0.01. Patterns of infection intensities among humans were found to match fish infection intensity, where higher infection intensities were associated with fish obtained from the reservoir waterbody type (p-value = 0.023).Conclusions/SignificanceThis study demonstrated the importance of environmental influence and healthcare focus as risk factors of infections in addition to the socio-economic, demographic, and behavioral factors commonly explored in existing studies. The reservoir was identified as a crucial source to target for opisthorchiasis intervention efforts and the need to consider infection intensity in disease control efforts was highlighted. The holistic approach in this study, which underscores the close relationship between the environment, animals, and humans in development of human infections or diseases, is an important contribution to the framework of One Health approach, where consideration of helminth diseases has largely been overlooked.

Liver Fluke-Associated Biliary Tract Cancer

“… 92 The level of precipitation, the change in flowing river and the man-made water reservoirs could also affect the habitat of fishes and snails, which could inevitably affect the prevalence of liver fluke. 93 , 94 …”

Parasites in Food: From a Neglected Position to an Emerging Issue

“…A cross-sectional study in Thailand found that prioritization of the parasite Opisthorchis viverrini by village-level health centers had an impact on risk of infection (Ong et al, 2016). Although, interestingly, behavior regarding consumption of raw fish did not have a significant impact on risk of infection, the authors emphasize the need for a holistic approach in considering control measures for this pathogen, particularly consideration of those factors that constitute the broader pathogenic landscape (Ong et al, 2016).…”

Current prevalence of Opisthorchis viverrini infection and associated risk factors in Nakhon Phanom Province, Northeastern Thailand

“…The differences in prevalence between the districts maybe due to their respective distance to the waterbodies where communities procure fish for consumption. A study by Ong et al (2016) has shown that the distance to waterbody had an impact on how villagers source the fish used in raw fish dishes. Differences in the infections levels in fish are also dependent on the waterbody, thus can affect the risk of human exposure to the infections (Ong et al, 2016).…”

“…A study by Ong et al (2016) has shown that the distance to waterbody had an impact on how villagers source the fish used in raw fish dishes. Differences in the infections levels in fish are also dependent on the waterbody, thus can affect the risk of human exposure to the infections (Ong et al, 2016). Compare to That Phanom and Na Kae, Wang Yang district is located within the waterway of the Nam Kam River which flows from the neighbouring province of Sakon Nakhon toward downstream of the Mekong River.…”