UNCOVERING THE PATHOGENIC LANDSCAPE OF HELMINTH (OPISTHORCHIS VIVERRINI) INFECTIONS: THE CONTRIBUTION OF PHYSICAL ENVIRONMENT, SOCIAL ENVIRONMENT, AND HEALTHCARE INTERVENTIONS

Ph.DDOCTOR OF PHILOSOPH

Dam influences on liver fluke transmission: Fish infection and human fish consumption behavior

10.1080/24694452.2015.1122508Annals of the American Association of Geographers1064755-77

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

<div><p>Background</p><p>Helminth 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 <i>Opisthorchis viverrini</i> infections.</p><p>Methodology</p><p>A 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.</p><p>Principal Findings</p><p>The importance attributed to <i>O</i>. <i>viverrini</i> infections varied among health centers in the four study villages. Villages where <i>O</i>. <i>viverrini</i> 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 <i>O</i>. <i>viverrini</i> infections in the study area, was 11.4% higher in villages that prioritized <i>O</i>. <i>viverrini</i> 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).</p><p>Conclusions/Significance</p><p>This 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.</p></div

Spatial variation in <i>O</i>. <i>viverrini</i> infection prevalence and mean infection intensity.

<p>Comparison of infection prevalence and mean intensity by (A) villages, (B) provincial health jurisdictions, and (C) waterbody types.</p

Factors associated with reasons for consumption among participants who consume raw fish dishes.

<p>Factors associated with reasons for consumption among participants who consume raw fish dishes.</p

Multivariate logistic regression model of infection prevalence.

<p>Only explanatory variables that are statistically significant in the model are displayed.</p

Multivariate Quasi Poisson regression of infection intensity.

<p>Only explanatory variables that are statistically significant in the model are displayed.</p

Location of study sites.

<p>Ubolratana reservoir in northeast Thailand and the four study sites, two in the north of the reservoir, and two in the south.</p

Summary of key findings on health centers’ chemotherapy efforts and current top health concerns by villages.

<p>Only infection prevalence was collected by the health centers, not infection intensity.</p

Socio-economic and demographic factors as risk factors for <i>O</i>. <i>viverrini</i> infection.

<p>(A) <i>O</i>. <i>viverrini</i> infection prevalence and (B) mean intensity of infected participants of various socio-economic and demographic factors.</p