Identifying Environmental Factors for Soil Transmitted and Food Borne Helminth Diseases in Border Regions of Northern Thailand

Parasitic worm infections (helminthiases) of humans greatly impact low to medium income countries such as Thailand, by undermining health and agricultural productivity. Particularly across Southeast Asia, the expansion of urban areas and the movement of people from countries with less developed public health programs, have increased disease transmission. This project will investigate environmental influences on helminth disease transmission. Many emerging helminthiases are linked to the environment through increased contact between humans and animals, the intensification and integration of food production systems, and the expansion of migration [1]. Therefore, effective control and treatment of many helminth diseases would benefit from better integration of clinical, veterinary and agricultural components embedded in an environmentally-driven research strategy.
Thailand is classified as an 'Upper Middle Income' Country. However due the nature of helminth diseases endemic sites are significantly impacted by border countries including Cambodia, Laos and Myanmar, all of which are classified as 'Least Developed' Countries. Our research team has recently established baseline human infection rates in three Thailand border regions, using highly sensitive molecular diagnostics. In the past the under-estimation of helminth infections in communities such as Thailand and our previous work in the Philippines [2], provides incomplete information for the development of government policy.
The proposed project will use already established human prevalence data [3] to focus on specific locations and parasite species in endemic regions of Northern Thailand, so that environmental components of disease transmission can be identified. One class of parasites, soil transmitted helminths (STH), requires significant environmental contamination for effective disease transmission. Approximately 1.5 billion or quater of the world's population are infected by STH, including the main species of Ascaris, Trichuris and hookworm. Parasite eggs found in the soil or unwashed vegetables are the primary source of infection. Similarly, food borne diseases, including the cancer-causing Opisthorchis, are contracted by consuming uncooked fish, and are linked to water sources, and the interaction between snail and fish hosts.
The student will spend considerable time in Thailand, collecting soil, vegetable and aquatic samples for diagnostics using traditional microscopy and more recently developed molecular analysis. Environmental foci of disease will be stratified using spatial modelling (GIS geographical information system) to demonstrating the importance of food and geography, in helminth disease transmission. Earth observation data will be used to build GIS layers of climatic and other relevant environmental factors, and enable intervention strategies to be assessed against likely future changes. Identification of environmental components of disease transmission will lead to predictive models for better informed government control policies.

[1] Gordon CA, McManus DP, Jones MK, Gray DJ, Gobert GN: The Increase of Exotic Zoonotic Helminth Infections: The Impact of Urbanization, Climate Change and Globalization. Adv Parasitol 2016, 91:311-397.
[2] Gordon CA, McManus DP, Acosta LP, Olveda RM, Williams GM, Ross AG, Gray DJ, Gobert GN: Multiplex real-time PCR monitoring of intestinal helminths in humans reveals widespread polyparasitism in Northern Samar, the Philippines. Int J Parasitol 2015, 45(7):477-483.
[3] Adisakwattana P, Yoonuan T, Phuphisut O, Poodeepiyasawat A, Homsuwan N, Gordon CA, McManus DP, Atkinson LE, Mousley A, Gobert GN: Clinical helminthiases in Thailand border regions show elevated prevalence levels using qPCR diagnostics combined with traditional microscopic methods. Parasit Vectors 2020, 13(1):416.