Food-borne trematodiasis: role in hepatobiliar and intestinal morbidity and risk patterns for infection in ecological and socio-economic distinct settings of Southeast Asia

Swiss Coordinator : Peter Odermatt, Swiss Tropical Institute, Basel
Main Foreign partner : Kongsap Akkhavong, National Institute of Public Health, Vientiane
Cooperation with : Lao PDR
Disciplines : Tropical Medicine, Epidemiology

Abstract
In the Mekong River basin parasitic infections are of major public health, economic and veterinary importance. Besides malaria, food- and water-borne trematode infections (worms) persist. Liver flukes (Opisthorchis viverrini, Fasciola sp.) and intestinal flukes (Fasciolopsis buski, Haplorchis sp.) are responsible for hepatobiliar and intestinal diseases, respectively. Schistosoma mekongi is the endemic water-borne trematode affecting liver and intestinal tract. Food- and water-borne trematodes exhibit a complex life cycle in which either aquatic snails, or crustacean, or fish, or water plants act as intermediate host(s). Consumption of these animals and plants (raw or undercooked) or exposure to contaminated water leads to infection. Ecological features of the Mekong River basin ascertain the presence of the environmental reservoir. The poor socio-economic status governs the exposure of mainly rural populations. Humans infections with two or more parasites are very frequent. The socioecological setting determines which parasites can be transmitted, and hence the characteristics of the multiple infections change according to the setting and as a consequence the combined morbidity. Further complications arise as the distinction of these parasites with standard laboratory diagnostic techniques is difficult and therefore misdiagnosis is common.
The goal of the present study is to analyse the characteristics and dynamics of polyparasitism of
hepatobiliary and intestinal trematodes in the Mekong River basin area and its community-attributable burden, which in turn will provide a basis for the design and implementation of control strategies.
Three main objectives will be pursued: (1) Analyse qualitatively and quantitatively the characteristics of the trematode polyparasitims with hepatobiliary and intestinal tropism in three distinctly different socio-ecological settings and to predict the spatial distribution by socio-economic and ecological factors; (2) Develop measures for individual and community experienced morbidity due to trematode infection with hepatobiliary and intestinal tropism by sonographical investigations, indicators of individual development (nutritional status and development) and reported/perceived hepatobiliary and intestinal morbidity; and (3) Design control strategies, based on the expected results from objectives 1 and 2 that are validated in the high risk communities of the Mekong River basin area.
Pursuit of these objectives will lead to the following outcomes: (i) The age-prevalence patterns of
trematodes with hepatobiliar and intestinal tropism in different socio-ecological settings in the
Mekong River basin and bordering areas. (ii) Validation of the standard diagnostic tools best suited for species-specific diagnosis. (iii) An assessment of the interrelationships of these trematode infections and other intestinal parasitic infections. (iv) An analys is of the risk factors that can predict tremtode
infection and morbidity in different socio-ecological settings. (v) An evaluation to what extend
hepatobiliar and intestinal morbidity is attributable to trematode infections. (vi) An assessment of the
dynamics of resolution of morbidity following treatment. (vii) An analysis of the impact of
multiparasitism and how trematode infections impact on individual development as measures by
nutritional status. Finally, (viii) the results generated from (i) through (vii) will allow to design best tailored intervention strategies for the village, district and national levels.
The study area consists of three distinctly difference socio-ecological setting of Lao PDR. They
represent the variety of socio-ecological setting present in the Mekong River basin and bordering
areas. Hospital- and community-based studies will be performed. Parasitological techniques will be used to detect infection and multiple infections. Standard clinical procedures will be developed to describe hepatobiliar and intestinal disease. Standardized ultrasonographic examination procedures will be developed and utilised to describe underlying pathological changes.
The present study will provide the first qualitative and quantitative, hospital and community based assessment of trematode infections, their interrelationship and association with other intestinal parasitic infections in the Mekong River. Based on this it will allow risk mapping and prediction and will help to tailor cost-effective control and surveillance strategies. Finally, the research partnership established through this research programme will significantly contribute to local capacity building at all levels.

Contact Addresses:

Dr Peter Odermatt
Swiss Tropical Institute
PO Box
4002 Basel, Switzerland
peter.odermatt@unibas.ch

Ass. Prof Kongsap Akkhavong
National Institute of Public Health
Nongbone-Phonggkheng Street 103
Vientiane, Lao PDR
kongsap@hotmail.com

 

Photo 1: Villagers on the islands of the Mekong River (South of Lao PDR) are at risk for infection with Schistosoma mekongi.

 

Photo 2: Insufficiently cooked fish and pork meat may transmit parasitic infection.