Foodborne trematode infections in Asia. Report of a joint WHO/FAO workshop, Ha Noi, Viet Nam, 26–28 November 2002, World Health Organization, WPRO

Overview

 The World Health Organization (WHO) and Food and Agriculture Organization (FAQ) held a joint workshop in Ha Noi, Viet Nam from 26 to 28 November 2002 to review the knowledge on foodborne trematode (FBT) infections, to discuss the possible measures for prevention and control of these infections and to inform Member States of the urgency for the implementation of control activities.

FBT infections affect the health of more than 40 million people throughout the world and are particularly prevalent in WHO's South-East Asia and Western Pacific Regions. These parasites originate an unacceptable burden of sufference and mortality and cause serious damage to aquaculture, which is a valuable source of food and employment in developing countries.

FBTs present particular epidemiological and clinical features that should be carefully considered for the development of appropriate preventive and control measures. Transmission to humans is almost entirely caused by consumption of food containing infective metacercariae. The distribution of these infections is highly focal, depending on the food habits of people and on the presence of susceptible snails. FBTs also present low host specificity, and a high number of definitive reservoir hosts can contribute to the contamination of water and snails, making it extremely difficult to control this aspect of the parasite cycle. From a clinical point of view, trematode eggs frequently cannot be detected in the stools or sputum of suspected cases and the disease presents a specific simptomatology, leading to frequent misdiagnoses. Tools such as serology and ultrasonography, which allow a precise diagnosis, are frequently not available in areas where FBT are endemic.

For all these reasons, the public health approach to control FBT should be based on "large-scale chemotherapy". Progress gained with pharmacological intervention should be sustained by practices that prevent the establishment of infection in fish and introduce high standards of food quality control in the commercial aquaculture sector. Health education significantly reduces risk habits and with good sanitation and hygiene represents a foundation for the prevention of parasitic disease.

Countries where FBT infections occur should establish an intersectoral working group to implement public health interventions, ensuring access to treatment for people living where these infections are endemic, and legislate for best practice for eliminating the risk of FBT infection from aquaculture products.

Two drugs are available for "large-scale chemotherapy". Praziquantel, a compound that is exceptionally well tolerated, is the drug of choice for the treatment of infection with most species of FBTs. In the case of fascioliasis, the only FBT infection for which the efficacy of praziquantel is not considered satisfactory, WHO recommends triclabendazole, a drug that has been used for treating fascioliasis for more tharr 20 years in the field of veterinary medicine; it is now available for human use.