Food-borne trematodiases

Abstract

An estimated 750 million people are at risk of infections with food-borne trematodes, which comprise liver flukes (Clonorchis sinensis, Fasciola gigantica, Fasciola hepatica, Opisthorchis felineus, and Opisthorchis viverrini), lung flukes (Paragonimus spp.), and intestinal flukes (e.g., Echinostoma spp., Fasciolopsis buski, and the heterophyids). Food-borne trematodiases pose a significant public health and economic problem, yet these diseases are often neglected. In this review, we summarize the taxonomy, morphology, and life cycle of food-borne trematodes. Estimates of the at-risk population and number of infections, geographic distribution, history, and ecological features of the major food-borne trematodes are reviewed. We summarize clinical manifestations, patterns of infection, and current means of diagnosis, treatment, and other control options. The changing epidemiological pattern and the rapid growth of aquaculture and food distribution networks are highlighted, as these developments might be associated with an elevated risk of transmission of food-borne trematodiases. Current research needs are emphasized.

FIG. 1.

Taxonomy of food-borne trematodes with emphasis on species parasitizing humans that are covered in the current review. (Based on data from reference .)

FIG. 2.

Life cycles of five different food-borne trematodes including intestinal flukes (Echinostoma hortense, Fasciolopsis buski, and Heterophyes heterophyes), a liver fluke (Clonorchis sinensis), and a lung fluke (Paragonimus westermani). Sizes of eggs and metacercariae are based on data from references and .

FIG. 3.

Age prevalence curves for Opisthorchis viverrini at three different locations in the Nam Theun 2 hydroelectric project area in central Lao PDR in the late 1990s.

FIG. 4.

Evolution of inland freshwater fish production in China from 1965 to 2005. (Based on data from http://www.fao.org/figis/servlet/TabLandArea?tb_ds=Aquaculture&tb_mode=TABLE&tb_act=SELECT&tb_grp=COUNTRY.)

FIG. 5.

Scanning electron microscope observations of the anterior part of an untreated Fasciola hepatica depicting the oral sucker (OS) and ventral sucker (VS) (A), a Fasciola fluke revealing blebbing (b) near the oral sucker and ventral sucker after administration of a single oral dose of 200 mg/kg artemether (B), the oral sucker region of a Clonorchis sinensis fluke with sensory papillae (SP) visible (C), sloughing (s) seen on the oral sucker of an artemether-treated C. sinensis fluke (D), oral sucker region of an Opisthorchis viverrini fluke with sensory papillae (E), and blebbing and closure of oral sucker observed on an O. viverrini fluke treated with a single oral dose of 400 mg/kg tribendimidine (F).