Clonorchiasis and opisthorchiasis: epidemiology, transmission, clinical features, morbidity, diagnosis, treatment, and control

Abstract

Clonorchis sinensis, Opisthorchis viverrini, and Opisthorchis felineus are important liver flukes that cause a considerable public health burden in eastern Asia, southeastern Asia, and eastern Europe, respectively. The life cycles are complex, involving humans, animal reservoirs, and two kinds of intermediate hosts. An interplay of biological, cultural, ecological, economic, and social factors drives transmission. Chronic infections are associated with liver and biliary complications, most importantly cholangiocarcinoma. With regard to diagnosis, stool microscopy is widely used in epidemiologic surveys and for individual diagnosis. Immunologic techniques are employed for screening purposes, and molecular techniques facilitate species differentiation in reference laboratories. The mainstay of control is preventive chemotherapy with praziquantel, usually combined with behavioral change through information, education and communication, and environmental control. Tribendimidine, a drug registered in the People's Republic of China for soil-transmitted helminth infections, shows potential against both C. sinensis and O. viverrini and, hence, warrants further clinical development. Novel control approaches include fish vaccine and biological control. Considerable advances have been made using multi-omics which may trigger the development of new interventions. Pressing research needs include mapping the current distribution, disentangling the transmission, accurately estimating the disease burden, and developing new diagnostic and treatment tools, which would aid to optimize control and elimination measures.

Keywords: Clonorchis sinensis; Opisthorchis felineus; Opisthorchis viverrini; clonorchiasis; opisthorchiasis.

Fig 1

(A) Life cycle of liver flukes. [Adapted from reference (13) with permission from Elsevier; the illustrations of adult C. sinensis, O. viverrini, and O. felineus were redrawn from illustrations in reference (11) with permission from Elsevier.] (B) Adult worm of C. sinensis (recovered from mice) (courtesy of Liu Liu and Hao Zhang, Qiqihar Medical University; used with permission). (C) Adult worm of O. viverrini (recovered from hamster) [reproduced from reference (20) with permission from Elsevier]. (D) Egg of C. sinensis (expelled from adult worms recovered from rat) [courtesy of Ting-Jun Zhu, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention (Chinese Center for Tropical Diseases Research); used with permission]. (E) Cercaria of O. viverrini (shed from Bithynia siamensis siamensis) [reproduced from reference (21), which is published under a CC BY 4.0 license]. (F) Metacercaria of C. sinensis (digested from Pseudorasbora parva) (courtesy of Ting-Jun Zhu, used with permission).

Fig 2

Endemic status of clonorchiasis and opisthorchiasis.

Fig 3

Morbidities associated with liver fluke infections. (A) Clonorchis sinensis eggs (white arrow) in gallbladder stone under scanning electron microscopy [reproduced from reference (135)]. (B) Liver with cholangiocarcinoma (white arrow) and Clonorchis sinensis (black arrow) [reproduced from reference (12) with permission from Elsevier].