Abstract
Clonorchiasis is a neglected tropical disease caused by the Chinese liver fluke, Clonorchis sinensis, and is often associated with a malignant form of bile duct cancer (cholangiocarcinoma). Although some aspects of the epidemiology of clonorchiasis are understood, little is known about the genetics of C. sinensis populations. Here, we conducted a comprehensive genetic exploration of C. sinensis from endemic geographic regions using complete mitochondrial protein gene sets. Genomic DNA samples from C. sinensis individuals (n = 183) collected from cats and dogs in China (provinces of Guangdong, Guangxi, Hunan, Heilongjiang and Jilin) as well as from rats infected with metacercariae from cyprinid fish from the Russian Far East (Primorsky Krai region) were deep sequenced using the BGISEQ-500 platform. Informatic analyses of mitochondrial protein gene data sets revealed marked genetic variation within C. sinensis; significant variation was identified within and among individual worms from distinct geographical locations. No clear affiliation with a particular location or host species was evident, suggesting a high rate of dispersal of the parasite across endemic regions. The present work provides a foundation for future biological, epidemiological and ecological studies using mitochondrial protein gene data sets, which could aid in elucidating associations between particular C. sinensis genotypes/haplotypes and the pathogenesis or severity of clonorchiasis and its complications (including cholangiocarcinoma) in humans.
Highlights
Eleven pathogens are recognised to cause one fifth of all human cancers worldwide [1]
Clonorchiasis is an important neglected tropical disease caused by the Chinese liver fluke, Clonorchis sinensis, which can induce malignant bile duct cancer
KY564177), revealing substantial depth at each position in each of the 12 protein genes. This mapping showed that most specimens (n = 164) had haplotypic sequences, while a small subset of C. sinensis specimens (n = 19) had sequences with 3 polymorphic positions (Table 2)
Summary
Eleven pathogens are recognised to cause one fifth of all human cancers worldwide [1]. The disease (clonorchiasis) caused by C. sinensis is of major public health concern in parts of Asia [3,4,5]; ~ 15 million people are infected, and the highest endemicity is in South Korea, Vietnam, China and the Russian Far East [6, 7]. Most of these people (~ 13 million) live within provinces in the southern (Guangdong, Guangxi, and Hunan) and north-eastern (Heilongjiang and Jilin) parts of China [4, 6,7,8]. Eggs produced by adult C. sinensis are released into aquatic environments to infect small snail intermediate hosts (order Mesogastropoda); larval stages (cercariae) released from the snails usually infect fish (family Cyprinidae) and encyst as metacercariae
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