Discovery of Paragonimus skrjabini in Vietnam and its phylogenetic status in the Paragonimus skrjabini complex

Abstract

Two members of the Paragonimus skrjabini complex, P. skrjabini and P. miyazakii, are now considered as two sub-species, P. skrjabini skrjabini and P. skrjabini miyazakii. They are well known as important pathogens for human paragonimiasis in China and Japan. Recently, members of this species complex have been reported from India. Here we report the first discovery of P. skrjabini from freshwater crab hosts in Thanh Hoa province, Vietnam. For morphological and molecular phylogenetic studies, adult worms were obtained by experimental infection in cats and dogs. Molecular analyses of metacercariae and adults revealed that the P. skrjabini population from Thanh Hoa, Vietnam was almost completely identical with that from Yunnan province, China. Those populations from Thanh Hoa, Vietnam and Yunnan, China and those from Manipur, India were significantly different from P. skrjabini populations reported from other localities of China in cytochrome oxidase subunit 1 (CO1) gene sequences, indicating considerable genetic variation within the P. skrjabini complex. Moreover, low bootstrap values in the CO1 tree suggested that more variant genotypes belonging to P. skrjabini complex may be found in other Asian countries in between Vietnam and India, such as Myanmar, Laos and Thailand. Since P. skrjabini is known as a pathogen for humans, paragonimiasis cases caused by P. skrjabini might be found in Vietnam and other Asian countries.

Paragonimus and Paragonimiasis in Vietnam: an Update

“…So far, 7 Paragonimus species have been found in Vietnam. In order of discovery, these are P. heterotremus , P. vietnamensis , P. proliferus , P. bangkokensis , P. westermani , P. harinasutai , and P. skrjabini [2,14-19]. …”

“…Since metacercariae of more than 1 species were sometimes found in the same individual crab host in the same sampling area [14-19], the identification of metacercariae requires experience and good eyes. Here are some keys to species identification.…”

“…We have determined ITS2 and CO1 sequences of all Paragonimus species in Vietnam and these are now available in GenBank [14-19]. …”

“…Recently, P. skrjabini was found in India [29] and Vietnam [19]. Genetically, the P. skrjabini population from Vietnam was almost completely identical with those from Yunnan, China [19].…”

Global status of fish-borne zoonotic trematodiasis in humans

“…In the mountain areas, local people consume lightly fried crabs and this constitutes a high risk of infection with lung fluke of Paragonimus spp. Doanh et al (2007Doanh et al ( , 2008Doanh et al ( , 2012 and Le et al (2006) isolated metacercariae of several Paragonimus species in crab and experimentally infected cats. The recovered flukes were collected and identified and two of these species were new.…”