Paragonimus and Paragonimiasis in Vietnam: an Update

Abstract

Paragonimiasis is a food-borne parasitic zoonosis caused by infection with lung flukes of the genus Paragonimus. In Vietnam, research on Paragonimus and paragonimiasis has been conducted in northern and central regions of the country. Using a combination of morphological and molecular methods, 7 Paragonimus species, namely P. heterotremus, P. westermani, P. skrjabini, P. vietnamensis, P. proliferus, P. bangkokenis and P. harinasutai, have been identified in Vietnam. Of these, the first 3, P. heterotremus, P. westermani and P. skrjabini, are known to infect humans in other countries. However, in Vietnam, only P. heterotremus, found in some northern provinces, has been shown to infect humans. Even nowadays, local people in some northern provinces, such as Lai Chau and Yen Bai, are still suffering from P. heterotremus infection. In some provinces of central Vietnam, the prevalence and infection intensity of P. westermani metacercariae in freshwater crabs (the second intermediate hosts) are extremely high, but human cases have not been reported. Likewise, although P. skrjabini was found in Thanh Hoa Province, its pathogenicity to humans in Vietnam still remains uncertain. The results of molecular phylogenetic analyses of Vietnamese Paragonimus species provides new insights on the phylogeny and taxonomy of the genus Paragonimus. Comprehensive molecular epidemiological and geobiological studies on the genus in Vietnam and adjacent countries are needed to clarify the biodiversity and public health significance of the lung flukes.

Climate Change and the Neglected Tropical Diseases

“…Nine species or species-complexes are known to affect humans (Blair, 2014;Chai, 2013). The main focus of infection with species of the Paragonimus westermani complex is SE Asia, where multiple individual species within the complex infect intermediate hosts with low specificity (Doanh et al, 2013). Other foci, consisting of highly distinct parasite species are located in West Africa (Paragonimus africanus and Paragonimus uterobilateralis) and (sub)-tropical parts of North, Central and South America (Paragonimus mexicanus and Paragonimus kellicotti).…”

Paragonimus spp.

“…The lung flukes of public health importance, Paragonimus spp., belong to the trematode family Troglotrematidae. More than 60 different species have been described in this genus (Blair et al, 1999;Narain et al, 2010;Doanh et al, 2013). Among them, 16-17 species were synonymized with the others (Blair et al, 1999), and 36 species were regarded as valid or potentially valid.…”

“…A new species, proposed as P. pseudoheterotremus, was reported from an experimentally infected cat with metacercariae from freshwater crabs in Thailand (Waikagul, 2007). More recently, in Vietnam, 4 new species, including P. vietnamensis, P. proliferus, P. bangkokenis, and P. harinasutai, have been identified by a combination of morphological and molecular studies (Doanh et al, 2013). However, human infections with these species are yet unknown.…”

“…The molecular techniques used for differentiation of Paragonimus spp. included PCR, DNA sequencing, RFLP, PCR-RFLP, multiplex PCR, random amplified polymorphic DNA (RAPD), and DNA hybridization (Narain et al, 2010;Sugiyama et al, 2013;Doanh et al, 2013).…”

Paragonimiasis

“…It then largely disappeared from many areas, and was forgotten until recent surveys revealed startlingly high prevalences in the SE of the country [ 8 , 104 , 105 ]. New foci are regularly being found in NE India [ 37 , 106 , 107 ], Vietnam [ 33 ], and Laos [ 108 , 109 ]. It seems highly likely that many more foci will be found, especially in Africa and the Americas where reported investigations are few.…”