Multilocus enzyme electrophoresis analysis of Echinostoma revolutum and Echinostoma malayanum(Trematoda:Echinostomatidae) isolated from Khon Kaen Province,Thailand

Objective:To explore the genetic variation and differentiation of 2 echinostomes from genus Echinostoma,i.e.Echinostoma revolutum(E.revolution) and Echinostoma malayanum(E. malayanum) from Khon Kaen Province,Thailand.Methods:These parasites were compared at 22 enzymes encoding a presumptive 30 loci by using multilocus enzyme electrophoresis (MEE) technique.Results:Twenty-two loci can be used as diagnostic markers to differentiate these 2 species.E.revolutum and E.malayanum had fixed genetic differences at 70%of loci, whereas both species had fixed genetic differences from the liver fluke,Opisthorchis viverrini at 91%of loci.Intraspecific variation within a population of E.revolutum was observed at 5 polymorphic loci.Conclusions:MEE is a powerful technique to investigate genetic variation and differentiation of E.revolutum and E.malayanum.

Investigation of cryptic diversity and occurrence of echinostome metacercariae infection in Anentome helena (von dem Busch, 1847)

Objective: To investigate the parasitic infection of Anentome helena(A. helena) and determine the validity of species boundaries for A. helena by combining molecular phylogeny and morphological approaches. Methods: A total of 325 individuals of A. helena were collected throughout northern Thailand. Shells were measured and compared by t-test. Radulae were investigated by using light and scanning electron microscope. Two partial mitochondrial DNA sequences of COI and 16S rRNA from 36 specimens of A. helena and related species were used to test the validity of the morphospecies. Phylogenetic trees were constructed using neighbour joining, maximum likelihood and Bayesian inference. Infection of A. helena with trematode larva was examined and observed. Results: Morphological examination of A. helena revealed 2 distinct morphospecies. Genetic divergences supported the separation of the two morphotypes into two distinct groups. Both individual and combined analyses of the two nucleotide fragments revealed two phylogroups that corresponded with shell and radula characteristics. In addition, A. helena was found infected with 37-collar spined echinostome metacercariae. The prevalence and intensity of metacercariae was highest in the San Kamphaeng district, Chiang Mai province, with 7.5% and 1.670±0.577, at comprehensive taxonomic respectively. Conclusions: These findings suggest thision of this unrecognised species complex is needed. This study represents the preliminary step to reveal new data on the recent distribution of trematode infection in A. helena. This information may be useful for developing conservation management of the snail and the practice of targeted regimes to reduce anthelmintic resistance in the future.

Genetic variation and phylogenetic relationship of Hypoderaeum conoideum(Bloch, 1782) Dietz, 1909(Trematoda: Echinostomatidae) inferred from nuclear and mitochondrial DNA sequences

Objective:To explore genetic variations of Hypoderaeum conoideum collected from domestic ducks from 12 different localities in Thailand and Lao PDR,as well as their phylogenetic relationship with American and European isolates.Methods:The nucleotide sequences of their nuclear ribosomal DNA(ITS),mitochondrial cytochrome c oxidase subunit 1(CO1),and NADH dehydrogenase subunit 1(ND1)were used to analyze genetic diversity indices.Results:We found relatively high levels of nucleotide polymorphism in ND1(4.02%),whereas moderate and low levels were observed in CO1(2.11%)and ITS(0.96%),respectively.Based on these polymorphisms,the 20 ND1,12 CO1,and 18 ITS haplotypes were classified,and several common haplotypes were observed in all samples.At least three major lineages,namely American,European and Asian lineages,have been classified by phylogenetic analyses based on ND1 sequences.Conclusions:Our report demonstrates that the ND1 gene is the most suitable genetic marker to explore genetic variation and phylogenetic relationship of Hypoderaeum conoideum.However,a combination of all loci for ND1,CO1 and ITS would be of great value toward further genetic investigation of this endemic worldwide parasite.Thus,comprehensive molecular genetic analyses of Hypoderaeum conoideum from its worldwide distribution is needed to further understanding of the evolutionary and systematic relationships of this parasite.

Each coin has 2 sides: a positive role of alien Potamopyrgus antipodarum (Grey, 1843) snails in reducing the infection of native lymnaeids with trematodes

The change in the distribution of organisms in freshwater ecosystems due to natural or manmade processes raises the question of the impact of alien species on local communities.Although most studies indicate a negative effect,the positive one is more difficult to discern,espe-cially in multispecies systems,including hosts and parasites.The purpose of the study was to check whether the presence of an alien host,Potamopyrgus antipodarum,reduces the intensity of Echinoparyphium aconiatum metacercariae in a native host,Radix spp.We additionally tested the impact of water temperature and the biomass of the alien host on the dilution effect.We experimentally studied(1)the lifespan of echinostome cercariae in different temperatures,(2)the infectivity of cercariae toward the alien host and native host,and(3)the impact of different biomass of the alien host on the intensity of metacercariae in the native host.We found that cercarial survival and infectivity were tem-perature dependent.However,cercarial survival decreased with increasing temperature,contrary to cercarial infectivity.Echinostome cercariae entered the renal cavity of both the native host and alien host,and successfully transformed into metacercariae.The number of metacercariae in the native host decreased with the increasing biomass of the alien host.Our results indicate that lymnaeids may benefit from the co-occur-rence with P antipodarum,as the presence of additional hosts of different origins may reduce the prevalence of parasites in native communities.However,the scale of the dilution effect depends not only on the increased spectrum of susceptible hosts but also on the other variables of the environment,including water temperature and host density.