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Several trematodes including Opisthorchis viverrini utilize Bithynia siamensis goniomphalos as a snail intermediate host in their life cycles. In order to capture a comprehensive range of host–parasite interactions and their transmission dynamic patterns, B. s. goniomphalos were sampled monthly over 4 consecutive years in an irrigated paddy-field habitat in northeast Thailand. Using a standard cercarial shedding method, a high diversity of trematodes (17 types) was recovered. Virgulate xiphidiocercariae were the most prevalent (7.84%) followed by O. viverrini (0.71%). In addition to seasonal and environmental factors, the quantity of irrigation water for rice cultivation correlated with transmission dynamics of trematodes in B. s. goniomphalos. The peak prevalence of all trematode infections combined in the snails shifted from the cool-dry season in 2010–2012 to the hot-dry season in 2013 associated with an increasing quantity of water irrigation. A low frequency of mixed trematode infections was found, indicating that the emergence of virgulate cercariae, but not of O. viverrini, was negatively impacted by the presence of other trematodes in the same snail. Taken together, the observed results suggest that interactions between host and parasite, and hence transmission dynamics, depend on specific characteristics of the parasite and environmental factors including irrigated water for rice cultivation. [ABSTRACT FROM AUTHOR]

AbstractThroughout Southeast Asia and China, eating raw and or partially cooked cyprinid fish causes liver (hepatobiliary) disease and cancer (cholangiocarcinoma) due to fishborne zoonotic trematodes (FZT), in particular Clonorchis sinensisand Opisthorchis viverrini.The primary source of transmission is by native fish, but aquaculture fish are also reported to have high infective potential. Here, a cross-sectional survey of FZT in fish farms was conducted in an endemic area in Khon Kaen Province, Thailand. By using conventional and polymerase chain reaction (PCR) methods, we detected O. viverriniand FZT metacercariae (Centrocestus formosanusand Haplorchis taichui) in two popular fish species, Barbonymus gonionotus(silver barb) and Cirrhinus mrigala(mrigal), from aquaculture farms. Both species were infected in five of six farms examined by PCR but not by conventional methods, yet the prevalence of FZT metacercariae in aquaculture fish was high (46.9%). In addition to O. viverrini(17.1%), the native fish Cyclocheilichthys armatusand Hampala disparhad a prevalence of FZT of 81.4%, which included 5.7% for C. formosanusand 17.1% for H. taichuiby conventional method. To our knowledge, this is the first discovery of O. viverriniin aquaculture fish in Thailand. More comprehensive studies are required to determine if human-induced disease transmission coupled with natural transmission cycle occurs throughout the aquaculture industry in the region. This has significant impact on food quality and safety, and provides the basis for the development of an effective strategy for the prevention and control of foodborne diseases.

Ticks from mainland Australia (Victoria, New South Wales and Queensland) and Tasmania, identified morphologically as either Ixodes holocyclusor Ixodes cornuatus, were compared genetically using 24 enzyme loci. The results showed that ticks from three localities in Victoria were genetically similar to I. cornuatusin Tasmania, but both groups had fixed genetic differences at >45% of loci compared with other ticks on the mainland. In addition, there were fixed genetic differences at 0–60% of loci among I. holocyclusfrom different localities on the mainland. Ixodes holocyclussamples could be divided into four distinct clusters (with fixed genetic differences >15%), three of which were represented by one or two specimens. Nonetheless, these electrophoretic data suggest that I. holocyclusrepresents a species complex. The results also showed that the morphological criteria used to identify specimens were not always accurate because several specimens had been mis-identified morphologically. Despite limitations with the morphological identification, this study has demonstrated that I. cornuatuscan be distinguished from the I. holocyclusspecies complex using six enzyme loci, providing the foundation for a re-examination of morphological characteristics. The present study has shown that I. cornuatusand the I. holocycluscomplexes have a greater distribution than previously reported, with both occurring in sympatry at Cape Patterson, on the southern coastline of Victoria.

Objective: To describe the features of infection with Scedosporium prolificansand to investigate the possibility of a common source of infection.

We investigated the population genetics of 23 isolates of H. pyloriby allozyme electrophoresis using 16 enzyme loci. Isolates were obtained from adult patients of whom 48% were of Greek extraction. Eight patients (35%) had an active duodenal ulcer. Allelic variation per loci ranged from 2 to 11 alleles. Four major genetic clusters were apparent, having >75% fixed genetic differences. There was no distinct clustering (clonal structure) on the basis of the geographical origin of the persons from whom isolates were obtained, indicating that this bacterium has not recently jumped a species barrier into humans. Isolates associated with ulcer disease were not monophyletic, with isolates from ulcer patients being found in phylogenetically diverse branches of the dendogram derived from the data. Based on the genetic diversity of H. pyloriisolates, we propose that isolates should be classified as belonging not to a single species but to a `Helicobacter pylorispecies‐complex'.

An electrophoretic analysis using 17 enzyme loci was carried out on specimens of the gastric nematode of macropodid marsupials, Rugopharynx australis (Mönnig, 1926), collected from Macropus eugenii (Desmarest), M. fuliginosus (Desmarest), M. giganteus Shaw, M. robustus Gould, M. rufogriseus (Desmarest), M. rufus (Desmarest), Thylogale billardierii (Desmarest) and Wallabia bicolor (Desmarest) from south-eastern Australia. The extent of fixed genetic differences between nematodes from different host species ranged from 0–53%. The two distinct morphological forms of the parasite found in M. rufogriseus differed at 50% of loci. Specimens present in M. fuliginosus and M. giganteus were indistinguishable genetically, as were nematodes from M. rufus and M. robustus. Of the two morphologically distinct congeners included in the analysis as controls, Rugopharynx epsilon (Johnston & Mawson, 1939) was genetically distinct (46–69% fixed genetic differences) from all specimens of the R. australis complex while R. rufogrisea Magzoub, 1964 was closely related to one of the two species occuring in M. rufogriseus. It was concluded that R. australis is a species complex, with a genetically distinct species present in M. eugenii, M. fuliginosus/M. giganteus, M. robustus/M. rufus, W. bicolor and T. billardierii, and two species in M. rufogriseus.

Reptile ticks mate while females are attached to their host. Following mating, females engorge, detach and then lay their eggs. This study examines whether the time that females of the reptile tick Amblyomma limbatum spend on hosts prior to mating and the time they take to engorge on hosts after mating influence their reproductive fitness, as measured by the number of viable eggs they produce. When compared with females that experienced no temperature-induced delay in mating, females attached for an initial period to hosts with body temperatures too low to induce mating had no decline in their reproductive fitness, once provided with suitable temperatures for mating. However, on hosts with suitable body temperatures for mating, female ticks that took longer to mate, took longer to engorge and had reduced reproductive fitness. In addition, females that spent more than 20 days feeding on hosts after mating had reduced reproductive fitness, irrespective of the time they spent on hosts prior to mating compared with females with shorter feeding periods. Thus, the time that A. limbatum females spent on hosts prior to mating and/or after mating has a significant bearing on the number viable progeny produced. The ecological implications of these results are discussed in relation to females colonizing marginal population areas at the edge of their distributional range.

This study examined whether the mating or feeding success of females of two tick species, Amblyomma limbatum and Aponomma hydrosauri, is influenced by their site of attachment on a host. Marked interspecific differences were detected in the preferred sites of attachment of females to their common host, the sleepy lizard Tiliqua rugosa, with Amb. limbatum found predominantly in the ears and on the lower back, while Ap. hydrosauri preferred to attach under the forelimbs and on the midback. Data from field surveys suggested that higher proportions of females were mated in the preferred sites for Ap. hydrosauri, and in one of the preferred sites for Amb. limbatum. However, laboratory and field experiments showed that for both species, the mean time before females were mated, mean engorgement time and mean feeding rate were independent of where they were attached to a host. Four hypotheses were considered as explanations of the observed niche segregation; intespecific competition, avoidance of pheromone jamming or adaptations, to maximize mating and feeding, and minimize physical disturbance. These could not totally explain the observed site specificity in either tick species. Site specificity may represent adaptations by each species to other host species encountered within their distributional range.

Few quantitative studies have examined the ecological consequences of similarities and/or differences in mating behaviour of parapatric species. Reproductive interference occurs between several parapatric species of Australian reptile tick, due to similarities in their mating behaviour (Andrews et al. 1982a). Attempts to determine whether reproductive interference serves to maintain parapatry between Amblyomma limbatum and Aponomma hydrosauri have been hindered because of difficulties in providing conditions conducive to conspecific mating in Amb. limbatum. The present study examined whether off-host and/or onhost temperature influenced the subsequent mating behaviour (i.e. the proportion of females that mate and the time when mating occurs) of these two species. Irrespective of the temperature experienced by ticks prior to host attachment, specific on-host temperatures were needed to induce mating in Amb. limbatum (i.e. host cloacal temperatures >32° C prior to the time of peak mating activity). Significantly more Amb. limbatum females were mated and the time taken by females to mate decreased with increasing on-host temperatures. mating in Ap. hydrosauri occurred over a wider range of on-host temperatures and the time when mating occurred did not alter at different on-host temperatures. In addition, significantly more Ap. hydrosauri males moved and each male made more moves on hosts than did Amb. limbatum males. It is suggested that Ap. hydrosauri may in consequence have a competitive mating advantage over Amb. limbatum at a boundary. Similarities in mating behaviour, on the other hand, increase the probability of reproductive interference, hence reduce the reproductive fitness of colonizing females of both species. We propose that similarities and differences in mating behaviour could play a critical role in the maintenance of parapatric boundaries.

We investigated the population genetics of 23 isolates of H. pylori by allozyme electrophoresis using 16 enzyme loci. Isolates were obtained from adult patients of whom 48% were of Greek extraction. Eight patients (35%) had an active duodenal ulcer. Allelic variation per loci ranged from 2 to 11 alleles. Four major genetic clusters were apparent, having >75% fixed genetic differences. There was no distinct clustering (clonal structure) on the basis of the geographical origin of the persons from whom isolates were obtained, indicating that this bacterium has not recently jumped a species barrier into humans. Isolates associated with ulcer disease were not monophyletic, with isolates from ulcer patients being found in phylogenetically diverse branches of the dendogram derived from the data. Based on the genetic diversity of H. pylori isolates, we propose that isolates should be classified as belonging not to a single species but to a ‘Helicobacter pylori species-complex'.

A regulatory relationship of beta-ecdysone to apolysis and new cuticle formation in soft ticks (Argasidae) is shown. Five concentrations of beta-ecdysone (0.001, 0.01, 0.1, 1.0, and 10.0 µg/µl olive oil) were injected into the hemocoels of virgin female Ornithodoros parkeri 48 h postfeeding. Apolysis and new epicuticle formation was induced by all concentrations of beta-ecdysone injected, with the percentage of ticks forming new cuticle increasing up to the 0.1 µg/µl oil concentration and decreasing slightly at the 1.0-and 10.0-µg concentrations. Mortality in some ticks was caused by doses of 0.1-, 1.0-, and 10.0-µg concentrations. No one has previously reported induction of apolysis and cuticle deposition as a result of injection of beta-ecdysone in ticks. Recently fed female 0. parkeri ticks might provide a useful bioassay of ecdysteroids.

Unfed 3rd-instar nymphal Ornithodoros parkeri (UN3s) were arranged into 7 weight classes, fed, and reared to adults. Fed 3rd-instar nymphs (N3s) produced 22.0% males, 3.8% females, and 57.2% 4th-instar nymphs (N4s); 17.0% died or were lost. The resulting N4s were fed and subsequently produced 14.7% males, 56.4% females, and 9.5% 5th-instar nymphs (N5s); 19.3% died or were lost. The N5s were fed and yielded 5.0% males and 70.0% females; 25.0% died or were lost. After rearing all UN3s to the adult stage, the final sex ratio was 0.77♂:1♀ (43.5% ♂, 56.5% ♀). UN3s weighing less than 2.6 mg produced males and N4s but no females after feeding. A few females were produced from N3s heavier than 2.6 mg. N4s resulting from all N3 weight classes developed into males, females, and N5s, and those originating from N3s in the lowest weight class (0.1–1.0 mg) produced more males than females. N4s originating from all other N3 weight classes produced more females than males. In a 2nd experiment, only females ecdysed from fed N4s weighing 25 mg and over, while those weighing 5–9 mg produced only males and N5s. The N5s in both experiments produced females almost exclusively (34 females and 1 male).

An electrophoretic study was conducted on ticks morphologically identified as either Ixodes cornuatus or I. holocyclus from Tasmania and several localities on mainland Australia. Ticks were characterised genetically at 27 enzyme loci encoding 24 enzymes. The extent of genetic divergence (52–69% fixed differences) between ticks from Tasmania and those from the mainland was equivalent to that found between these two groups and two morphologically distinct species, I. hirsti and I. fecialis. The Tasmanian ticks therefore represent a different species from the specimens from the mainland and the electrophoretic data show that the morphological characters currently used to distinguish I. holocyclus from I. cornuatus are inadequate. Genetic heterogeneity was detected in samples from different localities on the mainland. This could represent either population variation, or the existence of cryptic species, but more ticks from these mainland localities need to be examined electrophoretically to resolve this.