Hefin Wyn Williams

Contrasts between the cryoconite and ice-marginal bacterial communities of Svalbard glaciers

Cryoconite holes are foci of unusually high microbial diversity and activity on glacier surfaces worldwide, comprising melt-holes formed by the darkening of ice by biogenic granular debris. Despite recent studies linking cryoconite microbial community structure to the functionality of cryoconite habitats, little is known of the processes shaping the cryoconite bacterial community. In particular, the assertions that the community is strongly influenced by aeolian transfer of biota from ice-marginal habitats and the potential for cryoconite microbes to inoculate proglacial habitats are poorly quantified despite their longevity in the literature. Therefore, the bacterial community structures of cryoconite holes on three High-Arctic glaciers were compared to bacterial communities in adjacent moraines and tundra using terminal-restriction fragment length polymorphism. Distinct community structures for cryoconite and ice-marginal communities were observed. Only a minority of phylotypes are present in both habitat types, implying that cryoconite habitats comprise distinctive niches for bacterial taxa when compared to ice-marginal habitats. Curiously, phylotype abundance distributions for both cryoconite and ice-marginal sites best fit models relating to succession. Our analyses demonstrate clearly that cryoconites have their own, distinct functional microbial communities despite significant inputs of cells from other habitats.

Climate suitability for European ticks: assessing species distribution models against null models and projection under AR5 climate

BackgroundThere is increasing evidence that the geographic distribution of tick species is changing. Whilst correlative Species Distribution Models (SDMs) have been used to predict areas that are potentially suitable for ticks, models have often been assessed without due consideration for spatial patterns in the data that may inflate the influence of predictor variables on species distributions. This study used null models to rigorously evaluate the role of climate and the potential for climate change to affect future climate suitability for eight European tick species, including several important disease vectors.MethodsWe undertook a comparative assessment of the performance of Maxent and Mahalanobis Distance SDMs based on observed data against those of null models based on null species distributions or null climate data. This enabled the identification of species whose distributions demonstrate a significant association with climate variables. Latest generation (AR5) climate projections were subsequently used to project future climate suitability under four Representative Concentration Pathways (RCPs).ResultsSeven out of eight tick species exhibited strong climatic signals within their observed distributions. Future projections intimate varying degrees of northward shift in climate suitability for these tick species, with the greatest shifts forecasted under the most extreme RCPs. Despite the high performance measure obtained for the observed model of Hyalomma lusitanicum, it did not perform significantly better than null models; this may result from the effects of non-climatic factors on its distribution.ConclusionsBy comparing observed SDMs with null models, our results allow confidence that we have identified climate signals in tick distributions that are not simply a consequence of spatial patterns in the data. Observed climate-driven SDMs for seven out of eight species performed significantly better than null models, demonstrating the vulnerability of these tick species to the effects of climate change in the future.

Confirmation of Galba truncatula as an intermediate host snail for Calicophoron daubneyi in Great Britain, with evidence of alternative snail species hosting Fasciola hepatica

BackgroundFasciola hepatica is a highly prevalent parasite infecting livestock in Great Britain, while Calicophoron daubneyi is an emerging parasite within the GB livestock industry. Both F. hepatica and C. daubneyi require an intermediate host snail to complete their life-cycles and infect ruminants; however, there has been no confirmation of the intermediate host of C. daubneyi in GB, while there are questions regarding alternative host snails to Galba truncatula for F. hepatica. In this study, PCR was used to identify C. daubneyi hosting snail species on Welsh pastures and to identify any alternative snail species hosting F. hepatica.FindingsTwo hundred and sixty four snails were collected between May-September 2015 from six farms in mid-Wales known to have livestock infected with C. daubneyi and F. hepatica. Fifteen out of 134 G. truncatula were found positive for C. daubneyi, one of which was also positive for F. hepatica. Three snail species were found positive for F. hepatica [18/134 G. truncatula, 13/52 Radix balthica, and 3/78 Potamopyrgus antipodarum (New Zealand mud snail)], but no evidence of C. daubneyi infection in the latter two species was found.ConclusionThis study indicates that G. truncatula is a host for C. daubneyi in GB. Galba truncatula is also an established host of F. hepatica, and interactions between both species at intermediate host level could potentially occur. Radix balthica and P. antipodarum were found positive for F. hepatica but not C. daubneyi. This could indicate a role for alternative snail species other than G. truncatula in infecting pastures with F. hepatica in GB.

Rumen fluke Calicophoron daubneyi on Welsh farms: Prevalence, risk factors, and observations on co-infection with Fasciola hepatica

SUMMARY Reports of Calicophoron daubneyi infecting livestock in Europe have increased substantially over the past decade; however, there has not been an estimate of its farm level prevalence and associated risk factors in the UK. Here, the prevalence of C. daubneyi across 100 participating Welsh farms was recorded, with climate, environmental and management factors attained for each farm and used to create logistic regression models explaining its prevalence. Sixty-one per cent of farms studied were positive for C. daubneyi, with herd-level prevalence for cattle (59%) significantly higher compared with flock-level prevalence for sheep (42%, P = 0·029). Co-infection between C. daubneyi and Fasciola hepatica was observed on 46% of farms; however, a significant negative correlation was recorded in the intensity of infection between each parasite within cattle herds (rho = −0·358, P = 0·007). Final models showed sunshine hours, herd size, treatment regularity against F. hepatica, the presence of streams and bog habitats, and Ollerenshaw index values as significant positive predictors for C. daubneyi (P < 0·05). The results raise intriguing questions regarding C. daubneyi epidemiology, potential competition with F. hepatica and the role of climate change in C. daubneyi establishment and its future within the UK.

The prevalence and development of digenean parasites within their intermediate snail host, Galba truncatula, in a geographic area where the presence of Calicophoron daubneyi has recently been confirmed

Highlights • C. daubneyi, F. hepatica and H. cylindracea all commonly infect UK G. truncatula.• C. daubneyi may be less adept at infecting and developing in UK G. truncatula.• Paramphistomosis risk in the UK may increase if C. daubneyi can adapt to this host.• Evidence of interactions between digenean species infecting G. truncatula.

Detection of Galba truncatula , Fasciola hepatica and Calicophoron daubneyi environmental DNA within water sources on pasture land, a future tool for fluke control?

BackgroundIncreasing trematode prevalence and disease occurrence in livestock is a major concern. With the global spread of anthelmintic resistant trematodes, future control strategies must incorporate approaches focusing on avoidance of infection. The reliance of trematodes on intermediate snail hosts to successfully complete their life-cycle means livestock infections are linked to the availability of respective snail populations. By identifying intermediate snail host habitats, infection risk models may be strengthened whilst farmers may confidently apply pasture management strategies to disrupt the trematode life-cycle. However, accurately identifying and mapping these risk areas is challenging.MethodsIn this study, environmental DNA (eDNA) assays were designed to reveal Galba truncatula, Fasciola hepatica and Calicophoron daubneyi presence within water sources on pasture land. eDNA was captured using a filter-based protocol, with DNA extracted using the DNeasy® PowerSoil® kit and amplified via PCR. In total, 19 potential G. truncatula habitats were analysed on four farms grazed by livestock infected with both F. hepatica and C. daubneyi.ResultsGalba truncatula eDNA was identified in 10/10 habitats where the snail was detected by eye. Galba truncatula eDNA was also identified in four further habitats where the snail was not physically detected. Fasciola hepatica and C. daubneyi eDNA was also identified in 5/19 and 8/19 habitats, respectively.ConclusionsThis study demonstrated that eDNA assays have the capabilities of detecting G. truncatula, F. hepatica and C. daubneyi DNA in the environment. Further assay development will be required for a field test capable of identifying and quantifying F. hepatica and C. daubneyi infection risk areas, to support future control strategies. An eDNA test would also be a powerful new tool for epidemiological investigations of parasite infections on farms.

Additional file 4: of Climate suitability for European ticks: assessing species distribution models against null models and projection under AR5 climate

Projected current and future climate suitability under RCP 2.6, 6.0 & 8.5. Figures S3-S8 & Table S2. Figure S3. Current and future (RCP 2.6) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: A: Ixodes ricinus; B: Rhipicephalus annulatus; C: Dermacentor marginatus; D: Haemaphysalis punctata. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 2.6. Values range from 0 (unsuitable) to 1 (highly suitable). Figure S4. Current and future (RCP 2.6) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: E: Haemaphysalis sulcata; F: Hyalomma marginatum; G: Rhipicephalus bursa. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 2.6. Values range from 0 (unsuitable) to 1 (highly suitable). Figure S5. Current and future (RCP 6.0) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: A: Ixodes ricinus; B: Rhipicephalus annulatus; C: Dermacentor marginatus; D: Haemaphysalis punctata. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 6.0. Values range from 0 (unsuitable) to 1 (highly suitable). Figure S6. Current and future (RCP 6.0) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: E: Haemaphysalis sulcata; F: Hyalomma marginatum; G: Rhipicephalus bursa. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 6.0. Values range from 0 (unsuitable) to 1 (highly suitable). Figure S7. Current and future (RCP 8.5) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: A: Ixodes ricinus; B: Rhipicephalus annulatus; C: Dermacentor marginatus; D: Haemaphysalis punctata. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 8.5. Values range from 0 (unsuitable) to 1 (highly suitable). Figure S8. Current and future (RCP 8.5) projected climate suitability for tick species in the western Palearctic. Each row corresponds to a tick species: E: Haemaphysalis sulcata; F: Hyalomma marginatum; G: Rhipicephalus bursa. Columns correspond to 40-year temporal averages up to and including: 1: 2010; 2: 2050; 3: 2098. Figures in column 1 represent the average suitability derived from Maxent and MD SDMs based on observed climate; columns 2 and 3 contain suitability averaged across Maxent and MD SDMs produced from four GCMs following RCP 8.5. Values range from 0 (unsuitable) to 1 (highly suitable). Table S2: Similarity between current and future projected climate suitability for seven tick species. Schoeners D statistic represents the degree of overlap between climate suitability maps, ranging from 0 (no overlap) to 1 (complete overlap). Smallest values therefore indicate least overlap and so the greatest change between current and future projections of climate suitability. Average climate suitability produced by Maxent and MD SDMs for the 40-year period up to and including 2010 has been compared with climate suitability averaged across both SDMs over future 40-year periods up to and including 2050 and 2098 under all four RCP climates. This analysis was undertaken using ENMTools software v1.3. (PDF 1968 kb)