Epistemic_Statements  

CORD-19:f297ff6ac7a5dfde238e171ef3fff9a2c6e7877f JSONTXT 9 Projects

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Id Subject Object Predicate Lexical cue
T1 0-85 Epistemic_statement denotes Fish disease dynamics in changing rivers: Salmonid Ceratomyxosis in the Klamath River
T2 96-236 Epistemic_statement denotes The myxozoan parasite Ceratomyxa shasta has been identified as the main contributor of mortality in salmon in the Klamath River, California.
T3 237-323 Epistemic_statement denotes The life cycle of the parasite is complex, involving a polychaete and a salmonid host.
T4 742-967 Epistemic_statement denotes The analysis of the model shows that for current climate conditions, additional dam release can reduce the actinospore concentration up to 48% and the prevalence up to 40% thus providing a potential disease management option.
T5 968-1148 Epistemic_statement denotes However, the infection risk is likely to increase for future climate conditions by 10-54% and this will lead to an infection level comparable to that of a recent high-disease year.
T6 1292-1559 Epistemic_statement denotes We show that our detailed model system can be reduced to a simpler exponential dose-response function, which predicts infection levels based on transmission rates, travel time and mean spore concentration, quantities that can be measured in-situ or given empirically.
T7 1560-1640 Epistemic_statement denotes The dose-response function may therefore be a useful tool in disease management.
T8 1642-1852 Epistemic_statement denotes Myxozoans are a group of aquatic parasites that are known to cause several fish diseases that can have severe economic impact on fisheries and aquaculture (Hallett and Bartholomew, 2011; Okamura et al., 2015) .
T9 2033-2140 Epistemic_statement denotes Several emerging diseases caused by myxozoans have been linked with climate change (Okamura et al., 2015) .
T10 2141-2264 Epistemic_statement denotes The life cycle of myxozoans is complex and involves both invertebrate (mainly annelids) and vertebrate hosts (mainly fish).
T11 2727-2873 Epistemic_statement denotes The parasite can be found throughout the Pacific Northwest, but its negative impact on native salmon populations is greatest in the Klamath River.
T12 3190-3318 Epistemic_statement denotes However, quantifying the impact on wild fish populations is difficult due to the lack of long-term data (Okamura et al., 2015) .
T13 4213-4470 Epistemic_statement denotes Future climate scenarios in the Klamath River predict significant differences in both temperature and precipitation patterns compared to current conditions (Perry et al., 2011; Ray et al., 2015) and are likely to affect spore concentration and disease risk.
T14 4633-4777 Epistemic_statement denotes Therefore, determining the effect of changing environmental conditions on the disease dynamics is crucial to aid disease control and mitigation.
T15 4778-4906 Epistemic_statement denotes Furthermore, knowing about the effect of environmental parameters on infection prevalence can be used for targeted intervention.
T16 4907-5105 Epistemic_statement denotes Mathematical models can help to identify the important processes and critical points in the disease cycle and can help to evaluate the efficiency of disease management options before implementation.
T17 5106-5294 Epistemic_statement denotes However, the testing and implementation of predictive models for aquatic diseases is challenging due to a lack of data and the complexity of host-parasite interactions (Ray et al., 2015) .
T18 5886-6037 Epistemic_statement denotes However, neither model considers the spatial aspects of fish migration or spore concentration which should play a role in determining disease dynamics.
T19 6221-6366 Epistemic_statement denotes As infected adult carcasses produce myxospores that re-infect the polychaete host, they represent an important link in the pathogen's life cycle.
T20 6367-6492 Epistemic_statement denotes The potential significance of adult salmon in the infection cycle has also been mentioned by Ray (2013) and Fujiwara (2014) .
T21 6493-6791 Epistemic_statement denotes More recently, the role of infected adult salmon in the infection cycle and the possibility of removing adult carcasses to reduce the myxospore input into the river, so as to diminishing the disease induced mortality of juvenile salmon in the following spring, has been investigated by Foott et al.
T22 6801-6904 Epistemic_statement denotes However, they concluded that there are little effects on myxospore concentration by removing carcasses.
T23 6905-7269 Epistemic_statement denotes In order to gain a better understanding of the myxozoan disease dynamics, including the effects of spatial migration, adult salmon, climate scenarios and dam options, we consider a complex system including dynamic processes such as hydrodynamics, environmental conditions and host-parasite interactions, where each mechanism could be studied by a model on its own.
T24 7270-7483 Epistemic_statement denotes In an attempt to balance realism and analytical tractability, we simplify this complex system to one of three partial differential equations (PDEs) which retain, nevertheless, the dynamically important mechanisms.
T25 7902-7994 Epistemic_statement denotes To this end, we demonstrate how our PDE model can be transformed into a dose-response model.
T26 9266-9429 Epistemic_statement denotes Finally, we demonstrate how our model system can be reduced to a single equation, namely the dose-response model, which is applicable as a disease management tool.
T27 9430-9518 Epistemic_statement denotes The aim of the model is to predict the prevalence of infection in the adult salmon host.
T28 9705-9830 Epistemic_statement denotes In this section we first describe the model study area and the assumptions that are made for the spatial model (Section 2.1).
T29 10122-10172 Epistemic_statement denotes A conceptual diagram of the model is shown in Fig.
T30 11571-11678 Epistemic_statement denotes We assume that the zones are defined clearly, even though the transitions between the zones may be gradual.
T31 12352-12448 Epistemic_statement denotes To reduce the complexity of the model, we approximate the river by a spatially homogeneous line.
T32 12834-12941 Epistemic_statement denotes A positive relationship between temperature and mortality from C. shasta was first described by Udey et al.
T33 13196-13351 Epistemic_statement denotes host distribution and density, duration/timing of host-parasite interactions), the net effect of changing environmental conditions is difficult to predict.
T34 13569-13730 Epistemic_statement denotes Moreover, the water velocity is thought to influence the transmission rate (Bjork and Bartholomew, 2009; Ray, 2013) and the polychaete distribution additionally.
T35 13731-13894 Epistemic_statement denotes Little is known about the influence of environmental parameters on other factors such as the polychaete population, actinospore release or the disease progression.
T36 14224-14310 Epistemic_statement denotes The life time of actinospores in water is strongly correlated to the temperature (e.g.
T37 14444-14646 Epistemic_statement denotes Here, for simplicity, we assume a linear relationship of life time of actinospores with temperature T. The relative decay rate δ corresponds to the inverse of the average life time and can be written as
T38 14647-14787 Epistemic_statement denotes 124 C 1 and = ν 3 have been chosen to fit the two data points mentioned above and to give integer numbers for the ease of visual appearance.
T39 15301-15584 Epistemic_statement denotes Following Salinger and Anderson (2006) , we approximate the migration of adult salmon by a mean upstream velocity v u in − km d 1 that depends on the water temperature T and the encountered current speed v c in − km d 1 which could be expressed in terms of discharge according to Eq.
T40 15944-16054 Epistemic_statement denotes It should be noted that the studies by Salinger and Anderson (2006) have been performed in the Columbia River.
T41 16055-16232 Epistemic_statement denotes However, their results are similar to observations that have been made in other studies for different salmon and trout species, including both field experiments in (1) and (3)).
T42 16308-16559 Epistemic_statement denotes Since there is no empirical formulation available describing the functional relationship of temperature, water velocity and adult salmon migration speed in the Klamath River, we here assume the same approach presented by Salinger and Anderson (2006) .
T43 16880-17189 Epistemic_statement denotes It should be noted that we assume that not all transmitted actinospores successfully initiate an infection and we therefore distinguish between the total transmission rate β and the successful transmission rate β, which we assume to be approximately one tenth of the total transmission rate (Fujiwara, 2014) .
T44 17190-17331 Epistemic_statement denotes To estimate the successful transmission rate β as a function of the water temperature T, we assume the following functional relationship (Eq.
T45 17451-17556 Epistemic_statement denotes The constants and the corresponding standard deviations of the fitted parameter can be found in Table 1 .
T46 17685-17859 Epistemic_statement denotes However, due to the relatively small effect of water velocity on the transmission rate compared to the temperature we focused only on incorporating the effect of temperature.
T47 17860-18025 Epistemic_statement denotes Little is known about polychaete's life cycle and the influence of environmental parameters on factors such as the polychaete population or actinospore release rate.
T48 18988-19079 Epistemic_statement denotes The spatial steady-state solution for each zone can be found analytically (see Appendix A).
T49 19375-19492 Epistemic_statement denotes However, infected adult carcasses produce myxospores that cause infection of juvenile salmon in the following spring.
T50 19493-19637 Epistemic_statement denotes By predicting the infection prevalence in the adult salmon host, the infection risk of juvenile salmon in the following spring can be estimated.
T51 20720-20909 Epistemic_statement denotes Since the ratio between actinospore and myxospore particles in their model is constant, we can use outcome of this complex hydrodynamic model to validate our actinospore distribution model.
T52 21416-21589 Epistemic_statement denotes Since the total number of infected polychaetes in each year is unknown, we ran the simulations for the three defined disease risk cases (low/medium/high polychaete numbers).
T53 21637-21747 Epistemic_statement denotes (2016) show that an additional dam release can reduce the total spore concentration in the river by up to 50%.
T54 23716-23779 Epistemic_statement denotes An overview of the analysed scenarios can be found in Table 2 .
T55 24073-24178 Epistemic_statement denotes With the exponential dose-response model, the prevalence of infection POI in its general form is given by
T56 24179-24286 Epistemic_statement denotes where k is the probability to successfully initiate a response and D the dose of the substance or pathogen.
T57 24287-24459 Epistemic_statement denotes By using the methods of characteristics, we will show that our model system can be reduced to a single equation, which is equivalent to the exponential dose-response model.
T58 24460-24592 Epistemic_statement denotes As mentioned above, a steady state solution for the spatial distribution of actinospores can be found analytically (see Appendix A).
T59 25930-26056 Epistemic_statement denotes In total, the simulations of our PDE model show a very good correlation with the detailed hydrodynamic model ( = R 0.9795 2 ).
T60 26787-26850 Epistemic_statement denotes However this trend is less pronounced than that of temperature.
T61 27037-27157 Epistemic_statement denotes For three data points, the model shows an excellent correlation with the data points for a medium number of polychaetes.
T62 27244-27297 Epistemic_statement denotes The results indicate that the higher the additional .
T63 27387-27440 Epistemic_statement denotes The borders of the zones are indicated by grey lines.
T64 27441-27524 Epistemic_statement denotes The steady state solution for each zone can be found analytically (see Appendix A).
T65 28451-28568 Epistemic_statement denotes A dam release of = − Q s Δ 125 m 3 1 at temperatures below = ∘ T 14 C can result in a prevalence reduction up to 35%.
T66 28711-28861 Epistemic_statement denotes Compared to the climate conditions of the years 2005 -2013, climate change is likely to increase the prevalence of infection significantly (Table 2) .
T67 28951-29020 Epistemic_statement denotes Yet, climate change and dam removal still increase prevalence by 10%.
T68 29126-29274 Epistemic_statement denotes Since the infection prevalence for future climate conditions is high anyhow, dam removal seems to have little quantitative effect on the prevalence.
T69 29551-29624 Epistemic_statement denotes (6)), we can derive the exponential dose-response model (see Appendix B).
T70 29625-29736 Epistemic_statement denotes With the mean spatial actinospore dose A over the river section we can calculate the prevalence of infection as
T71 29737-29834 Epistemic_statement denotes With the existing empirical description of the transmission rate β Bartholomew and Foott (2010) .
T72 30037-30246 Epistemic_statement denotes (3)) and in-situ measurement of the mean actinospore concentration A , the infection risk of the years returning salmon population can be approximated easily, without simulating the entire presented PDE model.
T73 30247-30343 Epistemic_statement denotes Therefore, the dose-response model is suitable as a decision support tool in disease management.
T74 30680-30863 Epistemic_statement denotes In order to aid disease control and mitigation, it is necessary to predict the impact of changing water temperatures and flow regimes, whether caused by climate change or dam removal.
T75 31034-31204 Epistemic_statement denotes The model results and the scenario analyses provide useful information on how changing river discharge and temperature affect or can be used to affect the infection risk.
T76 31527-31679 Epistemic_statement denotes As the actinospore distribution feeds into the infection model, this is likely to be caused by the temperature dependence of the transmission rate (Fig.
T77 32092-32289 Epistemic_statement denotes Furthermore, we included the temperature dependence in the decay rate of the actinospores and the temperature-dependent travel time of salmon that both have not been considered by Fujiwara (2014) .
T78 32290-32499 Epistemic_statement denotes We investigated the influence of future environmental change scenarios and showed that the prevalence of infection for future climate change scenarios in comparison to current conditions is likely to increase.
T79 32597-32679 Epistemic_statement denotes These predictions are consistent across the climate change scenarios investigated.
T80 32880-33002 Epistemic_statement denotes Since host-parasite dynamics are complex, the total effect of environmental change on disease dynamics is hard to predict.
T81 33003-33179 Epistemic_statement denotes On the one hand, increasing water temperature could increase or decrease infection prevalence, depending on the current temperature and the number of infected polychaetes (Fig.
T82 33185-33388 Epistemic_statement denotes Higher temperatures can also lead to shifts in the invertebrate host distribution (Alexander et al., 2014) or in timing and duration of spore production and host-parasite interaction (Ray et al., 2015) .
T83 33389-33567 Epistemic_statement denotes Moreover, temperatures in Klamath River are already at the salmon's upper thermal limit (Ray et al., 2015) , which makes the future of the salmon population in the river unclear.
T84 33686-33811 Epistemic_statement denotes In addition, varying effects related to changing temperatures will interact with changes brought about different water flows.
T85 33900-34086 Epistemic_statement denotes On the one hand, this fragmentation is likely to increase due to a global boom in hydropower dam with at least 3700 major dams currently planned or in construction (Zarfl et al., 2015) .
T86 34319-34549 Epistemic_statement denotes Due to its relatively small predicted effect on temperature in comparison to the impact of climate change, our model suggests that dam removal is more likely to have little influence on the predicted level of infection (Table 2) .
T87 35012-35057 Epistemic_statement denotes However, if other factors were included (e.g.
T88 35058-35264 Epistemic_statement denotes the influence of environmental parameters on the polychaete's life cycle or temporal and spatial variation of the host-parasite interactions) then it could be possible that the conclusions would be changed.
T89 35337-35481 Epistemic_statement denotes In particular, dam removal not only alters water temperatures and flow, but will also change the spatial overlap between the host and parasites.
T90 35482-35652 Epistemic_statement denotes Migration of salmon to the upper Klamath basin after dam removal could provide new hosts for existing parasite genotypes that are currently isolated upstream of the dams.
T91 35653-35796 Epistemic_statement denotes Similarly, migrating salmon could transport new pathogenic genotypes of C. shasta to currently isolated salmon populations in the upper basin .
T92 35797-35939 Epistemic_statement denotes In addition, the influence of environmental parameters on the polychaete's life cycle is not yet understood (Stocking and Bartholomew, 2007) .
T93 35940-36087 Epistemic_statement denotes As we discussed before, changing environmental conditions like water temperature could lead to a range shift of the invertebrate host distribution.
T94 36088-36195 Epistemic_statement denotes The polychaete density P 0 or the release rate κ, for example, could be functions of the water temperature.
T95 36196-36348 Epistemic_statement denotes It has been shown elsewhere that flow manipulation can be used for reducing the polychaete density (Alexander et al., 2014) or the spore concentration .
T96 36349-36529 Epistemic_statement denotes Other management options, as for instance removing adult carcasses to reduce the myxospore input (Foott et al., 2016) , have been shown to have little effect on the infection risk.
T97 36530-36751 Epistemic_statement denotes Our model results show that dam release before the salmon run can reduce the actinospore concentration as well as the infection prevalence in returning salmon and can therefore be a useful tool for managing Ceratomyxosis.
T98 36752-36944 Epistemic_statement denotes We showed that our model, although based on a number of mechanistic subprocesses, can be simplified to an exponential dose-response function that can be integrated in decision support systems.
T99 36945-37083 Epistemic_statement denotes Despite the simplicity of this function, it encapsulates all significant mechanisms of the disease dynamics in adult fish considered here.
T100 37620-37824 Epistemic_statement denotes Discharge, temperature and spore concentration are easy to measure and can be used to estimate the infection risk with the dose-response model and evaluate the effectiveness of disease management options.
T101 38979-39056 Epistemic_statement denotes We assume the temperature T and the water velocity v c to be constant so that
T102 39057-39085 Epistemic_statement denotes In a first step we solve Eq.