Modeling the Effects of Climate Change on Disease Severity: A Case Study of Ceratonova (syn Ceratomyxa) shasta in the Klamath River

Abstract

Shifts in future temperature and precipitation patterns will have profound effects on host-parasite interactions and the dynamics of disease in freshwater systems. The aims of this chapter are to present an overview of myxozoan disease dynamics in the context of climate change, and to illustrate how these might be predicted over the next several decades by developing a case study of disease dynamics of Ceratonova (syn Ceratomyxa) shasta in the Klamath River, California USA. Our case study introduces a model ensemble for predicting changes in disease dynamics under different climate scenarios (warm/dry, moderate/median, and cool/wet) from 2020 to 2060. The ensemble uses Global Circulation Models (GCMs) and basin scaled models for the Klamath River to generate predictions for future water temperature and river discharge. The environmental data are used as inputs for a predictive model and a degree day model to simulate effects of climate change on polychaete host populations and on C. shasta spore viability, respectively. Outputs from these models were then used to parameterize an epidemiological model to predict changes in disease dynamics under each climate scenario. The epidemiological model outputs were measured against baselines established using real data for low (2006), high (2008) and intermediate (2011) disease risk years. In general, the epidemiological model predicts that except for infrequent high discharge years, C. shasta dynamics will be

Selection of suitable reference genes for gene expression studies in myxosporean (Myxozoa, Cnidaria) parasites

“…Furthermore, disease severity has been linked to increasing water temperatures (i.e. in Ceratonova shasta 13,14 ), predicting emerging numbers of these organisms in the future as a result of climate change.…”

Disease‐smart climate adaptation for wildlife management and conservation

“…In the western US, dam removal has been proposed as a means of recovering freshwater and diadromous fish populations through restoration of migratory corridors and spawning habitat. Four dam removals are planned along the mainstem of the Klamath River near the Oregon-California border (Figure 2d), where Pacific salmon populations are increasingly threatened by the myxosporean parasite Ceratonova shasta, whose spread has accelerated under climate warming and drought conditions (Ray et al 2015). Below the dams,…”

“…Four dam removals are planned along the mainstem of the Klamath River near the Oregon–California border (Figure 2d), where Pacific salmon populations are increasingly threatened by the myxosporean parasite Ceratonova shasta , whose spread has accelerated under climate warming and drought conditions (Ray et al . 2015). Below the dams, C shasta has been implicated in substantial mortality of Chinook salmon ( Oncorhynchus tshawytscha ) and coho salmon ( Oncorhynchus kisutch ).…”

Deconstructing dams and disease: predictions for salmon disease risk following Klamath River dam removals

“…Shifting patterns for two central abiotic factors, temperature (predicted to increase) and precipitation (timing and form predicted to alter), will have ramifications for host-pathogen dynamics. Aspects of climate change relevant to the Klamath Basin and salmonid disease are well considered for C. shasta (see case study by Ray et al, 2015) and many of those influences will also apply to other pathogens in the Basin; reiterating or delving further into these potential impacts are beyond the scope of this review.…”

“…The myxozoan parasite Ceratonova shasta is a primary factor affecting salmon recovery in the Klamath River (Fujiwara et al, 2011;Ray et al, 2014) because of its impacts on juvenile salmon, by direct mortality or predation associated with disease morbidity. Long-term monitoring and research on this parasite have informed current fisheries management, and resulted in models that can inform predictions on the effects of dam removal on this disease (Ray et al, 2015). Thus, our predictions in this paper will largely focus on C. shasta.…”