Correlation of environmental attributes with histopathology of native Yellowstone cutthroat trout naturally infected with Myxobolus cerebralis

Abstract

Infection by the invasive parasite Myxobolus cerebralis (causing whirling disease in salmonids) is strongly influenced by a stream's physico-chemical characteristics, which might affect host pathology. We examined whether environmental variables of a M. cerebralis-positive tributary to Yellowstone Lake, Yellowstone National Park, USA, correlated with the histopathology of naturally infected native cutthroat trout Oncorhynchus clarkii bouvieri. Host inflammatory response and cranial cartilage lesions were the main correlates with whirling behavior. Canonical correlation analyses showed that the prevalence of trout with severe lesions in the cranial and jaw cartilages was highest in stream sites with a combination of high temperature and low specific conductivity. Our results reveal that environmental components can affect when and where a pathogen resides within the host, and manifestation of disease. Recognition of the synergism among environmental and histopathology factors most conducive to whirling disease will increase our prediction and detection abilities for M. cerebralis in salmonid hosts.KEY WORDS: Whirling disease · Pathogen · Invasion-environment synergism · Canonical correlation · Yellowstone ecosystem Resale or republication not permitted without written consent of the publisherDis Aquat Org 93: [225][226][227][228][229][230][231][232][233][234] 2011 Hydrothermal and high elevation streams are examples of systems where the physical and chemical environments are variable (e.g. severe temperature or pH fluctuations) and can inflict additional stresses on the native biota beyond seasonal changes. In Lake Wabamun in Alberta, Canada, thermal effluents facilitated parasite transmission between hosts throughout the year and increased prevalence of certain parasites (Sankurathri & Holmes 1976). Synergisms between infection by metacercaria and exposure to pesticides and herbicides were reported as the cause of vertebral deformities in frogs (Kiesecker 2002). These are examples of environments where natural (e.g. hydrothermal) and anthropogenic (e.g. pollutant) stressors often have a strong influence on parasite-host interactions and development of diseases.However, synergisms between the effects of environmental stressors and development of disease from parasitic infection in wild fish are seldom examined through a histopathology approach (but see Roubal 1994). Histopathology is key to identifying target organs of parasitic infection and pathogens' mode of action at the biochemical level of organization (severity of disease), which may affect ecosystem function at the population level of organization (Schwaiger 2001). Histopathological anomalies in fish, for example, are frequently used as indicators of chemical pollution in marine and fresh water environments (Schwaiger 2001, Wester et al. 2002, Kent et al. 2004, identifying risks of population declines. But we found no examples in the scientific literature of studies on the potential relationships between environmental stress and histopatholog...

Myxobolus cerebralis (Hofer) infection risk in native cutthroat trout Oncorhynchus clarkii (Richardson) and its relationships to tributary environments in the Yellowstone Lake Basin

“…; Murcia et al . , ). Tributaries where the parasite was originally detected (1999, 2000, 2001; Koel et al .…”

“…; Murcia et al . , ), is cited as two reasons for listing this subspecies as threatened or endangered (USFWS: U.S. Fish & Wildlife Service ; Rahel et al .…”

“…; Murcia et al . , ). Assessing the environments where disease is most severe, identifying susceptibility (microscopic pathology) and infection responses of the Yellowstone cutthroat trout in the wild, are important steps for predicting parasite invasion across the lake basin.…”

“…Yellowstone cutthroat trout; Murcia et al . , ; or rainbow trout Oncorhynchus mykiss (Walbaum) ; O'Grodnick ; Hedrick et al . ) to resistant (e.g.…”

Weak effects of a microsporidian parasite on mottled sculpin in Michigan streams

“…Specifically, we hypothesized that the altered mottled sculpin population dynamics would manifest as lower densities, reduced relative abundances in fish assemblages, increased mortality rates, biased sex ratios (although the direction was not clear), reduced genetic diversity, and significant evidence of genetic bottlenecks for fish in streams infected with Glugea. We also evaluated environmental variables and fish assemblages in streams with and without Glugea to assess whether environmental conditions and community composition were associated with the parasite's presence in streams (e.g., Murcia et al 2011;McGinnis and Kerans 2013), which also allowed us to assess whether environmental conditions may confound effects of the parasite on fish condition, growth, and population-level characteristics. Additionally, because disease can result in community-level change (e.g., Packer et al 2003;Holt and Roy 2007), fish assemblages were compared between streams with and without the parasite to assess indirect effects on community composition.…”