Effects of environmental stressors and anthropogenic disturbances on infections with myxozoan parasites
Iwanowicz, Deborah Diann
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Environmental influences on myxozoan parasites are poorly understood. Theobjective of this dissertation was to determine the effects of environmental stressors andanthropogenic disturbances on myxozoan parasites. The two myxozoan parasites thatwere studied included a previously undescribed species of myxozoan parasite, Myxobolusstanlii n. sp. that infects largescale stonerollers (Campostoma oligolepis) and Myxoboluscerebralis, a salmonid pathogen. Myxobolus stanlii n. sp. was found in the connectivetissue of various organs, renal tubules, glomeruli, macrophage aggregates within thekidney, and in nerve tissue behind the eye. The intensity of infection and host responseto M. stanlii n. sp. in stonerollers was also assessed along an urban land use gradient(ULUG). Myxobolus stanlii n. sp. densities were highest in largescale stonerollersinhabiting sites at lower and middle ULUGs and lowest at sites with the high ULUGs.This suggests an abundance of the host(s) and vectors, or a decrease in the naturalresistance of the host to the parasite at sites at the lower and middle ULUGs. Conversely,at sites with higher ULUGs anthropogenic disturbances such as urbanization can affectthe intermediate host populations such that the abundance of their parasite load was 2reduced. With M. cerebralis, the effects of riparian zone and associated streamsubstratum on the oligochaete host, Tubifex tubifexwas investigated. Tubifex tubifexinhabiting streams of New York and Pennsylvania from four different land covercategories (deciduous, deciduous/meadowland, meadowland and coniferous) primarilyconsisted of genetic lineages I and III, which are the most susceptible lineages to M.cerebralis infection. Field and laboratory studies indicated that substrate type associatedwith land cover influenced the selection of lineages of T. tubifex that differ in theirsusceptibility to M. cerebralis. Lineage I and non-tubificid oligochaetes were greatest indeciduous sites; lineage III and M. cerebralis infection was greatest indeciduous/meadowland and coniferous sites. Laboratory studies further indicated thatsubstrate from the various sites affected T. tubifex infection with M. cerebralis,triactinomyxon release, and duration of release. While site variability was evident,environmental factors associated with land cover clearly impact the host pathogenrelationship between T. tubifex and M. cerebralis.