Assessment of surrogate biomakers for Ophthalmic Disease in Colinus virginianus infected by Oxyspirura petrowi
Hunter, Jordan W William
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The decline of northern bobwhite quail (Colinus virginianus) populations across Texas over the last few decades is of significant ecological importance. Old World (Phasiandiae) and New World (Odontophoridae) quail and related galliformes have been historically important birds as livestock, game, agriculture, and scientific study. The high incidence of the eye worm, Oxyspirura petrowi, and its infestation within the ocular tissue of northern bobwhites is a biotic factor with influence on C. virginianus physiology and behavior that has not been completely elucidated. Conjunctivitis, intraorbital gland fibrosis, atrophy, and bilateral cataract are conditions resulting from oxyspiruriasis that have been observed in avian species. Helminthiasis of birds is also known to alter the oxidative status of the host’s systems, facilitating oxidative stress and damage to host tissues. Oxidative stress (OS) is linked to etiology of many diseases including severe vision debilitating ophthalmic disorders, and OS can occur through persistent helminth induced dysregulation of host inflammatory immune responses. Under these conditions, host system immunopathology and oxidative stress induced by O. petrowi infestation can lead to the clinical manifestation of eye disorders within the intraocular microenvironment compromising the host’s vision. We have utilized histopathology, enzymatic and non-enzymatic antioxidants, oxidative damage by-products, and gene expression studies to assess surrogate biomarkers associated with the formation of intraocular disease in O. petrowi infected bobwhite quail. We report O. petrowi infected northern bobwhite exhibited a consistent and higher degree of inflammation within the uveal tract, manifesting as choroiditis, as well as abnormalities of the lens relating to the formation posterior sub capsular cataract. Variation in oxidative status of intraocular tissue was observed between bobwhites infected and those uninfected by O. petrowi. Antioxidant concentration and activity was observed to be either significantly reduced (glutathione and glutathione peroxidase), or increased (catalase and superoxide dismutase) among infected quail as compared to uninfected subjects. Lipid peroxidation markers were significantly elevated within infected quail intraocular tissue compared to uninfected bobwhites. We observed increased gene expression of T-helper 2 (Th2) cell immune response cytokines, anti-inflammatory cytokines, and avian uncoupling protein, as well as lower expression of glutathione peroxidase among eye worm infected quail relative to uninfected quail. These studies indicate that O. petrowi infected quail are mounting a Th2 immune response by signaling the recruitment of leukocytes and initiating respiratory bursts of cytotoxic reactive intermediates, altering the oxidative status of the host’s system and increasing intraocular tissue inflammation that could affect the host’s vision. The surrogate biomarkers used in this study can act as indicators of clinical endpoints for ophthalmic disease or symptoms of impaired vision, and can be useful in the study of animal vision, behavior and ophthalmic disease detection in human health.