The northern bobwhite (Colinus virginianus) is a economically important game species throughout its range in North America occurring in open forest, grassland, and brush vegetation communities. In the past few decades, bobwhites have been experiencing a long-term decline throughout their range in Texas. Though shrinking habitat and fragmentation have been intensively studied as the main culprits of decline, one factor needing further examination is the role parasites have in regulating wildlife populations. The objectives of this study were to (1) survey for Trichomonas gallinae in bobwhites; (2) assess helminth prevalence, intensity, and abundance; (3) statistically relate prevalence and abundance of common helminths (occurring in >25% prevalence) to host age, host sex, month, year collection, and northing (distance north); (4) assess bobwhite helminth community structure using numerical dominance, Percent Similarity Index, and Jaccard’s Coefficient of Similarity; (5) determine if the mean mass of bobwhites infected with helminth species occurring in >25% prevalence is statistically different from noninfected bobwhites by age class; and (6) identify pathological responses to eyeworm infection. This research furthers understanding of potentially pathogenic parasites occurring in bobwhites across the Rolling Plains ecoregion of Texas and western Oklahoma. One hundred and sixty one bobwhites were collected from 27 of the 31 collection sites in the Rolling Plains ecoregion of Texas and western Oklahoma in August and October 2011−2013 under the project Operation Idiopathic Decline (OID). Additionally, 128 bobwhites were donated by hunters in the Rolling Plains ecoregion of Texas during the 2012−2013 hunting season and necropsied for helminth survey. To assess pathological damage caused by the eyeworm, Oxyspirura petrowi, whole eye balls (n = 10) and whole heads (n = 12) were taken and preserved n 10% neutral buffered formalin. During OID, live bobwhites (n = 506) were also surveyed for the protozoan T. gallinae. All samples were PCR negative for T. gallinae. In the OID sample, 161 bobwhites were infected with 13 species of helminths. Aulonocephalus pennula was most common (73% prevalence), followed by O. petrowi (40%), Tetrameres pattersoni (14%), acanthocephalan larvae (cystacanths, 9%), Rhabdometra odiosa (7%), Physaloptera sp. (7%), Gongylonema phasianella (2%), Mediorhynchus sp. (1%), Mediorhynchus papillosus (1%), Dispharynx nasuta (1%), Cheilospirura spinosa (1%), Subulura brumpti (1%), and Eucoleus contortus (1%). In the hunter-shot sample, 128 bobwhites were infected with 8 species of helminths. The most common helminths in order of prevalence were A. pennula (91%) and O. petrowi (66%) followed by T. pattersoni (24%), acanthocephalan larvae (cystacanths, 19%), C. spinosa (14%), G. phasaniella (10%), Physaloptera sp. (9%), and R. odiosa (1%). The 2 most common species (>25% prevalence) were examined statistically by extrinsic and intrinsic effects variables. In both samples, A. pennula and O. petrowi occurred at >25% prevalence. In the OID sample, prevalence of O. petrowi and A. pennula was significantly greater in adults compared to juveniles. Prevalence of O. petrowi was significantly lower in 2012 compared to 2011 and 2013. Prevalence of A. pennula was significantly higher in August compared to October. Using a regression model fitted with a negative binomial distribution, results showed that the estimated mean of O. petrowi in bobwhites was greater in adult males, lowest in 2012, and decreased with northing. The estimated mean of A. pennula was greater in adults and also decreased with northing. In the hunter-shot sample, prevalence and the estimated mean of O. petrowi was significantly greater in adults. None of the analyses conducted on A. pennula were significant. Based on the present study using histopathological techniques, O. petrowi residing under the eyelid, nictitating membrane, and conjunctival sac is capable of causing corneal scarring and keratitis (and associated inflammatory responses). In addition, O. petrowi in the intraorbital glands elicits an immune response, displaces gland structure, and decreases secretory cells.
August 2, 2016
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