Auburn University, Dept. of Biological Sciences, Auburn University, Alabama, United States of America.
Alabama Natural Heritage Program, Auburn University, Alabama, United States of America.
PLoS One. 2019 Apr 5;14(4):e0214845. doi: 10.1371/journal.pone.0214845. eCollection 2019.
Upper respiratory tract disease (URTD) in North American tortoises (Gopherus) has been the focus of numerous laboratory and field investigations, yet the prevalence and importance of this disease remains unclear across many tortoise populations. Furthermore, much research has been focused on understanding diagnostic biomarkers of two known agents of URTD, Mycoplasma agassizii and Mycoplasma testudineum, yet the reliability and importance of these diagnostic biomarkers across populations is unclear. Gopher Tortoises (Gopherus polyphemus) have experienced significant declines and are currently protected range wide. Geographically, Alabama represents an important connection for Gopher Tortoise populations between the core and periphery of this species' distribution. Herein, we systematically sampled 197 Gopher Tortoises for URTD across seven sites in south-central and south-eastern Alabama. Plasma samples were assayed for antibodies to M. agassizii and M. testudineum; nasal lavage samples were assayed for the presence of viable pathogens as well as pathogen DNA. Lastly, animals were scored for the presence of external symptoms and nasal scarring consistent with URTD. External symptoms of URTD were present in G. polyphemus in all sites sampled in Alabama. There was no relationship between active symptoms of URTD and Mycoplasma antibodies, however the presence of URTD nasal scarring was positively related to M. agassizii antibodies (P = 0.032). For a single site that was sampled in three sequential years, seroprevalence to M. agassizii significantly varied among years (P < 0.0001). Mycoplasma agassizii DNA was isolated from four of the seven sites using quantitative PCR, yet none of the samples were culture positive for either of the pathogens. An analysis of disease status and condition indicated that there was a significant, positive relationship between the severity of URTD symptoms and relative body mass (P < 0.05). This study highlights the need for continued monitoring of disease in wild populations. Specifically, focus must be placed on identifying other likely pathogens and relevant biomarkers that may be important drivers of URTD in North American tortoises. Special consideration should be given to environmental contexts that may render wild populations more susceptible to disease.
北美龟类（Gopherus）的上呼吸道疾病（URTD）一直是众多实验室和实地调查的重点，但在许多龟类群体中，这种疾病的流行程度和重要性仍不清楚。此外，大量研究集中于了解 URTD 的两种已知病原体，即嗜菌体（Mycoplasma agassizii）和龟型支原体（Mycoplasma testudineum）的诊断生物标志物，但这些诊断生物标志物在不同种群中的可靠性和重要性尚不清楚。箱龟（Gopherus polyphemus）的数量显著减少，目前在其分布范围的核心和边缘地区都受到保护。在地理上，阿拉巴马州代表了该物种分布核心和边缘之间箱龟种群的重要连接点。在此，我们在阿拉巴马州中南部和东南部的七个地点系统地对 197 只箱龟进行了 URTD 采样。采集血浆样本以检测抗嗜菌体和龟型支原体的抗体；采集鼻腔冲洗样本以检测活病原体以及病原体 DNA 的存在。最后，对动物进行了外部症状和与 URTD 一致的鼻腔疤痕评分。在阿拉巴马州所有采样地点的 G. polyphemus 中都存在 URTD 的外部症状。URTD 的活动性症状与嗜菌体抗体之间没有关系，但是 URTD 鼻腔疤痕的存在与嗜菌体抗体呈正相关（P = 0.032）。对于一个在三个连续年份进行采样的单一地点，嗜菌体抗体的血清阳性率在不同年份之间有显著差异（P < 0.0001）。使用定量 PCR 从七个地点中的四个地点分离出嗜菌体 DNA，但没有一个样本对两种病原体进行培养呈阳性。疾病状况和状况的分析表明，URTD 症状的严重程度与相对体重之间存在显著的正相关关系（P < 0.05）。本研究强调了需要继续监测野生种群中的疾病。具体来说，必须将重点放在确定其他可能的病原体和相关生物标志物上，这些生物标志物可能是北美龟类 URTD 的重要驱动因素。应特别考虑可能使野生种群更容易患病的环境背景。
