Oral fluid collection in wild boar: a field protocol

Traditional wildlife sampling methods have limitations in providing a well-distributed, timely and accurate disease surveillance in wildlife. We developed a field protocol for collecting wild boar (Sus scrofa) oral fluid samples for non-invasive active disease surveillance using environmental ropes. We deployed ropes in field settings and tested the rope-sampled oral fluids for antibodies against Mycobacterium bovis and closely related members of the Mycobacterium tuberculosis complex (MTC). Oral fluid samples were collected from three wild boar populations in Spain with endemic tuberculosis across two seasons with contrasting natural food availability. Additionally, we studied the effect of placing the ropes close to aggregation points and of impregnating the ropes with corn powder. The results suggested that installing environmental ropes in summer, close to feeders or aggregation points, and baited with corn powder significantly increases the proportion of bitten ropes. No significant differences were observed in the effectiveness of ropes for oral fluid sampling across the three study sites. The average rate of antibody detection by ELISA was 38% (range 34 to 45%) of the bitten ropes. This method appears to be both precise and sensitive in detecting antibodies against MTC in oral fluid samples collected from environmental ropes, making it a potentially valuable tool for early detection and monitoring of MTC circulation. This noninvasive sampling method can easily be adapted for other relevant diseases of wild suids including African swine fever. Therefore, environmental ropes represent an effective, inexpensive, flexible, environmentally friendly, and noninvasive alternative for active wildlife disease surveillance.

传统野生动物采样方法在实现分布均匀、及时精准的野生动物疾病监测方面存在局限。本研究开发了一套利用环境绳索开展无创主动疾病监测的野外操作规程，用于采集野猪（Sus scrofa）的口腔液样本。研究人员在野外环境中布设绳索，并对绳索采集的口腔液样本开展牛分枝杆菌（Mycobacterium bovis）及结核分枝杆菌复合群（Mycobacterium tuberculosis complex, MTC）近缘成员的抗体检测。研究于西班牙三个存在结核病地方性流行的野猪种群中，在两个天然食物可获得性存在显著差异的季节采集口腔液样本。此外，本研究还探究了绳索布设位置靠近野猪聚集点，以及绳索浸渍玉米粉这两种因素对采样效果的影响。结果显示，在夏季于投喂点或野猪聚集点附近布设绳索，并以玉米粉作为诱饵，可显著提升绳索被啃咬的比例。三个研究区域的绳索口腔液采样有效性无显著差异。被啃咬绳索的酶联免疫吸附试验（ELISA）抗体平均检出率为38%（区间34%~45%）。该方法在检测环境绳索采集的口腔液样本中的MTC抗体时，表现出良好的精准性与灵敏度，有望成为MTC传播早期检测与监测的有效工具。该无创采样方法可轻松适配野生猪科动物的其他相关疫病监测，例如非洲猪瘟（African swine fever）。综上，环境绳索采样法是一种高效、低成本、灵活便捷、环境友好且无创的野生动物主动疾病监测替代方案。