Caffarena Rubén D, Castells Matías, Schild Carlos O, Casaux María L, Armendano Joaquín I, Colina Rodney, Giannitti Federico
Plataforma de Investigación en Salud Animal, Instituto Nacional de Investigación Agropecuaria (INIA), Estación Experimental La Estanzuela, Colonia, Uruguay.
Unidad Académica Salud de los Rumiantes, Departamento de Producción Animal, Facultad de Veterinaria, Universidad de la República, Montevideo, Uruguay.
Front Vet Sci. 2022 Aug 12;9:952197. doi: 10.3389/fvets.2022.952197. eCollection 2022.
Rotavirus A (RVA) is amongst the most widespread causes of neonatal calf diarrhea. Because subclinical infections are common, the diagnosis of RVA-induced diarrhea cannot rely solely on molecular viral detection. However, RT-qPCR allows for quantification of RVA shedding in feces, which can be correlated with clinical disease. Here, we determine an optimal cutoff of rotaviral load quantified by RT-qPCR to predict RVA causality in diarrheic neonate calves, using RVA antigen-capture ELISA as reference test. Feces from 328 diarrheic ( = 175) and non-diarrheic ( = 153), <30-day-old dairy calves that had been tested by ELISA and tested positive by RT-qPCR were included. Of 82/328 (25.0%) ELISA-positive calves, 53/175 (30.3%) were diarrheic, whereas 124/153 (81.0%) non-diarrheic calves tested negative by ELISA. The median log10 viral load was significantly higher in diarrheic vs. non-diarrheic and ELISA-positive vs. -negative calves, indicating a higher viral load in diarrheic and ELISA-positive calves. A receiver operating characteristic (ROC) analysis was conducted using the viral loads of the 175 diarrheic calves that had tested either positive ( = 53, cases) or negative ( = 122, controls) by ELISA. The optimal log10 viral load cutoff that predicted RVA causality in diarrheic calves was 9.171. A bootstrapping procedure was performed to assess the out-of-bag performance of this cutoff point, resulting in sensitivity = 0.812, specificity = 0.886, area under the curve = 0.922, and positive and negative diagnostic likelihood ratios of 11.184 and 0.142, respectively. The diagnostic accuracy of the cutoff was excellent to outstanding. This information will help in the interpretation of RVA RT-qPCR results in feces of diarrheic calves submitted for laboratory testing.
A组轮状病毒（RVA）是新生犊牛腹泻最常见的病因之一。由于亚临床感染很常见，RVA引起的腹泻诊断不能仅依赖分子病毒检测。然而，逆转录定量聚合酶链反应（RT-qPCR）可对粪便中的RVA排出量进行定量，这可与临床疾病相关联。在此，我们以RVA抗原捕获酶联免疫吸附测定（ELISA）作为参考检测方法，确定通过RT-qPCR定量的轮状病毒载量的最佳临界值，以预测腹泻新生犊牛的RVA病因。纳入了328头经ELISA检测且RT-qPCR检测呈阳性的30日龄以下腹泻（n = 175）和非腹泻（n = 153）奶牛犊的粪便样本。在82/328（25.0%）ELISA阳性犊牛中，53/175（30.3%）腹泻，而124/153（81.0%）非腹泻犊牛ELISA检测呈阴性。腹泻犊牛与非腹泻犊牛以及ELISA阳性犊牛与阴性犊牛相比，病毒载量的对数值中位数显著更高，表明腹泻和ELISA阳性犊牛的病毒载量更高。对175头经ELISA检测呈阳性（n = 53，病例）或阴性（n = 122，对照）的腹泻犊牛的病毒载量进行了受试者操作特征（ROC）分析。预测腹泻犊牛RVA病因的最佳病毒载量对数值临界值为9.171。进行了自抽样程序以评估该临界值的袋外性能，结果敏感性 = 0.812，特异性 = 0.886，曲线下面积 = 0.922，阳性和阴性诊断似然比分别为11.184和0.142。该临界值的诊断准确性极佳。这些信息将有助于解释提交实验室检测的腹泻犊牛粪便中RVA RT-qPCR结果。
