College of Veterinary Medicine, Animal Resources and Biosecurity (COVAB), Makerere University, Kampala, Uganda.
Foundation for Innovative New Diagnostics (FIND), Campus Biotech, Chemin des Mines, Geneva, Switzerland.
Parasit Vectors. 2017 Nov 3;10(1):546. doi: 10.1186/s13071-017-2487-8.
Serological tests for gambiense human African trypanosomiasis (gHAT) detect antibodies to antigens on the cell surface of bloodstream trypanosomes. As trypanosomes that cause animal African trypanosomiasis (AAT) also express related antigens, we have evaluated two rapid diagnostic tests (RDTs) on cattle in trypanosomiasis endemic and non-endemic regions, to determine whether gHAT serological tests could also be used to screen for AAT.
Two RDTs, 1G RDT, made with native antigens, and p2G RDT, made with recombinant antigens, were tested on 121 cattle in a trypanosomiasis-free region, and on 312 cattle from a rhodesiense HAT and AAT endemic region. A subset of samples from the endemic region were also tested with two immune trypanolysis (TL) tests. The sensitivity of the tests was estimated by evaluating the result of the RDT on samples that were positive by both microscopy and internal transcribed spacer (ITS) PCR, whilst specificity was the result of the RDT on samples that were negative by ITS PCR and microscopy, and others from the non-endemic region.
The specificity of the p2G RDT on cattle from the non-endemic region was 97.5% (95% CI: 93.0-99.2%), compared to only 57.9% (95% CI: 48.9-66.3%) for 1G RDT. The specificities of 1G RDT, p2G RDT and TL on endemic control cattle were 14.6% (95% CI: 9.7-21.5%), 22.6% (95% CI: 16.4-30.3%) and 68.3% (95% CI: 59.6-75.9%), respectively. The sensitivities of the tests on trypanosome positive samples were 85.1% (95% CI: 79.1-89.7%), 89.1% (95% CI: 83.7-93.0%) and 59.3% (95% CI: 51.8-66.4%), respectively. Among the same samples, 51.7% were positive by both TL and the 1G RDT.
These serological tests detect cross-reacting antibodies in cattle. The p2G RDT based on recombinant antigens had a high specificity in a non-endemic region, while the 1G RDT had a lower specificity, suggesting cross-reactivity with other pathogens.
冈比亚人体锥虫病（gHAT）的血清学检测方法检测到血液锥虫细胞表面的抗原抗体。由于引起动物锥虫病（AAT）的锥虫也表达相关抗原，我们在锥虫病流行和非流行地区的牛身上评估了两种快速诊断检测（RDT），以确定 gHAT 血清学检测方法是否也可用于筛查 AAT。
我们在无锥虫病地区的 121 头牛和罗得西亚锥虫病和 AAT 流行地区的 312 头牛身上测试了两种 RDT，1G RDT 采用天然抗原，p2G RDT 采用重组抗原。从流行地区采集的部分样本还使用两种免疫溶血（TL）检测进行了测试。通过评估显微镜和内部转录间隔区（ITS）PCR 均为阳性的样本的 RDT 结果来估计检测的敏感性，而特异性则是通过对 ITS PCR 和显微镜均为阴性的样本以及非流行地区的其他样本的 RDT 结果来确定。
非流行地区牛的 p2G RDT 特异性为 97.5%（95%CI：93.0-99.2%），而 1G RDT 的特异性仅为 57.9%（95%CI：48.9-66.3%）。流行地区对照牛的 1G RDT、p2G RDT 和 TL 的特异性分别为 14.6%（95%CI：9.7-21.5%）、22.6%（95%CI：16.4-30.3%）和 68.3%（95%CI：59.6-75.9%）。在检测阳性样本时，这些检测的敏感性分别为 85.1%（95%CI：79.1-89.7%）、89.1%（95%CI：83.7-93.0%）和 59.3%（95%CI：51.8-66.4%）。在相同的样本中，有 51.7%的样本同时通过 TL 和 1G RDT 检测呈阳性。
这些血清学检测方法在牛身上检测到了交叉反应性抗体。基于重组抗原的 p2G RDT 在非流行地区具有高特异性，而 1G RDT 的特异性较低，表明与其他病原体存在交叉反应。
