Asia Pacific Centre for Animal Health, Melbourne Veterinary School, The University of Melbournegrid.1008.9, Parkville, Victoria, Australia.
Australian Rickettsial Reference Laboratory, University Hospital Geelong, Geelong, Victoria, Australia.
J Clin Microbiol. 2022 Jul 20;60(7):e0023622. doi: 10.1128/jcm.00236-22. Epub 2022 Jun 2.
Kangaroos are considered to be an important reservoir of Q fever in Australia, although there is limited knowledge on the true prevalence and distribution of coxiellosis in Australian macropod populations. Serological tests serve as useful surveillance tools, but formal test validation is needed to be able to estimate true seroprevalence rates, and few tests have been validated to screen wildlife species for Q fever. In this study, we modified and optimized a phase-specific indirect immunofluorescence assay (IFA) for the detection of IgG antibodies against Coxiella burnetii in macropod sera. The assay was validated against the commercially available ID Screen Q fever indirect multispecies enzyme-linked immunosorbent assay (ELISA) kit (IDVet, Grabels, France) to estimate the diagnostic sensitivity and specificity of each assay, using Bayesian latent class analysis. A direct comparison of the two tests was performed by testing 303 serum samples from 10 macropod populations from the east coast of Australia and New Zealand. The analysis indicated that the IFA had relatively high diagnostic sensitivity (97.6% [95% credible interval [CrI], 88.0 to 99.9]) and diagnostic specificity (98.5% [95% CrI, 94.4 to 99.9]). In comparison, the ELISA had relatively poor diagnostic sensitivity (42.1% [95% CrI, 33.7 to 50.8]) and similar diagnostic specificity (99.2% [95% CrI, 96.4 to 100]) using the cutoff values recommended by the manufacturer. The estimated true seroprevalence of C. burnetii exposure in the macropod populations included in this study ranged from 0% in New Zealand and Victoria, Australia, up to 94.2% in one population from New South Wales, Australia.
袋鼠被认为是澳大利亚 Q 热的重要储存宿主，但对澳大利亚有袋目动物种群中衣原体病的真实流行率和分布情况了解有限。血清学检测是一种有用的监测工具，但需要进行正式的检测验证才能估计真实的血清流行率，而且很少有检测方法经过验证可用于筛查野生动物中的 Q 热。本研究中，我们对用于检测有袋目动物血清中抗柯克斯体 IgG 抗体的相位特异性间接免疫荧光测定法（IFA）进行了修改和优化。该检测法通过与市售的 ID Screen Q 热间接多物种酶联免疫吸附测定试剂盒（IDVet，法国格拉布勒斯）进行比较来进行验证，使用贝叶斯潜在类别分析来估计每种检测方法的诊断敏感性和特异性。通过检测来自澳大利亚和新西兰东海岸的 10 个有袋目动物种群的 303 份血清样本，对两种检测方法进行了直接比较。分析表明，IFA 的诊断敏感性相对较高（97.6%[95%可信区间[CrI]，88.0 至 99.9]），诊断特异性较高（98.5%[95% CrI，94.4 至 99.9]）。相比之下，根据制造商推荐的截止值，ELISA 的诊断敏感性相对较低（42.1%[95% CrI，33.7 至 50.8]），诊断特异性相似（99.2%[95% CrI，96.4 至 100]）。本研究中纳入的有袋目动物种群中，柯克斯体暴露的估计真实血清流行率从新西兰和澳大利亚维多利亚州的 0%到澳大利亚新南威尔士州一个种群的 94.2%不等。
