Background Scrub typhus is an understudied vector-borne bacterial infection. Methods We tested archived fever samples for scrub typhus seropositivity to begin charting its geographic distribution in Indonesia. We analysed 1033 serum samples from three sites. IgM and IgG enzyme-linked immunosorbent assay (ELISA) against Orientia tsutsugamushi was performed using Karp, Kato, Gilliam, TA 716 antigens. To determine the cutoff in the absence of a presumed unexposed population and gold standard tests, we identified the visual inflection point, performed change point analysis, and used finite mixture models. Results The optical density cutoff values used for IgM and IgG were 0.49 and 0.13, respectively. Across all sites, IgM seropositivity was 4.6% (95% CI: 3.4 to 6.0%) while IgG seropositivity was 4.4% (95% CI: 3.3 to 5.8%). The overall seropositivity across sites was 8.8% (95% CI: 8.1 to 11.7%). The overall seropositivity for Jambi, Denpasar, Tabanan were 9.7% (95% CI: 7.0 to 13.3%), 8.0% (95% CI: 5.7 to 11.0%), 9.0% (95% CI: 6.1 to 13.0%), respectively. Conclusions We conclude that O. tsutsugamushi exposure in humans occurred at all sites analysed and could be the cause of illness in some cases. Though it was not the main cause of acute fever in these locations, it is still important to consider scrub typhus in cases not responding to beta-lactam antibiotics. Future seroprevalence surveys and testing for scrub typhus in acute febrile illness studies will be essential to understand its distribution and burden in Indonesia.

中文翻译：

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印度尼西亚的恙虫病：对存档发烧研究样本的横断面分析

背景 恙虫病是一种尚未得到研究的媒介传播的细菌感染。方法 我们对存档的发烧样本进行了恙虫病血清阳性检测，以开始绘制其在印度尼西亚的地理分布图。我们分析了来自三个地点的 1033 份血清样本。使用 Karp、Kato、Gilliam、TA 716 抗原进行针对恙虫病东方体的 IgM 和 IgG 酶联免疫吸附测定 (ELISA)。为了在没有假定未暴露人群和金标准测试的情况下确定截止值，我们确定了视觉拐点，进行了变化点分析，并使用了有限混合模型。结果 用于 IgM 和 IgG 的光密度截止值分别为 0.49 和 0.13。在所有地点，IgM 血清阳性率为 4.6%（95% CI：3.4 至 6.0%），而 IgG 血清阳性率为 4.4%（95% CI：3.3 至 5.8%）。各站点的总体血清阳性率为 8.8%（95% CI：8.1 至 11.7%）。占碑、登巴萨、塔巴南的总体血清阳性率分别为 9.7%（95% CI：7.0 至 13.3%）、8.0%（95% CI：5.7 至 11.0%）、9.0%（95% CI：6.1 至 13.0%） 。结论 我们得出的结论是，在所有分析的地点都发生了人体暴露于恙虫病的情况，并且在某些情况下可能是导致疾病的原因。尽管它不是这些地区急性发烧的主要原因，但在对 β-内酰胺抗生素没有反应的情况下，考虑恙虫病仍然很重要。未来急性发热性疾病研究中的血清流行率调查和斑疹伤寒检测对于了解其在印度尼西亚的分布和负担至关重要。