Small mammals’ diversity into sector 1 and 3.

BackgroundPlague, a zoonosis caused by Yersinia pestis, is endemic in Madagascar but knowledge on the epidemiological situation in the northern focus remains unclear. The aim of this study was to investigate the circulation of Y. pestis in terrestrial small mammals in north eastern Madagascar, where suspected plague outbreaks have been reported.MethodsSampling of terrestrial small mammals and their fleas was carried out in 22 trapping sites within 9 localities of the two sectors (1 and 3) of Makira Natural Park (MNP) and surroundings, from 2020 to 2022. Yersinia pestis was investigated in terrestrial small mammal spleen samples and their fleas using bacteriological, serological and molecular methods.ResultsA total of 614 terrestrial small mammals composed of eight species and 1,754 individual fleas were collected following 4,880 trap-nights. The black rat (Rattus rattus) represented the majority (87.8%) of the small mammal species caught. Flea infestation rate was higher in sector 3 compared to sector 1. In sector 3, Xenopsylla brasiliensis, a plague vector, represented 66.4% of fleas identified. Further, one plague seropositive R. rattus individual, captured inside a house, and one Ctenocephalides felis specimen, collected on another R. rattus, was positive on PCR in this sector.DiscussionDespite low detection rates, we confirmed the circulation of Y. pestis in our study area (one rat seropositive and one flea PCR positive) and highlight the risk of potential human transmission. Our results also suggest that R. rattus contributes to the maintenance and transmission of plague in MNP, as described for other areas in Madagascar. Further, these findings contribute to documentation of the known geographic distribution of the endemic plague vector S. fonquerniei and X. brasiliensis.ConclusionThe confirmation of the circulation of the Y. pestis through serological and molecular diagnostics in small mammals and fleas underscores the urgent need to assess awareness levels of risk factors and symptoms to monitor among local communities and health workers and ensure that trained rapid response teams are prepared to intervene promptly upon suspect case detection. The risk and epidemiology of plague circulation in remote rural areas of Madagascar remains insufficiently studied. Addressing this gap is crucial, as a more comprehensive understanding of the distribution and dynamics of the wild animal hosts, their vectors and host-vector interactions will enhance risk assessment and prevention for plague emergence and improve mitigation and early control of potential outbreaks.研究背景（Background）：鼠疫（Plague）是由鼠疫杆菌（Yersinia pestis）引发的人兽共患病（zoonosis），在马达加斯加呈地方性流行，但学界对其北部疫源地的流行病学现状仍缺乏清晰认知。本研究旨在调查马达加斯加东北部的小型陆生哺乳动物体内的鼠疫杆菌循环情况，该区域曾有疑似鼠疫暴发的报道。 研究方法（Methods）：2020年至2022年间，研究团队在马基拉自然公园（Makira Natural Park, MNP）两个分区（1区与3区）及周边共9个地点的22个捕诱位点，开展小型陆生哺乳动物及其体表跳蚤的采样工作。采用细菌学、血清学及分子生物学方法，对小型陆生哺乳动物的脾脏样本及其体表跳蚤进行鼠疫杆菌检测。 研究结果（Results）：本次研究累计通过4880个捕夜（trap-nights，即单个捕兽夹放置一夜的采样单位）采集到614只小型陆生哺乳动物，隶属于8个物种，同时采集到1754只单个跳蚤样本。捕获的小型哺乳动物中，黑家鼠（Rattus rattus）占比最高，达87.8%。3区的跳蚤侵染率高于1区。在3区中，作为鼠疫媒介（plague vector）的巴西客蚤（Xenopsylla brasiliensis）占已鉴定跳蚤总数的66.4%。此外，该区域内1只于住宅内捕获的黑家鼠血清学鼠疫检测呈阳性，另有1只采自另一只黑家鼠的猫栉首蚤（Ctenocephalides felis）样本经聚合酶链式反应（PCR）检测为阳性。 讨论（Discussion）：尽管检测阳性率较低，但本研究已证实研究区域内存在鼠疫杆菌的循环（1只黑家鼠血清学阳性、1只跳蚤PCR阳性），并凸显了潜在人间传播的风险。本研究结果同时表明，黑家鼠在马基拉自然公园的鼠疫维持与传播中发挥作用，这与马达加斯加其他区域的相关研究结论一致。此外，本研究结果为已知的地方性鼠疫媒介S. fonquerniei与巴西客蚤的地理分布提供了补充记录。 结论（Conclusion）：通过血清学与分子生物学检测证实小型哺乳动物及跳蚤体内存在鼠疫杆菌循环，这凸显出迫切需要开展以下工作：评估当地社区与医护人员对鼠疫风险因素及临床症状的认知水平，确保配备经过培训的快速响应队伍，以便在疑似病例检出后能够迅速开展干预。马达加斯加偏远农村地区的鼠疫循环风险与流行病学特征仍未得到充分研究。填补这一研究空白至关重要，因为全面阐明野生宿主动物、媒介生物及其宿主-媒介相互作用的分布与动态，将有助于提升鼠疫暴发的风险评估与预防能力，改善潜在暴发的缓解与早期防控工作。