Domestic animals infected with <i>Mycobacterium ulcerans</i>—Implications for transmission to humans

Background The environmental pathogen, Mycobacterium ulcerans (MU) can infect both humans and animals and cause Buruli ulcer (BU) disease. However, its mode(s) of transmission from the colonized environment to human/animal hosts remain unclear. In Australia, MU can infect both wildlife and domestic mammals. Till date, BU-like lesions have only been reported in wildlife in Africa. This warrants a thorough assessment of possible MU in domestic animals in Africa. Here, we screened roaming domesticated animals that share the human microhabitat in two different BU endemic sites, Sedje-Denou in Benin and Akonolinga in Cameroon, for MU lesions. Methodology/Principal findings We screened roaming mammals and birds across 3 endemic villages of Sedje-Denou in Southern Benin and 6 endemic villages of Akonolinga in Cameroon. After approval from relevant authorities, specimens (wound swabs and tissue fragments) were collected from animals with open or active lesion and systematically screened to detect the presence of MU though the diagnostic DNA targets IS2404, IS2606 and KR-B. Out of 397 animals surveyed in Akonolinga, 44 (11.08%) carried skin lesions and all were negative for MU DNA. For Sedje-Denou, only 25 (6.93%) out of 361 animals surveyed carried external skin lesions of which 2 (8%) were positive for MU DNA targets. These MU infected lesions were found in two different villages on a goat (abdominal part) and on a dog (nape area of the neck). Source-tracking of MU isolates within infected animal lesions was performed using VNTR genotyping and further confirmed with sequencing. One MU VNTR genotype (Z) was successfully typed from the goat lesion. The evolutionary history inferred from sequenced data revealed a clustering of animal MU isolates within isolates from human lesions. Conclusion/Significance This study describes the first report of two MU infected lesions in domestic animals in Africa. Their DNA sequence analyses show close relationship to isolates from human cases. It suggests that MU infection should be suspected in domestic hosts and these could play a role in transmission. The findings further support the hypothesis that MU is a ubiquitous environmental pathogen found in endemic areas, and probably involved in a multiple transmission pathway.背景 溃疡分枝杆菌（Mycobacterium ulcerans, MU）是一种环境病原体，可感染人类与动物并引发布鲁里溃疡（Buruli ulcer, BU）疾病。然而，该菌从定殖环境向人类或动物宿主的传播途径至今仍不明确。在澳大利亚，MU可感染野生动物与家养哺乳动物；截至目前，非洲仅在野生动物中报道过类似BU的皮损。因此，有必要对非洲家养动物中潜在的MU感染情况开展全面评估。本研究针对贝宁塞杰-德努（Sedje-Denou）与喀麦隆阿科诺林加（Akonolinga）这两个BU流行疫区中，与人类共享微生境的流浪家养动物进行了MU相关皮损筛查。 材料与方法/主要研究结果 本研究对贝宁南部塞杰-德努的3个BU流行村落，以及喀麦隆阿科诺林加的6个BU流行村落内的流浪哺乳动物与鸟类开展了筛查。经相关主管部门批准后，我们从存在开放性或活动性皮损的动物体内采集了标本（伤口拭子与组织碎片），并通过靶向诊断性DNA序列IS2404、IS2606及KR-B，系统筛查样本中是否存在MU DNA。在阿科诺林加地区共调查397只动物，其中44只（11.08%）存在皮肤皮损，所有样本的MU DNA检测均为阴性。在塞杰-德努地区，361只受调查动物中仅25只（6.93%）存在皮肤外皮损，其中2只（8%）的MU DNA靶标检测呈阳性。这两例MU感染皮损分别发现于两个不同村落：1只山羊的腹部，以及1只犬的颈背区域。我们采用可变数目串联重复序列（VNTR）基因分型技术对感染动物皮损中的MU分离株进行溯源，并通过测序进一步验证。从山羊皮损样本中成功分型得到1株MU VNTR基因型（Z）。基于测序数据构建的进化分析显示，动物来源的MU分离株与人类皮损来源的MU分离株聚为同一进化枝。 结论与意义 本研究首次报道了非洲家养动物中的两例MU感染皮损。DNA序列分析显示，这些分离株与人类病例的分离株亲缘关系密切。研究结果提示，家养宿主中也应警惕MU感染，此类动物可能在MU传播中发挥一定作用。本研究结果进一步支持了以下假说：MU是流行区内广泛存在的环境病原体，其传播途径可能具有多样性。