Ndiaye El Hadji Ibrahima, Diouf Fatou Samba, Ndiaye Mady, Bassene Hubert, Raoult Didier, Sokhna Cheikh, Parola Philippe, Diatta Georges
Aix Marseille Univ, IRD, APHM, SSA, VITROME, Marseille, France.
IHU Méditerranée Infection, Marseille, France.
PLoS Negl Trop Dis. 2021 Apr 22;15(4):e0009184. doi: 10.1371/journal.pntd.0009184. eCollection 2021 Apr.
Tick-borne relapsing fever (TBRF) is the most common vector-borne bacterial disease in humans in West Africa. It is frequently clinically confused with malaria. Our study aims to determine, on a micro-geographic scale, the conditions for the maintenance and spread of TBRF in the Niakhar district of Senegal.
METHODOLOGY/PRINCIPAL FINDINGS: We conducted clinical, entomological and animal reservoir investigations. Field surveys were carried out in order to investigate the presence of Ornithodoros sonrai vector ticks and to detect Borrelia spp. by qPCR using the 16S rRNA and glpQ genes, respectively. Micromammal trapping series were carried out inside homes and Borrelia infection was detected using brain tissue qPCR. Capillary blood samples from febrile patients were also tested for Borrelia using qPCR. More than 97% (40/41) of the villages surveyed were infested with O. sonrai ticks. The prevalence of Borrelia spp. infections in ticks was 13% (116/910), and over 73% (85/116) were positively confirmed as being Borrelia crocidurae. Borreliosis cases accounted for 12% (94/800) of episodes of fever and all age groups were infected, with children and young people between the ages of 8-14 and 22-28 being the most infected by the disease (16% and 18.4%). TBRF cases occurred in all seasons, with a peak in August. In two species of small rodents that were found to be infected (Arvicanthis niloticus, Mus musculus), the proportion of Borrelia infection was 17.5% (10/57), and the highest prevalence of infection (40.9%, 9/22) was observed in A. niloticus.
CONCLUSION/SIGNIFICANCE: Our study indicates that TBRF is an endemic disease in the Niakhar district, where children and young people are the most infected. Arvicanthis niloticus and O. sonrai ticks are massively present and appear to be the main epidemiological reservoirs causing its extensive spread to humans.
蜱传回归热（TBRF）是西非人类中最常见的媒介传播细菌性疾病。它在临床上常与疟疾混淆。我们的研究旨在在微观地理尺度上确定TBRF在塞内加尔尼亚喀尔地区的维持和传播条件。
方法/主要发现：我们进行了临床、昆虫学和动物宿主调查。开展实地调查以调查桑氏钝缘蜱媒介蜱的存在情况，并分别使用16S rRNA和glpQ基因通过qPCR检测疏螺旋体属。在房屋内进行小型哺乳动物诱捕系列，并使用脑组织qPCR检测疏螺旋体感染情况。还使用qPCR对发热患者的毛细血管血样进行疏螺旋体检测。超过97%（40/41）的被调查村庄有桑氏钝缘蜱出没。蜱中疏螺旋体属感染率为13%（116/910），超过73%（85/116）被阳性确认为罗氏疏螺旋体。疏螺旋体病病例占发热病例的12%（94/800），所有年龄组均有感染，8至14岁和22至28岁的儿童和年轻人受该疾病感染最为严重（分别为16%和18.4%）。TBRF病例在所有季节均有发生，8月达到高峰。在两种被发现感染的小型啮齿动物（尼罗多乳鼠、小家鼠）中，疏螺旋体感染比例为17.5%（10/57），尼罗多乳鼠的感染率最高（40.9%，9/22）。
结论/意义：我们的研究表明，TBRF是尼亚喀尔地区的一种地方病，儿童和年轻人受感染最为严重。尼罗多乳鼠和桑氏钝缘蜱大量存在，似乎是导致其广泛传播给人类的主要流行病学宿主。
