Investigation on predominant Leptospira serovars and its distribution in humans and livestock in Thailand, 2010-2015

BackgroundLeptospirosis is a worldwide zoonotic bacterial disease caused by infection with leptospires. Leptospirosis in humans and livestock is an endemic and epidemic disease in Thailand. Livestock may act as reservoirs for leptospires and source for human infection.Methodology/Principal findingsData on leptospirosis infection in humans and livestock (Buffaloes, Cattle, and Pigs) species during 2010 to 2015 were analyzed. Serum samples were examined using Microscopic Agglutination Test (MAT) to identify antibodies against Leptospira serovars using a cut-off titer ≥ 1:100. The seroprevalence was 23.7% in humans, 24.8% in buffaloes, 28.1% in cattle, and 11.3% in pigs. Region specific prevalence among humans and livestock was found in a wide range. The most predominant serovars were Shermani, followed by Bratislava, Panama, and Sejroe in human, Shermani, Ranarum, and Tarassovi in buffaloes, and Shermani and Ranarum in cattle and pigs. Equally highest MAT titers against multiple serovars per one sample were found mainly in buffaloes and cattle showing equally titers against Ranarum and Shermani. The correlations of distribution of serovars across Thailand’s regions were found to be similar in pattern for cattle but not for buffaloes. In humans, the serovar distribution in the south differed from other regions. By logistic regression, the results indicated that livestock is more susceptible to infection by serovar Shermani when compared to humans.Conclusions/SignificanceThis study gives a detailed picture of the predominance of Leptospira serovars in relation to region, humans and typical livestock. The broad spatial distribution of seroprevalence was analyzed across and within species as well as regions in Thailand. Our finding may guide public health policy makers to implement appropriate control measures and help to reduce the impact of leptospirosis in Thailand.

背景 钩端螺旋体病（Leptospirosis）是一种由钩端螺旋体（leptospires）感染引发的全球性人畜共患细菌性疾病。在泰国，人类与家畜的钩端螺旋体病属于地方流行性与流行性疾病。家畜可作为钩端螺旋体的储存宿主，同时也是人类感染的传染源。

方法/主要研究结果 本研究分析了2010至2015年间人类及家畜（水牛、牛、猪）的钩端螺旋体感染数据。采用显微镜凝集试验（Microscopic Agglutination Test, MAT）检测血清样本，以截断滴度≥1:100作为判定阈值，鉴定抗钩端螺旋体血清型的抗体。结果显示，人类血清阳性率为23.7%，水牛为24.8%，牛为28.1%，猪为11.3%。人类与家畜的血清阳性率在不同区域存在显著差异。人类样本中的优势血清型依次为Shermani、Bratislava、Panama及Sejroe；水牛样本中的优势血清型为Shermani、Ranarum及Tarassovi；牛与猪样本中的优势血清型则为Shermani与Ranarum。单样本针对多种血清型的最高MAT滴度主要见于水牛与牛，二者均对Ranarum与Shermani呈现同等滴度。泰国各区域的血清型分布相关性分析显示，牛的血清型分布模式较为一致，但水牛并非如此；人类样本中，南部区域的血清型分布与其他区域存在明显差异。经logistic回归分析，相较于人类，家畜更易感染Shermani血清型。

结论/意义 本研究清晰阐明了不同区域、人类及典型家畜群体中钩端螺旋体血清型的优势分布特征。本研究分析了泰国境内跨物种、跨区域的广泛血清阳性率空间分布特征。本研究结果可为公共卫生政策制定者提供决策参考，助力其制定适宜的防控措施，以减轻泰国钩端螺旋体病带来的公共卫生影响。