Viral and Rickettsial Diseases Department, Infectious Diseases Directorate, Naval Medical Research Center, Silver Spring, MD 20910, USA.
Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Mil Med. 2022 Jul 1;187(7-8):802-807. doi: 10.1093/milmed/usab120.
Leptospirosis and rickettsial diseases are global zoonotic diseases. In severe infection cases, mortality can range from 10% to 30%. Currently most epidemiological data available are based on outbreak investigations and hospital-based studies from endemic countries. The U.S. soldiers at military bases in these countries are highly vulnerable due to the fact that most of them are immunologically naïve to these pathogens. No risk assessment of leptospirosis and rickettsial diseases among U.S. military personnel in Honduras is currently available. This study was aimed at determining the prevalence of leptospirosis and rickettsial diseases in U.S. military personnel deployed to Honduras using serological assays.
A cohort of pre- and post-deployment sera from the most recent 1,000 military personnel stationed in Honduras for at least 6 months between 2000 and 2016 was identified for this study. Serum specimens from these eligible subjects were retrieved. All post-deployment serum specimens were screened at a dilution of 1:100 for the presence of IgG antibodies to Leptospira and Rickettsia pathogens. The pre-deployment sera from those individuals with post-deployment IgG antibodies above cutoff (i.e., seropositive) were tested to determine seroconversion. Seroconversion was defined as conversion of an optical density value from below the cutoff (i.e., negative) in a pre-deployed specimen to above the cutoff (i.e., positive) in a post-deployed specimen at a titer of 100.
The seropositive post-deployment specimens for antibodies against Leptospira (causing leptospirosis), Rickettsia typhi (causing murine typhus [MT]), spotted fever group rickettsioses (SFGR, causing SFG Rickettsia), Orientia tsutsugamushi (causing scrub typhus [ST]), and Coxiella burnetii (causing Q fever [QF]) were 11.6%, 11.3%, 6%, 5.6%, and 8.0%, respectively. The seroconverted rate in those assigned to Honduras from 2000 to 2016 was 7.3%, 1.9%, 3.9%, 4.3%, and 2.7% for leptospirosis, MT, SFGR, ST, and QF, respectively. Among the seroconverted specimens, 27 showed seroconversion of at least two antibodies. These seroconverted individuals accounted for 8.8% (3 out of 34) of the personnel who looked for medical attention during their deployment.
Our results suggest a leptospirosis seroconversion rate of 7.3%, which is higher than the 0.9% and 3.9% seroconversion in Korea and Japan, respectively. The higher rate of seroconversion indicates potential risk of Leptospira exposure. Additional testing of water samples in the pools and pits around the training sites to locate the infected areas is important to eliminate or reduce future exposure to Leptospira during trainings. The rates of seroconversion for ST, MT, spotted fever Rickettsia, and QF were 4.3%, 1.9%, 3.9%, and 2.7%, respectively, indicating the potential exposure to a variety of rickettsial-related pathogens. Testing of vectors for rickettsial pathogens in the areas could inform effective vector control countermeasures to prevent exposure. Proper precaution and protective measures are needed to better protect military personnel deployed to Honduras.
钩端螺旋体病和立克次氏体病是全球性的人畜共患病。在严重感染的情况下，死亡率可能在 10%至 30%之间。目前，大多数可用的流行病学数据都基于爆发调查和来自流行国家的医院研究。由于这些国家的美国士兵对这些病原体在免疫上是幼稚的，因此他们非常容易受到感染。目前尚无关于洪都拉斯美国军人钩端螺旋体病和立克次氏体病的风险评估。本研究旨在使用血清学检测确定部署到洪都拉斯的美国军人中钩端螺旋体病和立克次氏体病的流行情况。
从 2000 年至 2016 年间在洪都拉斯至少驻扎 6 个月的最近 1000 名军人中确定了这项研究的前、后部署血清队列。从这些合格的受试者中检索血清标本。所有后部署的血清标本均以 1:100 的稀释度筛查存在针对钩端螺旋体和立克次氏体病原体的 IgG 抗体。对后部署 IgG 抗体高于截值（即血清阳性）的个体的前部署血清进行检测，以确定血清转化。血清转化定义为在 100 倍稀释度下，前部署标本中的光密度值低于截值（即阴性）转化为后部署标本中的光密度值高于截值（即阳性）。
针对钩端螺旋体（引起钩端螺旋体病）、伤寒杆菌（引起鼠伤寒[MT]）、斑点热群立克次体（引起斑点热立克次体）、恙虫病东方体（引起恙虫病[ST]）和柯克斯体（引起 Q 热[QF]）的后部署血清阳性标本分别为 11.6%、11.3%、6%、5.6%和 8.0%。2000 年至 2016 年期间被派往洪都拉斯的人员中，钩端螺旋体病、MT、SFGR、ST 和 QF 的血清转化率分别为 7.3%、1.9%、3.9%、4.3%和 2.7%。在发生血清转化的标本中，有 27 份标本至少发生了两种抗体的血清转化。这些血清转化个体占在部署期间寻求医疗的 34 名人员中的 8.8%（3 人）。
我们的结果表明，钩端螺旋体病的血清转化率为 7.3%，高于韩国的 0.9%和日本的 3.9%。更高的血清转化率表明存在钩端螺旋体暴露的潜在风险。对训练场地周围的水池和坑中水样进行额外检测，以确定感染区域，这对于消除或减少未来在训练期间接触钩端螺旋体非常重要。恙虫病、MT、斑点热立克次体和 QF 的血清转化率分别为 4.3%、1.9%、3.9%和 2.7%，表明存在接触各种立克次体相关病原体的潜在风险。在这些地区对立克次体病原体的媒介进行检测，可以为有效的媒介控制对策提供信息，以防止接触。需要采取适当的预防和保护措施，以更好地保护部署到洪都拉斯的军人。
