Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
PLoS Negl Trop Dis. 2011 Aug;5(8):e1265. doi: 10.1371/journal.pntd.0001265. Epub 2011 Aug 16.
In endemic areas, Rift Valley fever virus (RVFV) is a significant threat to both human and animal health. Goals of this study were to measure human anti-RVFV seroprevalence in a high-risk area following the 2006-2007 Kenyan Rift Valley Fever (RVF) epidemic, to identify risk factors for interval seroconversion, and to monitor individuals previously exposed to RVFV in order to document the persistence of their anti-RVFV antibodies.
METHODOLOGY/FINDINGS: We conducted a village cohort study in Ijara District, Northeastern Province, Kenya. One hundred two individuals tested for RVFV exposure before the 2006-2007 RVF outbreak were restudied to determine interval anti-RVFV seroconversion and persistence of humoral immunity since 2006. Ninety-two additional subjects were enrolled from randomly selected households to help identify risk factors for current seropositivity. Overall, 44/194 or 23% (CI(95%):17%-29%) of local residents were RVFV seropositive. 1/85 at-risk individuals restudied in the follow-up cohort had seroconverted since early 2006. 27/92 (29%, CI(95%): 20%-39%) of newly tested individuals were seropositive. All 13 individuals with positive titers (by plaque reduction neutralization testing (PRNT₈₀) in 2006 remained positive in 2009. After adjustment in multivariable logistic models, age, village, and drinking raw milk were significantly associated with RVFV seropositivity. Visual impairment (defined as ≤ 20/80) was much more likely in the RVFV-seropositive group (P<0.0001).
Our results highlight significant variability in RVFV exposure in two neighboring villages having very similar climate, terrain, and insect density. Among those with previous exposure, RVFV titers remained at > 1∶40 for more than 3 years. In concordance with previous studies, residents of the more rural village were more likely to be seropositive and RVFV seropositivity was associated with poor visual acuity. Raw milk consumption was strongly associated with RVFV exposure, which may represent an important new focus for public health education during future RVF outbreaks.
在流行地区，裂谷热病毒（RVFV）对人类和动物的健康构成重大威胁。本研究的目的是在肯尼亚 2006-2007 年裂谷热（RVF）流行后，测量高危地区的人类抗 RVFV 血清阳性率，确定间隔血清转化率的危险因素，并监测先前接触过 RVFV 的个体，以记录其抗 RVFV 抗体的持久性。
方法/发现：我们在肯尼亚东北部伊贾拉区进行了一项村庄队列研究。对 2006-2007 年 RVF 爆发前接受 RVFV 暴露检测的 102 人进行了重新研究，以确定自 2006 年以来间隔抗 RVFV 血清转化率和体液免疫的持久性。从随机选择的家庭中招募了 92 名额外的受试者，以帮助确定当前血清阳性的危险因素。总体而言，194 名当地居民中有 44 人（95%置信区间（CI）：17%-29%）RVFV 血清阳性。在随访队列中，重新研究的 85 名高危个体中，有 1 人自 2006 年初以来血清转化率增加。新检测的 92 名个体中有 27 名（29%，95%CI：20%-39%）血清阳性。2006 年用蚀斑减少中和试验（PRNT₈₀）检测出阳性滴度的 13 名个体在 2009 年仍为阳性。在多变量逻辑模型调整后，年龄、村庄和饮用生牛奶与 RVFV 血清阳性显著相关。视觉障碍（定义为≤20/80）在 RVFV 血清阳性组更为常见（P<0.0001）。
我们的结果突出表明，在两个气候、地形和昆虫密度非常相似的邻近村庄中，RVFV 暴露存在显著差异。在有既往暴露的人群中，RVFV 滴度超过 1∶40 持续了 3 年以上。与以往的研究一致，较农村村庄的居民更有可能呈血清阳性，RVFV 血清阳性与视力差有关。生牛奶的消费与 RVFV 暴露密切相关，这可能是未来 RVF 爆发期间公共卫生教育的一个新重点。
