The Epidemiology Of Scrub Typhus And Rickettsial Infections In A Highly Endemic Rural Setting In South India: Population-Based Cohort Study
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 32,566
- 试验地点
- 1
- 主要终点
- Incidence of spotted fever
研究概览
简要总结
There is enough evidence to suggest that scrub typhus and spotted fever group rickettsioses are common causes of febrile illness in India. Serological evidence also exists for murine typhus, but is rarely tested for. Incidence, risk factors, clinical features and molecular epidemiology of these three infections are poorly understood. Delays in disease recognition and treatment may cause thousands of preventable deaths across India.
The objectives of the research are to determine the incidence and risk factors of scrub typhus, spotted fever and murine typhus by severity, to determine clinical features of these neglected and often unrecognized infections. Further to study the effect of previous infection on incidence and severity of subsequent infections. Finally to study the association between vector parameters and scrub typhus risk.
Enrolled will be 30,000 individuals who will be followed up for the development of fever using active and passive surveillance. Active surveillance will include household screening every 3-6 weeks. Fever cases occuring in the past two months will be tested for Scrub typhus, murine typhus and spotted fever IgG/IgM. 4000 individuals will be followed up by annual serological testing to identify asymptomatic infections. Participants notifying the study team with ongoing fever will undergo blood testing for acute diagnosis of rickettsial infection (IgM, PCR). In addition, we will enroll fever cases at study clinics who are not part of the main cohort. The research includes spatial and socio-economic risk factor analysis. Rodents carrying mite larvae will be trapped to compare the intensity of mite infestation between areas of high and low risk for human scrub typhus.
The data on incidence, burden of disease and environmental determinants of scrub typhus, spotted fever and murine typhus will be used for health care planning and information campaigns for the public and medical professionals.
详细描述
The aim of the cohort study is to better understand the epidemiology, sero-epidemiology and transmission of scrub typhus, murine typhus and tick-borne spotted fever. The overall focus of the work will be on scrub typhus, being the most important of the three from the public health perspective. We aim to determine the "severity pyramid" of serological, symptomatic and severe infection. The results from this study will help clinicians to understand the natural course of scrub typhus infection, health policy makers to estimate the global burden and the scope for community-based interventions, and immunologists to better understand the immunogenicity of single and repeat infections.
The specific objectives are to:
- Estimate the incidence of symptomatic and severe scrub typhus infection in the community.
- Estimate the incidence of serological (asymptomatic) scrub typhus infection.
- Estimate the effect of previous scrub typhus infection (sero-positive at baseline) on the risk of subsequent infection and disease severity (subclinical vs clinically apparent). This includes the effect of antibodies in mothers on the risk of severe infection in young children via residual maternal antibodies.
- Estimate the effect of potential risk factors such as age, gender, occupation, water/sanitation access and comorbidity on the risk of scrub typhus infection.
- Estimate the effect of spatial-temporal risk factors for scrub typhus by identifying high risk areas, accounting for human population density and land use.
- Compare the rate of rodent trappings and vector parameters of chiggers between high risk and low risk areas identified under 5).
- Estimate the disease burden associated with scrub typhus and the economic impact of scrub typhus in terms of loss of earnings and health expenditure.
- Estimate the incidence of asymptomatic and symptomatic murine typhus and spotted fever infection and explore associated socio-demographic, spatial and vector-related risk factors.
STUDY OVERVIEW
The study will be a population-based cohort study over two years (i.e. two scrub typhus seasons) in about 30,000 people living in approximately 40 villages with a sero-prevalence of at least 15% (see flow diagram above). These individuals will be followed-up through active surveillance for recent febrile illnesses (clinical cohort). For passive surveillance, participants will be encouraged to notify the study team in case of fever or come to one of 4 local study clinics. At study clinics we will also enrol fever cases who are not part of the clinical cohort, i.e. have not been enrolled prior to their fever. The study will include a smaller cohort (sero-cohort) for serological surveillance of 4000 people drawn from the 30,000 people of the clinical cohort. Longitudinal serological surveys linked to active surveillance are essential to estimate true attack rates unbiased by disease severity. The sero-cohort will consist of three annual blood testing in the same group of participants over two scrub typhus seasons (baseline, inter-season, endline).
研究设计
- 研究类型
- Observational
- 观察模型
- Cohort
- 时间视角
- Prospective
入排标准
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •General population cohort: residing in study villages
- •serological cohort: aged 10 years or older
- •Hospital cohort: all ages
排除标准
- 未提供
结局指标
主要结局
Incidence of spotted fever
时间窗: 2 years
clinically apparent infection
Incidence of scrub typhus
时间窗: 2 years
clinically apparent infection
Incidence of murine typhus
时间窗: 2 years
clinically apparent infection
次要结局
- Incidence of serological infection (murine typhus)(2 years)
- Incidence of complicated infection (murine typhus)(2 years)
- Incidence of complicated infection (scrub typhus)(2 years)
- Incidence of complicated infection (spotted fever)(2 years)
- Incidence of serological infection (scrub typhus)(2 years)
- Incidence of serological infection (spotted fever)(2 years)