5 Monivong Boulevard, P.O Box. 983, Phnom Penh, Cambodia [email protected]

Cambodia is considered endemic for leptospirosis, though no routine surveillance system exists. Since leptospirosis is curable if suspected, diagnosed and treated at an early stage, identifying risk factors for incidence is crucial. From 2007 to 2009, the Institut Pasteur du Cambodge (IPC) conducted community-based surveillance for febrile illnesses, particularly dengue incidence, among 24,928 individuals in 42 communities of Kampong Cham province, Cambodia. Of the 8,295 fever cases observed during this period, a sample of 2,359 was drawn and tested for seroconversion of anti-Leptospira IgM antibodies. Through this, 100 individuals with newly acquired symptomatic Leptospira infection could be identified.

Financial support

This was made possible through a research grant obtained from the World Health Organization.

Studies

Studies on leptospirosis at IPC showed that the prevalence of antibodies and incidence of leptospirosis seroconversion are very high in rural Cambodia. Data are being extrapolated to estimate disease burden.

1. Leptospirosis prevalence and incidence study 2007-2009

[email protected] team leaders:

Tarantola A. ;  Ly S ; Hem S. (LABM)

Objective:

To determine the leptospirosis incidence and burden of disease in rural Cambodian communities

Core of the project

We conducted anonymous, unlinked testing for IgM antibodies to Leptospira spp (PanBio Leptospira IgM ELISA kit) on paired sera of Cambodian patients. These patients were part of a cohort of villagers <20 years of age followed from 2007 – 2009 by active, community-based surveillance for febrile illnesses in a convenience sample of 32 rural villages in four districts of Kampong Cham province, Cambodia. To maximize chances of leptospira positivity, tested samples were those negative for dengue, JEV, influenza A and B, RSV and HMPV as the fevers observed were considered to be due to those infections in samples positive for those viruses. The serostudy bore on a randomly selected subset of 2359 (33%) among 7162 subjects negative for the abovementioned viruses. Results: In total, 632 subjects were IgM positive and 100 subjects were found to have seroconverted. In this study the seroprevalence of leptospirosis among the samples analyzed was 26.7%. The overall seroconversion of infection among fever episodes of rural children in Kampong Cham province, Cambodia was 4.2%. After extrapolation to the entire study population, the global estimated attack rate for symptomatic infection by pathogenic leptospires for fever episodes among all persons aged <20 years and followed up is estimated at 1.40% [CI95%: 1.26% – 1.55%] for the cumulated study (exposure) periods totaling 28 months. Conclusion: Attack rates for symptomatic leptospirosis IgM seroconversion are high in rural Cambodia, even in the absence of identified epidemics. These preliminary and global results are being complemented by microscopic agglutination

Prospective: analyze at analytic and more macroscopic levels (see below)

Publications

S. Hem, S. Ly, N. Asgari, P. Buchy, S. Heng, T. Sok, S. Ly, C. Ngan, A.Tarantola, B. Guillard. Burden of Leptospirosis in Cambodia: preliminary results of an incidence study. Poster presentation at 15th ICID, Bangkok, Thailand, June 13-16, 2012 (Abstract number 53.055)

Article to be submitted.

 

2. Multivariate risk factors for documented leptospirosis infection

[email protected] team leaders

Tarantola A. ; Ly S.  w/ Dr. Florian Vogt, LSHTM, London

Objective:

To identify individual predictors and foci for leptospirosis incidence in Kampong Cham province, Cambodia.

Core of the project

From the 2007-2009 surveillance, clinical symptoms and socio-economic characteristics of the 2,359 sample were available. The 100 individuals with positive IgM leptospira results were linked with a larger set of additional variables to identify risk factors for leptospirosis incidence. Results: There was a higher risk for Leptospirosis in males compared to females. Moderately elevated odds among higher age groups were observed in the crude analysis of this study, though the multivariate analysis showed no effect. Low statistical power and non-differential biases aside, the absence of a pronounced demographic pattern in this study could also be explained by ubiquitous and permanent exposure in daily life, which affect children and adolescents regardless of age or sex. Three children showed seroconversion twice. While this number was subject to issues related to test accuracy and the sampling procedure, endemicity of Leptospirosis and persistent risk of exposure in Cambodia may have caused frequent re-infections.

Prospective:

See below

Publications

Leptospirosis-associated fever episodes among children and adolescents in Cambodia: Secondary analysis of a community-based surveillance study on Dengue 2007-2009. Submitted in part fulfillment of the requirements for the degree of MSc in Epidemiology 2012.

Article: to be submitted

 

3. Eco-epidemiological aspects of leptospirosis transmission at the country level

[email protected] team leaders

Tarantola A. ; Ly S.  w/ Dr. Julien Capelle, Cirad/IPC

Objective

To identify collective and environmental predictors for leptospirosis incidence in Kampong Cham province, Cambodia.

 

4. Modeling leptospirosis incidence and disease burden in Cambodia

[email protected] team leaders

Tarantola A. ; Ly S.  w/ Dr. Maria van Kerkhove, Imperial College, London

Objective

 To develop models to extrapolate incidence data per fever access to incidence per person-year