Estimating the duration of antibody positivity and likely time of Leptospira infection using data from a cross-sectional serological study in Fiji

Rees, E. M. , Lau, C. L., Kama, M., Reid, S., Lowe, R. and Kucharski, A. J. (2022) Estimating the duration of antibody positivity and likely time of Leptospira infection using data from a cross-sectional serological study in Fiji. PLoS Neglected Tropical Diseases, 16(6), e0010506. (doi: 10.1371/journal.pntd.0010506) (PMID:35696427) (PMCID:PMC9232128)

Abstract

Background: Leptospirosis is a zoonotic disease prevalent throughout the world, but with particularly high burden in Oceania (including the Pacific Island Countries and Territories). Leptospirosis is endemic in Fiji, with outbreaks often occurring following heavy rainfall and flooding. As a result of non-specific clinical manifestation and diagnostic challenges, cases are often misdiagnosed or under-ascertained. Furthermore, little is known about the duration of persistence of antibodies to leptospirosis, which has important clinical and epidemiological implications. Methodology and principal findings: Using the results from a serosurvey conducted in Fiji in 2013, we fitted serocatalytic models to estimate the duration of antibody positivity and the force of infection (FOI, the rate at which susceptible individuals acquire infection or seroconversion), whilst accounting for seroreversion. Additionally, we estimated the most likely timing of infection. Using the reverse catalytic model, we estimated the duration of antibody persistence to be 8.33 years (4.76–12.50; assuming constant FOI) and 7.25 years (3.36–11.36; assuming time-varying FOI), which is longer than previous estimates. Using population age-structured seroprevalence data alone, we were not able to distinguish between these two models. However, by bringing in additional longitudinal data on antibody kinetics we were able to estimate the most likely time of infection, lending support to the time-varying FOI model. We found that most individuals who were antibody-positive in the 2013 serosurvey were likely to have been infected within the previous two years, and this finding is consistent with surveillance data showing high numbers of cases reported in 2012 and 2013. Conclusions: This is the first study to use serocatalytic models to estimate the FOI and seroreversion rate for Leptospira infection. As well as providing an estimate for the duration of antibody positivity, we also present a novel method to estimate the most likely time of infection from seroprevalence data. These approaches can allow for richer, longitudinal information to be inferred from cross-sectional studies, and could be applied to other endemic diseases where antibody waning occurs.

• Item Type: Articles
• Additional Information: Funding: EMR was supported by Medical Research Council (grant number MR/N013638/1). RL was supported by a Royal Society Dorothy Hodgkin Fellowship. AJK was supported by Wellcome Trust and the Royal Society (grant Number 206250/Z/17/Z). CLL was supported by an Australian National Health and Medical Research Council Fellowships (grant numbers APP 1109035 and 1193826). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Rees, Dr Eleanor
• Authors: Rees, E. M., Lau, C. L., Kama, M., Reid, S., Lowe, R., and Kucharski, A. J.
• College/School: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Journal Name: PLoS Neglected Tropical Diseases
• Publisher: Public Library of Science
• ISSN: 1935-2727
• ISSN (Online): 1935-2735
• Copyright Holders: Copyright © 2022 Rees et al.
• First Published: First published in PLoS Neglected Tropical Diseases 16(6):e0010506
• Publisher Policy: Reproduced under a Creative Commons license