PLoS Neglected Tropical Diseases (Feb 2023)

Seroprevalence of anti-Lassa Virus IgG antibodies in three districts of Sierra Leone: A cross-sectional, population-based study.

  • Donald S Grant,
  • Emily J Engel,
  • Nicole Roberts Yerkes,
  • Lansana Kanneh,
  • James Koninga,
  • Michael A Gbakie,
  • Foday Alhasan,
  • Franklyn B Kanneh,
  • Ibrahim Mustapha Kanneh,
  • Fatima K Kamara,
  • Mambu Momoh,
  • Mohamed S Yillah,
  • Momoh Foday,
  • Adaora Okoli,
  • Ashley Zeoli,
  • Caroline Weldon,
  • Christopher M Bishop,
  • Crystal Zheng,
  • Jessica Hartnett,
  • Karissa Chao,
  • Kayla Shore,
  • Lilia I Melnik,
  • Mallory Mucci,
  • Nell G Bond,
  • Philip Doyle,
  • Rachael Yenni,
  • Rachel Podgorski,
  • Samuel C Ficenec,
  • Lina Moses,
  • Jeffrey G Shaffer,
  • Robert F Garry,
  • John S Schieffelin

DOI
https://doi.org/10.1371/journal.pntd.0010938
Journal volume & issue
Vol. 17, no. 2
p. e0010938

Abstract

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BackgroundLassa virus (LASV), the cause of the acute viral hemorrhagic illness Lassa fever (LF), is endemic in West Africa. Infections in humans occur mainly after exposure to infected excrement or urine of the rodent-host, Mastomys natalensis. The prevalence of exposure to LASV in Sierra Leone is crudely estimated and largely unknown. This cross-sectional study aimed to establish a baseline point seroprevalence of IgG antibodies to LASV in three administrative districts of Sierra Leone and identify potential risk factors for seropositivity and LASV exposure.Methodology and principal findingsBetween 2015 and 2018, over 10,642 participants from Kenema, Tonkolili, and Port Loko Districts were enrolled in this cross-sectional study. Previous LASV and LF epidemiological studies support classification of these districts as "endemic," "emerging," and "non-endemic", respectively. Dried blood spot samples were tested for LASV antibodies by ELISA to determine the seropositivity of participants, indicating previous exposure to LASV. Surveys were administered to each participant to assess demographic and environmental factors associated with a higher risk of exposure to LASV. Overall seroprevalence for antibodies to LASV was 16.0%. In Kenema, Port Loko, and Tonkolili Districts, seroprevalences were 20.1%, 14.1%, and 10.6%, respectively. In a multivariate analysis, individuals were more likely to be LASV seropositive if they were living in Kenema District, regardless of sex, age, or occupation. Environmental factors contributed to an increased risk of LASV exposure, including poor housing construction and proximity to bushland, forested areas, and refuse.Conclusions and significanceIn this study we determine a baseline LASV seroprevalence in three districts which will inform future epidemiological, ecological, and clinical studies on LF and the LASV in Sierra Leone. The heterogeneity of the distribution of LASV and LF over both space, and time, can make the design of efficacy trials and intervention programs difficult. Having more studies on the prevalence of LASV and identifying potential hyper-endemic areas will greatly increase the awareness of LF and improve targeted control programs related to LASV.