Prevalence of malaria and helminth infections in rural communities in northern Sierra Leone, a baseline study to inform Ebola vaccine study protocols

PLoS One. 2022 Jul 6;17(7):e0270968. doi: 10.1371/journal.pone.0270968. eCollection 2022.

Abstract

Introduction: Recurrent parasitic infections may influence the immune response to vaccines. In the Partnership for Research on Ebola VACcinations extended follow-UP and clinical research capacity build-UP (PREVAC-UP) study being undertaken in Mambolo, northern Sierra Leone, participants are being followed up to assess the potential impact of exposure to malaria and/or helminth infections on long-term immune response to two Ebola vaccines. To support the development of the assays that will be used in this evaluation, a parasitological survey was conducted in Mambolo between November 2019 and February 2020.

Methods: Healthy individuals aged ≥1 year who were resident in Mambolo Chiefdom were selected using a stratified sampling approach and questionnaires were administered to explore their sociodemographic characteristics. Microscopy was used to detect malaria parasites, intestinal helminths and urinary schistosome infections. Rapid blood tests were used to detect infections with Onchocerca volvulus and Wuchereria bancrofti. We estimated the overall prevalence of these infections and used adjusted logistic regression models to explore risk factors for malaria and hookworm infection.

Results: Eight hundred and fifteen (815) residents, 50.9% of whom were female were surveyed. Overall, 309 (39.1%) of 791 persons tested for malaria had a positive blood slide; Plasmodium falciparum was the dominant species. Helminth infection was detected in 122 (15.0%) of 815 stool samples including three mixed infections. The helminth infections comprised 102 (12.5%) cases of hookworm, 11 (1.3%) cases of Trichuris trichiura, 10 (1.2%) cases of Schistosoma mansoni and two (0.2%) cases of Ascaris lumbricoides. Being male (OR = 2.01, 95% CI 1.15-3.50) and residing in a non-riverine community (OR = 4.02, 95%CI 2.32-6.98) were the factors associated with hookworm infection. Onchocerca volvulus and Wuchereria bancrofti infections were found in 3.3% and 0.4% of participants respectively.

Conclusion: Malaria and hookworm are the most prevalent parasite infections and those most likely to influence long-term immune response to Ebola vaccines among the trial participants.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Ascaris lumbricoides
  • Ebola Vaccines*
  • Female
  • Hemorrhagic Fever, Ebola*
  • Humans
  • Malaria* / epidemiology
  • Male
  • Prevalence
  • Rural Population
  • Sierra Leone / epidemiology

Substances

  • Ebola Vaccines

Grants and funding

This project is part of the EDCTP2 programme supported by the European Union (grant number RIA2017S-2014 – PREVAC-UP) and by the US National Institute of Allergy and Infectious Diseases of the National Institutes of Health. This research was supported in part by the National Institutes of Health (NIH), by Institut national de la santé et de la recherche médicale (Inserm) and by the London School of Hygiene and Tropical Medicine (LSHTM). There are no grant numbers for the funding from the US NIAID, NIH, INSERM or LSHTM The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. FB, SF, BL, PA, DT, TO, BL, MT, MR, LO, MS, DI, DWJ & BG received full or partial salary support from the grant ‘RIA2017S-2014 – PREVAC-UP‘ through LSHTM. The authors did not receive specific funding for this work from any other funder.