Re-assessment of schistosomiasis in nine endemic districts with cluster sampling in Sierra Leone

Front Public Health. 2024 Jun 12:12:1415486. doi: 10.3389/fpubh.2024.1415486. eCollection 2024.

Abstract

Background: Baseline mapping showed that schistosomiasis was highly/moderately endemic in nine districts in Sierra Leone. Mass drug administration (MDA) with praziquantel started in 2009, and after multiple rounds of treatment, an impact assessment was conducted in 2016 followed by a second re-assessment in 2022 using cluster sampling to provide more granular data for refining chiefdom (sub-district) treatment strategies.

Methods: On average, 20 rural villages were systematically selected per district by probability proportional to population size across the nine districts. Surveys were conducted in schools, and 24 school children aged between 5 and 14 years were randomly selected, with an equal number of boys and girls. One stool sample and one urine sample were collected per child. Two Kato-Katz slides were examined per stool for Schistosoma mansoni infection. Hemastix strips were used as a proxy for S. haematobium infection with urine filtration used for egg counts on hematuria-positive samples.

Results: In total, 4,736 stool samples and 4,618 urine samples were examined across 200 schools in 125 chiefdoms. Overall, the prevalence of S. mansoni was 16.3% (95% CI: 15.3-17.4%), while the overall prevalence of S. haematobium was 2.0% (95% CI: 1.6-2.4%) by hematuria. The prevalence of heavy infections for S. mansoni and S. haematobium was 1.5% (95% CI: 1.1-1.9%) and 0.02% (95% CI: 0.0-0.14%), respectively. Among 125 chiefdoms surveyed, the overall schistosomiasis prevalence was <10% in 65 chiefdoms, 10-49.9% in 47 chiefdoms, and ≥ 50% in 13 chiefdoms. There was a mixed relationship between schistosomiasis in school children and WASH access in schools.

Conclusion: Sierra Leone has made significant progress in reducing schistosomiasis prevalence across the country after a decade of MDA intervention. However, high prevalence remains in some hotspot chiefdoms. The next steps are for the national program to investigate and address any potential issues such as low coverage or poor knowledge of schistosomiasis risk behaviors and, where appropriate, consider broadening to community-wide treatment in hotspot chiefdoms or communities.

Keywords: Schistosoma haematobium; Schistosoma mansoni; Sierra Leone; cluster sampling; impact assessment; schistosomiasis.

MeSH terms

  • Adolescent
  • Animals
  • Anthelmintics / administration & dosage
  • Anthelmintics / therapeutic use
  • Child
  • Child, Preschool
  • Cluster Analysis
  • Endemic Diseases / statistics & numerical data
  • Feces* / parasitology
  • Female
  • Humans
  • Male
  • Mass Drug Administration
  • Praziquantel* / administration & dosage
  • Praziquantel* / therapeutic use
  • Prevalence
  • Rural Population / statistics & numerical data
  • Schistosoma haematobium / isolation & purification
  • Schistosoma mansoni / isolation & purification
  • Schistosomiasis / epidemiology
  • Schistosomiasis mansoni / drug therapy
  • Schistosomiasis mansoni / epidemiology
  • Sierra Leone / epidemiology

Substances

  • Praziquantel
  • Anthelmintics

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. The surveys were made possible with funding from the United States Agency for International Development (USAID). The funding was granted to Helen Keller International under the Act to End Neglected Tropical Diseases | West Program, led by FHI 360 in partnership with Helen Keller International, Health and Development International, Deloitte, World Vision, and the American Leprosy Missions under Cooperative Agreement No. 7200AA18CA00011. The contents are the responsibility of the authors and do not necessarily reflect the views of USAID or the United States Government. The funders had no role in the study design, data Research Topic and analysis, decision to publish, or preparation of the manuscript.