# Updating the Endemicity Map of Soil-Transmitted Helminthiasis in Ten Local Government Areas of Ondo State, Southwestern Nigeria

## TL;DR

This study updated the endemicity map of soil-transmitted helminthiasis in ten local government areas of Ondo State, Nigeria, showing significant reductions in infection rates after preventive chemotherapy.

## Contribution

The study provides updated endemicity data and demonstrates the effectiveness of preventive chemotherapy in reducing helminthiasis prevalence in Ondo State.

## Key findings

- Significant reductions in STH prevalence were observed across all ten LGAs, with risk ratios ranging from 0.04 to 0.40.
- LGAs in C1 and C2 categories showed the most substantial decreases in infection rates following preventive chemotherapy.
- C3 LGAs maintained low STH prevalence below the baseline threshold, indicating low endemicity.

## Abstract

As Nigeria advances toward the elimination of soil-transmitted helminthiasis (STH), updated endemicity maps are essential for guiding programmatic decisions. A cross-sectional study was conducted to update the STH endemicity maps in ten local government areas (LGAs) of Ondo State from July to August 2024. LGAs were stratified into three categories (C1–C3) based on the history of preventive chemotherapy (PC), with C1 being endemic LGAs with ≥5 effective rounds of PC, C2 being endemic LGAs with <5 effective rounds of PC, and C3 being low-endemicity (STH prevalence <20%; PC not required). A total of 4507 school-aged children (5–14 years) from 151 systematically selected communities (15 per LGA) provided fresh stool samples to assess the prevalence and intensity of STH. Stool samples were examined using the Kato-Katz technique. Prevalence of STH was aggregated at the LGA level and compared with World Health Organization thresholds. In the first category (C1), the baseline prevalence was reduced significantly by 60–96%, with specific prevalence in Akoko Southwest (from 28.2% to 0.4%, Risk Ratio (RR): 0.01), Akure North (from 39% to 1.5%, RR = 0.04), Ifedore (from 25% to 2.5%, RR = 0.10), and Ondo East (from 45.2% to 8.2%, RR = 0.18). In the second category (C2), the baseline was reduced significantly by 66–100%, with Akure South (from 29% to 1.2%, RR = 0.04), Ose (from 20% to 2.2%, RR = 0.11), Owo (~100% reduction), and Odigbo (38% to 12.8%, RR = 0.34). In the C3 LGAs, infection was significantly below the baseline threshold, with Akoko Northwest (5.2% to 0.9%, RR = 0.17) and Idanre (from 14.2% to 1.8%, RR = 0.13). Overall, significant reductions in STH prevalence were observed across the surveyed LGAs, with risk ratios ranging from 0.04 to 0.40. These findings updated the endemicity map for the ten LGAs in Ondo State, demonstrating significant progress toward STH elimination following PC implementation.