Longitudinal Trends and Programmatic Gaps in Selected Neglected Tropical Disease Control Indicators in Nigeria, 2005–2023: A WHO Global Health Observatory Secondary Data Analysis

Technical Summary: Longitudinal Trends and Programmatic Gaps in Selected Neglected Tropical Disease Control Indicators in Nigeria, 2005–2023

Problem Statement
Neglected Tropical Diseases (NTDs) remain a persistent public health burden in Nigeria, affecting an estimated 100 million people and accounting for approximately one-quarter of all NTD cases on the African continent. Despite national commitments to the WHO NTD Roadmap 2021–2030, progress toward elimination targets has been uneven. While strategic frameworks exist, there is a lack of systematic, longitudinal analysis of publicly available NTD indicators in the peer-reviewed literature to identify where programmatic gains are consolidating and where critical deficits persist. The study addresses the need to characterize trends, identify treatment-need gaps, and assess the impact of external shocks, specifically the COVID-19 pandemic, on Nigeria's NTD control trajectory.

Methodology
This study employed a descriptive secondary analysis of national aggregate time-series data sourced exclusively from the WHO Global Health Observatory (GHO) database.

• Data Scope: The analysis covered the period from 2005 to 2023 (with some indicators extending to 2024).
• Indicators: Seven specific indicators were selected based on data availability and alignment with WHO 2030 targets:
  1. Individuals treated for onchocerciasis (NTD_ONCTREAT).
  2. Population requiring preventive chemotherapy for onchocerciasis (NTD_ONCHEMO).
  3. Suspected Buruli ulcer cases (NTD_BU_SUSP).
  4. Population requiring trachoma SAFE strategy (NTD_7).
  5. People receiving antibiotic treatment for trachoma (NTD_8).
  6. New Human African Trypanosomiasis (HAT) cases (NTD_4).
  7. People operated on for trachomatous trichiasis (NTD_TRA5).
• Analysis Tools: Data were downloaded in CSV format, cleaned to exclude non-numeric entries (e.g., "Endemic," "No data"), and visualized using Microsoft Power BI Desktop. Seven visualizations were generated, including line charts for trend analysis and combined charts for treatment-need gaps.
• Ethical Considerations: As the study utilized exclusively publicly available, aggregated secondary data with no personally identifiable information, ethical approval was not required.

Key Results
The analysis revealed an uneven trajectory characterized by significant scale-up achievements followed by persistent structural gaps and pandemic-era disruptions:

• Onchocerciasis: Treatment coverage scaled significantly from 20.8 million individuals in 2005 to a peak of 44.4 million in 2014. However, a persistent treatment gap existed throughout the study period, with estimated needs ranging between 47.5 and 56 million. Coverage declined sharply during the pandemic (dropping to 25 million in 2022) before partially recovering to 34.9 million in 2023.
• Trachoma: Antibiotic treatment delivery peaked at 9.3 million in 2019 but collapsed to 1.76 million by 2023, representing an 81.1% reduction. The population requiring SAFE strategy interventions peaked at 21.2 million in 2018 before declining to 7.98 million in 2020. Surgical output for trachomatous trichiasis generally plateaued at 8,100–8,200 operations annually, interrupted by a single-year spike to ~23,700 in 2019, followed by a decline to ~5,800–6,200 in 2023–2024.
• Buruli Ulcer: Suspected cases showed a marked increase from 2014, peaking at approximately 940 in 2019 before declining. The authors interpret this single-year spike and the subsequent decline as a likely surveillance artifact (enhanced case-finding) rather than a true incidence surge. Crucially, confirmed case data were listed as "No data" for almost all years, indicating a critical laboratory confirmation gap.
• Human African Trypanosomiasis (HAT): The study recorded zero new cases from 2011 onward, representing sustained zero-reporting consistent with WHO elimination criteria, though the authors note this may reflect surveillance limitations in remote areas.
• Cross-Disease Comparison: Onchocerciasis and trachoma indicators numerically dominate Nigeria's NTD profile, far exceeding Buruli ulcer, trichiasis, and HAT metrics.

Key Contributions

• Longitudinal Baseline: The study provides the first systematic secondary analysis of WHO GHO NTD indicators for Nigeria spanning nearly two decades (2005–2023), establishing a baseline for program monitoring.
• Gap Identification: It quantifies the persistent treatment-need gap in onchocerciasis, demonstrating that even at peak capacity (2014), millions remained untreated.
• Pandemic Impact Assessment: The analysis explicitly documents the "sharp pandemic-era contraction" in 2020–2022 across multiple indicators, highlighting the fragility of NTD programs without built-in resilience mechanisms.
• Surveillance Critique: The paper identifies critical data quality issues, specifically the absence of confirmed Buruli ulcer cases and the inability to distinguish between true incidence spikes and surveillance artifacts (e.g., the 2019 Buruli and trichiasis spikes).

Significance and Claims
The authors claim that while Nigeria has achieved notable gains in scaling up onchocerciasis treatment and maintaining zero HAT reporting, the program faces serious risks to achieving the 2030 elimination targets. The significance of the findings lies in the identification of "structural strain" within the program, characterized by:

1. Unsustainable Coverage: Treatment gaps that have never been fully closed.
2. Programmatic Fragility: A severe loss of ground in trachoma delivery and a vulnerability to external shocks like the COVID-19 pandemic.
3. Surveillance Deficiencies: A lack of laboratory confirmation capacity for Buruli ulcer and inconsistent data reporting that obscures true disease trends.

The paper concludes that achieving the 2030 targets requires moving beyond periodic scale-ups toward sustained, resilient delivery. This necessitates integrating NTD services into primary healthcare, investing in community health workforces, enhancing laboratory infrastructure for disease confirmation, and securing consistent domestic financing to reduce dependence on donor-funded cycles vulnerable to global crises. The study modestly positions itself as a call for future research to prioritize sub-national disaggregation and the verification of anomalous data points against primary program records.