São Tomé and Príncipe on the Verge of Eliminating Lymphatic Filariasis as a Public Health Problem

A Success Story of Accelerated Elimination through Triple‑Drug Therapy and Strong Country Leadership

Lymphatic filariasis (LF), a mosquito‑borne disease that can cause lifelong disability, has long been a public health challenge in many tropical countries. In São Tomé and Príncipe, however, a combination of strong political commitment, strategic adoption of WHO‑recommended tools, and sustained partner support has brought the country to the threshold of eliminating LF as a public health problem.

A Strategic Shift to Accelerate Elimination

Following confirmation of LF endemicity through national mapping conducted in 2015, the Ministry of Health of São Tomé and Príncipe launched a nationwide LF elimination programme aligned with the WHO Global Programme to Eliminate Lymphatic Filariasis. Mass drug administration (MDA) was implemented across all health districts, reaching the full population at risk.

• In 2018, the first nationwide MDA round was conducted using diethylcarbamazine and albendazole, achieving 86.4% epidemiological coverage.
• In response to evolving WHO guidance, the country rapidly adopted the triple‑drug regimen (ivermectin, diethylcarbamazine and albendazole – IDA) in 2019 and 2020, achieving sustained high coverage (74.2% in 2019 and 80.0% in 2020).

This strategic switch to IDA—shown to clear infection faster than traditional two‑drug regimens—marked a turning point in the programme’s trajectory.

Clear Evidence of Impact

To assess whether transmission had been successfully interrupted following cessation of MDA, São Tomé and Príncipe conducted post‑MDA IDA impact assessment surveys among adults aged 20 years and older.

• In 2022, over 14,000 adults were tested nationwide. Only 0.15% were positive for circulating filarial antigen.
• A follow‑up survey in 2024–2025, involving more than 14,600 adults, showed an even sharper decline, with antigen positivity dropping to 0.05%.

Crucially, no microfilariae were detected in any antigen‑positive individuals across both surveys, providing strong evidence that transmission is no longer being sustained. All evaluation units remained well below WHO decision thresholds for ongoing transmission.

A Country Close to Validation

The results place São Tomé and Príncipe among a small but growing group of African countries approaching validation of LF elimination as a public health problem. Several factors contributed to this success:

• Nationwide implementation of IDA, ensuring uniform impact across districts
• High treatment coverage, supported by strong community engagement
• Close collaboration between the Ministry of Health, WHO Country Office, ESPEN, and global partners
• Synergies with malaria elimination efforts, including vector control interventions targeting Anopheles mosquitoes

As a small island nation, São Tomé and Príncipe also benefitted from geographic advantages that facilitated high coverage and limited re‑introduction risks.

The Final Mile: Morbidity Management and Dossier Preparation

While transmission appears to have been effectively interrupted, the country recognizes that elimination is not complete without care for those already affected. National records document 190 cases of lymphoedema and nine cases of hydrocoele, underscoring the need to strengthen morbidity management and disability prevention (MMDP) services nationwide.

The next phase will focus on:

• Expanding access to lymphoedema management and hydrocoele surgery
• Documenting MMDP service availability and quality
• Finalizing the national elimination dossier for submission to WHO

A Model for Other Endemic Countries

São Tomé and Príncipe’s experience demonstrates that rapid progress toward LF elimination is achievable, even within a short timeframe, when evidence‑based strategies such as IDA are effectively implemented. The country’s journey offers valuable lessons for other endemic Member States seeking to accelerate elimination and move confidently toward validation.

São Tomé and Príncipe is not just close to eliminating lymphatic filariasis—it is showing what is possible with commitment, innovation, and sustained partnership.