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. 2025 Mar:152:107809.
doi: 10.1016/j.ijid.2025.107809. Epub 2025 Jan 30.

Recurrence of microfilaraemia after triple-drug therapy for lymphatic filariasis in Samoa: Recrudescence or reinfection?

Helen J Mayfield  1 , Ramona Muttucumaru  2 , Benn Sartorius  3 , Sarah Sheridan  3 , Selina Ward  3 , Beatris Mario Martin  3 , Shannon M Hedtke  4 , Robert Thomsen  5 , Satupaitea Viali  6 , Glen Fatupaito  5 , Colleen L Lau  3 , Patricia M Graves  7
Affiliations

Recurrence of microfilaraemia after triple-drug therapy for lymphatic filariasis in Samoa: Recrudescence or reinfection?

Helen J Mayfield et al. Int J Infect Dis. 2025 Mar.

Abstract

Objectives: Contrasting evidence is emerging on the long-term effectiveness of triple-drug therapy for elimination of lymphatic filariasis (LF) in the Pacific region. We evaluated the effectiveness of ivermectin, diethylcarbamazine and albendazole (IDA) for sustained clearance of microfilariae (Mf) in Samoa.

Methods: We enrolled two cohorts of Mf-positive participants. Cohort A were Mf-positive participants from 2018, who received directly observed triple-drug therapy in 2019 and were retested and retreated in 2023 and 2024. Cohort B were Mf-positive and treated in 2023 and retested in 2024. Participants were tested for LF antigen and Mf.

Results: In Cohort A, eight of the 14 participants from 2018/2019 were recruited in 2023; six were Mf-positive. In 2024, six participants were retested, and two were Mf-positive. Cohort B included eight participants, and two remained Mf-positive in 2024. Mf prevalence in 2023 for Cohort A (71.4%, 95% CI 29.0%-96.3%) was significantly higher than among their household members (12.0%, 95% CI 2.5%-31.2%).

Conclusion: One or two doses of directly observed IDA was not sufficient for sustained clearance of Wuchereria bancrofti Mf in Samoa. The high Mf prevalence in treated individuals compared to household members suggests recrudescence rather than reinfection.

Keywords: Albendazole; Diethylcarbamazine; Ivermectin; Lymphatic filariasis elimination; Mass drug administration; Neglected tropical diseases.

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Conflict of interest statement

Declarations of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Figures

Figure 1
Figure 1
Timeline of Surveillance and Monitoring for the Elimination of Lymphatic Filariasis and Scabies in Samoa (SaMELFS) surveys in Samoa in relation to triple-drug mass drug administration (MDA), 2018-2024.
Figure 2
Figure 2
Timeline and number of participants enrolled in the Surveillance and Monitoring for the Elimination of Lymphatic Filariasis and Scabies in Samoa (SaMELFS) 2024 cohort surveys in relation to the triple-drug mass drug administrations (MDA), 2018-2024.
Figure 3
Figure 3
Geometric mean of Mf density for cohort participants in Samoa from 2018 to 2024 for (a) all participants, (b) all Ag-positive participants with valid Mf slides (including Mf-positive and Mf-negative) and (c) all Mf-positive participants. Values are given in Supplementary Table S4.
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