Ongoing transmission of lymphatic filariasis in Samoa 4.5 years after one round of triple-drug mass drug administration

• Published in: PLoS neglected tropical diseases Vol. 18; no. 6; p. e0012236
• Main Authors: Mayfield, Helen J., Sartorius, Benn, Sheridan, Sarah, Howlett, Maddison, Martin, Beatris Mario, Thomsen, Robert, Tofaeono-Pifeleti, Rossana, Viali, Satupaitea, Graves, Patricia M., Lau, Colleen L.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.06.2024; Public Library of Science (PLoS)
• Subjects: Adolescent; Adult; Age groups; Aged; Albendazole; Albendazole - administration & dosage; Albendazole - therapeutic use; Animals; Antigens, Helminth - blood; Biology and Life Sciences; Child; Child, Preschool; Diethylcarbamazine - administration & dosage; Diethylcarbamazine - therapeutic use; Disease transmission; Distribution; Drug therapy; Drug Therapy, Combination; Drugs; Earth Sciences; Elephantiasis; Elephantiasis, Filarial - drug therapy; Elephantiasis, Filarial - epidemiology; Elephantiasis, Filarial - prevention & control; Elephantiasis, Filarial - transmission; Ethics; Female; Filariasis; Filaricides - administration & dosage; Filaricides - therapeutic use; Forecasts and trends; Geospatial data; Health aspects; Households; Humans; Ivermectin; Ivermectin - administration & dosage; Ivermectin - therapeutic use; Male; Mass Drug Administration; Medicine and Health Sciences; Middle Aged; People and Places; Physical Sciences; Polls & surveys; Prevalence; Public health; Samoa - epidemiology; Sample size; Self report; Surveys; Tropical diseases; Vector-borne diseases; Wuchereria bancrofti - drug effects; Wuchereria bancrofti - isolation & purification; Young Adult; Samoa; Samoa (Nation); Upolu
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0012236

Lymphatic filariasis (LF) remains a significant global issue. To eliminate LF as a public health problem, the World Health Organization (WHO) recommends multiple rounds of mass drug administration (MDA). In certain scenarios, including when elimination targets have not been met with two-drug MDA, triple-drug MDA (using ivermectin, diethylcarbamazine and albendazole) is recommended. In this study, we report on antigen (Ag) and microfilaria (Mf) prevalence in eight primary sampling units (PSUs) in Samoa 4.5 years after one round of triple-drug MDA. In 2023, community surveys were conducted in eight PSUs that had been surveyed previously in 2018 (between 1.5 and 3.5 months post triple-drug MDA) and 2019 (six to eight-months post triple-drug MDA). Fifteen houses were randomly selected in each PSU with household members aged ≥ 5 years invited to participate. Blood samples were tested for Ag and Mf. Ag-positive participants were observed in six of the eight PSUs, and Ag prevalence was significantly above the 1% threshold in four PSUs. The presence of Mf-positive participants in five PSUs confirms the presence of residual active infections. This study provides evidence of persistent LF transmission in Samoa 4.5 years after one round of triple-drug MDA, confirming that one round was insufficient for interruption of transmission in this setting. Our findings highlight the negative impact of delaying MDA rounds, for example, due to public health emergencies.