TY - JOUR
T1 - Comparing antigenaemia-and microfilaraemia as criteria for stopping decisions in lymphatic filariasis elimination programmes in Africa
AU - Stolk, Wilma A.
AU - Coffeng, Luc E.
AU - Bolay, Fatorma K.
AU - Eneanya, Obiora A.
AU - Fischer, Peter U.
AU - Hollingsworth, T. Déirdre
AU - Koudou, Benjamin G.
AU - Méité, Aboulaye
AU - Michael, Edwin
AU - Prada, Joaquin M.
AU - Rivera, Rocio M.Caja
AU - Sharma, Swarnali
AU - Touloupou, Panayiota
AU - Weil, Gary J.
AU - de Vlas, Sake J.
N1 - Funding Information:
The authors WAS, LEC, TDH, EM, JMP, RMCR, SS, PT and SJdV gratefully acknowledge funding of the NTD Modelling Consortium by the Bill & Melinda Gates Foundation [OPP1184344, https://www.gatesfoundation.org]. WAS, FKB, OAE, PUF, BGK, AM, GJW and SJdV, acknowledge funding from Bill & Melinda Gates Foundation [OPPGH5342, https://www.gatesfoundation.org]. LEC further acknowledges funding from the Dutch Research Council NOW [grant 016.Veni.178.023, https://www.nwo.nl/]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Publisher Copyright:
© 2022 Stolk et al.
PY - 2022/12
Y1 - 2022/12
N2 - Background Mass drug administration (MDA) is the main strategy towards lymphatic filariasis (LF) elimination. Progress is monitored by assessing microfilaraemia (Mf) or circulating filarial antigenaemia (CFA) prevalence, the latter being more practical for field surveys. The current criterion for stopping MDA requires <2% CFA prevalence in 6-to 7-year olds, but this criterion is not evidence-based. We used mathematical modelling to investigate the validity of different thresholds regarding testing method and age group for African MDA programmes using ivermectin plus albendazole. Methodolgy/Principal findings We verified that our model captures observed patterns in Mf and CFA prevalence during annual MDA, assuming that CFA tests are positive if at least one adult worm is present. We then assessed how well elimination can be predicted from CFA prevalence in 6-7-year-old children or from Mf or CFA prevalence in the 5+ or 15+ population, and determined safe (>95% positive predictive value) thresholds for stopping MDA. The model captured trends in Mf and CFA prevalences reasonably well. Elimination cannot be predicted with sufficient certainty from CFA prevalence in 6-7-year olds. Resurgence may still occur if all children are antigen-negative, irrespective of the number tested. Mf-based criteria also show unfavourable results (PPV <95% or unpractically low threshold). CFA prevalences in the 5+ or 15+ population are the best predictors, and post-MDA threshold values for stopping MDA can be as high as 10% for 15+. These thresholds are robust for various alternative assumptions regarding baseline endemicity, biological parameters and sampling strategies. Conclusions/Significance For African areas with moderate to high pre-treatment Mf prevalence that have had 6 or more rounds of annual ivermectin/albendazole MDA with adequate coverage, we recommend to adopt a CFA threshold prevalence of 10% in adults (15+) for stopping MDA. This could be combined with Mf testing of CFA positives to ensure absence of a significant Mf reservoir for transmission.
AB - Background Mass drug administration (MDA) is the main strategy towards lymphatic filariasis (LF) elimination. Progress is monitored by assessing microfilaraemia (Mf) or circulating filarial antigenaemia (CFA) prevalence, the latter being more practical for field surveys. The current criterion for stopping MDA requires <2% CFA prevalence in 6-to 7-year olds, but this criterion is not evidence-based. We used mathematical modelling to investigate the validity of different thresholds regarding testing method and age group for African MDA programmes using ivermectin plus albendazole. Methodolgy/Principal findings We verified that our model captures observed patterns in Mf and CFA prevalence during annual MDA, assuming that CFA tests are positive if at least one adult worm is present. We then assessed how well elimination can be predicted from CFA prevalence in 6-7-year-old children or from Mf or CFA prevalence in the 5+ or 15+ population, and determined safe (>95% positive predictive value) thresholds for stopping MDA. The model captured trends in Mf and CFA prevalences reasonably well. Elimination cannot be predicted with sufficient certainty from CFA prevalence in 6-7-year olds. Resurgence may still occur if all children are antigen-negative, irrespective of the number tested. Mf-based criteria also show unfavourable results (PPV <95% or unpractically low threshold). CFA prevalences in the 5+ or 15+ population are the best predictors, and post-MDA threshold values for stopping MDA can be as high as 10% for 15+. These thresholds are robust for various alternative assumptions regarding baseline endemicity, biological parameters and sampling strategies. Conclusions/Significance For African areas with moderate to high pre-treatment Mf prevalence that have had 6 or more rounds of annual ivermectin/albendazole MDA with adequate coverage, we recommend to adopt a CFA threshold prevalence of 10% in adults (15+) for stopping MDA. This could be combined with Mf testing of CFA positives to ensure absence of a significant Mf reservoir for transmission.
UR - http://www.scopus.com/inward/record.url?scp=85144596820&partnerID=8YFLogxK
U2 - 10.1371/journal.pntd.0010953
DO - 10.1371/journal.pntd.0010953
M3 - Article
C2 - 36508458
AN - SCOPUS:85144596820
SN - 1935-2727
VL - 16
JO - PLoS neglected tropical diseases
JF - PLoS neglected tropical diseases
IS - 12
M1 - e0010953
ER -