title: Elimination of African onchocerciasis: modeling the impact of increasing the frequency of ivermectin mass treatment.
abstract: The African Programme for Onchocerciasis Control (APOC) is currently shifting its focus from morbidity control to elimination of infection. To enhance the likelihood of elimination and speed up its achievement, programs may consider to increase the frequency of ivermectin mass treatment from annual to 6-monthly or even higher. In a computer simulation study, we examined the potential impact of increasing the mass treatment frequency for different settings. With the ONCHOSIM model, we simulated 92,610 scenarios pertaining to different assumptions about transmission conditions, history of mass treatment, the future mass treatment strategy, and ivermectin efficacy. Simulation results were used to determine the minimum remaining program duration and number of treatment rounds required to achieve 99% probability of elimination. Doubling the frequency of treatment from yearly to 6-monthly or 3-monthly was predicted to reduce remaining program duration by about 40% or 60%, respectively. These reductions come at a cost of additional treatment rounds, especially in case of 3-monthly mass treatment. Also, aforementioned reductions are highly dependent on maintained coverage, and could be completely nullified if coverage of mass treatment were to fall in the future. In low coverage settings, increasing treatment coverage is almost just as effective as increasing treatment frequency. We conclude that 6-monthly mass treatment may only be worth the effort in situations where annual treatment is expected to take a long time to achieve elimination in spite of good treatment coverage, e.g. because of unfavorable transmission conditions or because mass treatment started recently.
authors.affiliation: Department of Public Health, Erasmus MC University Medical Center Rotterdam, P.O. box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Luc E
authors.initials: LE
authors.lastname: Coffeng
authors.affiliation: Department of Public Health, Erasmus MC University Medical Center Rotterdam, P.O. box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Wilma A
authors.initials: WA
authors.lastname: Stolk
authors.affiliation: Institute of Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, Sigmund Freud Str. 25, 53105, Bonn, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Hoerauf
authors.affiliation: Department of Public Health, Erasmus MC University Medical Center Rotterdam, P.O. box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Dik
authors.initials: D
authors.lastname: Habbema
authors.affiliation: Department of Public Health, Erasmus MC University Medical Center Rotterdam, P.O. box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Roel
authors.initials: R
authors.lastname: Bakker
authors.affiliation: Mectizan Donation Program, 325 Swanton Way, Decatur, Georgia, 30030, United States of America.
authors.forename: Adrian D
authors.initials: AD
authors.lastname: Hopkins
authors.affiliation: Department of Public Health, Erasmus MC University Medical Center Rotterdam, P.O. box 2040, 3000 CA Rotterdam, The Netherlands.
authors.forename: Sake J
authors.initials: SJ
authors.lastname: de Vlas
mesh_terms: D000349:Africa / Q000453:epidemiology; D000818:Animals; D003198:Computer Simulation; D060740:Disease Eradication; D006801:Humans; D007559:Ivermectin / Q000008:administration & dosage* / Q000600:supply & distribution / Q000627:therapeutic use*; D008954:Models, Biological; D017181:Onchocerca volvulus; D009855:Onchocerciasis / Q000188:drug therapy* / Q000453:epidemiology / Q000469:parasitology / Q000517:prevention & control*; D011336:Probability; D012867:Skin / Q000469:parasitology; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D007559:Ivermectin