title: Does Increasing Treatment Frequency Address Suboptimal Responses to Ivermectin for the Control and Elimination of River Blindness?
abstract: Several African countries have adopted a biannual ivermectin distribution strategy in some foci to control and eliminate onchocerciasis. In 2010, the Ghana Health Service started biannual distribution to combat transmission hotspots and suboptimal responses to treatment. We assessed the epidemiological impact of the first 3 years of this strategy and quantified responses to ivermectin over 2 consecutive rounds of treatment in 10 sentinel communities.
  
  
  
  We evaluated Onchocerca volvulus community microfilarial intensity and prevalence in persons aged ≥20 years before the first, second, and fifth (or sixth) biannual treatment rounds using skin snip data from 956 participants. We used longitudinal regression modeling to estimate rates of microfilarial repopulation of the skin in a cohort of 217 participants who were followed up over the first 2 rounds of biannual treatment.
  
  
  
  Biannual treatment has had a positive impact, with substantial reductions in infection intensity after 4 or 5 rounds in most communities. We identified 3 communities-all having been previously recognized as responding suboptimally to ivermectin-with statistically significantly high microfilarial repopulation rates. We did not find any clear association between microfilarial repopulation rate and the number of years of prior intervention, coverage, or the community level of infection.
  
  
  
  The strategy of biannual ivermectin treatment in Ghana has reduced O. volvulus microfilarial intensity and prevalence, but suboptimal responses to treatment remain evident in a number of previously and consistently implicated communities. Whether increasing the frequency of treatment will be sufficient to meet the World Health Organization's 2020 elimination goals remains uncertain.
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon.
authors.forename: Kwadwo K
authors.initials: KK
authors.lastname: Frempong
authors.affiliation: London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London.
authors.forename: Martin
authors.initials: M
authors.lastname: Walker
authors.affiliation: London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London.|Natural Resources Institute, University of Greenwich at Medway, Chatham Maritime, United Kingdom.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Cheke
authors.affiliation: Council for Scientific and Industrial Research, Water Research Institute, Accra.
authors.forename: Edward Jenner
authors.initials: EJ
authors.lastname: Tetevi
authors.affiliation: Council for Scientific and Industrial Research, Water Research Institute, Accra.
authors.forename: Ernest Tawiah
authors.initials: ET
authors.lastname: Gyan
authors.affiliation: Department of Animal Biology and Conservation Science, University of Ghana, Legon.
authors.forename: Ebenezer O
authors.initials: EO
authors.lastname: Owusu
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Wilson
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Boakye
authors.affiliation: Department of Parasitology, Liverpool School of Tropical Medicine, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Taylor
authors.affiliation: Ghana Health Service, Accra.
authors.forename: Nana-Kwadwo
authors.initials: NK
authors.lastname: Biritwum
authors.affiliation: Council for Scientific and Industrial Research, Water Research Institute, Accra.
authors.forename: Mike
authors.initials: M
authors.lastname: Osei-Atweneboana
authors.affiliation: London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London.
authors.forename: María-Gloria
authors.initials: MG
authors.lastname: Basáñez
mesh_terms: D000328:Adult; D000977:Antiparasitic Agents / Q000008:administration & dosage* / Q000627:therapeutic use*; D015331:Cohort Studies; D005869:Ghana / Q000453:epidemiology; D006801:Humans; D007559:Ivermectin / Q000008:administration & dosage* / Q000627:therapeutic use*; D008297:Male; D015827:Onchocerciasis, Ocular / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology; D059208:Parasite Load; D015995:Prevalence; D012867:Skin / Q000469:parasitology; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin
keywords: biannual treatment; elimination; ivermectin; onchocerciasis; suboptimal responses