Sustainable control of onchocerciasis: ocular pathology in onchocerciasis patients treated annually with ivermectin for 23 years: a cohort study

PLoS One. 2014 Jun 2;9(6):e98411. doi: 10.1371/journal.pone.0098411. eCollection 2014.


The evolution and persistence of ocular pathology was assessed in a cohort of Onchocerca volvulus infected patients treated annually with ivermectin for 23 years. Patients were resident in rural Central and Kara Region of Togo and ocular examinations included testing of visual acuity, slit lamp examination of the anterior eye segment and the eye fundus by ophthalmoscopy. Before ivermectin treatment, vivid O.volvulus microfilariae (MF) were observed in the right and left anterior eye chamber in 52% and 42% of patients (n = 82), and dead MF were seen in the right and left cornea in 24% and 15% of cases, respectively. At 23 years post initial treatment (PIT), none of the patients (n = 82) presented with MF in the anterior chamber and cornea. A complete resolution of punctate keratitis (PK) lesions without observable corneal scars was present at 23 years PIT (p<0.0001), and sclerosing keratitits (SK) lessened by half, but mainly in patients with lesions at early stage of evolution. Early-stage iridocyclitis diminished from 42%(rE) and 40%(lE) to 13% (rE+lE)(p<0.0001), but advanced iridocyclitis augmented (p<0.001) at 23 years PIT compared to before ivermectin. Advanced-stage papillitis and chorioretinitis did not regress, while early-stage papillitis present in 28%(rE) and 27%(lE) of patients at before ivermectin regressed to 17%(rE) and 18%(lE), and early-stage chorioretinitis present in 51%(rE+lE) of cases at before ivermectin was observed in 12%(rE) and 13%(lE) at 23 years PIT (p<0.0001). Thus, regular annual ivermectin treatment eliminated and prevented the migration of O. volvulus microfilariae into the anterior eye chamber and cornea; keratitis punctata lesions resolved completely and early-stage sclerosing keratitits and iridocyclitis regressed, whilst advanced lesions of the anterior and posterior eye segment remained progressive. In conclusion, annual ivermectin treatments may prevent the emergence of ocular pathology in those populations still exposed to O.volvulus infection.

Trial registration: PACTR201303000464219).

Publication types

  • Clinical Trial, Phase III
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antiparasitic Agents / therapeutic use*
  • Cohort Studies
  • Double-Blind Method
  • Female
  • Humans
  • Ivermectin / therapeutic use*
  • Male
  • Middle Aged
  • Onchocerciasis / drug therapy*
  • Onchocerciasis / physiopathology
  • Onchocerciasis / prevention & control
  • Placebos
  • Treatment Outcome
  • Visual Acuity


  • Antiparasitic Agents
  • Placebos
  • Ivermectin

Associated data

  • PACTR/PACTR201303000464219

Grant support

This work was supported by WHO/TDR (ID 930543), Gesellschaft für Internationale Zusammenarbeit (giz), Deutsche Forschungsgemeinschaft (DFG grant no. 367/1–2), Commission of the European Community (CEC-TS*-CT92-0057 and FP6-INCO-SCOOTT contract no. 032321) and the Togolese Ministry of Health (Autorisation no. 0407/2007/MS/CAB/DGS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.