title: Onchocerciasis: the pre-control association between prevalence of palpable nodules and skin microfilariae.
abstract: BACKGROUND
  The prospect of eliminating onchocerciasis from Africa by mass treatment with ivermectin has been rejuvenated following recent successes in foci in Mali, Nigeria and Senegal. Elimination prospects depend strongly on local transmission conditions and therefore on pre-control infection levels. Pre-control infection levels in Africa have been mapped largely by means of nodule palpation of adult males, a relatively crude method for detecting infection. We investigated how informative pre-control nodule prevalence data are for estimating the pre-control prevalence of microfilariae (mf) in the skin and discuss implications for assessing elimination prospects.
  
  
  RESULTS
  We analyzed published data on pre-control nodule prevalence in males aged ≥ 20 years and mf prevalence in the population aged ≥ 5 years from 148 African villages. A meta-analysis was performed by means of Bayesian hierarchical multivariate logistic regression, accounting for measurement error in mf and nodule prevalence, bioclimatic zones, and other geographical variation. There was a strong positive correlation between nodule prevalence in adult males and mf prevalence in the general population. In the forest-savanna mosaic area, the pattern in nodule and mf prevalence differed significantly from that in the savanna or forest areas.
  
  
  CONCLUSIONS
  We provide a tool to convert pre-control nodule prevalence in adult males to mf prevalence in the general population, allowing historical data to be interpreted in terms of elimination prospects and disease burden of onchocerciasis. Furthermore, we identified significant geographical variation in mf prevalence and nodule prevalence patterns warranting further investigation of geographical differences in transmission patterns of onchocerciasis.
authors.affiliation: Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Luc E
authors.initials: LE
authors.lastname: Coffeng
authors.forename: Sébastien D S
authors.initials: SD
authors.lastname: Pion
authors.forename: Simon
authors.initials: S
authors.lastname: O'Hanlon
authors.forename: Simon
authors.initials: S
authors.lastname: Cousens
authors.forename: Adenike O
authors.initials: AO
authors.lastname: Abiose
authors.forename: Peter U
authors.initials: PU
authors.lastname: Fischer
authors.forename: Jan H F
authors.initials: JH
authors.lastname: Remme
authors.forename: K Yankum
authors.initials: KY
authors.lastname: Dadzie
authors.forename: Michele E
authors.initials: ME
authors.lastname: Murdoch
authors.forename: Sake J
authors.initials: SJ
authors.lastname: de Vlas
authors.forename: María-Gloria
authors.initials: MG
authors.lastname: Basáñez
authors.forename: Wilma A
authors.initials: WA
authors.lastname: Stolk
authors.forename: Michel
authors.initials: M
authors.lastname: Boussinesq
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000453:epidemiology; D000818:Animals; D000977:Antiparasitic Agents / Q000627:therapeutic use; D002648:Child; D006801:Humans; D007559:Ivermectin / Q000627:therapeutic use; D008297:Male; D017181:Onchocerca volvulus / Q000472:pathogenicity; D009855:Onchocerciasis / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D015995:Prevalence; D012867:Skin / Q000469:parasitology; D055815:Young Adult
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin