title: Onchocerciasis as a risk factor for night blindness.
abstract: OBJECTIVE
  In the Kaduna State Nigeria Onchocerciasis focus, the prevalence of reported night blindness (RNB) was 12.9%, higher than the national average (1%), and a control non-onchocercal community (0.83%, P < 0.0001). Risk factors for RNB were explored.
  
  
  METHODS
  This was an analysis of baseline data from the phase three ivermectin trials in Kaduna (1988-1995). 6831 subjects in the onchocercal zone and 1563 in the control zone were examined. Ordinal logistic regression was used to assess the relationship between microfilaria load (uninfected, low (<10 mf/mg), moderate (10-49 mf/mg) and high (50+ mf/mg)) and likelihood of RNB.
  
  
  RESULTS
  Ocular evidence of vitamin A deficiency (Bitot spots or xerophthalmia) was absent in both populations. The excess risk of nightblindness attributable to domicile in this onchocerciasis-endemic area was 11.9% with a population attributable fraction of 92.2%. The prevalence of RNB and age-adjusted odds ratio increased with higher microfilaria load (P < 0.0027.) Subjects with onchocerciasis-related ocular lesions such as optic nerve disease (OND; age-adjusted OR 2.29, 95% confidence interval, CI, 1.86-2.83), sclerosing keratitis (OR 2.75, 95% CI 2.10-3.50), and onchocercal chorioretinitis (OR 1.66, 95% CI 1.22-2.26) were significantly more likely to report night blindness. Overall, subjects with a primary diagnosis of 'ocular onchocerciasis' were 50% more likely to report night blindness. OND, cataract and trachoma together accounted for 52% of all RNB but OND (onchocerciasis-related in 80% of cases) emerged as the single most common associated pathology in 30% of cases.
  
  
  CONCLUSIONS
  Onchocercal infection probably accounted for the excess of RNB in this focus.
authors: Bingham University, New Karu, Nigeria. Bablo57@yahoo.com
authors: O E
authors: OE
authors: Babalola
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000977:Antiparasitic Agents / Q000008:administration & dosage; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007559:Ivermectin / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009549:Nigeria / Q000453:epidemiology; D009755:Night Blindness / Q000453:epidemiology*; D016017:Odds Ratio; D015827:Onchocerciasis, Ocular / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D015995:Prevalence; D012307:Risk Factors; D055815:Young Adult
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin