In the case-control investigation, while skin snip positivity for the presence of O. volvulus microfilariae was not associated with NS cases, seropositivity for antibodies to O. volvulus was, with 95% of cases positive for onchocerciasis serology compared with 54% of controls (p=0.03). The investigation also showed low serum vitamin B6 (pyridoxine) levels (<20) among the population of children between the ages of 5 and 15 in the region as a whole, both cases and controls. Deficiencies in vitamin A, selenium, and zinc, among both cases and controls were also noted.