Nodding Syndrome (cont.)
The mean age of patients in the case series was 13.1 years, with 91.7% reporting onset of disease at ages 5–15 years. Clinical findings included reports by caregivers of typical nodding episodes, other seizure-like activity, and apparent cognitive defects, but a relative lack of focal neurologic deficits. In-depth analysis of these clinical features and comparison with other nodding syndrome reports is under way.
To identify possible risk factors, a case-control study compared those who met the case definition to controls matched by age and location. Based on power calculations from previous investigations in Uganda, 38 matched pairs were enrolled in the case-control study from the two separate locations. Case finding was done through community mobilization. Persons with suspected cases of nodding syndrome were then brought to the study site by caregivers, along with potential neighbor controls, and after screening by investigators, the first 38 pairs that fulfilled the case definition were enrolled in the study. Eighteen (47.4%) of the 38 case-patients and 20 (52.6%) of the controls were female. The mean age of the case-patients was 11.1 years (range: 7–16 years), and the mean age of the controls was 10.6 years (range: 6–17 years).
Overall, prevalence of current onchocerciasis as diagnosed by skin snip was found to be significantly greater among case-patients (76.3%) than among controls (47.4%). Onchocerciasis was more prevalent among case-patients for the 25 pairs in Maridi (88.0% among case-patients and 44.0% among controls); among the 13 pairs in Witto, no significant association with onchocerciasis was observed (Table). In preliminary analyses, no association with nodding syndrome was found with other risk factors, including exposure to munitions, parents' occupations and demographic characteristics. Additional analyses of case-series data and additional exposures related to nutrition are under way. Results of laboratory testing (e.g., for vitamins A, B6, and B12; Onchocerca antibodies; heavy metals [urine analysis]; and genetic markers) are pending.
Public Health Response
Although the cause of nodding syndrome remains unknown, based on these preliminary findings, reinforcing mass ivermectin treatment for onchocerciasis and conducting seizure management using antiepileptic medications were recommended by CDC to the South Sudan Ministry of Health. Enhancing surveillance to identify new cases as they occur, their location, and the age of patients at onset will enable identification of epidemiologic patterns. Exploring the association of nodding syndrome with onchocerciasis and evaluating the role of malnutrition are important future priorities.
Last Editorial Review: 2/22/2012 5:19:15 PM