I've seen very little coverage of this strange disease in recent months, so this report in the July 18 Morbidity and Mortality Weekly Report is welcome new information: Prevalence of Nodding Syndrome — Uganda, 2012–2013. Excerpt from the discussion section:
Although an illness similar to NS has been reported in Tanzania since the 1960s, NS was only recently reported in South Sudan and Uganda. In 2009, the Ugandan MOH was notified of reports of possible NS cases in Kitgum District. These reports had apparently been increasing since 2003 (1), and few had been reported from other districts despite NS being widely publicized.
Studies have demonstrated that NS is a seizure disorder with a sentinel and defining feature of paroxysmal episodes during which the head bobs forward repeatedly because of atonic seizures (1). A case series in Uganda demonstrated abnormal electroencephalographic (EEG) and brain magnetic resonance imaging findings in children with NS, confirming that it is a type of epilepsy, and primarily affects children aged 3–18 years (1).
In South Sudan and Uganda, studies have indicated associations of NS with current or prior infection with the parasitic helminth Onchocera volvulus and vitamin B6 deficiency (4,8), but the etiology remains unclear. The mortality rate of NS is unknown, but deaths from injury similar to those associated with other forms of epilepsy have been reported (9). No proven effective treatment is available, but patients are empirically managed for their seizures with anti-epileptic medications.
The findings in this report are subject to at least four limitations. First, the census used for the sampling frame might have missed cases and resulted in an underestimation of NS prevalence.
Second, the classification of NS, similar to epilepsy, relies on caregiver report, because self-report is not reliable and confirmatory techniques such as EEG are not always available (10). Such information is subject to misclassification and recall bias, especially when someone other than the primary caregiver is being interviewed.
Third, NS questions used in this investigation were modeled on a previously validated epilepsy questionnaire (10); however, misclassification might still have resulted in over- or underestimation of NS cases and prevalence.
Finally, nonresponse bias might have occurred because respondents were called to a meeting point, which might have excluded persons who were far away or unable to walk.
The prevalence of probable cases of NS was systematically assessed for the first time in the three northern Ugandan districts where most NS cases have been reported, and found to be 6.8 probable NS cases per 1,000 children. This investigation was the first to attempt to use the consensus case definition to determine prevalence (7).
Modifications were necessary because certain criteria were difficult to assess based on caregiver recall or were not specifically defined. Also, the minor criterion of clustering alone did not clearly differentiate suspected from probable cases in this study population, but might be more useful in combination with other criteria or when used in other populations that have not already been screened.
These data can inform future decisions on consensus case definition modifications. These results can also provide a basis for additional studies to establish mortality rates and treatment effectiveness, and for future studies in other areas affected by NS, such as South Sudan and Tanzania.
This information is critical for guiding allocation of health-care resources to provide appropriate management of persons with NS in northern Uganda, and for designing a cohesive strategy to address this emerging public health problem in sub-Saharan Africa.
