Epidemiology of nodding syndrome in the Greater Mundri area, South Sudan: Prevalence, spatial pattern and environmental risk factors

Abstract

Background Nodding syndrome (NS) is a progressive neurological disease that has been described in several sub-Saharan African counties, but South Sudan is considered the most affected. However, knowledge about the exact burden and the epidemiological risk factors of NS in South Sudan is lacking. Objective To determine the prevalence, distribution and epidemiological risk factors of NS in the Greater Mundri area, the epicenter of NS in South Sudan. Methods A NS prevalence house-to-house survey was conducted in multiple villages between February 2018 and November 2019. Geographical distribution and clustering of NS cases was identified using spatial and binomial regression analysis. Epidemiological risk factors of NS were identified using univariate and multivariate models. Results Of the 22,411 persons surveyed in 92 villages, 607 (2.7%) persons with NS were identified, of which 114 (19%) were new-onset cases. The highest prevalence was found in Diko village with a prevalence of 13.7%. NS showed a significant spatial pattern with clustering of cases between adjacent households and along rivers. Risks factors for NS include all behaviors around rivers (drinking, cooking, handwashing and bathing) and exposure to poultry. On the other hand, ownership of mobile phone decreased the risk of NS. Many other factors, including prior ivermectin treatment and internal displacement were not associated with NS. Conclusion Our study demonstrates a very high burden of the NS disease in the Greater Mundri area, strengthens the association with rivers, and identified possible new clues for an underlying cause.

Nodding Syndrome: Clinical Characteristics, Risks Factors, Access to Treatment, and Perceptions in the Greater Mundri Area, South Sudan

“…However, several previous studies have reported a significantly strong association between NS and onchocerciasis [ 1 ]. The possible link of NS with the river has been confirmed by our most recent study in the Mundri area [ 6 ]. Also, a study in Maridi, in the Western Equatoria region of South Sudan, has reported that this link is with the blackfly breeding site at the Maridi dam [ 26 ].…”

“…Previously, we investigated epidemiological risks for NS at the household level, looking into socioeconomic status; source of water for drinking, cooking, and bathing; nutritional status; internal displacement; river distance; and CDTI. Ownership of poultry, behaviors around the rivers; and living near the rivers increased the risk of having NS in a household [ 6 ]. Here, we investigate the clinical characteristics of nodding syndrome (NS), individual-level risk factors, access to treatment, and perceptions about NS.…”

Parasitic, bacterial, viral, immune-mediated, metabolic and nutritional factors associated with nodding syndrome

“… 31 , 32 Moreover, from the larger epidemiological study in which the current study was embedded, less than half of households used ivermectin in the last five years, and its use was equal between cases and matched household and community controls. 4 Given the conflicting evidence from our and previous case-control studies, we urge that any interventions to prevent or reduce the NS burden are part of prospective randomized trials which are required to definitively proof or disprove causality.…”

“… 1–3 In high prevalence areas, one in five households can be affected. 4 Clinical features of NS may include atonic seizures with head nodding, other seizures types, cognitive deficits and stunted growth, and parkinsonism in advanced stages. 2 Patients are often stigmatized, isolated and sexually abused.…”

New clues to the elusive aetiology of nodding syndrome

“…Although not discussed by Edridge et al , 1 two of the authors reported previously an association between nodding syndrome in Mundri County and use of river water for drinking, cooking, hand washing and bathing. 11 Since South Sudan is permeated by rivers, but nodding syndrome is largely confined to parts of Western Equatoria, there must be other factors that drive the selective geographic risk for this childhood brain disease. One important consideration is that, prior to 1990, nodding syndrome was unknown in Mundri County, 2 a region impacted by episodic civil conflict resulting in population displacement reflected in widely different prevalence rates of nodding syndrome (2.3–13.7%).…”