A Systematic Review of the Geographic Locations and Epidemiologic Features of Nodding Syndrome Open Access

Abbate, Anne Elizabeth (2014)

Permanent URL: https://etd.library.emory.edu/concern/etds/th83kz87p?locale=en
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Abstract

OBJECTIVE: To review and clarify the geographic locations and the epidemiological features of nodding syndrome within and between countries that currently or previously reported cases of nodding syndrome or conditions with clinical presentations similar to nodding syndrome.

METHODS: A retrospective analysis was conducted to evaluate the case status of reported nodding syndrome cases from each country where they have been reported. Published clinical and epidemiological descriptions of these reported cases were reviewed and cross-referenced with the current nodding syndrome case definition to evaluate the true case status. The retrospective analysis was used to support the subsequent review of nodding syndrome risk factors. The strength and consistency of exposure data within and between countries with true nodding syndrome cases was evaluated through intra-country and cross-country analyses.

RESULTS: Cases of nodding syndrome or conditions with clinical manifestations similar to nodding syndrome have been reported from South Sudan, Uganda, Tanzania, Liberia, Cameroon, Taiwan, and Britain. Of these countries with reported cases, only South Sudan and Uganda met the criteria to be classified as confirmed case countries. Tanzania, Liberia, and Cameroon have suspected cases of nodding syndrome. Many risk factors for nodding syndrome were found to be supported by consistent and valid test results in the intra-country analysis. When evaluating common risk factors in the cross-country analysis of confirmed case countries, onchocerciasis was the only supported risk factor; current stunting and current wasting were partially supported. In the cross-country analysis of suspected case countries, onchocerciasis was the only supported risk factor; having a family history of epilepsy was partially supported. Across all case countries, onchocerciasis was the only supported risk factor.

CONCLUSIONS: Suspected nodding syndrome cases in Tanzania, Liberia, and Cameroon warrant further investigation in order to determine the true nature of the suspected illnesses. The intra-country and cross-country analyses indicate that further investigation into the relationship between onchocerciasis and nodding syndrome is justified. Additionally, future investigations should seek to evaluate whether stunting, wasting, and/or a positive family history of epilepsy are risk factors for nodding syndrome as they were determined to be partially supported risk factors in the cross-country analyses.

Table of Contents

CHAPTER 1: Introduction. 1

1.1 Background. 1

1.2 Scope of Problem.. 2

1.2.1 Problem Statement 5

1.3 Purpose of Study. 5

1.4 Research Questions. 5

1.5 Significance of the Study. 6

CHAPTER 2: Review of the Literature. 7

2.1 Clinical Features of Nodding Syndrome. 7

2.1.1 Burden of Disease/Prognosis. 7

2.2 Locations of Nodding Syndrome Case clusters. 8

2.2.1 South Sudan. 9

2.2.2 Uganda. 13

2.2.3 Tanzania. 14

2.2.4 Liberia. 16

2.2.5 Cameroon. 16

2.2.6 Taiwan. 17

2.3 Prominent Etiological Risk Factors. 18

2.3.1 Onchocerciasis. 18

2.3.1.a Precedent for Onchocerciasis as a Risk Factor: Epilepsy. 19

2.3.1.a. Precedent for Onchocerciasis as a Risk Factor: Nakalanga Syndrome. 20

2.3.1.b. Response to Onchocerciasis as a Risk Factor: Vector Control 25

CHAPTER 3: Methods. 27

3.1 Exclusion and Inclusion Criteria. 27

3.1.1 Items to be Included for Review.. 27

3.1.2 Reviewed Items to be Excluded from Analysis. 28

3.2 Retrospective Analysis of the Nature of Reported NS Case clusters. 28

3.3 Intra-Country Analysis of Risk Factors. 31

3.4 Cross-Country Analysis of Risk Factors. 33

CHAPTER 4: Results. 35

4.1 Results of Retrospective Analysis of the Nature of Reported NS Case clusters. 35

4.1.1 Retrospective Analysis: South Sudan (See Table 4.2 in Appendix) 35

4.1.2 Retrospective Analysis: Uganda (See Table 4.3 in Appendix) 36

4.1.3 Retrospective Analysis: Tanzania (See Table 4.4 in Appendix) 36

4.1.4 Retrospective Analysis: Liberia (See Table 4.5 in Appendix) 38

4.1.5 Retrospective Analysis: Cameroon (See Table 4.6 in Appendix) 38

4.2. Results of Intra-Country Analysis of Risk Factors. 39

4.2.1. Intra-Country Analysis: South Sudan (See Table 4.7 in Appendix) 39

4.2.2 Intra-Country Analysis: Uganda (See Table 4.8 in Appendix) 41

4.2.3 Intra-Country Analysis: Tanzania (See Table 4.9 in Appendix) 42

4.2.4 Intra-Country Analysis: Liberia (See Table 4.10 in Appendix) 42

4.2.5 Intra-Country Analysis: Cameroon (See Table 4.11 in Appendix) 42

4.3 Cross-Country Analysis of Risk Factors. 43

4.3.1 Cross-Country Analysis: Confirmed NS Case cluster Locations (See Table 4.12 in Appendix) 43

4.3.2 Cross-Country Analysis: Non-confirmed NS Case cluster Locations (See Table 4.13 in Appendix) 44

4.3.3 Cross-Country Analysis: Confirmed and Unconfirmed NS Case cluster Locations (See Table 4.14 in Appendix) 45

CHAPTER 5: Discussion and Recommendations. 46

5.1 Discussion of the Retrospective Analysis. 46

5.2 Discussion of Risk Factor Analyses. 47

5.3 Etiological Hypotheses. 48

5.3.1 Toxic Encephalopathy. 49

5.3.2 Psychological and Physical Trauma as a Result of Living in Conflict Zones. 51

5.3.3 Encephalopathy Caused by Nutritional Deficiencies. 52

5.3.4 Infectious Encephalopathy. 54

5.4 Recommendations. 59

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