Simulating the effect of evaluation unit size on eligibility to stop mass drug administration for lymphatic filariasis in Haiti Público

Abstract

Background : As more and more countries have implementation units that are entering their sixth year of annual mass drug administration (MDA) for lymphatic filariasis (LF), there is a need to assess whether transmission has been reduced below the threshold required for sustainable transmission and MDA can be stopped. Currently, the main tool used to assess this threshold is the Transmission Assessment Survey (TAS). The guidelines for TAS limit the population in the evaluation units (EUs) to <2 million. This study uses simulations to investigate the effect of population size on the classification of EUs as either passing or failing TAS.

Methodology : The data come from TAS conducted in 14 EUs in Haiti during 2014-2015. To simulate the effects of population size, larger "combination-EUs" were created by forming eight combinations of adjacent EUs. Several approaches to simulate TAS were carried out, with the intent to see how the classification of EUs as passing or failing TAS would change when the larger units were considered.

Results: The results of the simulations show that in some combinations, the vast majority of the time the classification of the combination-EU would agree with both the expected decision, obtained by passing or failing the combination-EU based on the overall expected prevalence, calculated from positive results, sample size and target population from the original EUs, and the desired decision, that is the programmatic decision to fail any combination-EU in which one or more of the original EUs failed. However, a non-negligible proportion of combination-EUs were misclassified.

Conclusions : Misclassifying an EU as failing would result in continued MDA in a region where prevalence is lower than the threshold required for sustainable transmission, translating into additional rounds of MDA and TAS. Misclassifying an EU as passing when transmission persists is even more troubling, given the programmatic implications of stopping MDA too early. The guidelines should be carefully reconsidered to ensure that TAS is a valid and reliable tool to assess the possibility of stopping LF MDA.

Table of Contents

Chapter I: Background ..........................................................................................1

Lymphatic filariasis ...............................................................................................1

Mass Drug Administration (MDA) ...........................................................................3

Transmission Assessment Surveys and Guidelines for Stopping MDA ........................5

Need for Reevaluation of Guidelines .......................................................................8

Diagnostic tests ....................................................................................................10

Haiti: Overview .....................................................................................................13

Lymphatic Filariasis in Haiti ...................................................................................15

Vector distribution .................................................................................................18

References .............................................................................................................20

Chapter II: Manuscript ............................................................................................25

Abstract .................................................................................................................25

Introduction ...........................................................................................................26

Methods .................................................................................................................30

Results ...................................................................................................................37

Discussion ..............................................................................................................48

References ..............................................................................................................55

Tables .....................................................................................................................58

Figures ....................................................................................................................68

Chapter III: Summary, Public Health Implications, and Future Directions .....................71

Summary ..................................................................................................................71

Public Health Implications .........................................................................................72

Possible Future Directions ..........................................................................................75

References .................................................................................................................77

Appendices ................................................................................................................78

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Global Epidemiology - MPH & MSPH
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Palabra Clave	mass drug administration lymphatic filariasis Haiti transmission assessment survey
Committee Chair / Thesis Advisor	Kirby, Amy, Emory University
Committee Members	Gass, Katherine, Task Force for Global Health
Partnering Agencies	International Non-governmental organization (e.g., CARE, Inc.) National or regional non-profit organization (e.g., American Cancer Society) CDC

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