Bioefficacy Evaluation of a Metofluthrin Emanator as Protection Against Aedes albopictus Open Access

Abstract

Globalization and climate-change have contributed to the migration of arboviral transmitting vectors Aedes aegypti and Aedes albopictus and subsequently, the wide-spread emergence of the diseases Zika and Chikungunya. Historically, Aedes aegypti has been considered as the primary host, but in recent decades large locally-transmitted Chikungunya epidemics have occurred with the responsible vector identified as Aedes albopictus. Currently, no vaccine or prophylactic measure exists for these diseases with the main prevention and control methods aiming to prevent vector-human contact. This study tested the impact of a new spatial repellency vector control product, the 10% metofluthrin (SumiOne) emanator, on Aedes albopictus feeding behavior with interest in providing evidence on how, where, and when to use the product to maximize its efficacy. Previous research tested this device on Aedes aegypti, but no trials had been done on Aedes albopictus. Four trials evaluated the product’s protective ability at reducing Aedes albopictus landings by repelling and inducing mosquito paralysis in indoor and outdoor environments. Analysis by mixed models determined that sitting in close proximity to an emanator outdoors reduced landings by 89.5% and by 74.6% indoors. Secondary objectives tested the spatial protective coverage by the product in both environments and investigated emanator longevity. Results presented that emanator spatial coverage outdoors was only protective at 5 m but was protective at all tested distances from the device indoors. A survival analysis exemplified that mortality of mosquitos exposed to the device was about 2 times higher than those who were not exposed. Finally, a Generalized Additive Model (GAM) determined continuous use of an emanator outdoors became non-protective at reducing landings after 1.25 weeks and stopped inducing paralysis after 3 weeks of use. Dissemination of this product is intended in endemic arboviral areas. Thus, it is vital that the product is used properly to protect at risk-communities from transmission by a primary vector. Study results provide evidence that product use requires adaptive implementation based on the surrounding environment. If this device is used properly, it delivers viable protection from Aedes albopictus, a wide-spread mosquito species responsible for transmitting detrimental and challenging arboviral diseases.

Table of Contents

INTRODUCTION ..............................................................................................................1

Arboviruses .......................................................................................................................2

Dengue Virus..............................................................................................................3

Chikungunya Virus ....................................................................................................5

Zika Virus...................................................................................................................5

The Aedes albopictus Life-cycle.........................................................................................6

Vector Control Methods ...................................................................................................8

Chemical Insecticide Classifications ............................................................................... 9

Evaluation of Spatial Repellency Products......................................................................11

Metofluthrin (SumiOne®) ............................................................................................. 12

Objectives ......................................................................................................................13

MATERIALS AND METHODS ......................................................................................14

Study area ......................................................................................................................14

Trial Design ...................................................................................................................14

I. Testing the Effect of Metofluthrin Emanators on Aedes albopictus Behavior Outdoors ............................ 15

II. Testing Emanator Range of Impact Outdoors........................................................................................... 16

III. Testing the Effect of Metofluthrin Emanators on Aedes albopictus Premise Entry Behavior ...................17

IV. Testing Emanator Range of Impact Indoors..............................................................................................19

DATA ANALYSIS...............................................................................................................20

Selection of a Linear Model...............................................................................................21

Overdispersion ................................................................................................................ 22

Model Fit Tests .................................................................................................................23

Final Model Selection.......................................................................................................23

RESULTS..........................................................................................................................24

I. Testing the Effect of Metofluthrin Emanators on Aedes albopictus Behavior Outdoors......................... 24

II. Testing Emanator Range of Impact Outdoors....................................................................................24

Range of Emanator.................................................................................................................................25

III. Testing the Effect of Metofluthrin Emanators on Aedes albopictus Premise Entry Behavior ............... 25

IV. Testing Emanator Range of Impact Indoors.............................................................26

Landing Counts .........................................................................................................26

Knock Downs.............................................................................................................27

Mortality ...................................................................................................................28

Longevity of Emanator...............................................................................................28

DISCUSSION.................................................................................................................. 29

Using the Emanator Outdoors.........................................................................................29

Using the Emanator Indoors .......................................................................................... 31

CONCLUSIONS ............................................................................................................. 32

REFERENCES ............................................................................................................... 34

TABLES..........................................................................................................................43

Table 1. Final Generalized Linear Mixed Model by Trials.............................................. 43

Table 2. ..........................................................................................................................45

Table 3. ..........................................................................................................................45

Table 4. ..........................................................................................................................47

Table 5. ..........................................................................................................................47

Table 6. ..........................................................................................................................48

Table 7. ..........................................................................................................................49

FIGURES ...............................................................................................................................................................................50

Figure 1. Experimental Design for Testing the Range of Emanator Impact Outdoors............................................................50

Figure 2. Emanator Implementation Technique for Testing the Range of Emanator Impact Outdoors..................................51

Figure 3. Experimental Design for Testing the Effect of Metofluthrin Emanators on Premise Entry Behavior.......................51

Figure 4. Experimental Design and Mosquito Positioning for Testing the Range of Emanator Impact Indoors......................52

Figure 5. Normality Analysis of the Response Variable...........................................................................................................53

Figure 6. Mean Landing Counts of Each Treatment by Date and Distance.............................................................................. 55

Figure 7. Landing Counts by Time of Exposure and by Distance From Treatment...................................................................57

Figure 8. Mosquito Survival Probability Over Time....................................................................................................................58

Figure 9. Modeling the Impact of Emanator Age Over Time.......................................................................................................59

About this Master's Thesis

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School	Rollins School of Public Health
Department	Environmental Health
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Environmental Health
Keyword	Aedes albopictus Aedes-borne disease Vector control
Committee Chair / Thesis Advisor	Gonzalo Vazquez-Prokopec, Emory University

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