distribution patterns, dispersal and population genetics of anopheline mosquitoes along the ...

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DISTRIBUTION PATTERNS, DISPERSAL AND POPULATION
GENETICS OF ANOPHELINE MOSQUITOES ALONG THE
KENYAN COAST
BY
JANET THERESA MIDEGA B.Sc (Kenyatta), MPhil, University of Ghana.
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA,
LEGON IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR
THE AWARD OF PhD ZOOLOGY DEGREE.
UNIVERSITY OF GHANA
April, 2008
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DECLARATION
I hereby declare that with the exception of references to other people’s work which I have
duly acknowledged all the experimental work described in this thesis was carried out by
me and this thesis, either in whole or in part, has not been presented elsewhere for
another degree.
Janet T. Midega
(PhD candidate)
Prof. Charles M. Mbogo
(Supervisor)
Prof. Michael D. Wilson
(Supervisor)
Prof. Daniel Atrfttjuayefio
(Supervisor)
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dedication
To Jerry and Jimmy
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ACKNOWLEDGEMENTS
I wish to express my sincere gratitude to my supervisors; Professor Michael D. Wilson,
of the Noguchi Memorial Institute for Medical Research, University of Ghana and Prof.
Daniel Attuquayefio of the Zoology Department, University of Ghana for their
supervision. Their patience, guidance and interest in this work gave me the
encouragement to carry on. I am also deeply grateful to Prof. Charles Mbogo of the
Entomology Department, KEMRI-CGMR-C for training me in Medical Entomology. His
patience, treasured advice, concern, stimulating discussions and co-operation throughout
the course of this research contributed greatly to the final result of this work. Special
thanks to Professor Kevin Marsh and Dr. Norbert Peshu, Directors KEMRI/Wellcome
programme, and Mrs. Pauline Lowe for their constant support in many different ways.
Special thanks to all the staff of the Entomology Department, KEMRI-CGMR-C: Mr. J.
Nzovu who together with Dr. J. Mwangangi and Mr. Moses Mosobo were part of
important discussions during the planning and implementation stages of these studies.
Thanks to all the entomology field workers, Messrs Gabriel Nzai, Festus Yaa and Shida
David for their substantial assistance during the fieldwork. I am equally grateful to Dr.
Ephantus Muturi and Mr. D. Muiruri. I also express my gratitude to Prof. John Beier and
Dr Henry Mwambi for their support.
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I acknowledge the tremendous assistance, encouragement and friendly support from my
friends and colleagues at the KEMRI-CGMRC, Kilifi. I am particularly indebted to Dr. E
Okiro, Dr. L. Ochola, Dr. Jane Chuma, Ms. Edna Ogada, Ms. Rosemary Wamae and Mr.
Eric Ohuma.
This study couldn’t have been possible without the co-operation from the community
members and household heads who allowed us entry into their houses for adult mosquito
sampling during the study. I am truly grateful for their support. I am also grateful to the
German Academic Exchange Programme (DAAD) and The National Institutes of Health
(NIH) for providing the funds for this study.
Finally, I express my gratitude to The Senanu family and friends in Ghana for their
hospitality during my visits to work on this thesis; to my husband Charles and my sons
Jerry and Jimmy for the time I spent away from them while working on this dissertation;
and to my entire family for their prayers. May God richly bless you. Above all, I am
most grateful to the almighty God for his provision.
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TABLE OF CONTENTS
Declaration ii
iii
Dedication
iv
Acknowledgements
vi
Table of contents
List of illustrations xiii
xv
List of Tables
List of Plates xvi
List of Appendices xix
List of Abbreviations XX
Abstract xxi
CHAPTER ONE 1
1.0 GENERAL INTRODUCTION 1
1.1 Introduction 1
1.1.1 Study Objectives 7
1.1.1.1 Specific Objectives 7
CHAPTER TWO
8
2.0 LITERATURE REVIEW
8
2.1 Malaria: The disease and symptomatology
8
2.2 Vectors of Malaria 10
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2.2.1 The Anopheles gambiae complex 1°
2.2.2 The Anopheles funestus complex 12
2.3 Malaria Transmission
16
2.3.1 Factors influencing malaria transmission 17
2.3.1.1 Climatic factors 17
2.3.1.2 Host factors 23
2.3.1.3 Vector factors 25
2.3.1.4 Parasite factors 26
2.4 Evaluation of malaria parasite transmission 28
2.4.1 Detection of mosquito blood meal sources 28
2.4.2 Determination of sporozoite infection rates in wild
mosquitoes 29
2.4.3 Entomological inoculation rates (EIR) 30
2.5 The Socio-economic Impact of Malaria 31
2.6 Entomologic Methods in Malaria vector population studies 33
2.6.1 Direct ecological methods
33
2.6.2 Indirect methods 36
2.6.2.1 Molecular biology methods 36
2.6.2.1.1 DNA Based methods
37
2.6.3 The population genetics of Anopheles vectors of malaria 38
2.6.3.1 Microsatellite DNA analysis of Anopheles populations
39
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CHAPTER THREE
3.0 GENERAL METHODOLOGY
41
3.1 The study area
41
3.1.1 Geographic location of the study sites 41
3.1.2 The inhabitants
44
3.1.3 Climate
44
3.1.4 Selection of the study sites 50
3.1.4.1 Jaribuni 50
3.1.4.2 Majajani 51
3.I.4.3. Mtepeni 51
3.1.5 Development of base maps, mapping of compounds and larval
habitats 53
3.2 Entomological sampling methods 53
3.2.1 Day Resting Indoor Collections 54
3.2.2 Human bait collections 54
3.2.3 Light Traps 55
3.2.4 Pyrethrum Spray Catches 55
CHAPTER FOUR 56
THE SPATIAL AND TEMPORAL DISTRUBUTION PATTERNS OF
ANOPHELES GAMBIAE AND ANOPHELES FUNESTUS ALONG THE
KENYAN COAST 56
4.1 Introduction
56
4.2 MATERIALS AND METHODS
59
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4.2.1 The study area
4.2.2. Mapping of study compounds and the development of base maps 59
4.2.3 Field sampling of Anopheles mosquitoes 60
4.2.4 Morphological identification of adult Anopheles gambiae s.l. 60
4.2.5 Sample Preservation 62
4.2.6 PCR methods for species identification 62
4.2.7 Determination of blood meal source using ELISA-based method 62
4.2.8 ELISA detection of Plasmodium falciparum sporozoite infections 63
4.2.9 Data analysis 63
4.3 RESULTS 64
4.3.1 Meteorological data 64
4.3.2 Mosquito species 64
4.3.3 Relative abundance of Mosquito species 64
4.3.4 Monthly changes in population fluctuation 69
4.3.5 Relationship between climatic factors and anopheline species
composition and abundance 70
4.3.6 Blood meal and sporozoite ELISA results 79
4.4 The spatial distribution of Anopheles gambiae and An. funestus in
Jaribuni and Mtepeni Kilifi SI
4.5 Discussion
33
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CHAPTER FIVE 86
ESTIMATING POPUATION SIZE, DISPERSAL AND SURVIVAL
FOR ANOPHELES GAMBIAE AND ANOPHELES FUNESTUS
POPULATIONS ALONG THE KENYAN COAST USING MARK
RELEASE RECAPTURE METHODS
5.1 Introduction
86
5.2 MATERIAL AND METHODS 92
5.2.1 The study sites 92
5.2.2. Mapping of study compounds and larval habitats 92
5.2.3 Mosquito rearing and Mark release recapture experiments 94
5.2.4 Recapture 98
5.2.5 Data analysis 99
5.2.6 Ethical clearance and informed consent 101
5.3 RESULTS 102
5.3.1 Recapture rates 102
5.3.2 Estimates of population size 102
5.3.3 Survival 106
5.3.4 Dispersal 108
5.4 DISCUSSION H
0
CHAPTER SIX
114
POPULATION GENETICS OF ANOPHELES GAMBIAE AND
ANOPHELES FUNESTUS POPULATIONS ALONG THE
KENYAN COAST
Introduction ,, _
6.1
1
X