Addis Ababa University Faculty of Veterinary Medicine
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ADDIS ABABA UNIVERSITY FACULTY OF VETERINARY MEDICINE RETROSPECITVE AND CROSS-SECTIONAL INVESTIGATION OF RIFT VALLEY FEVER IN SMALL RUMINANTS IN PASTORAL AREAS OF ETHIOPIA BY MELESSE BALCHA GHELAN JUNE 2004 DEBRE ZEIT, ETHIOPIA ADDIS ABABA UNIVERSITY FACULTY OF VETERINARY MEDICINE RETROSPECITVE AND CROSS-SECTIONAL INVESTIGATION OF RIFT VALLEY FEVER IN SMALL RUMINANTS IN PASTORAL AREAS OF ETHIOPIA A thesis submitted to the Faculty of Veterinary Medicine, Addis Ababa University in the partial fulfilment of requirements of Master of Science in Tropical Veterinary Medicine BY MELESSE BALCHA GHELAN JUNE 2004 DEBRE ZEIT, ETHIOPIA RETROSPECITVE AND CROSS-SECTIONAL INVESTIGATION OF RIFT VALLEY FEVER IN SMALL RUMINANTS IN PASTORAL AREAS OF ETHIOPIA BY MELESSE BALCHA GHELAN Board of examiners 1. Professor Ph Dorchise ________________________ 2. Professor Feseha Gebreab ________________________ 3. Dr. Wondwossen Abebe Gebreyes ________________________ 4. Dr. Giles Innocent ________________________ 5. Dr. Andy Catley ________________________ 6. Dr. David Barrett ________________________ Academic Advisors 1. Dr. Ademe Zerihun ________________________ 2. Dr. Laikemariam Yigezu ________________________ DECLARATION I, the under signed, declare that the thesis is my original work and has not been presented for a degree in any University. Name Melesse Balcha Ghelan. Signature_____________________________________________ Date of Submission ____________________________________ This thesis has been submitted for the examination with our approval as University advisors. ___________________________________________________________________________ ACKNOWLEDGEMENTS I am greatly indebted to my advisors Dr. Ademe Zerihun (AAU) and Dr. Laikemariam Yigezu (NAHRC) for they stood besides me to tackle any challenge faced from the starting to the end of the study and for they meticulously reviewed my paper. My special thanks also extends to Dr. Kassaye Hadgo (FAO, National consultant, Addis Ababa) who encouraged me not to interrupt my survey with problems related to kits and others, really he did all the bests for the success of this project. I am forced to thank Dr. Bayeleyegn Molla for his enthusiastic follow up of the whole programme. I am also indebted to Professor Feseha G/Ab (AAU), Dr. Nega Tewolde, Dr. Amsalu Demisse, and Dr Dagnenet (MoA) for their provision of reference materials. The following persons share the acknowledgement Dr. Tesfaye Haile, Roman Zewdu, Berhan Ayalew (NAHRC, Sebeta), and Mariame DIOP (Senegal, Dakar FAO RVF reference laboratory) for they shared their experiences in the laboratory work. Ejigu Zeben, Dereje Shegu, Bizuneh Abera and Dereje Bonsa (NAHRC) for their participation in the field work. I want to thank Dr. Mathew Lesnoff, for his support in data analysis and Dr. Zelalem Tadesse and Hana Weldetensay (FAO, Food security section, Addis Ababa) for their help in the preparation of distribution map of the disease. The Ethiopian Agriculture Research Organization (EARO) and NAHRC for they facilitated by provision of vehicles and its staffs and costs related with them; as well as its every staff who made the work to be done by creating good working atmosphere will never be forgotten. The following institutions and organizations are not forgotten for they solved electric power and related problems during the field work FARM Africa (NGO) Gewane and Dewey branch Action FAEM (NGO), Dubti Ephrem Hotel, Mille Hagere Mariam Hospital Dilla Hospital And finally the Federal Ministry of Agriculture of Ethiopia for it allowed the study to be conducted. I TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................. I LIST OF TABLES ............................................................................................................ IV LIST OF ABBREVIATIONS ........................................................................................ VIII ABSTRACT.........................................................................................................................X 1. INTRODUCTION............................................................................................................1 2. LITERATURE REVIEW ................................................................................................5 2.1 Aetiology .........................................................................................................................5 2.1.1 Taxonomy .................................................................................................................5 2.1.2 Structure of Rift Valley Fever Virus ..........................................................................5 2.1.3 Types of Rift Valley Fever Virus ...............................................................................6 2.1.4 Genomic Structure and Organization .........................................................................7 2.2 Epidemiology ..................................................................................................................8 2.2.1 Host Range and Susceptibility ...................................................................................8 2.2.2 Occurrence and distribution .......................................................................................9 2.2.3 Modes of Transmission............................................................................................12 2.2.5 Profile of RVF in Ethiopia.......................................................................................17 2.2.6 Economic Importance..............................................................................................18 2.3 Clinical appearance of Rift Valley Fever.....................................................................21 2.3.1Animals....................................................................................................................21 2.3.2 Rift Valley Fever in human......................................................................................22 2.4 Pathology ......................................................................................................................23 2.5 Diagnosis.......................................................................................................................24 2.5.1 Specimens Taken for Laboratory Examinations .......................................................24 2.5.2 Virus isolation and Identification.............................................................................25 2.5.3 Antigen Identification..............................................................................................25 2.5.4 Detection of virus specific antibodies.......................................................................25 2.5.5 Detection of virus RNA ...........................................................................................26 2.5.6 Histopathology ........................................................................................................26 2.6 Prevention and Control................................................................................................27 2.6.1 Immunity.................................................................................................................27 2.6.1.1 Natural..............................................................................................................27 2.6.1.2 Vaccination.......................................................................................................27 2.6.2 Control in RVF free Areas.......................................................................................28 2.6.3 Control in Human....................................................................................................28 3 MATERIAL AND METHODES....................................................................................29 II 3.1 General Description of the Study Areas ......................................................................29 3.2 Study Design.................................................................................................................31 3.2.1 Study Animals.........................................................................................................33 3.2.2 Sources of Sample ...................................................................................................33 3.2.3 Sampling Frame and Sample Size Determination.....................................................34 3.3 Data Collection .............................................................................................................35 3.3.1 Serum Sample Collection and Submission...............................................................35 3.3.2 Questionnaire survey ...............................................................................................38 3.3.3 Gathering georeferenced data...................................................................................38 3.4 Laboratory Analysis.....................................................................................................38 3.4.1 Types and Purposes of ELISA Tests ........................................................................38 3.4.3 Test Proper ..............................................................................................................39 Preparation of reagents and working dilutions ..............................................................39 3.5 Data storage and Analysis............................................................................................44