Surveillance of vector-borne diseases in cattle with special emphasis on bluetongue disease in Switzerland INAUGURALDISSERTATION zur Erlangung der Würde einer Doktorin der Philosophie vorgelegt der Philosophisch-Naturwissenschaftlichen Fakultät der Universität Basel von Vanessa Nadine Racloz Bouças da Silva aus Genève Basel, 2008 1 Surveillance of vector-borne diseases in cattle with special emphasis on bluetongue disease in Switzerland INAUGURALDISSERTATION zur Erlangung der Würde einer Doktorin der Philosophie vorgelegt der Philosophisch-Naturwissenschaftlichen Fakultät der Universität Basel von Vanessa Nadine Racloz Bouças da Silva aus Genève Basel, 2008 2 Genehmigt von der Philosophisch-Naturwissenschaftlichen Fakultät Der Universität Basel auf Antrag von Prof. Dr. Marcel Tanner, P.D. Dr. Christian Griot und Prof. Dr. Katharina Stärk, Basel, den 8. Februar 2008 Prof. Dr. Hans-Peter Hauri Dekan 3 dedicated to my family- Jacques, Helga, Amaro and Alberto 4 Table of contents Acknowledgments ………………………………………………………………………………..iv Summary ………………………………………………………………………………….………v List of Tables …………………………………………………………………………………... .vi List of Figures …………………………………………………………………………………...vii Abbreviations …………………………………………………………………………………….ix Chapter 1. Introduction 1.1 Overview of vector borne diseases on a global scale……………………………………...1 Factors affecting vector-borne disease spread 2 Relevance of vector-borne diseases in Switzerland 4 1.2 Epidemiology of vector-borne diseases relevant to this project…………………………...4 Bluetongue disease Bluetongue disease in Switzerland 6 Bovine Anaplasmosis 7 Anaplamsa marginale in Switzerland 9 Bovine Babesiosis Babesia divergens in Switzerland. 1.3 Vector biology ...................................................................................................................10 Midge biology Culicoides species in Switzerland 11 Tick biology 12 Ixodes ricinus in Switzerland 13 1.4 Surveillance of vector-borne diseases…………………………………………….……...14 Summary of surveillance systems Sentinel herd surveillance in Switzerland 1.5 Background of methods used in thesis…………………………………………………...15 Use of Geographic Information Systems in disease surveillance Basic reproduction number (R 0) calculations for vector-borne diseases i Table of contents Chapter 2 Objectives Aim of study……………………………………………………………………………………...16 Chapter 3 ………………………………………………………………………………………...17 Review of sentinel surveillance systems with special focus on vector-borne diseases. Chapter 4 ………………………………………………………………………................……...35 Establishment of an early warning system against bluetongue virus in Switzerland. Chapter 5. ………………………………………………………………………..............……...47 Unpublished results of sentinel herd serological blood sampling Choice of sentinel herds Sampling strategy Results Discussion Chapter 6. .......................................................................................................................………..49 Use of mapping and statistical modeling for the prediction of bluetongue occurrence in Switzerland based on vector biology. Chapter 7. .............................................................................................................……………….58 An investigation on the Culicoides species composition at seven sites in southern Switzerland. Chapter 8. .................................…………………………………………………………………71 Estimating the temporal and spatial risk of bluetongue related to the incursion of infected vectors into Switzerland. ii Table of contents Chapter 9. ..........................................................................................................................……....84 Establishing a national surveillance system for bluetongue in Switzerland using Scenario Tree modelling Chapter 10. Discussion and conclusions …………………………………………….……….97 Fulfilments of study objectives Limitations of study 101 Application of results from this study Implications of the recent bluetongue cases in Switzerland 103 Conclusions 104 References........................................................................................................................………105 Appendix …......................................................................................................................………114 Curriculum vitae …………………………………………………………………...…………..120 iii Acknowledgments Acknowledgments First and foremost, I would like to thank my supervisor Prof. Katharina Stärk for her expert guidance and continuous support throughout my PhD, especially for knowing how to nudge me into action. I would also like to thank both her and PD Dr. Christian Griot for their feedback, encouragements and discussions which have helped me enormously. I would also like to thank everyone in the monitoring team and at BVET, who one way or the other have assisted and provided me with advice be it technical or supportive. Special thanks go to Dr. Barbara Häsler, Dr. Cornelia Neff, and Dr. Sonia Menendez who helped me tackle the cows, as well as Dr. Simona Casati and Monika Kuhn in fighting through all those bugs. My thanks also goes to Michelle Vock for answering my unending stream of questions. Likewise, I would like to thank Dr. Patrick Presi and Dr. Heinzpeter Schwermer for their critical approach to my work and support in GIS matters, and to Dr. Penelope Vounatsou for helping me plough through the statistics. I would also like to show my appreciation to Dr. Martin Reist, Dr. Eric Breidenbach and Dr. Daniela Hadorn for their fruitful collaborations. A big thanks also to those who have provided me with impromptu advice and tips and to all the new people I have met through conferences and meetings for making me always feel welcome. I would like to thank Dr. Barbara Thür and Dr. Ariane Cagienard for their help, as well as colleagues from the Institute of Parasitology in Zürich, the Swiss Tropical Insitute in Basel, and the Center for Zoonoses, Bacterial animal diseases and Antibiotic resistance (ZOBA) in Bern. Furthermore, I would like to thank Prof Katharina Stärk, PD Dr. Christian Griot, Dr. Francois Roger and Prof. Marcel Tanner, the members of my PhD committee for their interest and confidence in this study. Many thanks to all my friends, whose laughter and entertainment have been great throughout the continents and years. And last but not least, my deepest appreciation goes to my parents Jacques and Helga as well as my little brother Amaro and my husband Alberto, for their trust, humour, love, encouragement and faith in me, of which without I would not be who I am today. iv Summary Summary Due to previous climatic conditions in Switzerland, vector-borne diseases were not of primary importance to the Swiss Federal Veterinary Office. It has now been established that global warming has had a major impact on vector species ecology due to temperature shifts, humidity and precipitation changes amongst many factors, which influence vector habitats and their distribution, and allowed in some instances for vectors already present in an area to transmit a disease, or aid in the extension of habitats of exotic vectors species. In Switzerland, several vector-borne diseases have and are emerging, causing alarm due to the eventual consequences in health and economic matters that they can bring with them. Such examples are Bluetongue disease (BT), cattle anaplasmosis and cattle babesiosis, which have, at the time of writing, now all been reported in Switzerland. In order to aid decision and policy makers in planning eventual surveillance, prevention and control measures, disease surveillance needs to be focused on aspects of vector ecology and the epidemiology of the mentioned diseases. In this study, surveillance took form as a sentinel herd strategy through serological and entomological sampling over the past three years. The aim was to establish an early warning system for the primary incursion of BT virus via infected Culicoides species vectors, or the re- emergence of anaplasmosis and babesiosis through endemic tick species. Hence, as a risk based approach, it was important to identify areas considered at higher likelihood of disease occurrence located within Switzerland. This was achieved through the collection of climatic, environmental, altitude, entomological and vector population dynamics data. These data were incorporated into a Geographic Information System and a mathematical model and finally developed into a Scenario Tree pathway to help decide upon different surveillance system components. Models developed in this study through the collected data have proved useful as the first cases of reported BT disease in Switzerland were in areas highlighted by the suitability maps, as well as mirroring calculated prevalence estimates. Results from this study were also implemented into a national surveillance plan for bluetongue disease in Switzerland. v List of Tables List of Tables Table 1.1 Vector-borne diseases in previous OIE ‘A’ list and their geographic distribution...3 Table 1.2 Some Culicoides species/groups and their geographic distribution……………….7 Table 1.3 List of tick species causing anaplasmosis and their geographic distribution……...8 Table 1.4 List of tick species causing babesiosis and their geographic distribution…………9 Table 3.1 Examples of sentinel herd surveillance programs……………………………….32 Table 6.1 Table of suitability classes used for altitude, temperature and precipitation based on values found in literature- influencing the vector biology……………..55 Table 7.1 Characteristics of the 7 farms included in the entomological surveillance for Culicoides