Thayas Final Thesis Type Setting 3
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A SERO-EPIDEMIOLOGICAL STUDY OF LEPTOSPIROSIS IN SARAWAK, MALAYSIA. By SIVAPIRAGASAM THAYAPARAN BVSc, MSc, Postgrad Certificate in Conservation Medicine. College of Veterinary Medicine School of Veterinary and Life Sciences Murdoch University Western Australia This thesis is presented for the degree of Doctor in Philosophy Murdoch University 2014 DECLARATION I declare this thesis is my own account of my research and contains as its main content work, which has not been submitted for a degree at any tertiary education institution. ------------------------------------------------------------ Sivapiragasam Thayaparan ii ABSTRACT Several recent outbreaks of leptospirosis involving human deaths have alarmed health professionals in Malaysia. The study outlined in this thesis was conducted to increase the understanding of the involvement of wildlife in the disease in Malaysia. A strain of Leptospira (designated Lepto 175 Sarawak) was isolated from water in Sarawak, Malaysia. This strain did not produce any titres towards other known Leptospira sera, and thus represents a novel serovar. This serovar had 99.1% 16S rRNA gene sequence similarity with Leptospira wolffii and was the dominant strain present in the region. In this study eight of the 12 non-human primates sampled (66.6%; 95% CI 34.9- 90.1) and 73 of 155 wild small mammals (47.1%: 95% CI 39.0-55.3) were seropositive to leptospires. The seroprevalence was slightly higher in rats than in squirrels or bats. Seropositive animals were detected in all localities sampled, with the highest prevalence at Mount Singai (64.7%; 95%CI 38.3-85.8). Antibodies were detected to two different serovars in non-human primates, eight serovars were detected in rats, six serovars in bats and five in squirrels. Of 155 kidney samples from individuals, 17 were positive for Leptospira on PCR analysis (11%; 95% CI 6.5-17). A cross-sectional serological survey of 198 humans was conducted in four villages around Kuching, Sarawak with 35.9% (95%CI 29.2-43.0) testing positive on the MAT. Antibodies to serovar Lepto 175 Sarawak were most commonly detected (31.3%; 95%CI 24.9-38.3) and were detected in individuals at all four locations. The presence of skin wounds (OR 3.1), farm animals (OR 2.5) and rats (OR 11.2) were iii all significantly associated with seropositivity in a multivariable logistic regression model. The results of the current study are important as wildlife may act as reservoirs of leptospires for humans. Health authorities should expand disease control measures to minimise the spill-over from wildlife to humans visiting, living or working in the sampled locations. The pathogenic status of serovar Lepto 175 Sarawak also requires further investigation. iv ACKNOWLEDGEMENTS First of all I would like to thank Almighty God Shiv Baba who I believe to be the source of knowledge, wisdom and understanding. Secondly I would like to express my sincere gratitude to the following people who have helped me make the presentation of this thesis possible: I am very grateful to my primary supervisors Ian Robertson and Mohd Tajuddin Abdullah. I offer my sincerest gratitude for your support, ideas, constructive criticism and scientific acumen I have valued during the project. To Professor Ian Robertson, for giving me the honour and the privilege of accepting to be my scientific supervisor. Professor Ian is an acknowledged world expert on Epidemiology with admirable vast knowledge, published work and experience in many aspects of this field and it has been not only a privilege but also a wonderful opportunity to work under his direction and guidance and to benefit from his experienced advice and sharp insight. To Professor Mohd Tajuddin Abdullah for co-supervising this work, especially in what concerns the fieldwork on animals and sharing his animal sample collection permit for his participation as principal investigator of the primate project, under which part of the work presented in this thesis was done. I am grateful to thank Dr. Fairuz Amaran, Institute for Medical Research, Kuala Lumpur for her invaluable advice and help in culturing and techniques in performing the Microscopic Agglutination Test (MAT) and culturing the leptospires for testing antigen. Her analytic and positive spirit, her genuine interest and incentive to the general development of this work have further provided useful discussions and v fundamental support and encouragement which greatly helped me in the progression and conclusion of this work. Professor Lela Suut has a recognised experience of relevant work in bacteriology, and her help and advice on human sample collection from the community in Sarawak. Dr. Nan Schaffer (President SOS rhino) and Dr. Rajasingham (Jay) Jayendran for supporting financially to carry out my research successfully and also Murdoch University for finance support for the molecular work. I wish to thank Universiti Malaysia Sarawak (UNIMAS) School of Science, Medical Faculty and Institute for Medical Research, Kuala Lumpur. Also thankful to the Malaysia and Sarawak Economic Planning Unit (EPU) (UPE: 40/200/19/2669), National Medical Research Register (NMRR ID-10-879-7153), Sarawak Forestry Department (NCCD.907.4.4 (V)-235) for issuing the relevant permits to make this research successful. I am also thankful to all those at UNIMAS Medical faculty laboratory staff Albert Jugah AK Paon and Joseph Tau AK Katip for collecting human blood samples and students especially Isham, Kishen, Madinah, Aida, Ridzuan, Ikhwan and Ridwan Rahman for helping me to carry out my field work, they are numerous to list. Finally to my family, for support, with special thanks to: My mother, Peria Mama & Mami and brothers and sisters for love and support, to my brother-in-law M.Sivaparan, for being like a personal adviser during my research, finally to my lovely wife Maithil for much patience, advice and support for making me happy, also provided her unreserved trust in me when I doubted my capability of finishing this thesis, which enabled me to finish this thesis. May God bless you all for your loving contributions to my achievement. vi TABLE OF CONTENTS DECLARATION ............................................................................................................ ii ABSTRACT ................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................ v LIST OF TABLES ...................................................................................................... xiii LIST OF FIGURES ...................................................................................................... xv PUBLICATIONS ......................................................................................................... xvi CHAPTER 1: GENERAL INTRODUCTION ............................................................. 1 1.1 Background ............................................................................................................. 2 1.2 Study hypothesis ..................................................................................................... 4 1.3 Objectives ................................................................................................................ 4 1.4 Anticipated outcomes ............................................................................................. 5 1.5 Study constraints and limitations .......................................................................... 6 1.6 Thesis structure ....................................................................................................... 7 CHAPTER 2: LITERATURE REVIEW ...................................................................... 9 2.1 Introduction ............................................................................................................ 9 2.2 History of leptospirosis ......................................................................................... 10 2.1.1 World wide .................................................................................................. 10 2.1.2 Southeast Asia .............................................................................................. 11 2.1.3 Malaysia ....................................................................................................... 13 2.1.4 Sabah and Sarawak ...................................................................................... 19 2.3 Taxonomy and classification ................................................................................ 21 2.3.1 Serological classification ............................................................................. 22 2.3.2 Genotypic classification ............................................................................... 23 vii 2.4 Biology of leptospires ........................................................................................... 25 2.4.1 Morphology ................................................................................................. 25 2.4.2 Genomic organization .................................................................................. 26 2.5 Pathogenesis .......................................................................................................... 27 2.5.1 Entry ............................................................................................................ 27 2.5.2 Spread and growth ......................................................................................