Disease threats to Belgian anurans – Implications for amphibian conservation and human health Mojdeh Sharifian Fard Thesis submitted in fulfillment of requirements for the degree of Doctor in veterinary science (PhD), Faculty of Veterinary Medicine, Ghent University, 2014 Promoters: Prof. dr. An Martel Prof. dr. Frank Pasmans Faculty of Veterinary Medicine Department of Pathology, Bacteriology and Poultry Diseases Sharifian Fard Mojdeh Disease threats to Belgian anurans – Implications for amphibian conservation and human health 2014 Faculty of Veterinary Medicine, Ghent University Printed by University Press, Zelzate ISBN: 9789058643889 Dedicated to my mother (Giti) and father (Hafez) In memory of Sepanta CONTENTS Table of Contents INTRODUCTION .................................................................................................................... 1 1. Indigenous Amphibians of Belgium ................................................................................... 3 1.1. Indigenous species: definition ...................................................................................... 3 1.2. Indigenous amphibians of Belgium .............................................................................. 3 1.2.1. Anura ..................................................................................................................... 3 1.2.1.1. Alytes obstetricans, Common midwife toad ................................................... 4 1.2.1.2. Bombina variegata, Yellow-bellied toad ......................................................... 5 1.2.1.3. Bufo bufo, Common toad ............................................................................... 6 1.2.1.4. Epidalea calamita, Natterjack toad ................................................................. 7 1.2.1.5. Hyla arborea, Common tree frog .................................................................... 8 1.2.1.6. Pelobates fuscus, Common spadefoot toad..................................................... 9 1.2.1.7. Pelophylax lessonae, Pool frog .................................................................... 10 1.2.1.8. Pelophylax kl. esculentus, Edible frog ......................................................... 11 1.2.1.9. Rana arvalis, Moor frog ................................................................................ 12 1.2.1.10. Rana temporaria, Common frog .................................................................. 13 1.2.2. Caudata ................................................................................................................ 14 1.2.2.1. Ichthyosaura alpestris, Alpine newt .............................................................. 15 1.2.2.2. Lissotriton helveticus, Palmate newt ............................................................ 16 1.2.2.3. Lissotriton vulgaris, Smooth newt ................................................................ 17 1.2.2.4. Salamandra salamandra, Fire salamander ................................................... 18 1.2.2.5. Triturus cristatus, Great crested newt ........................................................... 19 2. Invasive amphibians ......................................................................................................... 20 2.1. Invasive species: definition ........................................................................................ 20 2.2. Invasive amphibians of Belgium ................................................................................ 21 2.2.1. Lithobates catesbeianus, American bullfrog ....................................................... 22 2.2.2. Pelophylax ridibundus, Marsh frog ..................................................................... 24 3. Amphibian Diseases ......................................................................................................... 26 3.1. Ranavirosis ................................................................................................................ 27 3.1.1. Background ......................................................................................................... 27 3.1.2. General characteristics ......................................................................................... 29 3.1.3. Replication cycle ................................................................................................. 30 3.1.4. Transmission and pathogenesis ........................................................................... 31 I CONTENTS 3.1.5. Clinical signs and pathology ............................................................................... 33 3.1.6. Diagnosis ............................................................................................................. 35 3.1.7. Conservation strategies ....................................................................................... 36 3.2. Chytridiomycosis ........................................................................................................ 37 3.2.1. Background ......................................................................................................... 37 3.2.2. Phylogenetic characteristics of B. dendrobatidis ................................................ 40 3.2.3. Lifecycle stages ................................................................................................... 40 3.2.4. Susceptibility to B. dendrobatidis ....................................................................... 41 3.2.5. Clinical signs, gross pathology and pathogenesis ............................................... 43 3.2.6. Transmission ....................................................................................................... 44 3.2.7. Amphibian defense against chytridiomycosis ..................................................... 44 3.2.8. Diagnosis ............................................................................................................. 45 3.2.9. Preventative management strategies ................................................................... 46 3.3. Zoonotic bacterial diseases ........................................................................................ 48 3.3.1. Chlamydia ........................................................................................................... 48 3.3.2. Salmonella ........................................................................................................... 49 3.4. Mesomycetozoans ...................................................................................................... 50 3.5. Parasites .................................................................................................................... 50 3.6. Non-infectious diseases .............................................................................................. 53 3.6.1. Heavy metal disorders ......................................................................................... 53 3.6.1.1. Trace metals ................................................................................................. 53 3.6.1.1.1. Copper .................................................................................................... 54 3.6.1.1.2. Zinc ......................................................................................................... 55 3.6.1.2. Xenobiotic metals ......................................................................................... 57 3.6.1.2.1. Lead ........................................................................................................ 57 3.6.1.2.2. Mercury .................................................................................................. 58 3.6.1.2.3. Cadmium ................................................................................................ 59 4. References ........................................................................................................................ 61 SCIENTIFIC AIMS ............................................................................................................... 89 STUDY 1 ................................................................................................................................. 93 Road-killed common toads (Bufo bufo) in Flanders (Belgium) reveal low prevalence of ranaviruses and Batrachochytrium dendrobatidis II CONTENTS STUDY 2 ............................................................................................................................... 103 Ranavirosis in invasive bullfrogs, Belgium STUDY 3 ............................................................................................................................... 109 The novel ‘Candidatus Amphibiichlamydia ranarum’ is highly prevalent in invasive exotic bullfrogs (Lithobates catesbeianus) STUDY 4 ............................................................................................................................... 119 Chironomidae bloodworms larvae as aquatic amphibian food STUDY 5 ............................................................................................................................... 139 Migrating common toads (Bufo bufo) in rural temperate regions: reservoirs of Salmonella? STUDY 6 ............................................................................................................................... 151 The absence of zoonotic agents in invasive bullfrogs (Lithobates catesbeianus) in Belgium and The Netherlands GENERAL DISCUSSION ..................................................................................................