Gastrointestinal Nematodes of Sheep and Cattle: Biology and Control

A unique resource for all those interested in the impact of worms on livestock, the anthelmintics used to get rid of them and the emerging problem of anthelmintic resistance.  This book provides an over-arching view of past, present and suggested future strategies for control of gastrointestinal nematode parasites in sheep and cattle. The book begins with descriptions of the biology of gastrointestinal nematodes, the harm they cause to the host and their economic impact.  The main body of the book deals with the control of worms, focusing on the use of anthelmintic drenches. The relationship between drenching practices and the development of drug resistance is discussed, as well as resistance management. The authors also break new ground by discussing alternative options for worm control, including: nutritional interventions, biological control, breeding for desirable genetics and artificially improving immunity to infection. They also offer useful recommendations for program development.

Table of Contents:
Foreword ix Preface xi Acknowledgements xiii 1 Nematode parasites 1 The nematodes 1 The important nematode genera and species parasitizing ruminant livestock 2 Abomasal genera 3 Small intestinal genera 4 Large intestinal genera 6 Nematode evolution 6 The transition to parasitism 8 Nematode biology 9 Nematode genetics 14 Nematode physiology 15 The dauer larva 17 Anhydrobiosis 17 The nematode life cycle 18 Niches occupied by parasitic nematodes within the vertebrate host 23 The lifespan of parasitic nematodes 26 2 Pathophysiology of nematode infections 33 Are parasites always harmful? 33 Defi ning ‘harm’ 34 The abomasum 36 The small intestine 42 The large intestine 43 The impact of parasites on overall gut function 43 Effects beyond the gut 47 3 Epidemiology of gastrointestinal nematodes in grazing ruminants 61 Ecology of GINs – pasture 61 Egg to L3 development 62 Effect of host 63 Survival of L3 63 Translation of infective larvae 64 Grazing behaviour and the avoidance of parasites 65 Patterns of infection 66 Overdispersion of parasites 67 Epidemiology of ‘parasitism’ 67 An increase in the infective mass 68 Alteration in the susceptibility of stock 69 Arrested development and hypobiosis 70 Introduction of susceptible stock onto an infected area 70 Insuffi cient age-related immunity 71 The introduction of infected stock to a clean environment 71 Epidemiology of cattle parasites 72 Population biology in the parasitic phase 72 Sheep parasites 73 Cattle parasites 75 4 The principles of gastrointestinal nematode control 83 Control of parasites with anthelmintic drenches 83 Drench programmes 84 Strategic drenching programmes 85 Principles of worm control in cattle 88 Control of GIN by grazing management 88 Alternate/mixed grazing with different host species or stock classes 89 Resistance to treatment 91 5 Anthelmintics 95 What are anthelmintics? 96 How effective does an anthelmintic have to be? 96 Which species does an anthelmintic against GIN need to remove? 97 Description, effi cacy, profi le and mode of action of anthelmintic families 98 Combination of anthelmintic treatments 107 Modifying the delivery of anthelmintics 107 Parenteral administration 108 Controlled release of anthelmintics 108 Injectable formulations 109 6 Anthelmintic resistance 117 Evolution of anthelmintic resistance 118 Worldwide occurrence of anthelmintic resistance 118 Resistance to one or more active families by one or more species 119 Impact of resistance on productivity 120 Mechanisms of resistance 120 Inheritance of resistance 123 Detection of resistance 124 7 Drenching and resistance 133 Frequency of treatment 134 Under-dosing 134 Persistent anthelmintics 135 Why use persistent drenches? 137 The provision of safe pasture and resistance 137 Persistence and effi cacy 138 Therapeutic effi cacy and resistance – ‘head selection’ 139 Prophylactic effi cacy and resistance – ‘tail selection’ 140 Heads or tails? 141 Persistent activity, immunity and resistance 142 Persistent activity, density dependence and resistance 143 Drench rotation 143 Controlling resistance by drench rotation 143 Drench rotation within seasons 145 Modelling drench rotation 145 Combination anthelmintics 146 Removing resistant worm burdens 146 Effi cacy of single actives vs. combinations 146 The odds are against multiple mutations 147 Resistance is already present to one or more constituent active 148 8 Worm control and resistance management 153 What is refugia? 155 Why do we need refugia? 155 How to produce and utilise refugia 157 Importation of resistant parasites 159 A twin approach to worm control and resistance management – utilising refugia and combination drenches 160 9 ‘Non-chemical’ control options 163 Anthelmintic plants 163 Plant material 165 Plant extracts 166 PSM as anthelmintics 167 Forage legumes 168 Practical applicability on-farm 169 Other anthelmintic plants 170 Micro-predacious fungi 170 Homoeopathy 171 10 Nutrition and parasitism 177 Metabolic cost of parasitism 177 Metabolic cost of infection 178 Metabolic costs of immunity 180 Parasites and nutrition: a nutrient utilisation framework 183 Supplementation for increased resilience to parasites 184 Supplementation for increased resistance to parasites 185 Reproducing animals 185 Undernutrition and parasitism 186 Micronutrients and parasitism 187 Improving nutrient availability 188 Forage plants and parasitism 188 Supplementation and immunity: increasing or enabling? 189 11 Animal genetics and parasitism 195 Inter-species variability 195 Inter-breed variability 196 Intra-breed variability 198 Resistance vs. productivity 199 Resilience 200 Pasture contamination, resistance and resilience 201 Markers for resistance and resilience 201 Phenotypic markers 202 Genotypic markers 203 Genetics, worm control and resistance management 204 12 The immune response to parasites 211 Evolution of the host–parasite relationship 212 Immunity and GIN population dynamics 213 The immune phenotype 214 Immunological unresponsiveness 214 Components of host responses to GI parasites 215 Adaptive immune responses to GINs 218 The anti-GIN immune response in cattle to O. ostertagi 221 Impact of immunity on parasites 222 Immunopathology 223 Periparturient rise 223 Utilising immune responses to control GIN 223 Natural antigens 224 Hidden antigens 225 What next for immunoparasitology research? 226 Postscript 235 Index 237

About the Author :
Ian Sutherland has a BSc in Parasitology from the University of Glasgow, UK and a PhD in Diagnosing Anthelmintic Resistance from the University of Leeds, UK. Ian has over twenty years experience in parasitology research in the UK, Australia and New Zealand. He is currently the Team Leader for Molecular Immunology and Parasitology at The Hopkirk Research Institute, AgResearch, Palmerston North, New Zealand. Ian Scott obtained his veterinary degree and PhD at the University of Glasgow, UK. Most of his postgraduate career has been in research/teaching, interspersed with periods in veterinary practice. Ian is currently a Senior Lecturer in Veterinary Parasitology at Massey University, New Zealand.

Review :
"This very readable book is a refreshing change from most books on parasitology. The authors provide a wonderful review of current research efforts and present it in a way to provide readers with useable information. They also delve into more futuristic ideas on parasite control by vaccination as well as genetic resistance and nutritional interactions." (Doody's, 23 September 2011) "This is definitely a book for anyone who wants to know a lot of detail about gastrointestinal parasites of sheep and cattle, but not for those after a quick and definitive guide to solving common problems encountered in veterinary practice." (The Australian Veterinary Journal, January/February 2011)