Gastrointestinal Nematodes of Sheep and Cattle

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.

"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)

• Foreword ixPreface xiAcknowledgements xiii1 Nematode parasites 1The nematodes 1The important nematode genera and species parasitizing ruminant livestock 2Abomasal genera 3Small intestinal genera 4Large intestinal genera 6Nematode evolution 6The transition to parasitism 8Nematode biology 9Nematode genetics 14Nematode physiology 15The dauer larva 17Anhydrobiosis 17The nematode life cycle 18Niches occupied by parasitic nematodes within the vertebrate host 23The lifespan of parasitic nematodes 262 Pathophysiology of nematode infections 33Are parasites always harmful? 33Defi ning ‘harm’ 34The abomasum 36The small intestine 42The large intestine 43The impact of parasites on overall gut function 43Effects beyond the gut 473 Epidemiology of gastrointestinal nematodes in grazing ruminants 61Ecology of GINs – pasture 61Egg to L3 development 62Effect of host 63Survival of L3 63Translation of infective larvae 64Grazing behaviour and the avoidance of parasites 65Patterns of infection 66Overdispersion of parasites 67Epidemiology of ‘parasitism’ 67An increase in the infective mass 68Alteration in the susceptibility of stock 69Arrested development and hypobiosis 70Introduction of susceptible stock onto an infected area 70Insuffi cient age-related immunity 71The introduction of infected stock to a clean environment 71Epidemiology of cattle parasites 72Population biology in the parasitic phase 72Sheep parasites 73Cattle parasites 754 The principles of gastrointestinal nematode control 83Control of parasites with anthelmintic drenches 83Drench programmes 84Strategic drenching programmes 85Principles of worm control in cattle 88Control of GIN by grazing management 88Alternate/mixed grazing with different host species or stock classes 89Resistance to treatment 915 Anthelmintics 95What are anthelmintics? 96How effective does an anthelmintic have to be? 96Which species does an anthelmintic against GIN need to remove? 97Description, effi cacy, profi le and mode of action of anthelmintic families 98Combination of anthelmintic treatments 107Modifying the delivery of anthelmintics 107Parenteral administration 108Controlled release of anthelmintics 108Injectable formulations 1096 Anthelmintic resistance 117Evolution of anthelmintic resistance 118Worldwide occurrence of anthelmintic resistance 118Resistance to one or more active families by one or more species 119Impact of resistance on productivity 120Mechanisms of resistance 120Inheritance of resistance 123Detection of resistance 1247 Drenching and resistance 133Frequency of treatment 134Under-dosing 134Persistent anthelmintics 135Why use persistent drenches? 137The provision of safe pasture and resistance 137Persistence and effi cacy 138Therapeutic effi cacy and resistance – ‘head selection’ 139Prophylactic effi cacy and resistance – ‘tail selection’ 140Heads or tails? 141Persistent activity, immunity and resistance 142Persistent activity, density dependence and resistance 143Drench rotation 143Controlling resistance by drench rotation 143Drench rotation within seasons 145Modelling drench rotation 145Combination anthelmintics 146Removing resistant worm burdens 146Effi cacy of single actives vs. combinations 146The odds are against multiple mutations 147Resistance is already present to one or more constituent active 1488 Worm control and resistance management 153What is refugia? 155Why do we need refugia? 155How to produce and utilise refugia 157Importation of resistant parasites 159A twin approach to worm control and resistance management – utilising refugia and combination drenches 1609 ‘Non-chemical’ control options 163Anthelmintic plants 163Plant material 165Plant extracts 166PSM as anthelmintics 167Forage legumes 168Practical applicability on-farm 169Other anthelmintic plants 170Micro-predacious fungi 170Homoeopathy 17110 Nutrition and parasitism 177Metabolic cost of parasitism 177Metabolic cost of infection 178Metabolic costs of immunity 180Parasites and nutrition: a nutrient utilisation framework 183Supplementation for increased resilience to parasites 184Supplementation for increased resistance to parasites 185Reproducing animals 185Undernutrition and parasitism 186Micronutrients and parasitism 187Improving nutrient availability 188Forage plants and parasitism 188Supplementation and immunity: increasing or enabling? 18911 Animal genetics and parasitism 195Inter-species variability 195Inter-breed variability 196Intra-breed variability 198Resistance vs. productivity 199Resilience 200Pasture contamination, resistance and resilience 201Markers for resistance and resilience 201Phenotypic markers 202Genotypic markers 203Genetics, worm control and resistance management 20412 The immune response to parasites 211Evolution of the host–parasite relationship 212Immunity and GIN population dynamics 213The immune phenotype 214Immunological unresponsiveness 214Components of host responses to GI parasites 215Adaptive immune responses to GINs 218The anti-GIN immune response in cattle to O. ostertagi 221Impact of immunity on parasites 222Immunopathology 223Periparturient rise 223Utilising immune responses to control GIN 223Natural antigens 224Hidden antigens 225What next for immunoparasitology research? 226Postscript 235Index 237