Gastrointestinal Nematodes of Sheep and Cattle Biology and Control

by Scott, Ian; Sutherland, Ian

• ISBN13: 9781405185820
• ISBN10: 1405185821
• Edition: 1st
• Format: Hardcover
• Copyright: 2009-11-02
• Publisher: Wiley-Blackwell

Summary

An important resource for all interested in worm control in sheep and cattle, and the impacts of drug resistance. This book provides an over-arching view of past, present and suggested future strategies for control of gastrointestinal nematode parasites. Essential reading for those with a vested interest in the development of sustainable parasite control programs.

Author Biography

Ian Sutherland is Team Leader for Parasite Biotechnology, Hopkirk Research Institute, AgResearch, Palmerston North, New Zealand.

Ian Scott is a Senior Lecturer in Parasitology, Massey University, New Zealand.

Table of Contents

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