Gastrointestinal Nematodes of Sheep and Cattle. Biology and Control

  • ID: 2222708
  • Book
  • 256 Pages
  • John Wiley and Sons Ltd
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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.

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Foreword by Professor Sir James Armour.

Preface.

Acknowledgements.

1. Nematode parasites.

The nematodes.

The important nematode genera and species parasitising ruminant livestock.

Abomasal genera.

Small intestinal genera.

Large intestinal genera.

Nematode evolution.

The transition to parasitism.

Nematode biology.

Nematode genetics.

Nematode physiology.

The dauer larva.

Anhydrobiosis.

The nematode life cycle.

Niches occupied by parasitic nematodes within the vertebrate host.

The lifespan of parasitic nematodes.

2. Pathophysiology of nematode infections.

Are parasites always harmful?

Defining harm .

The abomasum.

The small intestine.

The large intestine.

The impact of parasites on overall gut function.

Effects beyond the gut.

3. Epidemiology of gastrointestinal nematodes in grazing ruminants.

Ecology of GINs pasture.

Egg to L3 development.

Effect of host.

Survival of L3.

Translation of infective larvae.

Grazing behaviour and the avoidance of parasites.

Patterns of infection.

Overdispersion of parasites.

Epidemiology of parasitism .

An increase in the infective mass.

Alteration in the susceptibility of stock.

Arrested development and hypobiosis.

Introduction of susceptible stock onto an infected area.

Insufficient age–related immunity.

The introduction of infected stock to a clean environment.

Epidemiology of cattle parasites.

Population biology in the parasitic phase.

Sheep parasites.

Cattle parasites.

4. The principles of gastrointestinal nematode control.

Control of parasites with anthelmintic drenches.

Drench programmes.

Strategic drenching programmes.

Principles of worm control in cattle.

Control of GIN by grazing management.

Alternate/mixed grazing with different host species or stock classes.

Resistance to treatment.

5. Anthelmintics.

What are anthelmintics?

How effective does an anthelmintic have to be?

Which species does an anthelmintic against GIN need to remove?

Description, efficacy, profile and mode of action of anthelmintic families.

Combination of anthelmintic treatments.

Modifying the delivery of anthelmintics.

Parenteral administration.

Controlled release of anthelmintics.

Injectable formulations.

6. Anthelmintic resistance.

Evolution of anthelmintic resistance.

Worldwide occurrence of anthelmintic resistance.

Resistance to one or more active families by one or more species.

Impact of resistance on productivity.

Mechanisms of resistance.

Inheritance of resistance.

Detection of resistance.

7. Drenching and resistance.

Frequency of treatment.

Under–dosing.

Persistent anthelmintics.

Why use persistent drenches?

The provision of safe pasture and resistance.

Persistence and efficacy.

Therapeutic efficacy and resistance head selection .

Prophylactic efficacy and resistance tail selection .

Heads or tails?

Persistent activity, immunity and resistance.

Persistent activity, density dependence and resistance.

Drench rotation.

Controlling resistance by drench rotation.

Drench rotation within seasons.

Modelling drench rotation.

Combination anthelmintics.

Removing resistant worm burdens.

Efficacy of single actives vs. combinations.

The odds are against multiple mutations.

Resistance is already present to one or more constituent active.

8. Worm control and resistance management.

What is refugia?

Why do we need refugia?

How to produce and utilise refugia.

Importation of resistant parasites.

A twin approach to worm control and resistance management utilising refugia and combination drenches.

9. Non–chemical control options.

Anthelmintic plants.

Plant material.

Plant extracts.

PSM as anthelmintics.

Forage legumes.

Practical applicability on–farm.

Other anthelmintic plants.

Micro–predacious fungi.

Homoeopathy.

10. Nutrition and parasitism.

Metabolic cost of parasitism.

Metabolic cost of infection.

Metabolic costs of immunity.

Parasites and nutrition: a nutrient utilisation framework.

Supplementation for increased resilience to parasites.

Supplementation for increased resistance to parasites.

Reproducing animals.

Undernutrition and parasitism.

Micronutrients and parasitism.

Improving nutrient availability.

Forage plants and parasitism.

Supplementation and immunity: increasing or enabling?

11. Animal genetics and parasitism.

Inter–species variability.

Inter–breed variability.

Intra–breed variability.

Resistance vs. productivity.

Resilience.

Pasture contamination, resistance and resilience.

Markers for resistance and resilience.

Phenotypic markers.

Genotypic markers.

Genetics, worm control and resistance management.

12. The immune response to parasites.

Evolution of the host parasite relationship.

Immunity and GIN population dynamics.

The immune phenotype.

Immunological unresponsiveness.

Components of host responses to GI parasites.

Adaptive immune responses to GINs.

The anti–GIN immune response in cattle to O. ostertagi.

Impact of immunity on parasites.

Immunopathology.

Periparturient rise.

Utilising immune responses to control GIN.

Natural antigens.

Hidden antigens.

What next for immunoparasitology research?

Postscript.

Index.

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Ian Scott
Ian Sutherland
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