Helminth parasites are found in cattle, sheep and goats in all countries and regions of the world. Many of these parasites are commonly associated with poor production and unthriftiness and can produce acute disease and even death. Their presence in an animal, however, does not mean that they are necessarily the cause of any overt disease in that animal, so it is important to assess the type and level of parasitism in a herd or flock in order to be able to determine the significance of parasite infections and to recommend the most cost-beneficial control measures.
We were stimulated to prepare the first edition of this handbook for several reasons. We have both lived and worked in various tropical and subtropical environments for several years, where we became conscious that helminth parasites play a controversial role. Sometimes their presence and identity are confirmed, after which they erroneously receive the blame for the ill health of an animal or a herd; sometimes they are identified but are perceived rightly or wrongly as unimportant and are ignored; and many times, of course, their presence and identity remain unknown. Superimposed on this is a system of parasite diagnosis in use in much of the world that places great emphasis on parasite identification procedures at the expense of quantitative and economic assessments of infections. In the few circumstances where quantitative assessments are made, they are usually confined to parasite egg counts, which have severe limitations when carried out in isolation.
Most of the procedures for the diagnosis of helminth parasites are simple and require simple equipment. Much of this equipment is available in even the smallest of veterinary diagnostic laboratories. This handbook therefore presents procedures and techniques for the identification, diagnosis, survey and control of helminth parasites of ruminants that can be applied in a variety of circumstances and institutions, including universities, national laboratories and the more rudimentary veterinary outposts. The epidemiology of helminth parasites is reviewed, and procedures for their diagnosis are given in a simple cookbook style. Guidelines for the design and interpretation of field investigations, as well as the principles of control based on the results of such investigations, are presented. We hope, therefore, that the handbook will have a wide application in the world.
In the first edition, we focused on gastro-intestinal helminths in Africa. In this second edition, while maintaining the simple style, we have expanded the scope of the handbook to include helminth parasites of other body systems, and have widened the geographical range beyond Africa to include other areas of the world.
We are grateful to the many people who helped US translate our ideas into reality. This work was initiated when we were Associate Professors of Parasitology (JH) and Epidemiology (BP) at the Virginia-Maryland Regional College of Veterinary Medicine, Virginia, USA. The original preparation of photographs of diagnostic techniques was supported by a Title XII grant from the Office of International Development, Virginia Polytechnic Institute and State University. We are grateful to Ms. Lee Bishop and Ms. Derry Hutt for the assistance in the preparation of laboratory materials and to Mr. Jerry Baber, Mr. Dave Elsworth and Mr. Don Massie for taking the photographs. We thank Ms. Janet Schultz for original manuscript preparation, and Ms. Lucy Kirori for preparing the manuscript of the second edition. Camera ready copy of the manuscript was prepared by Mr. Peter Werehire, to whom we are extremely grateful. We also thank the following people for reviewing and commenting on earlier drafts of the original handbook: Professor James Armour, Dean of the Faculty of Veterinary Medicine, University of Glasgow, Scotland; Professor Peter Nansen, Royal Veterinary and Agricultural University, Copenhagen; Dr. K. Pfister, Faculty of Veterinary Medicine, University of Berne; and Dr. P.J. Waller, Director of the McMaster Laboratory, University of Sidney, New South Wales. Dr. L. Baker of the International Livestock Centre for Africa (ILCA) provided valuable comments on sections of the second edition. We are extremely grateful to Dr. M. Smalley and Mr. P. Neate of ILCA for arranging for the printing of the second edition to be undertaken by ILCA in Addis Ababa. Finally, we thank Merck Agvet Division, Rahway, New Jersey, USA, for contributing to the costs of producing this handbook.
JWH
BDP
Nairobi, November, 1993
