Advances in PARASITOLOGY VOLUME 41 Editorial Board C. Bryant Division of Biochemistry and Molecular Biology, The Australian National University, Canberra, ACT 0200, Australia M. Coluzzi Director, Istituto di Parassitologia, Universita Degli Studi di Roma “La Sapienza”, P. le A. Moro 5, 00185 Roma, Italy C. Combes Laboratoire de Biologie Animale, Universite de Perpignan, Centre de Biologie et d’Ecologie Tropicale et Mediterrankenne, Avenue de Villeneuve, 66860 Perpignan Cedex, France S.L. James Chief, Parasitology and Tropical Diseases Branch, Division of Microbiology and Infectious Diseases, National Institute for Allergy and Infectious Diseases, Bethesda, MD 20892-7630, USA W.H.R. Lumsden 16A Merchiston Crescent, Edinburgh EHlO 5AX, UK Lord Soulsby of Swaffham Prior Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 OES, UK K. Tanabe Laboratory of Biology, Osaka Institute of Technology, 5-16-1 Ohmiya, Asahi-Ku, Osaka 535, Japan P. Wenk Falkenweg 69, D-72076 Tubingen, Germany Advances in PARASITOLOGY Edited by J.R. BAKER Royal Society of Tropical Medicine and Hygiene, London, England R. MULLER International Institute of Parasitology, St Albans, England and D. ROLLINSON The Natural History Museum, London, England VOLUME 41 ACADEMIC PRESS San Diego London Boston New York Sydney Tokyo Toronto ACADEMIC PRESS 525 B Street, Suite 1900, San Diego, California 92101495, USA http://www.apnet.com ACADEMIC PRESS 24-28 Oval Road LONDON NWI 7DX http://www.hbuk.co.uWap/ Copyright 0 1998, by ACADEMIC PRESS This book is printed on acid-free paper All Rights Reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher A catalogue record for this book is available from the British Library ISBN 0-12-031741-9 Typeset by J&L Composition Ltd, Filey, North Yorkshire Printed in Great Britain by MPG, Bodmin, Cornwall 98 99 00 01 02 03 MP 9 8 7 6 5 4 3 2 1 CONTRIBUTORS TO VOLUME 41 T.J.C. ANDERSON,Wellcome Trust Centre for Epidemiology of Infectious Disease, Department of Zoology, South Parks Road, Oxford, OX1 3PS, UK R.M. BEECH,Institute for Parasitology, 21111 Lakeshore Road, Ste-Anne de Bellevue, Quebec, H9X 3 V9, Canada R.G. BELL,James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, N Y 14853, USA M.S. BLOUIN,Department of Zoology, Cordley Hall 3029, Oregon State University, Corvallis, O R 97331-2714, USA D.W.T. CROMPTON,WHO Collaborating Centre for Soil-transmitted Helminthiases, University of Glasgow, Glasgow, GI2 8QQ, Scotland, UK J. DE BOW, Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Salisburylaan 133, 9820 Merelbeke, Belgium Y. NAKAMURA, Department of Tumor Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan W. PETERS, CABI Bioscience, Tropical Parasitic Diseases Unit, 395a Hatjield Road, St Albans, Herflordshire, AL4 OXU UK J. VERCRUYSSE, Department of Parasitology, Faculty of Veterinary Medicine, University of Gent, Salisburylaan 133, 9820 Merelbeke, Belgium M. WADA,Department of Tumor Biology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan PENGWE