Tsetse Biology and Ecology:: Their Role in the Epidemiology and Control of Trypanosomosis by S.G.A. Leak

Abstract

CABI Publishing, 1998. £65.00/$120.00 (hbk) (592 pages)ISBN 0 85199 300 1In the 170 years or so since the first formal description of a tsetse fly, there has been an enormous number of publications concerned with the insect itself and with the impact that it has on the African rural scene. This intense scientific interest can be attributed to two factors: (1) the intriguing and virtually unique reproductive biology of tsetse flies and their consequent low potential for increase compared to almost all other insects; and (2) (and inter-related) their role as vectors of human and animal trypanosomosis, diseases which have had, and still have, profound influences on rural people and economies in tropical Africa. Over the years, there has been a succession of single-author books, which have attempted to synthesize and interpret this extensive literature; some have concentrated on reviewing the literature and the production of a work of reference, whereas others have been more selective in their sources and have attempted a personal assessment of aspects of the tsetse fly/trypanosomosis problem.Stephen Leak's book reviews the literature and is a worthy successor to P.A. Buxton's The Natural History of Tsetse Flies, published in 1955. The more recent (1970) The African Trypanosomiases, edited by H.W. Mulligan, is also a valuable source book but, because of its multi-authorship, is somewhat patchy in its coverage. The scope of Leak's book and the extent of the information explosion during the past 40 years is indicated by the fact that, whereas Buxton quoted some 630 references in some 740 pages of text, Leak quotes more than 2000 in some 430 pages of text. Most of the references are post-Buxton, but sufficient earlier ones are included to put the more recent findings into context. Readers will appreciate that the references include reports and other less readily available publications.The book is divided into four sections dealing with (1) tsetse biology and ecology, (2) the epidemiology of the trypanosomiases, and (3) vector control. The short final section (4) puts the three main sections of the book into context, correctly pointing out that control of trypanosomosis is, in most affected countries, by control of the disease using curative and prophylactic trypanocidal drugs. It is ironic that, despite the mass of information about the vector and the diseases, control is still based on drugs that have been around for at least 40 years and which are generally administered, in the case of trypanosomosis of domestic animals, by the owners of livestock themselves, with no formal diagnosis and limited attention to recommended drug regimens. As Leak points out, it is generally not too difficult to control tsetse flies (mainly because of their low potential rate of increase) and this is theoretically a more effective option than the use of drugs to which varying degrees of resistance occurs. The difficulty lies in sustaining control at an acceptable cost – whatever ancient or modern technique is employed.Within the defined structure of the book, coverage is deliberately selective. Topics that are adequately reviewed in earlier books are not dealt with in detail, allowing particular attention to be given to subject areas in which there have been significant developments in recent years. These include: (1) an understanding of those factors that affect the composition of samples of tsetse populations (including the related topic of behavioural ecology); (2) tsetse population dynamics; (3) the use of molecular techniques for identifying trypanosomes and for detecting infections in tsetse; (4) the nature of the inter-relationships between tsetse and trypanosomes; (5) the modelling of trypanosomosis transmission; and (6) the use of traps and targets (including the identification and exploitation of host odours that are attractive to tsetse) and pour-on insecticides as vector control techniques.All those interested in tsetse and trypanosomosis will welcome this comprehensive and readable guide through the more recent literature. It might even remind those responsible for rural development in Africa that we have an in-depth knowledge of trypanosomosis and, given political stability, sound organization and adequate funding, these diseases could be controlled much more effectively than is generally the case today.