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Veterinary epidemiology and economics in Africa: A manual for use in the design and appraisal of livestock health policy
Preventive VeterinaryMedicine, 8 (1990) 309-311
309
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Book Review E P I D E M I O L O G Y IN AFRICA
Veterinary Epidemiology and Economics in Africa: A Manual for use in the Design and Appraisal of Livestock Health Policy by S.N.H Putt, A.P.M. Shaw, A.J. Woods, L. Tyler and A.D. James. ILCA Manual No. 3, Agribooks, Winrock International, 1611 N. Kent St., Arlington, VA 22209, 1986, 130 pp., U.S.$22. With the appearance of new textbooks in veterinary epidemiology, it is important to try to demonstrate where this manual comes in the order and family of such publications. In the academic sphere, we can teach epidemiology to first- or second-year veterinary students for whom Thrusfield (1986) and similar introductory texts are ideal. With final-year students, more background can be assumed so a text with additional emphasis on demonstrating appropriate specific statistical techniques for epidemiologic applications may be used. This type of text merges into the applied texts for graduate students reading for a Master's degree. It is not a tidy group, but the text of Martin et al. (1987) is as good an example as any, with some chapters more suited to graduate students and others for veterinary students; Lilienfeld and Lilienfeld (1980) is a similar bridging text for medical and public health students. A good text for advanced graduate students in veterinary epidemiology has yet to appear, but the medical texts would be Hennekens and Buring (1987) for epidemiology, and Kleinbaum et al. (1982) for statistics. A characteristic of all these academic texts is that little experience of reality is needed to learn from them. This immediately differentiates them from reference texts that demand prior knowledge and experience. This manual by the Veterinary Epidemiology and Economics Research Unit at Reading University is neither an academic text nor for reference. It is written for people with plenty of field experience, but little theoretical knowledge. It simplifies epidemiology, statistics and economics down to a "how-to" level. It is methodology simplified. It is comfortably written in a friendly style, tidily laid out, has an adequate index, is cheaply priced and, if one were giving a short course to field veterinarians, whether in Africa or the United States, it might well be the text of choice. It is good reading for someone wanting a short introduction. One can recommend it to all directors of national veterinary services as it does brief one nicely on the questions to ask of one's highly trained junior officers, while allowing one to appear to know what they are talking about. In context, there are some useful chapters, such as "Economics and decisionmaking in disease control policy"; in fact, the three economic chapters are a useful introduction. Overall, the mathematical examples are well worked out so that the reader can easily fit in his or her own data. If you are willing to take
310
BOOK REVIEW
the time, there is a nice appendix on herd production modeling. The pragmatic and terse comments on the pitfalls in interviewing are gems and will bring back valuable, but embarrassing memories to many readers with field experience. The words of wisdom in the introductory section on statistical methods are worth framing. Unfortunately, the many and sometimes extensive simplifications used in this text bring on repeated attacks of the "Yes-buts". To take but a few examples, the definition of pathogenicity confuses it with virulence. The term "diagnosibility" of a test (p. 41 ) is used instead of predictive value. It does not show the economic value of a two-stage serologic screening. The section on interviews and questionnaires is far too shallow to allow one to either structure an interview or design a proper questionnaire. There are frequent references to the use of microcomputers as if nothing can be done without one. Are they selling something? Considering its audience, the sentence "Extensive literature searches can often be performed quickly and easily by using modern information processing techniques" has a certain distant charm, even for us, on occasion, in northern latitudes. All one can say about the description of monitoring and surveillance is that the authors are confused and unclear. They suggest a very restricted methodology for determining sample size. Without wanting to labor the point, the first four chapters on epidemiology, data, and investigation, which have several minor but annoying mathematical mistakes, should be read with caution. There are weaknesses in the theoretical underpinning of this text. The statistical presentation (Chapter 5) is entirely too brief and the theory is so lacking as to be gravely in doubt even as a working manual. Had I not understood a priori much of the text, the descriptions would have been relatively meaningless in this cookbook format. For example, how were the multipliers of the standard error derived in Table 16 (p. 50)? I know, but how will the average lay reader? If they do not understand this very small piece of theory, how will they ever understand what a confidence interval really means? Chi-square calculations (pp. 60-61) are presented almost as magic. Time series are introduced and dismissed in one and a half pages; linear regression and correlation in two pages. There is a cavalier attitude to basics. All in all, using this manual would be like navigating with an undamped compass such that one is always traveling in only more or less the right direction. It is only a manual, it is not a textbook. It is defined by the subtitle "for use in the design and appraisal of livestock health policy". The puffery in the Foreward should be disregarded. It is very like the manual given you when buying a car. It tells you how to start the engine and where the spare wheel and jack are, and it tells you when and why you should take your vehicle into the garage, whether for routine maintenance or repair. This manual does much the same for veterinary epidemiology and economics. It is suitable only for the corporals of this world; junior veterinary officers, who will be collecting or overseeing the collection of predefined data, so that they better understand why they are in-
BOOKREVIEW
311
volved in such a project. It would be courting disaster for it to be used by those planning projects and disease control, analyzing field data, assessing past programs or recommending future policy. Like a car owner's manual, if you use it for driving you will certainly find yourself in a ditch and sooner rather than later. M. HUGH-JONES Department of Epidemiology and Community Health Louisiana State University Baton Rouge LA 70803 U.S.A.
REFERENCES Hennekens, C.H. and Buring, J.E., 1987. Epidemiology in Medicine. Little Brown, Boston, MA. Kleinbaum, D.G., Kupper, L.L. and Morgenstern, H., 1982. Epidemiologic Research: Principles and Quantitative Methods. van Nostrand Reinhold, New York, NY. Lilienfeld, A.M., and Lilienfeld, D.F., 1980. Foundations of Epidemiology, 2nd edition. Oxford University Press, New York, NY. Martin, S.W., Meek, A.H. and Willeberg, P., 1987. Veterinary Epidemiology: Principles and Methods. Iowa State University Press, Ames, IA. Thrusfield, M., 1986. Veterinary Epidemiology. Butterworths, London.
309
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Book Review E P I D E M I O L O G Y IN AFRICA
Veterinary Epidemiology and Economics in Africa: A Manual for use in the Design and Appraisal of Livestock Health Policy by S.N.H Putt, A.P.M. Shaw, A.J. Woods, L. Tyler and A.D. James. ILCA Manual No. 3, Agribooks, Winrock International, 1611 N. Kent St., Arlington, VA 22209, 1986, 130 pp., U.S.$22. With the appearance of new textbooks in veterinary epidemiology, it is important to try to demonstrate where this manual comes in the order and family of such publications. In the academic sphere, we can teach epidemiology to first- or second-year veterinary students for whom Thrusfield (1986) and similar introductory texts are ideal. With final-year students, more background can be assumed so a text with additional emphasis on demonstrating appropriate specific statistical techniques for epidemiologic applications may be used. This type of text merges into the applied texts for graduate students reading for a Master's degree. It is not a tidy group, but the text of Martin et al. (1987) is as good an example as any, with some chapters more suited to graduate students and others for veterinary students; Lilienfeld and Lilienfeld (1980) is a similar bridging text for medical and public health students. A good text for advanced graduate students in veterinary epidemiology has yet to appear, but the medical texts would be Hennekens and Buring (1987) for epidemiology, and Kleinbaum et al. (1982) for statistics. A characteristic of all these academic texts is that little experience of reality is needed to learn from them. This immediately differentiates them from reference texts that demand prior knowledge and experience. This manual by the Veterinary Epidemiology and Economics Research Unit at Reading University is neither an academic text nor for reference. It is written for people with plenty of field experience, but little theoretical knowledge. It simplifies epidemiology, statistics and economics down to a "how-to" level. It is methodology simplified. It is comfortably written in a friendly style, tidily laid out, has an adequate index, is cheaply priced and, if one were giving a short course to field veterinarians, whether in Africa or the United States, it might well be the text of choice. It is good reading for someone wanting a short introduction. One can recommend it to all directors of national veterinary services as it does brief one nicely on the questions to ask of one's highly trained junior officers, while allowing one to appear to know what they are talking about. In context, there are some useful chapters, such as "Economics and decisionmaking in disease control policy"; in fact, the three economic chapters are a useful introduction. Overall, the mathematical examples are well worked out so that the reader can easily fit in his or her own data. If you are willing to take
310
BOOK REVIEW
the time, there is a nice appendix on herd production modeling. The pragmatic and terse comments on the pitfalls in interviewing are gems and will bring back valuable, but embarrassing memories to many readers with field experience. The words of wisdom in the introductory section on statistical methods are worth framing. Unfortunately, the many and sometimes extensive simplifications used in this text bring on repeated attacks of the "Yes-buts". To take but a few examples, the definition of pathogenicity confuses it with virulence. The term "diagnosibility" of a test (p. 41 ) is used instead of predictive value. It does not show the economic value of a two-stage serologic screening. The section on interviews and questionnaires is far too shallow to allow one to either structure an interview or design a proper questionnaire. There are frequent references to the use of microcomputers as if nothing can be done without one. Are they selling something? Considering its audience, the sentence "Extensive literature searches can often be performed quickly and easily by using modern information processing techniques" has a certain distant charm, even for us, on occasion, in northern latitudes. All one can say about the description of monitoring and surveillance is that the authors are confused and unclear. They suggest a very restricted methodology for determining sample size. Without wanting to labor the point, the first four chapters on epidemiology, data, and investigation, which have several minor but annoying mathematical mistakes, should be read with caution. There are weaknesses in the theoretical underpinning of this text. The statistical presentation (Chapter 5) is entirely too brief and the theory is so lacking as to be gravely in doubt even as a working manual. Had I not understood a priori much of the text, the descriptions would have been relatively meaningless in this cookbook format. For example, how were the multipliers of the standard error derived in Table 16 (p. 50)? I know, but how will the average lay reader? If they do not understand this very small piece of theory, how will they ever understand what a confidence interval really means? Chi-square calculations (pp. 60-61) are presented almost as magic. Time series are introduced and dismissed in one and a half pages; linear regression and correlation in two pages. There is a cavalier attitude to basics. All in all, using this manual would be like navigating with an undamped compass such that one is always traveling in only more or less the right direction. It is only a manual, it is not a textbook. It is defined by the subtitle "for use in the design and appraisal of livestock health policy". The puffery in the Foreward should be disregarded. It is very like the manual given you when buying a car. It tells you how to start the engine and where the spare wheel and jack are, and it tells you when and why you should take your vehicle into the garage, whether for routine maintenance or repair. This manual does much the same for veterinary epidemiology and economics. It is suitable only for the corporals of this world; junior veterinary officers, who will be collecting or overseeing the collection of predefined data, so that they better understand why they are in-
BOOKREVIEW
311
volved in such a project. It would be courting disaster for it to be used by those planning projects and disease control, analyzing field data, assessing past programs or recommending future policy. Like a car owner's manual, if you use it for driving you will certainly find yourself in a ditch and sooner rather than later. M. HUGH-JONES Department of Epidemiology and Community Health Louisiana State University Baton Rouge LA 70803 U.S.A.
REFERENCES Hennekens, C.H. and Buring, J.E., 1987. Epidemiology in Medicine. Little Brown, Boston, MA. Kleinbaum, D.G., Kupper, L.L. and Morgenstern, H., 1982. Epidemiologic Research: Principles and Quantitative Methods. van Nostrand Reinhold, New York, NY. Lilienfeld, A.M., and Lilienfeld, D.F., 1980. Foundations of Epidemiology, 2nd edition. Oxford University Press, New York, NY. Martin, S.W., Meek, A.H. and Willeberg, P., 1987. Veterinary Epidemiology: Principles and Methods. Iowa State University Press, Ames, IA. Thrusfield, M., 1986. Veterinary Epidemiology. Butterworths, London.