Veterinary epidemiology and economics in Africa - A manual for use in the design and appraisal of livestock health policy













Table of Contents


S.N.H. Putt, A.P.M. Shaw, A.J. Woods, L. Tyler and A.D. James

Veterinary Epidemiology and Economics Research Unit,
Department of Agriculture,
University of Reading, Reading,
Berkshire, England

First published in January 1987
Second edition, March 1988

Original English
Designed and printed at ILCA
Typeset on Linotype CRTronic 200 in Baskerville 10pt and Helvetica

ISBN 92-9053-076-6

This electronic document has been scanned using optical character recognition (OCR) software and careful manual recorrection. Even if the quality of digitalisation is high, the FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.


Table of Contents


Acknowledgements

Foreword

1. An introduction to the planning and evaluation of disease control policy

1.1 Introduction
1.2 The planning process

1.2.1 The systems approach to livestock development
1.2.2 Stages in the planning process
1.2.3 The role of various disciplines in the planning process

2. Epidemiology: some basic concepts and definitions

2.1 Introduction
2.2 Intrinsic determinants of disease

2.2.1 Disease agents as determinants of disease
2.2.2 Host determinants

2.3 Extrinsic determinants of disease

2.3.1 Climate
2.3.2 Soils
2.3.3 Man

2.4 Describing disease events in populations

3. The use of descriptive statistics in the presentation of epidemiological data

3.1 Introduction
3.2 Tables and graphs
3.3 Bar and pie charts
3.4 Classification by variable
3.5 Quantification of disease events in populations
3.6 Methods of summarising numerical data

4. The epidemiological approach to investigating disease problems

4.1 Introduction
4.2 Types of epidemiological study

4.2.1 Prospective studies
4.2.2 Retrospective studies
4.2.3 Cross-sectional-studies

4.3 Sampling techniques in epidemiological studies

4.3.1 Random sampling
4.3.2 Multi-stage sampling
4.3.3 Systematic sampling
4.3.4 Purposive selection
4.3.5 Stratification
4.3.6 Paired samples
4.3.7 Sampling with and without replacement

4.4 Sample sizes

4.4.1 Sample sizes for estimating disease prevalence in large populations
4.4.2 Sample sizes needed to detect the presence of a disease in a population

4.5 Methods for obtaining data in epidemiological studies

4.5.1 Interviews and questionnaires
4.5.2 Procedures involving measurements
4.5.3 Errors due to observations and measurements

4.6 Basic considerations in the design of epidemiological investigations

4.6.1 Objectives and hypotheses

4.7 The use of existing data

4.7.1 Advantages and disadvantages
4.7.2 Sources of data

4.8 Monitoring and surveillance

4.8.1 Epidemiological surveillance
4.8.2 Epidemiological monitoring

5. Statistical methods in the analysis of epidemiological data

5.1 Introduction
5.2 Estimating population parameters

5.2.1 Estimating a population mean
5.2.2 Sample size needed to estimate a population mean
5.2.3 Estimating a population proportion or rate from a simple random sample
5.2.4 Estimating a rate or proportion from a cluster sample

5.3 Formulating and testing statistical hypotheses in large-sized samples

5.3.1 Testing for a difference in two means
5.3.2 Testing for a difference in two proportions
5.3.3 Sample size for detecting differences between two proportions in prospective and cross-sectional studies
5.3.4 Sample size for detecting differences between two proportions in retrospective studies
5.3.5 Testing for differences in prevalence between several groups simultaneously
5.3.6 Testing for differences in several means simultaneously

5.4 Formulating and testing hypotheses in small-sized samples
5.5 Matched comparisons
5.6 A word of warning
5.7 Linear correlation and regression
5.8 Time series

6. An introduction to the use of economics in the planning and evaluation of disease control programmes

6.1 Introduction

6.1.1 Basic philosophy
6.1.2 Application of economics disease control policy

6.2 Prices appropriate for use in economic analyses

6.2.1 Theoretical aspects
6.2.2 Opportunity cost and the choice of prices in economic analysis
6.2.3 Adjusting for inflation - price conversions and price indexes

6.3 Compound interest, discounting, annual rates of growth and annual loan repayments

6.3.1 Simple vs compound growth (or interest) rates
6.3.2 Discounting and compounding tables
6.3.3 Estimating present and future values using annuity tables
6.3.4 Loan repayments
6.3.5 Interest or discount rates and inflation

7. Estimating the costs of diseases and the benefits of their control

7.1 Introduction
7.2 Economic aspects of livestock production systems

7.2.1 Inputs and outputs
7.2.2 Factors influencing output and offtake
7.2.3 The relationship between livestock prices and output

7.3 Estimating the cost of disease

7.3.1 Quantifying the direct losses due to disease
7.3.2 Methods for estimating annual losses
7.3.3 Losses due to disease acting as a constraint on production
7.3.4 Other losses due to animal diseases
7.3.5 Secondary effects, externalities and intangible effects

7.4 The costs of controlling disease

7.4.1 Introduction
7.4.2 The components of disease control costs
7.4.3 The importance of fixed and variable costs in planning disease control policy

8. Economics and decision-making in disease control policy

8.1 Introduction
8.2 The principles of partial analysis
8.3 The principles and criteria of benefit-cost analysis

8.3.1 The role of the discount rate
8.3.2 Dealing with inflation
8.3.3 Layout of a benefit-cost analysis
8.3.4 The decision-making criteria
8.3.5 Dealing with risk and uncertainty
8.3.6 The scope of a benefit-cost analysis

References and recommended reading

Appendix one: tables

Appendix two: modelling in veterinary epidemiology and economics

1. Introduction
2. Types of model
3. Examples of models used in veterinary epidemiology and economics

3.1 The basic parameters required for herd modelling
3.2 Dynamic herd models
3.3 Incorporating the effect of disease into herd models
3.4 Static herd productivity model

List of abbreviations