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Modelling means different things to different people. Interpretations include the graphical representation of concepts or processes, such as organograms and flow charts, the statistical manipulations of data to determine associations (or the lack of them) between factors and the mathematical expression of dynamic processes. All three of these examples can be validly applied to diseases, both animal and human. But which types of models fit which types of problems, and what are the problems which lend themselves to modelling? Modelling science is relatively young and although the answers to these questions might be clear and straightforward to a few people, they are not clear to many, including those working in infectious diseases and in the modelling sciences themselves. Many biological scientists tend to be put off by the equations and by the abundance of assumptions; many modellers on the other hand are fearful of the complexities of biological processes, and how these conflict with the ability to represent processes numerically. Successful use of modelling therefore requires an integration of these different skills and understandings, and it was in search of such interdisciplinary integration that this workshop was conceived.

The International Laboratory for Research on Animal Diseases (ILRAD) is conducting basic strategic research on the improved control of livestock diseases and traditionally attempts to address research issues through experiments. As such, the use of mathematical models to screen hypotheses and question the validity of experimental results has not featured strongly. Recently, ILRAD has been paying increased attention to the impact of its research on enhanced livestock productivity and here, given the paucity of data in many subject areas, the use of modelling appears intuitively more valuable. It was thus decided to hold a workshop to explore both of these areas, bringing together ILRAD scientists, with statements of their research goals, and experienced modellers prepared to display and discuss their wares. In the early stages of developing plans for the workshop, it was learnt that the Food and Agriculture Organization (FAO) was intending to embark on a similar project, exploring the potential use of models to better deliver technologies to improve animal health and productivity to the field. The workshop objectives of the two organizations, ILRAD and FAO, were then rationalized and united as follows:

1. To present the perceived modelling requirements of ILRAD and FAO.
2. To review the modelling procedures appropriate to meet these requirements.
3. To identify relevant approaches.
4. To determine the database requirements for the development of such modelling approaches.
5. To explore potential collaborations.

Formal sessions covered the six major subject areas, namely vector and helminth population dynamics, parasite transmission, host-parasite interaction, parasite variation and polymorphism, effect of disease control programs and modelling systems. Within each session, the perceived requirements of ILRAD and/or FAO were presented and then examples of appropriate developed models presented. Further sessions provided examples of the application of modelling to vector-borne and other parasitic disease control, and considered the database and training requirements. This proceedings provides a comprehensive report of all scientic sessions, and of the discussions and recommendations which ensued.

We wish to thank the many people who assisted in running of the workshop, and in the preparation of the proceedings. In particular, we thank Dr. Rob Eley and Mr Kepher Nguli for taking charge of the logistic arrangements for the workshop, Miss Lucy Kirori for preparing the manuscripts and Mr Peter Werehire for laboriously typesetting and proof reading the entire volume.

B.D. Perry
International Laboratory for Research on Animal
Nairobi, Kenya

J. W. Hansen
Animal Production and
Health Division
Food and Agriculture
Rome, Italy

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