The control of infectious diseases of livestock: Making appropriate decisions in different epidemiological and socioeconomic conditions

B D PERRY, J J MCDERMOTT AND T F RANDOLPH

Introduction

This book describes the many infectious diseases that affect livestock in sub-Saharan Africa, and indeed in many other regions of the world, and discusses in detail the technical aspects of their diagnosis, treatment and control/eradication. In an environment with unlimited resources, and with the technical capacity to undertake the appropriate measures, many of the diseases described here could be brought under control or even eradicated. Indeed, in the past, a few of them have been eradicated, but usually at enormous cost. Remarkably, in many cases, these costs are not available in the records, indicating that they may not have been of prime importance in the decision to eradicate. Take for example the eradication of East Coast fever (ECF) from southern Africa. In his detailed account of the eradication programme that spanned the years 1901 to 1960, Lawrence¹¹⁴ estimated, from what he called ‘fragmentary data’, that a total of 1,4 million cattle died as a result of the disease, and an additional 100 000 were slaughtered. However, he noted that data on the costs of control were ‘non-existent’. One cannot help asking the question: would such an intensive control and eradication programme, involving compulsory weekly dipping of all cattle, strict movement controls, quarantine of affected herds, compulsory examination of spleen smears from all animals that were slaughtered or died, and slaughter of infected animals with compensation, all sustained over decades, be carried out if ECF were to break out in certain southern African countries today?

It is in the answering of this question that one confronts the stark interaction between the technical feasibility and the socioeconomic feasibility of infectious disease control/ eradication. There are several important differences in circumstances that would affect the nature of a decision made today. These include changed political and socioeconomic circumstances, different disease-control institutions and authorities, and different decision criteria for allocating public and private funds and other resources to infectious disease control, to name but a few.

Why would we today expect the answer to be ‘probably not’? Much has changed in the intervening years since the initiation of ECF control in southern Africa in 1904. The magnitude of the threat presented by even the most virulent of infectious diseases is different, and is probably much smaller now due to our increased understanding of the risks and impacts of different infections, and a greater inventory of measures at our disposal to control them. It is doubtful that ECF would threaten the very existence of the entire agricultural sector today as it did at the beginning of the previous century for settler agricultural development. At the time, the region was recovering from the devastation caused by the rinderpest pandemic, and in an era when the world was preoccupied by the perils of infectious diseases, South Africa was also struggling to recover from the ravages of the Anglo-Boer War (1899 to 1902).

Furthermore, it is difficult to imagine the determined application of a technical solution being successfully implemented today given the political and organizational realities of much of the developing world. Part of this doubt is related to the more complicated nature of decisions on resource allocation and how (and by whom) these decisions are made today. It appears that an extraordinary degree of authority was given to the highly successful group of scientists active in investigating the causes and control of ECF, and this outweighed many of the bigger economic questions. There have been substantial changes in the seat of authority for disease control in virtually all corners of the world, from a very centralized, powerful and autocratic government involvement to a decentralized and often impoverished public sector, and this change has accelerated in most countries of the African continent in the last few years. The change has been complicated by a deterioration in the veterinary infrastructures of many African countries, and thus the feasibility of delivering even highly technically efficacious control measures is increasingly questionable. In addition, several decisionsupport tools (such as cost-benefit analysis, for example) to aid in decision-making are now available and widely used, but did not exist in the early part of the twentieth century.

In summary, decisions regarding disease control have changed radically due to a combination of improved knowledge about infectious diseases and of the need to take into account a whole range of socioeconomic considerations that were not previously considered.

This chapter evaluates how decision-making for the control of infectious diseases can be improved at all levels (e.g. farm, community, country, region) by the consideration of both epidemiological and socioeconomic issues. We review what the impacts of diseases and their control are, how these can be quantified, how such information can be used in the choice of disease control interventions, and how such interventions can be best implemented under different sets of circumstances.

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