GLOBAL PERSPECTIVE ON INFECTIOUS DISEASES OF LIVESTOCK AND POULTRY WITH SPECIAL REFERENCE TO FOREIGN ANIMAL DISEASES

Basil O. Ikede
Department of Pathology and Microbiology, Atlantic Veterinary College
University of Prince Edward Island, Charlottetown, PEI, Canada, C1A, 4P3

 

INTRODUCTION

Although the world is becoming more and more a global village, different species and breeds of animals still predominate in different regions or continents, just as different human races predominate in different continents. A large number of diseases affect domestic animals worldwide, but some are more prevalent and more damaging than others. Infectious diseases of livestock in different continents may differ depending on prevailing climatic conditions, animal breeds, and animal husbandry methods. Climate influences the vegetation, the culture of the people, and the species or breeds of animals they keep. Climate also affects the survival and proliferation of infectious agents and their vectors.

Developing countries lie mainly in the southern hemisphere (see map) and are endemic to some of the more devastating diseases that have been controlled or eradicated in developed countries that have the resources to do so. Such diseases are generally referred to as foreign, exotic, or emerging animal diseases wherever they do not normally occur. In spite of current control methods, including a ban or quarantine of animals and animal products from countries in which such diseases are endemic, some of them have continued to cross geographical boundaries. This has led to the concept of international epizootics, or more recently, trans-boundary diseases. However, places like Australia, New Zealand, the United Kingdom, and to a large extent, North America have the advantage of the oceans acting as wide natural barriers.

Regrettably, the threat now exists that such barriers may be broken intentionally through acts of agricultural bioterrorism, the risk of which appears to be increasing. Furthermore, new diseases of humans and animals can emerge spontaneously anywhere in the world. Of recent, such diseases appear to be emerging in unprecedented rates in people and their livestock. Examples include mad cow disease, the new fruit bat viruses (Nipah and Hendra), salmonellosis due to multiresistant Salmonella enterica DT104, and E. coli disease due to Escherichia coli 0157:H7.

Click on the images throughout this module for a larger view.

World Map, Peters' projection based on equal area. The projection emphasizes the size of the poor countries of the South compared with the rich countries of the North (after Standord, 1998). Diseases occurring in the vast South must be of interest to the relatively small North.

The value of the livestock and poultry industry worldwide is enormous. The industry is reported to be the fastest-growing agricultural sector, with livestock now being the world's largest land user. For example, the value of just the bovine industry in the United States of America was estimated to be $58.5 billion in 1999, more than the gross domestic product (GDP) of many developing countries in Africa, Asia or Latin America. Consequently, world trade in livestock products is mostly among developed countries. Participation by developing countries is as net importers, even though paradoxically, agriculture as a whole contributes greatly to their GDPs. Canada, with its demand for cattle and pig exports exceeding $5 billion in 1999, is the second largest net exporter of red meat in the world. Yet agriculture shares less than 6% of Canada's GDP compared to over 20% share in the GDPs of most of sub-Saharan Africa and Asia, according to World Bank reports.

Maintaining the health of livestock and poultry is also expensive. The animal health industry worldwide is estimated to be worth 14 billion dollars annually (Boudreau, 2002) and most of this money is spent in developed countries where the monetary value of the industry is high. Yet this region accounts for less than 25% of the world’s livestock and poultry populations (Boudreau, 2002, citing the Food and Agriculture Organization of the United Nations). That means that the vast majority of the world's livestock and poultry most likely receive inadequate health care, and could be harboring infectious agents transmissible to livestock in the developed world.

In this module, an overview is presented of the global animal disease problem with special reference to factors that influence the occurrence of major foreign animal diseases, mostly in the tropical regions of the world. At the end of the module, the student should have had an overview of the following issues:

Next | Top