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Introduction

ANIMAL DISEASE EMERGENCIES: THEIR NATURE AND POTENTIAL CONSEQUENCES

Animal disease emergencies may occur when there are unexpected outbreaks of epidemic diseases or other animal health-related events which have the potential to cause serious socio-economic consequences for a country.

These emergencies are frequently caused by outbreaks of transboundary animal diseases (TADs), which are of significant economic, trade and/or food security importance for many countries. Such diseases can spread easily and reach epidemic proportions; control/management, including exclusion, requires cooperation among several countries.

The occurrence of one of these diseases may have disastrous consequences for a country when they:

The International Office of Epizootics (OIE) recognizes 15 List A diseases, most of which could also be regarded as being TADs. These are foot-and-mouth disease(FMD), rinderpest, peste des petits ruminants (PPR), contagious bovine pleuropneumonia (CBPP), Rift Valley fever (RVF), lumpy skin disease, vesicular stomatitis, swine vesicular disease, bluetongue, sheep and goat pox, African horsesickness, African swine fever, hog cholera (classical swine fever), fowl plague and Newcastle disease. Examples of the serious consequences that these and other diseases have had internationally are shown in the Box (p. 2–3). However, this list is not exclusive. Other viral, bacterial, rickettsial and mycoplasmal diseases may also be regarded as having the potential to cause animal disease emergencies under some circumstances. Indeed, they may not necessarily be infectious diseases. For example, animal pests such as the New World and Old World screwworm flies may fit into this category.

EXAMPLES OF THE POTENTIAL CONSEQUENCES OF TRANSBOUNDARY ANIMAL DISEASES
Rinderpest is perhaps the most serious cattle plague. When this virus disease was first introduced to Africa in the late nineteenth century, it spread over almost the whole continent within ten years, killing an estimated 10 million cattle and untold numbers of wildlife-irrevocably changing livestock husbandry and wildlife ecology. In 1994, rinderpest spread to remote mountainous areas of northern Pakistan that had previously been free of the disease, killing an estimated 40 000 cattle and yaks.
Foot-and-mouth disease is a highly contagious virus disease of cloven-hoofed animals. A major epidemic of type O FMD in Taiwan Province of China in 1997 caused the death of some 184 000 pigs and a further 3.85 million pigs were slaughtered as part of the eradication campaign. The price of pigs dropped to a quarter of the price in force immediately before the outbreak.
Rift Valley fever is a mosquito-borne viral zoonotic disease. The first recorded outbreak of RVF in Egypt in 1977 caused an estimated 200 000 human cases of the disease with some 600 deaths as well as large numbers of deaths and abortions in sheep and cattle and other livestock species. An outbreak of the disease in East Africa in 1997–98 not only caused livestock losses and human deaths but also seriously disrupted the valuable livestock export trade to the Near East.
Bovine spongiform encephalopathy, a prion disease of cattle, was first recognized in the United Kingdom in 1986. Since then, more than 170 000 cattle have either died or been slaughtered. The discovery of a probable link between BSE and new variant Creutzfeld-Jakob disease of humans in 1996 led to major disruptions of world beef markets.
Contagious bovine pleuropneumonia is a serious mycoplasmal disease of cattle. There has been a catastrophic spread of CBPP over the last few years in Africa where it now affects some 27 countries and causes estimated losses of up to US$2 billion annually. In 1995, the disease was reintroduced to Botswana for the first time in 46 years. As part of the eradication campaign, all cattle (approximately 320 000) in an area of northern Botswana had to be slaughtered at a direct cost of US$100 million; indirect losses were over US$400 million.
Hog cholera (or classical swine fever) is a generalized virus disease affecting only pigs. A serious outbreak of the disease in the Netherlands in 1997-98 led to the death or slaughter of some 12 million pigs as part of the eradication campaign. The cost of this outbreak was estimated to be US$2.5-3 billion, half of which was public money and the other half was more or less equally shared between farmers and other participants in the livestock production chain. The effects of the epidemic were so severe that the Government of the Netherlands approved a national pig restructuring plan that foresaw a reduction in the national pig herd of about 25 percent within two years.
African swine fever is another generalized virus disease affecting pigs. In 1996 it occurred for the first time in Côte d'lvoire, where it killed 25 percent of the pig population and, according to various estimates, cost the country between US$13 million and 32 million in direct and indirect losses and eradication costs. There has since been a serious spread of the disease to Togo, Benin and Nigeria.
Virulent avian influenza is a lethal virus disease of poultry with some zoonotic potential. An economic analysis of outbreaks of VAI in Pennsylvania, United States in 1983–84 showed that the direct costs of eradication were US$64 million, and the indirect costs to consumers were $500 million through increased prices of products. On the other hand, it was estimated that VAI would have cost the United States poultry industry $2 billion annually had it become endemic. The influenza virus causing an outbreak of VAI in Hong Kong in 1997 was found to be capable of transfer to humans and, as a consequence, a decision was taken to depopulate chickens there completely.

Most people tend to equate emergency animal diseases with exotic or foreign animal diseases, although this is not necessarily so. Unusual outbreaks of endemic diseases may also cause an emergency when there is, for instance, the appearance of a new antigenic type such as a significantly different FMD virus subtype in an endemic country or when there is a significant change in the epidemiological pattern of the disease such as an unusually severe outbreak of anthrax. The emergence of previously unknown diseases may also cause an emergency, as in the case of bovine spongiform encephalopathy (BSE) in the United Kingdom in 1986, equine paramyxovirus disease (Hendra virus) in Australia in 1994 and Nipah virus disease of pigs and humans in peninsular Malaysia in 1999. There are other animal health emergencies that may be caused by non-disease events, for example a major chemical residue problem in livestock or a food safety problem such as haemorrhagic uraemic syndrome in humans caused by verotoxic strains of E. coli contaminating animal products.

While this manual will focus on the major transboundary animal diseases, the preparedness planning principles discussed can and should be applied equally to all types of disease and non-disease animal health emergencies described.

THE BENEFITS OF ANIMAL DISEASE EMERGENCY PREPAREDNESS PLANNING

As can be seen from the foregoing, an animal disease emergency such as an outbreak of a transboundary animal disease can have serious socio-economic consequences which, in extreme cases, may affect the whole national economy. If a new disease can be recognized quickly while it is still localized and prompt action taken to contain and then progressively eliminate it, the chances of eradication of the disease are markedly enhanced. Conversely, eradication may be extremely difficult, costly and even impossible if the disease is not recognized and appropriate control action taken before it becomes widespread or established in wildlife.

The target should always be to eliminate progressively and finally eradicate a transboundary animal disease (and prove that national or zonal freedom has been regained) if epidemiological and other circumstances are favourable. The alternative approach of simply “living with the disease” through the institution of routine vaccination campaigns and/or other disease control measures will in the end prove far more costly and will be a permanent constraint to efficient livestock production systems. Furthermore, the continuing presence of a TAD in a country, even if losses are minimized by effective disease control programmes, will inhibit the opening of export trade opportunities for livestock and livestock products. Eradication of the disease and provision of scientific proof of freedom from the disease to a level of international acceptability will remove this constraint to international trade.

Contingency planning and other preparedness programmes for animal disease emergencies should be regarded as providing the key to mounting early effective action in the face of an emergency. In fact these should be recognized as some of the more important core functions of national animal health services.

THE PRINCIPLES OF ANIMAL DISEASE EMERGENCY PREPAREDNESS PLANNING

The two fundamental components of animal disease emergency preparedness planning are the development of capabilities for:

These require advance preparation of both generic and disease-specific written contingency plans and operating procedures, the testing of such plans and training of staff; the development of capabilities at national, provincial and local veterinary headquarters, including field and laboratory services; development of mechanisms to involve other necessary government and private sector services and farming communities in the emergency response; development of the capacity to apply all the necessary resources to counter the disease or other animal health emergency in the most efficient way (including equipment, personnel and finances); and, finally, advance establishment of the appropriate legal and administrative structures to deal with an emergency.

Early warning of diseases

Early warning enables rapid detection of the introduction of, or sudden increase in, the incidence of any disease of livestock which has the potential of developing to epidemic proportions and/or causing serious socio-economic consequences or public health concerns. It embraces all initiatives, mainly based on disease surveillance, reporting and epidemiological analysis that would lead to improved awareness and knowledge of the distribution and behaviour of disease outbreaks (and of infection) and which allow forecasting of the source and evolution of the disease outbreaks and the monitoring of the effectiveness of disease control campaigns.

The success of a country's capability for rapid detection of the introduction or increased incidence of transboundary and potentially epidemic animal diseases depends on:

Early reaction to disease outbreaks

Early reaction means carrying out without delay the disease control activities needed to contain the outbreak and then to eliminate the disease and infection in the shortest possible time and in the most cost-effective way, or at least to return to the status quo and to provide objective, scientific evidence that one of these objectives has been attained.

For this to be achieved, the following elements need to be in place:


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