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II. Factors determining the level of control

In recent years, the challenge of transboundary pest and disease movements has become greater, and the ability to regulate such movements has failed to keep pace. This has occurred in part because of the increasing need to integrate international considerations and consider private sector capacities in the design and establishment of effective protection services. Although the involvement of more stakeholders can lead to more effective and efficient decisions, it also complicates and lengthens the process of implementation. In spite of these trends, national considerations still drive decisions regarding protection against pests and diseases and responsibility rests primarily with national agencies.

A combination of the following national and international factors affects countries in their efforts to combat transboundary pests and diseases:

Some countries are more vulnerable than others to invasions of transboundary pests and diseases. International cooperation is one way to reduce the disparity of control capacities and resources between neighbouring regions or countries. When establishing international approaches to transboundary pest and disease control, it is important to identify the vulnerable regions, probable pathways and existing limitations.

Country and regional differences derive from perceived economic impacts, political conditions and civil unrest; regulatory regimes, including resources for prevention and enforcement measures and attitudes and views concerning risk; and biological and physical conditions.


Because of the importance of national factors and financial resources in limiting the spread of transboundary pests and diseases, the poorer regions of the world are greatly affected. However, there is no direct correlation between country income levels and the ability of animal and plant protection measures to stave off threats to agriculture. In addition to the factors listed above, the following economic considerations affect efforts to prevent the spread of transboundary pests and diseases:


The dissolution of the former Soviet Union and the formation of new trading blocs have increased the risk of pest and disease entry from neighbouring countries. The new governments have had to create new institutions and regulations for sanitary and phytosanitary control. Different trading relationships have been formed from these political realignments, and they sometimes serve as pathways for the spread of transboundary pests and diseases. Improving sanitary and phytosanitary capabilities in these neighbouring countries may become an important way for countries with good quarantine systems to step up protection of their agriculture sector.

Civil unrest leads to the breakdown of phytosanitary and animal health controls as well as to the displacement of substantial numbers of people. Displaced people often attempt to take their belongings with them, including their livestock - and hence their diseases. It was in this way that rinderpest was introduced into Turkey by people seeking refuge in the eastern part of the country during the Iran-Iraq conflict in the late 1980s.

Areas where there is civil unrest or war are vulnerable to the entry of pests and diseases because of the lack of inspections and border controls and because of increased unregulated movement of military personnel and refugees. Foreign food aid has been accused of introducing unwanted pests into a number of countries throughout Africa. This was the case of the larger grain borer, unintentionally introduced into the United Republic of Tanzania in a food aid shipment in 1979 (see Map 9). The spread of the corn rootworm (Diabrotica virgifera) into Europe after an introduction into Yugoslavia as a result of military movements is well known.


Regulatory systems for managing transboundary pests and diseases are heavily dependent on the actions of both the government and private sectors. The effectiveness of such systems is determined by the level of resources that governments can provide as well as by the technical capacity that exists within the country concerned. The private sector has considerable responsibility in monitoring, inspecting and reporting. Different countries tolerate the risk of transboundary pest and disease entry to varying degrees.

Regulatory systems can also break down or be inadequate to respond effectively to new challenges faced in transboundary pest and disease control, either because of systemic deficiencies or because safeguards are evaded. For example, seven out of eleven primary outbreaks of foot-and-mouth disease that occurred in Europe between 1991 and 1996 are likely to have been caused by the illegal importation of livestock or livestock products.


Plant, insect and pathogen movements within Europe or the Americas have had considerable effects, both beneficial and destructive. Overall, however, these movements have been less significant than trans-Atlantic and trans-Pacific introductions. The major threat for transboundary plant pest movement comes from intercontinental movements between the four large landmasses (the Americas, Europe/Africa, Asia and Australasia) because of the ecological separation of these distinct regions. Furthermore, plant and animal trade has increased across all these regions.

Map 10 shows the ecological zones across the world that serve as barriers to pest movement. Many of the most damaging and unexpected pest and disease problems occur when an organism moves across natural barriers. However, movements within a zone can also be significant; for example, the potential for the medfly to move into Chile from other parts of South America.

Regardless of the ecological zone of movement, many plants, animals and microbes that are classified as pests are simply more invasive and manage to dominate over other species because of their adaptability or genetic elasticity. These species, or at times subspecies, can switch hosts or may already have a broad host range, thus allowing them to survive and establish in new geographic areas more effectively than their competitors. This biological mechanism is what makes introduced, or exotic, pests particularly harmful.


Most control measures are aimed at preventing the entry and/or spread of a pest or disease when a human action - such as trade or travel - or natural contagion could carry the organism into a previously unaffected location. Many individual pests and infected animals move across borders every year. The majority of these introductions do not activate an official response. This may be because the introduction is expected to have only a minor economic impact, it dies out in the country's environment, there is no capacity for detecting the introduction, or there is no known control measure that is effective.

However, some pest and disease movements pose a significant threat to national agriculture sectors and/or food security and therefore necessitate a response. The method of response is both a public and private decision and is dictated by the severity of the risk and extent of the impact. Two economic concepts, public good and externality, can provide a guide as to when control should be left to individual farmers and when it should involve public agencies.

A public good is one that offers benefits to a large group (potentially everyone) without reducing the amount of that good available to each person. The distinctive characteristics of a pure public good are non-excludability and non-rivalry in consumption. In contrast to a purely private good, such as the vaccination of an individual cow by a farmer, the provision of vaccine research is a public good that is often supplied by government. A problem that can arise with public goods is that of "free riding", in which people believe the good will be provided whether or not they pay a share of the cost. Furthermore, there may be incentives for individuals (or countries) to disguise their actual demand for such a good - sometimes understating it and sometimes overstating it, depending on their expected gain or potential cost burden.

An externality exists when the action (or inaction) of one individual (or enterprise) imposes costs on or creates benefits for another but the effect is not taken into consideration by the person (or enterprise) who carries out the action. An example of a negative externality is when a communicable disease affects livestock herds in a community, and one farmer chooses not to participate in the disease eradication programme. Although non-participation might be the best strategy for that farmer, it may create a reservoir of the disease in the area that could contaminate animals included in the eradication programme.

When a pest or disease affects only a small area and number of individuals (farms and others at risk), or if the consequences of an introduction are not severe, private responses from affected individuals can provide an economically efficient solution. The responses might be in the form of legal action or private negotiations, and will depend on the socio-economic conditions and risk tolerance of affected parties.

Similarly, when only one country or part of a country is affected by a pest or disease, the externality effects are relatively contained. The response is more likely to involve government action, but it may be based solely on domestic conditions and preferences and may occur relatively quickly. However, in the case of transboundary pests and diseases, large regions and many people are potentially affected by these threats, and proper management usually requires a regional or international effort guided by public authorities. This requires a system both for deciding which control decisions are supranational and which are national and for implementing international decisions efficiently.

The control of transboundary pests and diseases calls for the provision of public goods at the global or regional levels. The movement of pests and diseases across boundaries generally imposes a negative externality on a recipient country, which the country of origin has some obligation to prevent or minimize. The action taken by a given country to protect other countries from the invasion of pests and diseases through control measures and the provision of timely information can be considered a public good. As with the protection of human health, a global system of plant and animal health is a global public good, available to all countries and populations on an equal basis.

The specific aspects of pest and disease control that fall clearly within the realm of public goods are surveillance, information provision and research on improved methods of prevention or diagnostics. The development of agreed rules and protocols can also be efficiently supported by public institutions, although success in this area depends on the participation of the greatest number of countries possible.

The framework offered by Jamison, Frenk and Knual6 in discussing human health also applies to the provision of international public goods in the domain of plant and animal health. They suggest that core functions should be provided internationally to all countries because they meet the definition of global public goods. These functions include information, standards and regulations, policy development and research and development. Additional functions should be provided to developing countries in the light of their scarce resources to provide for them, and in view of the externalities that are imposed on other countries if they are absent. These functions include enhancing the capacity and performance of the plant and animal health sector. The framework recognizes the interdependence of countries in the battle to control transboundary pests and diseases as well as disparities in the ability of countries to participate in the battle.

How much protection should be provided and by whom?

One challenge facing national and international authorities responsible for plant and animal protection is to determine how much protection is appropriate and who should be responsible for providing it.

Both questions can be answered more readily in theory than in practice. Actions to prevent the movement of pests and diseases across borders can be taken by individuals, by one or several country governments, by international organizations or by any combination of these. Efficiency requires that the effort invested in plant and animal protection by an individual, a government or an organization be proportional to the damage that would be caused in the absence of protection. Equity demands that the burden of providing protection be borne by those who impose the risk or allow it to spread (in the case of a preventable hazard) or those who benefit from protection against risk or, most often, a combination of the two.

In practice, it is difficult to assess the damage that may result from the introduction of a transboundary pest or animal disease. Countries use past experience, together with a scientific assessment of the organism, to judge the extent of the damage. In doing so, they should weigh the possible losses from an outbreak or introduction against the costs of taking action to prevent it. Yet, the difficulty of measuring both the scientific likelihood and the economic extent of damage may prevent authorities from choosing the most efficient level of protection. Furthermore, the actual loss of crops or livestock that arises from a pest or disease can be far outweighed by the loss of trade opportunities for a country that becomes infested. Therefore, it is especially difficult to determine the proper amount of protection that a country should provide in cases where significant volumes of trade are at risk.

Until recently, the criterion for combating transboundary pests and diseases was to choose the more cost-effective of several control options, or to decide on an objective and aim to achieve it without regard to cost. However, the past ten years have yielded a greater number of studies examining both the costs and the benefits of pest and disease control - although largely still in developed countries - with a view to determining how much control is worth while in given situations. This greater scrutiny of control options has also occurred at the international level in compliance with WTO requirements for scientific studies to justify barriers to trade, including sanitary and phytosanitary measures (see Box 10, on related international agreements).

Local, national and international control efforts (pesticides, vaccines, integrated pest management, etc.) against transboundary pests and diseases should be aimed at achieving the "optimal" level of protection (if it is known), where the marginal cost of control is equivalent to the marginal benefit.7 An international response is warranted if the damage - and hence the control effort - affects multiple countries. Thus, this approach would recommend additional spraying against the desert locust only if the benefits of an additional day of spraying (in terms of damage averted) would exceed the cost - including environmental or other hidden costs - of spraying for one more day.

It is far more difficult both to calculate and to meet such a clearcut standard at the transboundary level than at the national level. Transboundary pest and disease scenarios do not have the same uniformity or history of research as do national control experiences to support decision-making. Scientific uncertainty makes economic analysis difficult. Furthermore, control programmes involve multiple governments and organizations whose risk acceptance and willingness or ability to reduce risk vary.

The issue of who should provide protection is also more complicated in practice than in theory. Largely as a result of the globalization of trade in agriculture, pest and disease control is increasingly driven by countries' global interests, although domestic agriculture sectors remain a major influence. Countries' international obligations are guided by the WTO Agreement on the Application of Sanitary and Phytosanitary Measures (see Box 10). National policy is determined by economic and political factors, both domestic and international.

A country is expected to take reasonable action through its quarantine system, or through other built-in responses in the case of migratory pests, to prevent the spread of transboundary pests and diseases. Importing countries are also expected to have safeguards in place to prevent spreading if an introduction occurs. However, it is not always clear what a country's obligations are in preventing the spread of transboundary pests and diseases. Not all of these pests and diseases are likely to affect all countries; hence, countries will not be equally willing to participate in a control effort. In addition, even if a country is vulnerable to a transboundary pest or disease, its government may feel that its own control mechanisms are adequate to prevent damage domestically and therefore be unwilling to participate in an international control campaign.

Countries may not meet their obligations to prevent the spread of transboundary pests and diseases for several reasons. For instance, technical and scientific knowledge about the spread of pests and diseases is often incomplete and inexact. It is expensive to conduct the kind of economic and environmental impact studies required by the donor community or trading partners. Second, countries do not all have access to the same technology or institutional response capacity.

A third complication arises from the "free rider" problem of public goods. This is because all countries can benefit when the goods are provided and, therefore, countries become reluctant to carry out unilateral control efforts. Moreover, for political or humanitarian reasons, donor countries often foot the bill for protection services that help other countries combat pests and diseases. Because of differing incentives, donor countries may provide insufficient protection relative to the "optimal" amount required, while countries that are in need of protection from transboundary pests and diseases may overstate their need. Affected countries may also see disincentives to adopting practices that improve or maintain their systems of transboundary control. This situation arises, for example, when migratory pests begin in one country and move to others. Expenditures for desert locust control have exceeded $500 million over a ten-year period (1987-1996) and have largely been funded by donor countries as opposed to affected countries (FAO,1998).8 Some observers believe that conflicting incentives among countries involved in regional desert locust control organizations have resulted in insufficient funding of monitoring and prevention operations, although the stated need for protection is very high. Incentive-compatible solutions can be devised but they require more complicated financing arrangements - such as copayments - or better information on the actual risks and costs of locust invasions.

Ultimately, it is understood that even good systems are not infallible and pests and diseases do spread. The globalization or regionalization of regulatory and control systems has many benefits, however, in reducing negative externalities and expanding the beneficiaries of public goods.

After it has been determined that an international response is warranted, the different control strategies needed for migratory and quarantine pests and diseases must be considered. The choice of approach depends on how the risk is spread (via natural pathways or via humans), the severity of damage if introduction occurs, and the nature of control options. International authorities must also consider whether their role involves the provision of public goods only - such as surveillance and research - or also the establishment and coordination of protocols and control efforts.

The primary goals of any control programme against transboundary pests or diseases are, first, to establish the "optimal" level of disease or pest presence to meet a country's goals and, next, to choose the most cost-effective way of achieving that level of control. For instance, a policy of pest or disease freedom is a high standard that can impose significant costs on a country. This standard is attainable if the following criteria are met:9

Lower standards are more efficient if the above criteria are not met. The "optimal" level of control can vary from one country to another, depending on the results of analysis.

Control of migratory pests

The control of migratory pests raises the most obvious transboundary issues, as pest populations can expand quickly from a localized outbreak to an upsurge, with serious infestations occurring simultaneously in several areas and neighbouring countries. The fast initial multiplication may occur unnoticed in remote and unpopulated areas and follow a natural (biologically induced) pathway. Once cropping areas are invaded, there is rarely sufficient time to prevent damage through control operations.

The widespread destruction that can accompany an outbreak or swarm of migratory plant pests makes it a political imperative for many countries to attempt control. Because of the high proportion of migratory pest damage occurring in poor regions, there is added pressure to prevent impacts on scarce food resources. Control is carried out as a response to the appearance of migratory pests, with the main effort aimed at eradicating them once they appear in significant numbers. The primary response is widespread pesticide spraying in affected areas once these have been defined. The rapid identification of early stages of swarms in the country of origin is critically important to minimize the damage to other countries.

This presents a classic externality issue: the inaction of one or more countries can impose major damage on other countries. The country paying for control may not face the same risk of damage as surrounding countries. The major decision faced by national governments and international organizations is in timing the response: which can be either in the early stages of gregarization or after swarms have arrived at their destinations. It is not clear from the science and history of experience which is the most cost-effective, but the cost burden falls on different countries depending on this decision.

Control of quarantine plant pests

Changes in trade flows and trade practices over the past 20 years have increased the number and diversity of risks to plant health faced by national governments. The rapid increase in leisure travel by the public is also a contributing factor. Unlike migratory pests, the introduction of quarantine pests normally involves human intervention, either by importing products or accidentally or deliberately smuggling them into a country. Most of these introductions are undetectable and, although most are also harmless, without improved detection methods for pests with cryptic life stages, exclusion efforts will not be successful. This problem is chronic for the control of virus and other disease organisms that are not readily observed at the time of inspection.

The challenge of quarantine plant protection is the fast pace of change occurring in trade flows and technology. Because of the ease and multiplicity of ways in which invasive species can move, countries with important agriculture sectors must carefully assess risks to their production from plant pests on a frequent basis. Those countries engaged in international trade must be particularly vigilant in their normal prevention efforts (monitoring, inspection, etc.), but they must also maintain an ever-higher technological capacity to detect and prevent pests. In order to comply with sanitary and phytosanitary obligations, they must also devote resources to risk assessment. Because of a scarcity of data, this requirement can be a burden for developing countries.

Control of animal diseases

As with quarantine plant pests, the primary responsibility for controlling the spread of animal disease belongs to the country of origin as well as the receiving country. Both face the burden of requiring elaborate quarantine systems, as well as the risk of production losses - and worse if introductions occur. Yet the capacity of countries to provide these services frequently varies.

Animal diseases are spread either through natural pathways or human intervention. The transmission of certain diseases requires an insect to serve as a vector, which relies on external environmental conditions and possibly appropriate plant hosts to carry out its life cycle.10 Therefore, for biological reasons, these disease pathways have limited geographical scope, which simplifies the task of identifying pathways for disease transmission compared with plant pest introduction.

In regions with a good veterinary infrastructure the movement of livestock and derived products is regulated and controlled to prevent the entry and subsequent spread of exotic disease agents. Furthermore, disease surveillance systems with good laboratory diagnostic support are maintained to ensure the early detection of disease outbreaks and contingency plans are in place to respond rapidly to an epidemic. In addition, emergency funds have been set aside and farmers usually receive at least partial compensation for losses incurred. In many countries, however, public funding of veterinary services is insufficient and even declining. Diagnostic capacity is poor and livestock movements are uncontrolled. Farmers are not usually compensated for disease losses.

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