international trade, animal health and veterinary epidemiology: challenges and opportunities

International trade, animal health and veterinaryepidemiology: challenges and opportunities

C. Zepedaa,*, M. Salmana, R. Ruppannerb

aCenter for Veterinary Epidemiology and Disease Surveillance Systems, College of Veterinary Medicine and

Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USAbINRS-Institut Armand-Frappier, UniversiteÂ du QueÂbec, Laval, QC, Canada H7V 1B7

Accepted 20 September 2000

Abstract

The link between international trade, animal health and epidemiology has been recognized for a

long time and has taken an additional importance in the aftermath of the Uruguay Round of

Multilateral Trade Negotiations of the General Agreement on Tariffs and Trade (GATT) and of the

inception of the World Trade Organization. The Agreement on the Application of Sanitary and

Phytosanitary Measures of the World Trade Organization demands that sanitary and phytosanitary

measures be scientifically based, placing epidemiology at the center of decisions related animal

health and trade. This paper analyses the interactions between international trade of animals (and

animal products) and epidemiology with discussion on the inputs of epidemiology in surveillance,

risk analysis and regionalization. # 2001 Elsevier Science B.V. All rights reserved.

Keywords: International trade; SPS Agreement; Epidemiology; Risk analysis; Regionalization; Surveillance

1. Introduction

International trade in live animals and animal products occasionally has led to the

spread of disease between countries Ð resulting in severe consequences for the

agricultural economy of a country. Several examples of trans-boundary spread of diseases

have been documented. The spread of rinderpest to Belgium from cattle originating in

India destined for Brazil and transiting in the port of Antwerp in 1920 reintroduced the

cattle plague to Europe (OIE, 1999a). Foot-and-mouth disease (FMD) was introduced to

Mexico from Brazil in the 1950s and led to the destruction of one million cattle, sheep

Preventive Veterinary Medicine 48 (2001) 261±271

* Corresponding author. Present address: 555 S. Howes Street, Fort Collins, CO 80526, USA.

Tel.: �1-970-490-7975; fax: �1-970-490-7999.

E-mail address: [email protected] (C. Zepeda).

0167-5877/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.

PII: S 0 1 6 7 - 5 8 7 7 ( 0 0 ) 0 0 2 0 0 - 2

and goats and to a severe socio-economic crisis (Machado, 1968). In 1978, an African

swine fever epidemic broke out in the island of Hispaniola and could be controlled only

by the destruction of the entire swine population on the island. In Haiti, in particular, this

had a dramatic effect in the already precarious livelihood of the rural population (Zepeda,

1989). More recently, in 1997, classical swine fever was introduced to the Netherlands

and forced the destruction of roughly 11 million pigs (Dijkhuizen, 1999). The same year

FMD caused the destruction of Taiwan's swine industry (OIE, 1999b) and currently

affects several Asian countries1 (OIE, 2000a).

The introduction of rinderpest to Belgium in 1920 highlighted the need to have an

international body to help coordinate disease control efforts Ð and in particular, to

regulate international trade in animals and animal products. In 1924, the Office

International des Epizooties (OIE) was established by an international agreement signed

by 28 countries. Its main purpose has been to inform Governments of the occurrence and

course of animal diseases throughout the world and of ways to control these diseases; to

coordinate (at the international level) studies devoted to the surveillance and control of

animal diseases; and to harmonize regulations for trade in animals and animal products

among member countries (OIE, 2000b).

In April 1994, the Final Act of the Uruguay Round of Multilateral Trade Negotiations

of the General Agreement on Tariffs and Trade (GATT) was signed; this led to the

creation of the World Trade Organization (WTO) in January 1995. Among the

agreements that were included in the treaty that established the WTO is the Agreement on

the Application of Sanitary and Phytosanitary Measures (SPS Agreement) which sets out

the basic rules for food safety, and animal and plant health standards (WTO, 1995).

The SPS Agreement specifically empowers the OIE as the organization responsible to

draft international standards for animal health. The renewed importance conferred by the

SPS Agreement on the OIE has spurred the interest of countries across the globe; in 1989,

114 countries were members and by December 1999 membership had reached 155

countries (OIE, 2000b).

The main goal of the SPS Agreement is to allow increased trade of agricultural

products while recognizing the right of countries to protect human, animal and plant

health.

2. Risk, trust and trade

Over the years, one of the most important means to prevent the introduction of disease

through trade has been a policy of risk avoidance (i.e. a `̀ zero-risk'' approach to trade).

The driving philosophy behind this approach is captured in a phrase widely used in past

decades by animal health officials: `̀ if in doubt, keep it out''. Although the `̀ zero-risk''

approach has prevented disease introductions, it is widely understood that it often led to

unnecessarily stringent measures that frequently had no scientific basis and were in fact

used as barriers to trade.

1 Promed-mail: 05-APR-00 South Korea, 06-APR-00 Japan, 10-MAY-00 Mongolia, 26-MAY-00 Kyrgyzia

(Bishkek), 19-MAY-00 Georgia, 19-MAY-00 Kazakhstan.

262 C. Zepeda et al. / Preventive Veterinary Medicine 48 (2001) 261±271

Zero-risk is not attainable. The validity of the zero-risk approach to trade issues can be

questioned with the following points:

� In all areas of safety, risk can be reduced to an unimportant level Ð but scientifically it

is impossible to reduce it to zero. Scientific evidence cannot prove the absence of risk;

rather, it gives some certainty of the potential for the absence of risk.

� Nature does not respect political boundaries. Thus, a disease can pass a political

boundary without notice, with or without international trade.

� Unnecessary restrictive technical barriers to trade can lead to smuggling as a means of

getting around such barriers. This can threaten agricultural security seriously Ð the

opposite effect to that intended. They also can lead to a country finding itself isolated

from overseas market opportunities.

� International travel and trade is a fact of our current global community and risk always

will be present (no matter how small).

In short, trade implies risk; however, the lack of officially regulated trade also implies

risk because it stimulates informal, unregulated trade.

3. The SPS agreement and epidemiology

Some of the key notions contained in the SPS Agreement are risk analysis,

regionalization, harmonization, equivalence and transparency. Both, risk analysis and

regionalization depend on the data generated by a comprehensive surveillance system

with a sound epidemiological design. Thus, epidemiology is a key element in providing

the scientific basis to satisfy international trade requirements. Harmonization,

equivalence and transparency are the basis for mutual trust between veterinary services

Ð essential to ensure safe trade.

The SPS Agreement defines harmonization as the establishment, recognition and

application of common sanitary and phytosanitary measures and encourages countries to

participate actively in the development of international standards through the relevant

international organizations. However, embedded within the concept of equivalence, the

agreement also recognizes that different measures may achieve the appropriate level of

protection deemed by the importing country and allows the establishment of bilateral and

multilateral agreements on recognition of equivalence of specified measures. All changes

in the application of SPS measures should be published and made available to WTO and

trading partners, ensuring thus transparency (WTO, 1995).

4. International animal health standards

SPS measures should be science-based and should follow international standards laid

out in OIE's International Animal Health Code (OIE, 1999c). The OIE Code covers the

most important diseases and provides guidelines on issues like surveillance, risk analysis

and regionalization. If a country chooses to adopt a higher standard of protection, it must

C. Zepeda et al. / Preventive Veterinary Medicine 48 (2001) 261±271 263

provide a scientific justification and base its decision on a risk analysis. Article 3 of the

SPS Agreement provides the basis upon which valid SPS measures can be applied:

`̀ Members shall ensure that their sanitary and phytosanitary measures do not

arbitrarily or unjusti®ably discriminate between members where identical or similar

conditions prevail, including between their own territory and that of other members.

Sanitary and phytosanitary measures shall not be applied in a manner which would

constitute a disguised restriction on international trade'' (WTO, 1995).

In other words, a country may impose sanitary measures only if the disease of concern

is exotic or if it is under an official control program. Furthermore, measures can be

applied to trading countries only if they are also required internally within the importing

country. The flow to establish valid SPS measures is presented in Fig. 1.

5. Epidemiology and risk analysis

As mentioned above, the relationship between epidemiology and international trade

revolves around risk analysis and regionalization. Animal-health risk analysis relies on

epidemiological input; without such input, the process could become a mere probabilistic

exercise that is not biologically coherent. In the following paragraphs, we will describe

Fig. 1. Validity criteria for sanitary and phytosanitary measures in international trade.


the epidemiological components linked to the risk analysis process. Table 1 summarizes

these interactions.

Animal-health risk analysis is a process composed of hazard identification, risk

assessment, risk management and risk communication. Its objectives are to identify the

potential hazards associated with a commodity, to assess the probability of introduction,

establishment and spread within the importing country; and to estimate the potential

consequences related to its introduction (OIE, 1999c). Although, risk analysis as a formal,

documented, methodological approach is relatively new for veterinary services, the

concept has been applied informally for many years.

5.1. Hazard identification

The risk analysis process is initiated by identifying the hazards. The first step is to

prepare a complete list of pathogenic agents that could be associated with the

commodity.2 To do this, a thorough knowledge of the infectious diseases affecting the

species and the commodity of concern is required. Once this list is established, it needs to

be contrasted with the diseases existing (or potentially existing) in the export country.

Epidemiological information will then help to determine whether diseases may be present

in the exporting country but do not affect the species of interest, or whether the diseases

may affect the species but the agents are not present in the export product.

Hazard identification may be initiated by a request from the exporting country to be

recognized as free from a specific disease. In this situation, the methods used to

demonstrate the absence of disease and the measures taken to avoid its introduction or

reintroduction need to be reviewed.

Importing countries need to determine for which diseases valid SPS measures can be

established; this is done by defining which diseases are exotic and which diseases are

under an official control program. The pathogens identified during hazard identification

are arranged by importance of the disease(s) Ð usually according to OIE criteria for the

categorization of diseases: List A and B (OIE, 1999c). However, diseases (hazards) other

than those listed by the OIE may be included in the list.

5.2. Risk assessment

In theory, a risk assessment should be conducted for each hazard; in practice, however,

a risk assessment is conducted initially for the most important hazard; if the risk is

deemed to be acceptable, then the remaining hazards are assessed. Alternatively, all

hazards can be assessed qualitatively; and, a more thorough, quantitative assessment is

performed only on those hazards for which the risk (i.e. likelihood and consequences) is

perceived to be high.

Risk assessment consists of three interrelated steps: release assessment, exposure

assessment and consequence assessment (OIE, 1999c). Each of these steps requires a

thorough epidemiological knowledge of the disease in question. In the case of

2 According to the OIE Code (OIE, 1999c), the term commodity is used to include live animals, animal

products, semen, embryos and pathological material.


Table 1

Epidemiological components within risk assessment

Risk assessment steps Epidemiological components Data/knowledge requirements

Hazard identification List of pathogenic agents that could be associated with the commodity Existing control programs

Exotic diseases

Emerging diseases

Epidemiology of each disease in relation to the commodity

Knowledge on the presence or absence of disease in a country or zone Methods to demonstrate absence of disease

Release assessment Prevalence of disease in the importing country/risk of introduction of

disease from neighboring countries or zones or from trade with other countries

Survey and surveillance results

Survey methodology

Confidence level, precision, expected prevalence

True prevalence

Herd-level sensitivity and specificity

Animal-level sensitivity and specificity

Role of commercial and backyard operations

Regionalization

Epidemiological characteristics of the disease and the agent Incubation period

Carriers

Role of wildlife

Morbidity

Mortality

Method of spread

Pathogenesis

Target organs

Susceptible species

Agent inactivation procedures

Diagnostic tests Test Se and Sp

Cut-off values

Testing strategies

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Exposure assessment Characteristics of the susceptible populations and environmental factors

in the importing country

Pathways for exposure

Herd and animal densities

Immune status

Vectors

Seasonality

Cultural practices

Volume

Intended use of the commodity

Consequence assess-

ment

Biologic and economic consequences Susceptible species

Method of spread

Contact rates

Morbidity

Mortality

Number of affected herds/animals

Direct economic impact (mortality, impact on production)

Cost of control and eradication

Indirect economic impact: interrupted trade,

loss of international markets

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quantitative risk assessments, an understanding of probabilistic and statistical methods

also is needed.

Release assessment describes the biological pathways leading to the introduction

(`̀ release'') of the hazard into the importing country and estimates the associated

probabilities. One asks, whether the disease is present (or potentially present) in the

country of origin. To answer this question, one must analyze available survey and

surveillance findings, the survey methods, characteristics of the diagnostic systems used

and the relationship between different production systems. Most importantly, the

epidemiological characteristics of the disease and the agent must be taken into account

(e.g. the length of the incubation period, the range of susceptible species, transmission

mechanisms and agent inactivation procedures).

The next step in the process is the exposure assessment; it describes the pathways that

could lead to infection of human or animal populations in the importing country and

estimates the associated probabilities. This requires information on the demographics of the

susceptible populations, immune status, geographic distribution of herds, types of production

systems, presence and distribution of vectors and seasonality. Exposure pathways often are

shaped by economic forces that regulate the volume of trade and the potential for distribution

of the commodity within an importing country. It is important to understand the factors

influencing trade to analyze the potential consequences of disease introduction.

Risk is the combination of the likelihood of occurrence of an adverse event and the

magnitude of the consequences (Ahl et al., 1993). Once the probability of occurrence has

been determined, the last step in the risk assessment is the consequence assessment,

which deals with both the biologic and economic impacts following a disease

introduction. The expected number of affected herds, mortality and morbidity rates,

contact rates and wildlife susceptibility Ð as well as direct and indirect economic costs

must be assessed to estimate the magnitude of the impact of the adverse event. Thus,

epidemiological information about the disease and agent under investigation is of prime

importance at each of the three steps of the risk assessment process.

6. Risk analysis and regionalization

Previously, when a country declared the presence of a disease, its entire territory was

considered affected. The SPS Agreement recognizes that either a zone within an infected

country or a region (comprised of several countries or parts thereof within an infected

sub-continent) could be declared disease-free based on factors such as geography,

ecosystems, veterinary infrastructure Ð and in particular, animal-movement control and

disease-surveillance systems (WTO, 1995). This has opened the possibility to concentrate

disease-control efforts on areas with greater export potential, without the need to

eradicate disease on a countrywide basis.

Risk analysis and regionalization are closely linked. When conducting a risk analysis

to assess a commodity originating from a disease-free region or a zone, two perspectives

should be considered: (1) the probability of disease reintroduction into the zone or region

and the potential for spread of the disease; and (2) the probability of introducing a

pathogen through the importation of animals or animal products from that zone or region


(given the probability of reintroduction). In this context, the evaluation of the veterinary

services in the country is of utmost importance. The veterinary services should have the

ability to provide appropriate services within their country and to provide reliable

epidemiological data and information to other countries. In 1993, the OIE published

guidelines for the evaluation of veterinary services, including a model questionnaire used for

self-evaluation of a national veterinary service (OIE, 1993). The rationale behind this

evaluation is twofold, to assist the national authorities in the decision making process

regarding priorities to be given to its own veterinary services; and to assist the process of risk

assessment related to international trade in animals and animal products. In both cases, the

evaluation is to demonstrate the veterinary service's ability to effectively control the health

status of the national herd and the sanitary status of animal products marketed.

Although the process includes evaluation of the resources, of the management

capability, of legislative and administrative support, and of performance history (among

other items), the main issue is one of trust Ð the confidence of trading partners in each

other's competence and integrity.

These zones and regions have to respond to internationally accepted criteria to be

recognized as disease-free. Epidemiology has an important role to play in proposing such

criteria based on scientific reasoning and which eventually can be adopted by

international organizations such as OIE and WTO. Efforts now are being made by some

of our fellow epidemiologists to assess the validity of survey and surveillance systems

critically, in view of declaring a zone, country or region `̀ disease-free'' (taking into

account that tests are not perfect, that diseases are not necessarily randomly distributed

within a national herd, and that surveys and surveillance systems must be specifically

designed and statistically represented to yield valid results) (Salman and Ruppanner,

1999; Dufour, 1997).

6.1. Risk management

One of the objectives of risk analysis is to determine the most appropriate methods to

achieve the desired level of protection. Risk assessment identifies the points along the

pathway of introduction that have the greatest effect on risk (an appropriate selection of

mitigating measures applied to the most sensitive points in the process, usually allows for

substantial reductions in risk). Decision analysis is a method applied to several

epidemiological health problems (Dargatz and Salman, 1990; Carpenter and Norman,

1983) and has a direct application to international trade. This method integrates economic or

biological consequences and the probability of an event occurring so that the selection of

options in decision making process can be optimized. Evaluating the efficacy of the options

selected is an iterative process that involves their incorporation into the risk assessment and

the comparison of the resulting level of risk to that considered acceptable (OIE, 1999c).

7. Acceptable risk

The notion of `̀ acceptable risk'' has been debated for a long time. The SPS Agreement

does not indicate how to determine the acceptable level of risk (also termed the


appropriate level of protection (ALOP)). A current line of thought is to include

economics in the determination of the appropriate level of protection by taking into

consideration the benefits of trade and the potential costs of disease introduction and its

associated probability of occurrence. However, this is an idea that has not yet gained wide

acceptance Ð particularly at political levels. Regardless of the method used to determine

the ALOP, a country must be consistent in its application and should try to minimize the

negative effects on international trade (WTO, 1995).

8. Challenges and opportunities

The SPS Agreement has opened vast opportunities for veterinary epidemiologists. Still,

the solutions required to facilitate safe trade call for an integrated multidisciplinary

approach including other disciplines such as economics, statistics, geography and

geographic information systems, ecology, sociology and politics.

Epidemiologists have always dealt with the concept of health and disease in

populations; however, the promotion of international trade presents an additional

challenge, it requires a shift from herd-level epidemiology to a much larger scale that

encompasses zones, countries and regions.

There is a need to develop new methods to determine the disease status of countries

and zones as prevalence approaches zero Ð methods to be applied when an area (zone,

country or region) is to be declared free from disease. These methods need to be

statistically valid and at the same time economically viable and sufficiently practical to be

applicable under different field conditions (particularly in developing countries where

different production systems might co-exist).

An additional challenge is the quantitative integration of the results for the evaluation

of veterinary services into the risk analysis process. Although, there is a widespread

recognition that the quality of the veterinary services is linked to the level of risk, at

present, there is lack of methods to assess this relationship in a quantitative way.

Today, perhaps more than ever before, training in veterinary epidemiology is essential

for veterinary services staff at every level. Formal postgraduate training programs

currently offered need to be expanded to include risk analysis and economics in the broad

context of international trade.

The OIE, through several of its collaborating centers, offers training in these fields.

However, the role of collaborating centers is to complement formal epidemiological

training Ð not be a surrogate for it.

9. Conclusions

The SPS Agreement has had a strong impact on the organizational structures of

veterinary services, internationally. Veterinary epidemiology has been always closely

linked with international trade of animals and animal products; nonetheless, the

Agreement on the Application of Sanitary and Phytosanitary Measures of the World

Trade Organization has ratified epidemiology's role, placing it at the center of animal


health trade-related decisions. Today, veterinary services worldwide acknowledge this,

and are strengthening their disease surveillance systems and are integrating specialized

multidisciplinary groups to deal with risk analysis and regionalization. Unfortunately,

several countries Ð particularly in the developing world are facing considerable

difficulties in the implementation of the SPS Agreement (WTO, 1999).

Disease surveillance systems play a central role in providing the science-based

information needed to conduct risk assessments and regionalization appraisals.

In the past, SPS measures often were applied in a defensive, reactive mode. Today,

there is the opportunity to shift to a proactive approach that truly promotes agricultural

production and enhances international trade. The common threads supporting this effort

are the scientific basis in the application of SPS measures, transparency and trust.

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