For the Bulletin of the World Health Organization, Geneva, 1999





Prof. Dr Vaclav Kouba

Former Chief, Animal Health Service, Food and Agriculture Organization of the United Nations, Rome, Italy

Present address: P.B. 516, 17000 Praha, Czech Republic




  The paper discuses the risk of zoonoses global spreading through export and import of animals and their raw products. Many recent cases of specific zoonoses spread through imported animals have proved that current veterinary conditions, certifications and measures do not correspond with the new situation. Alarming danger of introducing zoonoses by import is rapidly increasing due to intensification of international trade. The paper identifies the factors facilitating the zoonoses spread which are related to  disease particularities, legal and regulatory arrangements, trade aspects, veterinary measures and human behaviour. It is called for strengthening the protection of specific zoonoses free populations, countries and continents. Trade globalization must not cause diseases globalization.


KEYWORDS : disease spreading -  early warning - global threat - international trade - risk assessment - zoonoses





   The purpose if this paper is to analyze the risk of the global spread of zoonoses due to increasing international trade in animals and their raw products. Import of these commodities represents a potential risk not only of diseases introduction but also of after-import spreading with multiplying negative, often long-term or permanent, consequences. The detection, control and eradication of introduced and spread zoonoses are usually very difficult and costly. These facts are the main difference in comparison with the risk when importing any other commodities.


    There are many publications documenting individual specific zoonoses introduction by international trade.  Historical review of international trade and animal diseases including zoonoses was presented by Blancou and Meslin (1). Data documenting zoonoses introduction by trade were published in statistical yearbooks of the Food and Agriculture Organization of the United Nations - FAO (11) and of the International Office of Epizootics - OIE (16) as well as by individual authors such as Davies (2), Kouba (3,4), Meslin (5,6), Stoehr (7), etc. The papers dealing with the disease risk published by World Health Organization (10) and International Office of Epizootics (9,14) are of particular importance.


   Material and methods     


a) For the analysis, official data on zoonoses occurrence in animals and on trade in animals and their raw products as reported to international organizations were used.


b) Data on zoonoses introduction by import of animals were selected from FAO-OIE-WHO Animal Health Yearbooks (10) and from OIE World Animal Health yearbooks (15). Particular data collection system was introduced by the author when he was the Editor-in-Chief of the first yearbook.


c) Data on international trade in animals and their products were used from FAO Trade Yearbooks (11). There have been selected the most important animal species and products. Data  on the amount and values of these commodities cover the period of 30 years between 1965 and 1995. For the forecasting of probable development linear regression of 1965-1995 data and 2025/1965 index of the amounts as the continuation of previous trend, were applied.


d) Factors influencing international spreading such as specific disease particularities, legal and regulatory arrangements, trade aspects, veterinary measures and human factors were identified based upon author's experience.




a) Diseases introduction by imported animals


aa)  There have been a lot of cases of zoonoses introduction by import, some of them discovered and reported to international organizations , some discovered and not reported (e.g., overwhelming majority of zoonoses in animals are not notifiable and usually not controlled) and much more cases not discovered at all. Emerging diseases represent a new global threat (WHO, 10). Due to biological complexity, it is not easy and often impossible to identify how and when the disease was introduced if discovered after quarantine period. Examples of officially reported zoonoses introduction by import into specific diseases free countries see in Table 1.


bb)  There have been many cases when, in spite of favorable risk assessment, risk reducing measures and standard veterinary certification, specific disease spread through import into  a country free of this disease. Of particular importance for diseases globalization were the introductions from very distant territories, i.e. from other continents.    Example: Screwworm (Cochliomyia hominivorax) introduced from Southern America into Africa in 1987;  foot-and-mouth disease (FMD) from Southern America into U.K. in 1967 (spread into 2364 outbreaks; lost of 430000 animals).


cc)  An other group is represented by cases in which different diseases were reintroduced by trade, i.e into countries where specific disease had been eradicated previously. Examples: FMD was reintroduced into Italy in 1993 after eradication in 1989; Newcastle disease was reintroduced into Finland in 1996 after eradication in 1971; screwworm was reintroduced in USA in 1997 after eradication in 1987.


  Cases of introduction of particular etiological agents into countries where specific zoonosis occurs contributed to morbidity increase and complicated control programmes.


dd)  Not all introduced diseases could be blocked in the quarantine avoiding creating secondary outbreaks. Examples: Ratios secondary/primary outbreaks of FMD during 1977-1987: Portugal - 591, Italy - 42, France - 19, Denmark - 10, etc. (Davies, 2).


ee)  Not all introduced diseases could be eradicated or only after longer period requiring a lot of economic and other inputs. Example: Eradication of the screwworm introduced into North Africa cost 80 million US$ plus local input ( FAO, 15).


ff)  Imported diseases represent the risk also for neighbouring countries (e.g., in case of vectorial diseases). Example: "For the first time in history, relentlessly destructive New World screwworm had become established outside its natural range in the Americas and, if left uncontrolled, it would inevitably spread to neighbouring countries, eventually into sub-Sahara Africa, Near East and Mediterranean Europe." (FAO, 14).


b)  Export/import of animals and their raw products


    Official international trade data document increasing risk of zoonoses spreading through export/import of animals and animal commodities. Absolute export/import data and 1995/1965 indexes as well as estimates of future development including 2025/1965 indexes see in tables 2,3,4.


  If the regression lines are applied for following 30 years, i.e. up to 2025, then the increase can be estimated in comparison with 1965 values: in cattle 2.36 times, in pigs 6.97 times, in sheep/goats 4.27 times, in fresh edible offals 6.32 times, in fresh milk 30.88 times and in eggs in shell 4.07 times.(See tables 2,3,4 and graphs 1,2).


In 1995 the value of the above mentioned selected commodities reached 58 billion US$ (FAO Trade yearbook 1996).


c) Other factors increasing globalization risk


    Beside the general underestimation of the alarming danger, there are many factors facilitating directly or indirectly zoonoses spreading through trade:


aa)  When assessing the risk not properly considering disease particularities such as: real occurrence (lack of complete and reliable data), stage and dynamics; ways and speed of spreading under given conditions; spectrum and population size of susceptible animals species; incubation period, grade of clinical manifestation, carriers; ability of diagnostic methods to discover all affected herds and animals and their products (false negative results); availability and feasibility of effective monitoring, preventive, control and eradication methods and measures; multi-etiological occurrence and carriers; etc..


bb)  Legal and regulatory arrangements: lack of legal codes requiring effective protection of animal populations and territory and declaring activity conducing to dangerous zoonoses spreading as criminal punishable act; benevolent international regulations, i.e. not enough demanding for protection of importing countries and not respecting that the trade in animals and their raw products is much more risky than in all other commodities; missing legal duties for traders to cover direct and indirect losses caused by disease introduction; etc..


cc)  Trade aspects: not applying normal fair trade practice, i.e. when the importing side is not free to decide if or not and where to purchase the given animal commodity and to define the health quality conditions; larger import due to reduction of national animal production (low self-sufficiency); instable trade partnerships, too many and too distant origin and destination places; trade agreements unfavourable for importing countries disease protection or without sufficient guarantee for specific health quality (disease free) and reclamation procedure; illegal import, black-market, re-export, dumping prices; etc..


dd)  Veterinary measures: lack of or deficiencies in protective veterinary measures; lack of ability to apply effective monitoring and control measures, import quarantine and post-import surveillance; weak government veterinary services being not able to monitor animal population health situation at field level, to inspect the export/import on the spot and to issue certificates without being dependent upon not fully reliable non-government services; benevolent import conditions (unjustified concessions) reducing barriers against disease introduction instead of strengthening them; mono-etiological instead of poly-etiological risk assessment based only on theoretical mathematical calculations without considering diseases occurrence reality, biological complexity, veterinary services ability, human factors, possible post-introduction consequences, etc..


e)  Human factors: not reporting true situation, not taking lesson from previous disease introduction, inexperience, errors, irresponsibility, cheating, corruption, lobbying, risk underestimation, identity/ health certificates falsification, distrust due to bad experience with previous import, abusing "disease regionalization", low discipline when implementing of regulations and measures, etc.




    The results reconfirm the anxiety of many authors such as Blancou & Meslin (1) about the risk of zoonoses spread through international trade.  The presented facts on zoonoses introduction by trade and on increasing global export/import in animals and their raw products are self- explanatory. It is obvious that the grade of global risk is directly correlated with trade size and frequency as well as with the number and distances between origin and destination places.


    Controlling only a few selected diseases and confirming their "free status" in exporting animals and products means omitting not notifiable, not internationally controlled and new emerging diseases. Therefore, it can be supposed that among imported animals and their raw products can be carriers of etiological agents which for importing country are considered as exotic species, types, subtypes or strains. Not all can be controlled. Absolute "filter" doesn't exist. In spite of the best possible protective measures, disease introduction cannot be always avoided. This is the reason for minimizing international animal trade size, frequency, number of origin and destination places and distances.


    Example: In 1972 Czech Republic being eight years free of Brucella abortus (BA) decided as exception to import about one thousand heifers from officially BA free region and ranches of a neighbouring country after sending specialists to reconfirm the situation. After series of pre-import and post-import complex serological investigations with negative results (quarantine up to first calving), imported animals were distributed into several farms of a ranch and systematically tested with negative results. However during second calving the brucellosis "exploded" and all imported animals and thousands heads of local cattle must go to slaughter. Several persons became sick.


    Animal disease import risk is generally underestimated giving priority to instantaneous profit ignoring the potential disease spread and consequences, often irreparable. There were hundreds of cases of importing diseases which destination country was not able to control and eradicated them. The losses and cost of measures have been usually very high. Most of introduced diseases, mainly chronic without clinical manifestation, if widely spread and particularly if penetrated among wild animals are today almost impossible to eradicate and negative consequences can last for ever.


    The impact of disease introduction can be disastrous. It is difficult to accept the practice when post-introduction losses and cost of measures are covered by government budget (by tax-payers) only and not by profiting traders who usually do not contribute anything. In all other commodities the traders must cover losses due to hidden defects.


    Today's extreme pressure of international organizations such as World Trade Organization (8) and traders to limit protective import conditions, general tendency to reduce trade controlling government veterinary services (e.g., the proportion of government veterinarians decreased from 34 % in 1983 to 25 % in 1996) and to restrict animal health programmes as well as disease testing can cause much worse and difficult-to-solve situation for the generations to come. E.g. from 1997 international reporting system was significantly reduced eliminating previous grading of animal diseases occurrence and information on the disease introduction, i.e on occurrence in imported animals (in quarantine). This means less information on diseases occurrence than before computer era !


  For exporting country is easier and cheaper to manage importing country to reduce protection barriers than demanding diseases reduction/eradication programmes at home. Recently was introduced so called "disease regionalization", when in spite of unfavorable and instable disease situation  (which in the past blocked the export) the exporting country declares one or several "islands" of territory also without their borders' control (usually without international clearance) as "specific disease free" and the export can go on. Very complicated network of daily transfer of animals and their products within the country or block of countries without internal borders' inspection, is almost impossible to control by veterinary services. In the past these territories were understood for export purposes as one unit and thus reducing the risk of diseases spreading outside the country.


    The principle to protect specific diseases free populations and territories should be defended in spite of strong pressure and unilateral monetary arguments. The trade in animals and their products is a big business. If we consider reported value of the import of all animal species and products including illegal trade, then globally the annual estimate is about one hundred billion US$.


    International trade organizations press importing countries to justify the refusal to import what they do not want when assessing disease introduction risk, i.e. ask for scientific evidence supporting the need for the trade restriction. This discriminating demand is not applied in any other goods. How to evaluate "scientifically" all introduction risk criteria, in particular the non-biological ones ?  


  Every import of animals and their raw products is a risk of diseases introduction. Increasing intensity of international trade in animals and raw animal products causes increasing spread of zoonoses among the countries and continents. The situation is getting worse every day as never before in spite of having much better scientific knowledge as in the past. Imminent risk of the globalization calls for urgent revision of existing leaky measures with the aim to achieve much better protection of specific diseases free populations, territories and countries.




    All cases of disease introduction to be analyzed and correcting measures applied. To reinforce countries protection, the factors increasing zoonoses introduction risk, as presented above, to be avoided. The key criterium of the country and continent protection measures effectivity is practical result avoiding animal diseases introduction.


   In importing countries the increase of animal production to be supported, i.e. to be self-sufficient as much as possible and thus to reduce the need for risky import. The protection of country territory is the first responsibility of any official veterinary service. Therefore, it must have the right to make the final decision about the import conditions which has never been easy due to disparate interests.


    In order to transfer into field practice  extremely useful recommendations and methods for zoonoses prevention and control elaborated by WHO, mostly in collaboration with FAO and OIE, government veterinary services must be significantly reinforced, to be able to cope with the new situation defending community interests effectively .


   Alarming risk linked with increasing trade requires to revise urgently national and international regulations such as of WTO (8) and OIE (12) and to adjust them to the new developing situation and conditions strictly defending specific zoonoses free populations and territories.


    General tendency in international trade is to increase the quality requirements on the commodities. Trade in animals and their products must not be the exception. Improvement of animal health quality of exporting countries  through diseases reduction and eradication is the best way how to facilitate the trade in these commodities. Trade globalization must not cause globalization of zoonoses. The priority should be given to globalization of the health.





















1. Blancou J, Meslin FX. International trade and human or animal diseases: a historical review. Proceedings of the World Veterinary Congress, Yokohama, 1995,p.4.


2. Davies G. Risk assessment in practice: a foot and mouth disease control strategy for the European Community., 1993, 12(4), 1009-1119.


3. Kouba V. [General epizootiology], 2nd edit. Havana, Edicion Pueblo y Educacion, Instituto del Libro, 1987 (in Spanish), 867 pp.


4. Kouba V. Computerized methods for animal health risk assessment using the EPIZOO 2.6 program., 1997, 16(3), 793-799.


5. Meslin FX. Surveillance and control of emerging diseases. World Health Statistics Quarterly, 1992, 45, 2/3, 200-207


6. Meslin FX. Zoonoses in the world: current and future trends. Schweiz. med. Wochenschr., 1995, 125


7. Stoehr K. Prevention and control of foodborne Salmonella. Southeast Asian J.Trop.Med.Pub.Health, 1995


8. Agreement on the Application of Sanitary and Phytosanitary Measures. In: The results of the Uruguay Round of multilateral trade negotiations: the legal texts. GATT. World Trade Organization (WTO), Geneva, 1994, 69-84.


9. Contamination of animal products: prevention and risk for public health. Off.Int.Epiz, 1997, 16,2.


10. Emerging and re-emerging infectious diseases: WHO responds to a global threat. Press release WHO/37, 26 April 1994


11. FAO-OIE-WHO Animal Health Yearbook 1981-1995. Rome, FAO, 1982-1996.


12. FAO Trade Yearbook 1965-1995. Rome, FAO, 1966-1996


13. International Animal Health Code, Special edition 1997. International Office of Epizootics, Paris, 1997, 642 pp.


14. Risk analysis, animal health and trade., 1993, 12(4), 1005-1362.


15. The New World Screwworm Eradication Programme, North Africa 1988-1992. FAO, Rome, 1992, 192 pp.


16. World Animal Health 1990-1997. International Office of Epizootics, Paris, 1991-1998.







Table 1. Examples of zoonoses occurrence in imported animals             (quarantine) only               


Table 2. World export/import of cattle, pigs and sheep/goats             as reported during 1965-1995 and estimates for years            2000-2025


Table 3. World export/import of meat as reported during 1965-            1995 and estimates for years 2000-2025


Table 4. World export/import of fresh offals, milk and eggs as           reported during 1965-1995 and estimates for years               2000-2025







Figure 1. Export/import of pigs in the world (reported, trend)


Figure 2. Export/import of meat in the world (reported, trend)






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