This article was prepared by the technical officers of the Animal Health Service, headed by its Chief, Mr Y. Cheneau, Animal Production and Health Division, FAO, Rome, Italy.
Epidemic diseases: eradication versus control
Control of endemic diseases
Non-infectious and production diseases
Livestock production is constrained by a multitude of factors including disease, malnutrition, poor management and ineffective utilization of the best-suited genetic material. The major objectives of animal health activities are to secure food supply for a growing human population, to safeguard human health by combating zoonoses and to facilitate domestic and international trade in animals and animal products. The necessary interventions need to be both technically sound and cost-effective.
During the last two decades spectacular developments in biotechnology, informatics and information systems have been achieved, and the results are now being utilized in the planning and execution of animal disease prevention and control programmes in many countries. This article outlines the strategies of FAO in the field of animal health, with particular reference to the needs of developing countries.
The control of epidemic diseases of livestock has, by definition, a geographical emphasis (country, region, continent), while health and productivity improvement schemes are usually designed for the farmer and/or local community. In the former case, veterinary interventions are most successful if uniformly applied over a prescribed area. In the latter, interventions can vary from farm to farm, depending on clinical conditions and farming practices.
There is a growing desire among veterinary services to assess current disease control programmes and, if possible, move from the control phase to an eradication phase. In order to facilitate this, the International Office of Epizootics (OIE) is defining new guidelines based on a three-stage pathway that a country will need to follow before it can obtain international recognition as being free from an epizootic disease. For Stage 1 - Provisional freedom from disease - the director of veterinary services will declare this free state to the OIE following the absence of disease in the country and the cessation of vaccination. Stage 2 - Freedom from disease - requires that the country has ceased vaccination for a prescribed minimum period, has had no outbreaks of the disease after declaring provisional freedom and demonstrates results of prescribed surveillance before being internationally recognized. To attain Stage 3 status - Freedom from infection - the country must have extended surveillance after achieving freedom from disease status, have demonstrated evidence of the absence of the causative agent within the livestock population and have in place adequate measures to prevent the reintroduction of infection.
National, subregional and regional eradication will, of course, have beneficial effects for the areas involved. Yet it may not be cost-effective to achieve this, since emergency preparedness to assure the state of freedom is expensive and needs to be maintained continuously at a high level. It can be concluded, therefore, that total eradication gives the best economic return in the long term.
Based on the experience of the FAO European Commission for the Control of Foot-and-Mouth Disease and current activities of the FAO-coordinated Global Rinderpest Eradication Programme (GREP), the following guidelines have been defined as essential components for successful disease eradication:
· coordinated mass vaccination campaigns leading to a verifiable elimination of persistent endemicity;
· use of high-quality internationally recognized vaccines, independently tested for efficacy and safety;
· establishment and proper management of national veterinary services capable of organizing an intensive and sustained control and surveillance programme;
· adherence to the relevant OIE guidelines and time frame for the declaration of freedom from disease and from infection;
· provision of a national laboratory service capable of providing or developing rapid and effective differential diagnostic services;
· articulation of an effective strategy to prevent the reintroduction of the etiological agent;
· development of effective national/regional emergency plans, including a prerehearsed action programme in case of an outbreak. This should include provision for the implementation of a stamping-out policy.
These measures must be sustained by the following legal powers vested in national veterinary authorities:
· compulsory notification of any suspected cases by the owner and/or relevant local authorities;
· authority to collect samples for laboratory investigation;
· powers to enforce compulsory quarantines of infected premises, preferably with slaughter of infected animals, and ring vaccination, and powers of seizure of relevant material;
· payment of compensation;
· sanitation measures and other appropriate procedures on infected premises;
· powers to introduce control of livestock movements and to stop vehicles and herds so that animals may be inspected;
· powers to designate protection and surveillance zones for the purpose of implementing further intensive control measures; powers to implement emergency vaccination campaigns.
Although global or regional eradication of epidemic diseases would be the ultimate achievement, control remains the sole reasonable goal in most situations, either because of the epidemiological complexity, for example, vector-transmitted diseases such as African horse sickness, African swine fever and Rift Valley fever, or because of the inadequacy of available tools to achieve eradication, such as effective and safe vaccines and systems for accurate diagnosis and surveillance coupled with the availability of adequate financial and operational resources.
Eradication at the global or regional level cannot be accomplished without a coordinated international effort in gathering disease intelligence and implementing control procedures. International agencies such as FAO, OIE and the World Health Organization (WHO) have a crucial role to play in this since their mandates enable them to operate; in the international arena relatively free from political constraints.
A major component in the eradication of any major epidemic disease is a viable prevention programme. Realizing this, FAO has initiated a new priority programme called Emergency Prevention System (EMPRES) for Transboundary Animal and Plant Pests and Diseases. The animal-diseases component of EMPRES aims at strengthening the response of member countries in prevention and/or their immediate response to emergencies caused by major transboundary pests and diseases through FAO assistance, including technical coordination of control/eradication activities.
A strategy for disease eradication at the global level
FAO is coordinating the Global Rinderpest Eradication Programme (GREP) aimed at total eradication of rinderpest from the world by the year 2010. In order to facilitate the execution of this programme, FAO's Animal Production and Health Division has created the GREP Secretariat with the following responsibilities:
· organization of coordinating meetings;
· endorsement of targeted investigations, applied research and global monitoring of viruses by the World Reference Laboratory;
· creation of scientific advisory groups to support the project;
· harmonization of campaigns and risk analysis studies;
· support of global monitoring;
· production of technical guidelines and information/data dissemination.
The GREP Secretariat within FAO will therefore provide the technical linkage between the three regional campaigns in Africa, West Asia and South Asia, which are, respectively, the Pan-African Rinderpest Campaign (PARC), the Western Asia Rinderpest Eradication Campaign (WAREC) and the South Asia Rinderpest Eradication Campaign (SAREC). The success of the regional campaigns ultimately depends on the effectiveness of the operations at the national level, including the veterinary services, the regional infrastructures and the availability of adequate financing. In order to ensure national success, FAO is making technical contributions within each of the regional campaigns in the areas of epidemiology, such as surveillance and sero-monitoring, vaccine quality control and the design of communication programmes to promote community participation.
A strategy for disease eradication at the continental level
Foot-and-mouth disease (FMD) is the most important animal disease constraining world trade. In addition, it also directly limits agricultural production through losses in weight gain, milk yield and draught power. The present global distribution of FMD somehow mirrors the world economic order: all Organisation for Economic Cooperation and Development (OECD) countries are free of the disease and operate a policy aimed at total exclusion of the virus. Middle-income countries, such as many South American countries, run major FMD control campaigns to be able to maintain their international trade capability, while in low-income countries, with negligible participation in international trade in animals and animal products (sub-Saharan Africa and some parts of Asia), there are only few examples of effective control programmes.
To a large extent, the success of the ongoing continental plan for the eradication of FMD from the Americas, the Hemispheric Programme for Eradication of Food and Mouth Disease - which has already resulted in several countries in the region attaining disease-free status, can be credited to the national veterinary services and the coordinating role of the South American Commission for the Control of Foot-and-Mouth Disease (COSALFA), together with the technical support of the Pan-American Foot-and-Mouth Disease Center (PANAFTOSA). This illustrates the effectiveness of international collaboration and should serve as a model for other developing countries engaged in regional disease control/eradication efforts. It is befitting that an in-depth long-range review of FMD eradication strategies in the next millennium will take place in South America, where the first Joint FAO/OIE/Pan-American Health Organization (PAHO) Conference on the Perspective for the Eradication of Foot and Mouth Disease in the Next Millennium and the Impact on Food Security and World Trade will be convened in 1996, most probably in Brazil.
Brucellosis continues to be a problem in many countries and it is the most important zoonotic disease in the Near East. FAO, together with WHO and OIE, is preparing project documents for a regional brucellosis control programme according to guidelines established in collaboration with the countries of the region. The strategy of the programme is based on whole herd/flock vaccination of cattle, buffaloes, sheep, goats and camels regardless of age or sex. It is expected that after a period of 15 to 20 years of mass vaccination, the incidence of the disease will be brought to a level that will make the concept of disease eradication realistic. In the meantime, improved tools to fight the disease - a more potent vaccine and/or serological tests that can differentiate between infected and vaccinated animals - will have been made available to match the new goal.
Ticks and tick-borne diseases
The strategy of the FAO ticks and tick-borne diseases programme aims at promoting integrated tick and tick-borne disease control methods that include immunization when applicable and increasing awareness of the fact that tick acaricide resistance is spreading worldwide.
This approach has been the philosophy behind the Coordinated Programme for the Control of Ticks and Tick-borne Diseases in Central, East and Southern Africa currently entering its third phase. The programme's objective is the control of ticks and tick-borne diseases in cattle based on immunization against theileriosis, heart-water, anaplasmosis and babesiosis on a sustainable cost-recovery basis, coupled with strategic tick control.
To complement this approach, FAO supports work on the assessment of acaricide resistance on a worldwide basis in collaboration with the World Acaricide Resistance Reference Centre in Berlin, Germany, and through the organization of workshops such as those held in Zimbabwe, Malawi and Brazil in 1994.
Tick eradication is considered when special circumstances facilitate this concept, such as in the case of Amblyomma variegatum infestation in the Caribbean. After more than seven years of studies and negotiations, the Programme for the Eradication of Amblyomma variegatum and Its Associated Diseases, Heart-water and Dermatophilosis, from the Caribbean has been declared operational. This followed agreements between FAO and the Inter-American Institute for Cooperation on Agriculture (IICA) and FAO and the Caribbean Community Secretariat (CARICOM).
The programme has now begun, and work is in progress to map the occurrence of the tick through carefully designed surveys. A pilot eradication programme including maximum community participation has been launched in Anguilla, and this will be followed by the planning and execution of a large-scale eradication programme aimed at eliminating this serious pest from the region before the year 2000. The start of the programme is very timely as new foci of A. variegatum infestation have recently been reported from Dominica and new areas in Barbados.
African animal trypanosomiasis (AAT), transmitted by tsetse flies, is arguably the most important animal health constraint in sub-Saharan Africa. FAO, through its Programme for the Control of African Animal Trypanosomiasis and Related Development, provides the coordination required for a concerted approach to this complex, multifaceted problem. The FAO group dealing with insect-borne diseases has established a Geographical Information System (GIS) to quantify the economic and agricultural impact of AAT and to identify the areas where AAT control is most likely to translate into increased agricultural productivity. The disease is gradually assuming more importance in the semi-arid and subhumid areas. Control efforts are particularly successful in areas of expanding agriculture. A noteworthy development is the availability of novel bait techniques such as traps, targets and insecticide-treated livestock. FAO's contributions in this regard involve support to training, applied research and education of rural community groups.
Non-tsetse-transmitted animal trypanosomiasis (NTTAT) has a much wider geographical distribution and comprises the mechanically transmitted Trypanosomiasis evansi, or Surra, the sexually transmitted Trypanosomiasis equiperdum, otherwise known as Dourine, and the non-cyclical transmitted Trypanosomiasis vivax. The situation with regard to the distribution of T. evansi is also dynamic. Transboundary movement of humans and animals is believed to be associated with recent flare-ups of Surra in cattle in Indonesia and in carabaos, the swamp buffalo, in the Philippines. The latter outbreaks are being investigated under the FAO Field Programme.
With the successful conclusion of the screw worm eradication campaign in the Libyan Arab Jamahiriya supported by the Screw worm Emergency Centre for North Africa (SECNA) - which involved the active participation and collaboration of the Mexico/United States Commission on Screw worm - FAO has shifted attention towards the prevention of new outbreaks of both New World Screw worm (NWS) and Old World Screw worm (OWS), as well as of other exotic diseases. Training activities have so far mainly concentrated on North Africa. A proposal for NWS eradication in Jamaica has been submitted for donor funding. It is envisaged that this programme will lead to a large-scale eradication campaign in the Caribbean. Activities continue to improve techniques for NWS surveillance, control and the use of the Sterile Insect Technique (SIT) for eradication, in the anticipation that the results will yield significant benefits to all infested countries.
To a large extent, the great effort to control the major infectious and parasitic diseases has been successful in many parts of the world. It has not always resulted in the expected increase in livestock production and productivity, however. The reasons for this are many and varied, including a number of important production-related diseases, such as helminth infections, as well as reproductive disorders, nutritional factors and other non-infectious conditions that have been neglected. These are only part of a complex set of circumstances - other factors may include the lack of government incentives, erroneous price policies and a failure to deliver animal health service - that impede production.
During the last few years FAO has put more emphasis on the development of programmes for the control of helminths and non-infectious diseases. A number of activities have been aimed at increasing governments' awareness of the economic importance of these diseases and conditions and the constraints they put on efforts to accelerate livestock productivity. Activities include the publishing of informative materials and the generation of production data through pilot projects.
The rapidly increasing problem of anthelmintic resistance in sheep parasites is of great concern to FAO, and funds have been allocated to activities attempting to map the extent of the problem in developing countries. Through a recent survey supported by the FAO Technical Cooperation Programme (TCP), the situation in the southern part of Latin America has been evaluated. The results are critical, with more than 75 percent of farms showing problems of resistance to two of the three main groups of anthelmintics currently available for chemical control and a growing number showing resistance to all three. A consultancy to evaluate the situation in selected African countries has pointed out that similar problems exist in eastern and southern Africa.
Parasitic zoonotic diseases (hydatidosis, cysticercosis, trichinellosis) continue to be a major problem causing human suffering and significant losses from condemned meat and organs. FAO, in collaboration with the Veterinary Public Health Units of WHO and PAHO, is developing control strategies, and TCP has supported the evaluation of current programmes in some South American countries.
Micromineral deficiencies affecting animals (P. Cu. Co, Zn, Cu-Mo-S interactions) are well known in many districts of the world. They may greatly reduce animal productivity and food security for livestock owners and consumers alike. Because of the unavailability of mineral supplements or fertilizers, however, control cannot always be achieved, even though the knowledge for control is available.
Animal health delivery at herd level
FAO's livestock programme is increasingly emphasizing an integrated approach to livestock production and enhancement of food security. This strategy aims at focusing much technical and social expertise on priority livestock systems. Two such systems are mixed farming (crop and livestock) in high potential areas and peri-urban dairy production.
One arm of this integrated approach is a Herd Health and Production Programme (HH&PP) protocol, which includes the following interactive steps for delivering animal health within farming systems:
· agree with farm management on proposed production and acceptable risk targets;
· define and develop the tools and technologies required to collect the necessary data;
· interpret the data gathered from all sources;
· develop and agree upon a plan of action that includes concrete steps to reach the production and acceptable risk targets set in step one;
· monitor and evaluate progress and begin again at step one.
This approach allows private veterinary practice to deliver clinical and HH&PP services and defines areas of responsibility in a manner that promotes close cooperation between the private sector and public services through the implementation pilot programmes using the HH&PP protocol and by closely monitoring results. In addition, national consultative groups of interested persons for HH&PPs can be established to define further the concept and its delivery, to modify the approach to local conditions and to disseminate results. These consultative groups would include government and private-sector providers, producers of livestock inputs, educators and other interested parties.
The key tools for the international control of animal diseases are the availability of adequate information, proper services for the diagnosis of disease conditions, vaccines of appropriate quality and a functional veterinary service. Emerging trends in all four areas will affect future strategies for the control of animal diseases.
The international exchange of information concerning animal diseases is coordinated by OIE, which classifies infectious diseases into List A and List B, reflecting the contagiousness of the disease and its relative economic importance for international trade in animals and animal products. It is the responsibility of the Chief Veterinary Officer of each country to notify the international community, through the OIE, whenever an outbreak of an epizootic disease is encountered and periodically to update OIE on the disease situation in the country. Every year FAO publishes the FAO/OIE/WHO Animal Health Yearbook, which details the disease status of each member country of OIE, WHO and FAO.
The three international organizations have recently been evaluating the quality and impact of the information contained in the yearbook, and it is widely acknowledged that the official information given in the yearbook often represents the minimum known about the disease situation in many developing countries. Therefore, it is now well recognized that veterinary services need to develop sound information systems that would strengthen the services and improve the accuracy of disease incidence data and of diagnostic testing or surveillance results. This would also enable governments to devise appropriate livestock health and productivity improvement schemes at community level. OIE, together with FAO, the Inter-American Institute for Cooperation on Agriculture (IICA) and other agencies, has commissioned the development of such a computer program, HANDISTATUS. The objective of FAO and OIE is to provide a system that would greatly improve such an exchange of disease information, enabling each national veterinary service to be readily aware of the disease status of every member country of OIE and/or FAO. The international challenge will be to ensure that developing countries have access to the system and use it effectively.
A similar comprehensive disease-notification system for vesicular diseases has been developed for South America by PANAFTOSA, which, together with IICA and others, is currently developing various information systems. In this connection, the project "Prevención de las principales enfermedades exóticas de los animales en América Latina y el Caribe" (PROPEXAN) has a crucial complementary role. This project has been operating mainly in Central America, the Caribbean and Andean region countries. Based in Panama, it offers formal and practical in-service training to officers from countries in the region on animal health inspection, animal quarantine and the epidemiology, prevention, identification and eradication of exotic animal diseases.
Current trends in animal disease diagnostic technology are moving towards an improved flow of samples and data from herd level to the veterinary clinic, national laboratories, regional reference laboratories and world reference laboratories. While conventional techniques in veterinary diagnosis should not be overlooked, the use of modern diagnostic technology based on molecular biotechnology is dramatically gaining ground, and polymerase chain reaction (PCR), monoclonal antibody probes, enzyme-linked immunosorbent assays are now becoming standard, primary diagnostic tools in industrialized countries. There is a need for technology transfer, however, in order to establish these technologies in developing countries.
FAO has been addressing this issue from four aspects:
· Training and awareness of decision-makers. The approach has been through a series of awareness workshops directed at senior scientists in developing countries, enabling them to appreciate the potential offered by the new technologies in animal health. Where a defined role has been identified, FAO, either alone or with other organizations such as the International Atomic Energy Agency (IAEA), has convened special expert consultations to advise on the specific subject matter.
· Practical training of technicians and laboratory scientists. This has taken the form of training at the bench in specific techniques for specific purposes. The most extensive programme has been the training of personnel from developing countries in the enzyme-linked immunosorbent assay (ELISA) technology conducted by the Joint FAO/IAEA Division. Through this initiative, it has been possible to develop surveillance programmes such as the rinderpest sero-monitoring network for GREP and the FMD sero-monitoring network that is being developed in South America in collaboration with PANAFTOSA.
· FAO biotechnology networks. These are currently being developed in eastern Europe, India and South America. The activities in South America are primarily geared towards strengthening the regional capability of diagnosing those diseases that are not yet covered by the excellent programme of PAHO. Thus, the FAO Regional Office in Latin America and the Caribbean has been developing a network of leading laboratories, called REDLAB, in order to promote the exchange of expertise, information and reagents through a system of TCDC (Technical Cooperation among Developing Countries).
· Global monitoring of pathogens of major diseases. This is being achieved through a network of reference laboratories selected on the basis of their established expertise in providing referral diagnosis for the disease(s) for which the laboratory is designated. For example, for FMD, FAO has designated the Pirbright Laboratory of the United Kingdom's Institute for Animal Health as the FAO World Reference Laboratory, while PANAFTOSA is the FAO Regional Reference Laboratory for the Americas. Similarly, FAO has just designated the Pirbright Laboratory as the FAO World Reference Laboratory for Rinderpest to support GREP. The data being generated by the network of reference laboratories are proving to be of crucial importance in molecular epidemiology and global disease monitoring. The networks of FAO, OIE and WHO complement each other.
Recent trends in vaccine development have involved three principal issues: vaccine technology, vaccine quality and vaccination monitoring.
Developments in vaccine technology with an immediate impact have been associated with the consolidation of cell culture and fermentation technologies, gene deletion, gene manipulation of vaccine viruses and viral-vector recombinant vaccines, while subunit genetically engineered or synthetic peptide vaccines, so far, have not yielded spectacular results. FAO hat published a comprehensive review of and guidelines for veterinary vaccines.
Perceptions and attitudes regarding vaccine quality have also been evolving. It is now widely accepted by most developing countries that vaccines should be manufactured under conditions of good manufacturing practices (GMP). The concept that FAO currently promotes is one that was originally provided by the United Kingdom Veterinary Medicines Directorate and that was endorsed by the FAO Expert Consultation on Quality Control of Veterinary Vaccines in Developing Countries held in 1991, namely:
"Medicines (vaccines) must be manufactured with appropriate quality control procedures in premises that are inspected and licensed; the ingredients must be of appropriate purity, in correct proportions and correctly processed; the containers must be robust with secure closure; the labelling must be accurate and informative."
In Africa, these concepts of vaccine quality have been championed by the Pan African Veterinary Vaccine Centre (PANVAC), which is a programme of the Organization of African Unity/Interafrican Bureau for Animal Resources (OAU/IBAR) with technical assistance from FAO. The greatest impact of PANVAC has been in the improvement of the quality of rinderpest vaccine, as evidenced by the fact that the proportion of African-produced vaccine lots meeting international standards of quality has risen from 33 percent in 1985 to about 80 percent in 1992. Also, the quality of testing has reached international standards as reflected by the diversity of causes for vaccine rejection.
In Latin America and the Caribbean, PANAFTOSA/PAHO has promoted and trained technical personnel in the production, quality control and use of FMD vaccines. The Pan-American Institute for Food Protection and Zoonoses (INPPAZ)/PAHO has played an important role in training in quality control and production of vaccines against rabies and brucellosis.
The advent of ELISA technology has made sero-monitoring a practical reality for vaccination monitoring. The Pan-African Rinderpest Campaign (PARC) sero-monitoring network coordinated by the Joint FAO/IAEA Division is the most extensive sero-monitoring network in the world. The crucial elements of this network are the application of the ELISA technique using standardized and highly specific reagents, standardized equipment and computer software, supported by a well-controlled quality-assurance programme for the reagents and techniques by consistent technical advice from FAO/IAEA personnel and the scientist responsible for developing and standardizing the technique. A standardized training programme is also included for all individuals responsible for the national testing programme. It is now FAO policy to extend the approach to other parts of the world involved in GREP. A similar scheme is being developed by the Joint FAO/IAEA Division to monitor the effectiveness of FMD and brucellosis control programmes in South America.
A strong veterinary service with a clearly defined chain of management and reporting command is a prerequisite for effective control of animal diseases. The veterinary service should also have adequate laboratory support for disease diagnosis and surveillance. The national Chief Veterinary Officer (or Director of Veterinary Services) should have a direct line of functional command to the laboratory regarding responsiveness to priority contagious diseases and aspects of their control requiring laboratory support.
An effective veterinary service does not necessarily mean government action in all veterinary matters. Schemes for fostering a healthy private veterinary programme need to be strongly supported by national veterinary associations and international organizations. From the point of view of controlling animal diseases, it should be noted that a disease outbreak is initially encountered by the farmer, herder or pastoralist or those responsible for on-farm routine animal health activities, normally private veterinary personnel and/or community-based extension workers. Structures that encourage licensing of private veterinarians to undertake such activities as routine vaccinations, on-farm testing and even clinical inspections need to be developed. Such licensed veterinary inspectors should be adequately remunerated by the government for activities subcontracted to them, however, and they should be allowed to charge fair fees for services rendered.
Control of animal diseases demands that national veterinary services operate within both a regional and an international context. An outbreak of a major epizootic disease in one country is of immediate concern to neighbouring countries and should be reported to OIE and FAO, and, in the case of zoonotic diseases, to WHO as well. To be effective in controlling epizootic diseases, each country within a region must have a strong national veterinary service that freely exchanges information about disease with other countries. And as control of epizootic diseases must often take "public interest" into account more than just "farmer interest", services are largely government financed and directed.
It is evident from the trends in the international control of epizootic diseases that countries, particularly developing countries, will need to strengthen and modernize their veterinary services and not regard them simply as a mere component of an agricultural extension service.
A prerequisite for economic livestock development is the containment of infectious and epizootic diseases. For major epidemic diseases (OIE List A), the international goal is to achieve disease eradication rather than simply control. This calls for the concerted strengthening of all aspects of veterinary services and a clearly defined chain of management command in member countries.
The control of endemic diseases, whether caused by bacteria, viruses or parasites, is often approached differently in neighbouring countries. Harmonization and standardization of control strategies is being pursued.
Control of chronic or non-infectious, and production diseases requiring the delivery of strategic clinical veterinary services at farm level is also under discussion The magnitude of losses resulting from non-infectious and production diseases needs to be recognized, and government services need to accommodate the private sector in their effort to deliver veterinary services on a continuous basis to livestock owners. Legislation should be in place permitting private veterinary practices and manufacture or import of essential inputs. All these services need to function with the goals of improved food productivity, increased food security and enhanced producer profitability.
Tools to facilitate animal disease-control activities are also under discussion.
FAO's Animal Health Service, through its many various interventions, continuously attempts to promote the concept of a comprehensive veterinary service that relies on an effective public service and a viable private sector.