Veterinary Medicine, the science dealing with health and disease in vertebrates, has application to 4 broad domains: domestic animals, wildlife, comparative medicine and Public Health. In Canada in 1987, there were approximately 5700 professionally active veterinarians; this number will rise by 250 annually. Veterinarians are distributed in roughly equal numbers in private rural practice, private urban practice and institutional employment, but the proportion in urban practice is rising. Veterinary education requires at least 2 years of university preveterinary training, followed by 4 years of professional instruction. Postgraduate training in clinical or research programs is undertaken by 10-20% of veterinary graduates. The veterinary curriculum is similar to that of human medicine. The veterinary profession is organized nationally in the Canadian Veterinary Medical Association and in each province as a provincial association.
Clinical veterinary medicine, including food-animal, small-animal and equine practices, or some mixture of these specializations, provides primary health care to an owner's animals. In rural settings, veterinarians deal with all types of animals, most being food animals. In urban centres, many veterinarians practise exclusively on pets or horses. Veterinarians practise singly, in partnerships or in corporations, depending on personal preferences. Income derives from fees charged to clients. Veterinary practitioners must be licensed by a provincial authority, normally the provincial veterinary association, upon successful completion of appropriate examinations.
Food-animal practice involves dairy and beef cattle, pigs, sheep, goats and poultry (see animal agriculture). Animals are treated on the farm or in a large-animal hospital. Food-animal practice may be subsidized by provincial or municipal governments. Subsidies vary from hospital grants, as in Manitoba, to direct assistance in paying professional fees, as in Québec, which has the only "veticare" scheme in N America. In NB all food-animal veterinarians are employed by the province. Veterinarians dealing with poultry disease tend to specialize and are usually employed by government or private industry.
Small-animal practice deals most commonly with dogs and cats but can also include rabbits and rodents (eg, mice, gerbils), birds (eg, budgerigars, parrots, finches), fish and more unusual animals (eg, primates, reptiles).
Federal, provincial and municipal governments employ veterinarians to provide services that protect animal and human health. Under the departments of agriculture, health, environment and wildlife, veterinarians conduct laboratory diagnosis, field investigation, food and animal inspection, administration, research and extension education. University veterinarians teach and do research in veterinary medical science. Most are employed in Canada's colleges of veterinary medicine. A few are also located in faculties of agriculture or medicine or departments of biology and in specialized research institutions such as the Veterinary Infectious Disease Organization (VIDO), U Sask. A few veterinarians find employment in industry, particularly in companies producing or selling pharmaceutical and biological products. Their work includes research, sales, administration and extension of both advice and information to veterinarians in animal-related industries.
The growth of knowledge and technology in veterinary science is motivating some veterinarians to specialize in a branch of veterinary science (eg, internal medicine, pathology, dermatology, microbiology, radiology) or in a class of animal (eg, laboratory animals, food animals, horses, small pets). To specialize, a veterinarian must have appropriate practical experience, must undertake formal postgraduate training and must pass rigorous examinations. Most specialists are employed by institutions. Many practising veterinarians confine their work to one or a few species, but this limitation is not considered specialization, in the formal sense, by the profession.
In Canada about one-half of the cash income from farms comes from animals or animal products. The protection of the health of this resource is the responsibility of practising veterinarians and appropriate government agencies. Food-animal practitioners are concerned with the treatment and prevention of indigenous diseases in animals on individual farms. Their primary objective is the economic benefit of the owner; thus, treatment must be economically sensible or must be imperative because of humane considerations. In food-animal practice, the major emphases are on prevention of disease and on reproductive management for optimal productivity (see animal breeding). Practitioners must be skilled in diagnosis, surgery, livestock reproduction practices, use of drugs, and analysis of production data. Preventive medicine involves monitoring the health of individual animals and of the herd by measuring, recording and analysing production performance.
Agriculture Canada is responsible for major legislation protecting Canada's livestock from diseases identified by law as reportable, and for excluding from Canada exotic diseases such as foot-and-mouth and African swine fever. International travel and transportation of animals is a constant threat because of the risk of introducing exotic, contagious animal diseases. The department's enviable record in controlling such diseases gives Canada's livestock access to world markets. Federal programs also seek to control or eradicate important indigenous diseases, eg, rabies, tuberculosis, brucellosis (contagious abortion). A milestone was reached in 1985 when the Canadian domestic cattle population was declared free of brucellosis. Federal veterinarians also ensure the quality and safety of food-animal products, eg, through meat inspection (see Food Legislation).
Major health problems in livestock include high neonatal mortality from intestinal and respiratory diseases, poor reproductive efficiency and suboptimal production associated with subclinical disease and mismanagement. Veterinary research in food-animal disease and health maintenance is conducted principally by the federal government and the universities. Government research gives priority to detection and control of contagious diseases, especially those reportable by law. An example of an important Canadian contribution to the control of animal disease worldwide is a vaccine against neonatal diarrhea in calves, caused by certain strains of the bacterium Escherichia coli. Developed by VIDO, the vaccine was marketed by a Canadian firm. New technology in reproduction (eg, embryo transfer, freezing embryos) promises to make livestock production more efficient and to promote more rapid genetic improvement.
Wildlife, including animals, fish and birds, is an especially rich component of Canada's natural environment. In addition to its intrinsic value, wildlife provides food, clothing and economic benefits, particularly to native people, and is a major source of recreation for naturalists and hunters. Wild animals also serve as monitors of environmental problems. Veterinary medicine is among the professions taking an active interest in health and disease in these populations. Wild animals are important in the epidemiology of certain animal and human diseases (eg, rabies, tularemia) because they act as disease reservoirs. For example, tuberculosis and brucellosis are present in bison in Wood Buffalo National Park.
Public Health, Laboratory Animals and Comparative Medicine
Public-health veterinarians help ensure a wholesome supply of food of animal origin. This complex government responsibility involves the detection of infectious agents and undesirable chemicals (eg, feed additives, drugs, environmental pollutants) in meat, milk and eggs. Zoonoses are diseases transmissible from animals to humans. Over 200 such diseases may exist in wildlife (eg, rabies, western encephalitis, tularemia, plague) or in domestic animals (eg, tuberculosis, brucellosis). Veterinarians help protect humans from zoonoses, eg, through the immunization of dogs against rabies. The veterinary profession informs the public about other potentially dangerous factors in the relationship between animals and man, eg, the connection between rabies and stray dogs.
Laboratory animals are widely used in medical research and in the identification and investigation of hazards to human health. The care and use of such animals has become an area of specialization. Laboratory animals provide natural and experimental models of human or animal diseases and their study is essential to a better understanding of disease. A primary concern of those working with laboratory animals has been the assurance of high standards of humane care. The Canadian Council on Animal Care has been very successful in working toward this end (see Animal Issues; Humane Societies).
Comparative medicine is the study of phenomena that are basic to diseases of all species, through research into natural and experimental disease. Insights gained can be extrapolated to diseases of individual species, including man. Veterinarians and others in the field have recognized many naturally occurring animal diseases that may be used as models for similar or identical conditions in human or other animals. Such model diseases may be numerous because the phenomena of disease causation are similar throughout the animal kingdom.
The study of experimental disease in animals has facilitated major advances in medicine, eg, the elucidation of germ theory and the discovery of insulin. Comparative medicine is also responsible for the discoveries that arthropods act as vectors of infectious disease and that viruses cause cancer. The transmission by ticks of a protozoan disease of cattle (Texas fever) was the first demonstration that such a phenomenon was possible, and it led to an understanding of the transmission of malaria and other diseases by mosquitoes and other arthropods. That viruses can cause cancer was first demonstrated in chickens and subsequently recognized in many animals.
A Canadian contribution to comparative medicine was the discovery of a mycotoxin in 1922 by Francis Schofield of the Ontario Veterinary College. He found that mold growing on damp sweet clover produced a toxin which caused a fatal bleeding disorder in cattle. This toxic material, dicoumarol, a powerful blood anticoagulant, is now used medicinally in humans. Many other mycotoxins have since been described. The discovery of dicoumarol also portended the discovery of other biologically active materials produced by molds, eg, antibiotics.
Companion Animals or Pets
There are several million pets in Canada. Health services are provided almost entirely by private practitioners who must build up their own hospitals or clinics and employ animal-health technicians and other support staff. Facilities accommodating 50-100 animals and providing equipment for surgery, radiology, laboratory diagnosis and various other specialties are common. The capital investment required to establish a hospital is substantial. Small-animal medicine is similar to human medicine, since pet animals are normally kept for a natural life span and succumb to the infirmities of old age as well as to disease. There are fewer economic constraints on medical treatment of pets in comparison to food animals.
Work and Recreation Animals
The health care of domestic animals used in recreation or work is a major field of veterinary medicine. Canadian society is highly mechanized; consequently, animals have a limited role in performing work. In recent years, horses have increased in number: a few are still used as draft animals and for herding cattle, but most are used for recreation and sports (see Harness Racing; Thoroughbred Racing). These athletes of the animal world are prone to injuries and to problems associated with racing or other sports activities. Many veterinarians confine their practice to horses and become skilled at dealing with their special problems, for example, lameness. Dogs are used for a number of chores: herding sheep, pulling sleds and providing surrogate eyes or ears for handicapped individuals. Their occupational health needs are met by small-animal practitioners.
Fibre and Furs
Sheep, the only significant animal fibre producers in Canada, are attended by veterinarians, usually in preventive medical programs. Several other animal species provide woollike fibres that can be used to make clothing. In Canada the native muskoxen produce a high-quality fibre called qiviut. In the future, northerners may manage muskoxen in some form of semidomestication to allow the harvesting of qiviut. Veterinary researchers are studying the muskox with a view to its more intensive management.
Fur-bearing animals are raised across Canada. Economically important species are mink and fox. Disease control is crucial to the success of fur farming, since the relatively close confinement of a large number of animals makes them vulnerable to various highly contagious diseases, eg, distemper, parvovirus intestinal infection. The latter was first described at Fort William and bears this name. Mink have provided an important example of how animals serve as monitors of chemical pollution. The poor reproductive performance developed by ranch mink fed a diet of fish from Lk Michigan was shown to be caused by PCBs (polychlorinated biphenyls) in the fish. This incident was the first indication that PCBs and related compounds were a biological hazard.
The health and reproductive performance of zoo animals are the principal concerns of zoo veterinary medicine, an emerging practice specialty. High population density and unnatural feeding conditions make zoo animals particularly vulnerable to disease and poor reproductive performance. Canada's zoos and aquariums employ veterinarians full- and part-time.
Fish and Aquatic Species
Health management of fish or other marine food sources in nature and in captivity is an emerging concern. Confinement of fish in ponds or by mechanical devices to give high population densities puts them at increased risk from infectious disease. The emergence of fish farming (aquaculture) as an economically viable industry depends on an assured supply of disease-free stock. In Canada various aquatic habitats are adaptable to fish farming, including ocean waters, streams, lakes and prairie sloughs.