Role of the Veterinarian in Public Health/One Health
Most veterinarians contribute, directly or indirectly, to public health goals and outcomes. Veterinary public health contributions can be categorized into six core domains, described below.
Most private veterinary practitioners contribute to public health during routine practice. Both large and small animal practitioners become skilled diagnosticians for acute and chronic diseases of animals that may affect the owners and their families and the surrounding communities. Specific examples of public health activities include performing routine health examinations, maintaining immunization regimens, implementing parasite control programs, advising on the risks of animal contact for immunocompromised individuals, facilitating the use of guide and service dogs for people with disabilities, and promoting the benefits of the human-animal bond for the disabled and elderly, as well as war veterans and others suffering from post-traumatic stress disorder. Communities are best served when veterinarians approach collective health issues with a “herd health” perspective, applying relevant epidemiologic principles. In addition to these direct services, veterinary practitioners report disease events and trends to state public health and regulatory agencies, collaborate with human medical counterparts on zoonotic diseases, and advise local health boards and commissions. These relationships would not exist if not for the inextricable link between animal and human health.
In addition to managing direct zoonotic diseases in animals, veterinarians also diagnose, investigate, and control indirect zoonoses and non-zoonotic communicable diseases that affect human health. Examples include West Nile disease and coccidioidomycosis among pet animals, and bovine leukosis, foot and mouth disease, fowlpox, and many other diseases that affect the food supply, the national economy, and the livelihood of the nation’s farmers.
Many factors contribute to the increasing vulnerability of livestock to infectious disease. These include increasing intensity and concentration of production agriculture, genetic convergence of many food-producing species, accessibility of livestock to external contact (despite rigorous biosecurity measures), scale and frequency of animal transport (domestic and international), increasing size of feedlots, lack of immunity to foreign animal diseases, the relatively porous nature of national borders, and the significant shortage of trained foreign animal disease diagnosticians and epidemiologists. Although many significant diseases transmitted by food-producing animals (eg, brucellosis, tuberculosis, coxiellosis/Q fever, etc) have been eradicated or controlled in North America and Europe by pasteurization and inspections at slaughter, still many others are seemingly ubiquitous (eg, listeriosis, salmonellosis, staphylococcosis, etc) and cause a significant fraction of the national burden of foodborne morbidity and mortality. Each year in the USA, there are reported approximately 20,000 foodborne illnesses, 4,200 hospitalizations, and 80 deaths, most of which are caused by pathogens of animal origin.
The challenges of recognizing resurgent infectious diseases and developing novel therapeutics have placed unprecedented emphasis on managing and maintaining laboratory animal colonies for research and diagnostic efforts. Providing these services both successfully and humanely falls to the veterinarians in these institutions. Because few nations have the individual capacity to provide these services internally, increasing emphasis is being placed on international collaboration and reference centers, many of which focus on zoonotic diseases and comparative medicine. Because most outbreaks of zoonotic disease occur in tropical regions devoid of local surveillance and diagnostic and response capacity, the role of these international collaboration and reference centers likely will expand, requiring larger numbers of trained, experienced veterinary personnel.
Building on the information from public health surveillance, research institutions must follow with a greater understanding of the interactions between hosts, parasites, vectors, pathogens, and the environment. Establishing a causal link between human and animal disease relies on such research efforts, often through some combination of molecular studies, mathematical theory, and experimental epidemiology, using either field or laboratory research. As highlighted by the World Health Organization, research of endemic and resurgent zoonoses is often handicapped by a lack of basic knowledge of host-parasite interactions. For many zoonotic species, even the route of transmission to people remains uncertain. In some cases, the molecular biology of the agents in human and animal hosts may be very different. For example, there are major research efforts aimed toward the identification of virulence factors for E coli O157:H7 and the reasons for their differential expressions in people and cattle.
Although training new veterinary practitioners and disseminating new capabilities to those already in practice falls largely on the nation’s academic (especially land-grant) institutions, virtually all veterinarians help educate the public on the threat of infectious and noninfectious diseases. At the collegiate level, this will increasingly involve multidisciplinary relationships between schools of medicine, veterinary medicine, sociology, and basic sciences. Enabling appropriate knowledge and awareness among the public requires a skillful blend of risk perception and risk awareness, especially because community stakeholders play significant roles in risk resolution. Most epidemiologists are employed by governmental or industrial stakeholders that have not historically been viewed as valid proxies for the public. This represents an important opportunity, perhaps responsibility, for veterinary practitioners to remain knowledgeable about disease threats and credible sources of that knowledge for their communities.
Ensuring that animal drugs, vaccines, and devices are safe and efficacious is a shared responsibility between the FDA, the USDA, and the EPA. In general, the FDA, specifically the Center for Veterinary Medicine, regulates animal drugs, animal feeds, and veterinary devices, whereas the USDA regulates animal vaccines and biologics. Specific to pesticides, FDA regulates certain flea and tick products for animals, whereas the EPA regulates others. Within each of these governmental agencies, veterinarians serve to encourage the development of novel products and, at the same time, protect the consumers of those products from false or misleading claims.
Another important function regarding biologic agents is the regulation of their storage, use, and transfer. Because of inherent virulence and transmissibility, access to many disease pathogens, termed select agents, has increasingly been limited to legitimate facilities for legitimate uses. The Federal Select Agent Program is jointly administered by the CDC and the USDA’s Animal and Plant Health Inspection Service (APHIS). This effort oversees the possession, use, and transfer of certain biologic agents and toxins that have the potential to pose a severe threat to the public, to animal or plant health, or to animal or plant products.
Significant numbers of veterinarians are employed at various levels of state and federal government. More than 3,000 veterinarians are employed at the federal level, nearly two-thirds of which are with the USDA. Other federal agencies employing large numbers of veterinarians include the DoD (Army and Air Force) and DHHS (CDC, FDA, and NIH). Public health programs comprise the vast majority of these opportunities, with direct animal care being a minor fraction. Examples include oversight of food safety inspection programs, disease surveillance and outbreak investigation, laboratory animal care, biomedical research, and public health program management and leadership.
At the state level, each department of agriculture typically has a State Veterinarian who is responsible for protecting the livestock, poultry, and aquaculture industries directly, and the public indirectly, through the prevention, early detection, containment, and eradication of economically important livestock, poultry, and fish diseases that, in many cases, are transmissible to people. The State Veterinarian regulates the importation, transportation, and processing of animals and is responsible for the control and eradication of poultry and livestock diseases, regulation of fish farming, and emergency response programs. Welfare of farm animals is monitored, and when necessary, the Office of the State Veterinarian conducts investigations and prosecutions relating to cases of cruelty to animals.
Currently, 41 states and territories employ veterinarians in their state health departments as State Public Health Veterinarians (SPHVs). SPHVs generally work in zoonotic disease control and prevention, directly focusing on protecting public health. They typically are located in health department divisions of epidemiology, toxicology, or environmental health.
A final category of governmental activity is legislative; a relatively small number of veterinarians serve at various levels to promulgate laws, rules, and regulations that serve to protect public health, domestic preparedness, and national defense. Veterinarians serve in the United States House of Representatives, in senior leadership positions of several United States Cabinet-level departments (including USDA, DHHS, DoD, and DHS), and as legislative liaisons for professional associations such as the AVMA. They are assisted in their legislative efforts by the communicative action of practicing veterinarians across the nation. It is through this pathway that ideas and issues are effectively transmitted to legislators and translated into improved legal and policy outcomes.