Animal health surveillance: navigation amidst the flotsam of human frailty and fiscal inertia.

National veterinary services monitor endemic, emerging and exotic disease situations. They intervene when epidemic tendencies demand. They unravel complex disease situations. They do so as monopolies, in environments of political influence and budgetary restraint. When human, animal health and trade protection dictate, they design import or domestic disease control programs. As much as 80% of program expenditures are on surveillance. Their initiatives are scrutinized by treasuries from which they seek funding, industries from which they seek collaboration and trading partners from whom they seek recognition. In democracies, surveillance and control programs are often the products of a complicated consultative process. It involves individuals who have both a commitment to improving an existing animal health situation and access to the required resources. The generations that designed traditionally risk-averse national surveillance and control programs have given way to a new one which is more epidemiologically informed. Their successors design programs bearing epidemiologically based improvements. The transition, however, has not been overwhelmingly welcomed. Expenditures on surveillance are tolerated out of fear during outbreaks of foreign or re-emergence of indigenous disease. Between epidemics, they decline at the hands of producers' unwillingness and budgetary restraint. Human nature responds to the high cost of surveillance in forms ranging from naïveté through to conspiracy. While legislation cannot subdue such human frailty, several other opportunities exist. Education can remove the majority of problems caused by ignorance, leaving the minority that arise intentionally. Technology decreases the high cost of testing which tempts individuals to cut corners. International standards assist National Veterinary Services to overcome domestic resistance.

Portrait of the national veterinary service as a surveillance continuum.

National veterinary services emerged in response to the animal disease challenges of centuries past. Their often singular preoccupation with exogenous disease preclusion yielded, by the early 1900s, to parallel commitments to control a number of serious indigenous, zoonotic infections. Advances in clinical pathology and epidemiology opened the door in many countries to disease, if not agent, eradication initiatives by the latter part of that century. The attending interval witnessed the explosive growth of international trade and the emerging or re-emerging conditions that threaten to accompany it. Animal disease agents, their hosts and the environments within which they interact vary considerably from nation to nation. Depicted as a medieval metaphor, the exogenous cluster around the walls of the castle, awaiting entry upon the next uninspected, unsuspecting fomite or beast. Some of these threats reside comfortably within the structure's bedding and detritus, sapping the vitality of its residents until detected and exterminated. Others emerge from the least expected crevices, growing insidiously or explosively in tandem with changes wrought by humans or nature. In anticipation of, or in response to, these myriad challenges, national veterinary services mount surveillance campaigns. From the national survey that denies the presence of exogenous disease to the post-eradication assessment that confirms its demise, surveillance forms the sensory acumen of the service. From the passive assessments that detect the emerging to the active regimens that plot progress against the indigenous, they form a continuum that defines the very nature of the national veterinary service.

Risk management of the transmissible spongiform encephalopathies in North America.

As North American Free Trade Agreement partners, Canada, the United States of America (USA) and Mexico apply independent but harmonised transmissible spongiform encephalopathy (TSE) risk management strategies in observance of Office International des Epizooties guidelines. The divergence between bovine spongiform encephalopathy (BSE) risk management approaches in North American and Europe reflects comparatively reduced external and internal BSE risks in North America. The external quarantine and internal surveillance measures adopted for BSE respond to several iterations of national risk assessments initiated in the early 1990s and revised as recently as 2002. Feed bans applied since 1997 to preclude establishment of BSE also bear the potential to limit intra-species and inter-species exposure to scrapie, chronic wasting disease (CWD) and transmissible mink encephalopathy (TME). Surveillance continues for the four TSEs through collaborative efforts of national and sub-national veterinary infrastructures and accompanying laboratory networks. Mexico has never identified the presence of any TSE. The last diagnosed case of TME in North America dates back to 1985. Since the only recognised appearance in Canada through an import from Great Britain in 1993, BSE has not been detected in North America. Scrapie and CWD remain at generally low prevalence in Canada and the USA. Independent but harmonised eradication programmes target elimination of the latter two diseases.

Traceability in cattle and small ruminants in Canada.

Traceback systems for cattle and small ruminants are of international concern after the outbreaks of bovine spongiform encephalopathy in the European Union and foot and mouth disease in the United Kingdom and South America. Implementation of a national or international identification system depends on meeting a balance between cost, reliability/durability, ease of use, data transfer speed, protection from fraud, avoidance of entry into the food chain and animal welfare issues. As of 1 January 2001, Canada has instituted a national identification programme for cattle, which will have annual operating and administrative costs of Can$0.20 per head, excluding ear tags. The system will provide herd of origin traceback and individual animal identification by ear tags for all beef cattle. A number of identification technologies are available that would have advantages over visual tags, but these are currently too costly without government support (electronic identification, deoxyribonucleic acid [DNA] fingerprinting), too slow (DNA fingerprinting) or have not been tested sufficiently (retinal imaging) to warrant mandatory inclusion in a national traceback/identification system.

The application of risk analysis to international trade in animals and animal products.

In an era when arduous land and sea journeys separated exporting and recipient nations, the duration and stress of transport dictated localised sourcing of stock and provided an implicit quarantine. Clinically latent infection, which remained undetected prior to embarkation, often surfaced and was eliminated before reaching the importing country. Many nations which would not accept the risk of importation, on clinical grounds, could effectively isolate themselves by prohibiting entry. Passive acceptance characterised much of the response of industry to the perceived wisdom behind such decisions. Advances in transportation technology now permit the accumulation of an export consignment from across an entire country. The assembled shipment is a sentinel for the infection experience of the national herd. The journey to the final destination is measured in hours, rather than weeks. Parallel diagnostic and epidemiological advances face the challenge of compensating for the risks attendant in such widespread and rapid sourcing of stock. Nations which judge the risks as unacceptable face a concerted legal challenge on a series of levels, both domestic and international. Refusal of legal importation can be circumvented easily through the smuggling of germ plasm. National Veterinary Services must respond to the economic, social and political realities of this new international trading environment. The means of facing this challenge through quantitative risk analysis are described. The theory of risk analysis, as well as the qualitative and quantitative evolution of the import applications of this analysis, is explained. Current challenges and potential solutions are discussed.

National Swine brucellosis survey.

A national survey was conducted in 1985 to investigate the brucellosis status of the Canadian swine herd. Serum samples were collected from cull sows slaughtered over a forty week period in 1985; 15,707 samples were suitable for brucellosis testing, and 48 (0.31%) gave some degree of reaction on the buffered plate agglutination screening test. All 48 samples were negative on the 2-mercaptoethanol and modified complement fixation test. We therefore conclude that the Canadian swine herd remains free of brucellosis.