Use of molecular epidemiology in veterinary practice

The advent of molecular or DNA-based typing methods for microorganisms has opened up a new world of possibilities in veterinary epidemiology. Molecular epidemiology deals with the detection of sources and transmission dynamics of microorganisms using molecular methods and with the identification of determinants of health, disease, spread, and control. Examples of such determinants include virulence genes, antimicrobial resistance genes, and potential vaccine targets. Using molecular epidemiologic methods, it is possible to monitor global spread of pathogens, to identify highly virulent or highly contagious strains of pathogens, to differentiate between persistence and reintroduction of infectious agents in the farm environment, to distinguish between chronic and recurrent infections at the animal level, to detect transmission of vaccine strains, and to classify the epidemiology of an infectious disease as contagious or environmental. The use of molecular tools provides a level of detail and insight that is not available with traditional culture methods or species-level identification of viruses, bacteria, protozoa, or parasites. Molecular epidemiology can pinpoint not only sources of infection or contamination in humans, animals, farm environments, and animal products but also environmental or host factors that contribute to the introduction and spread of microorganisms. As a result, old paradigms can be reassessed, specific targets for intervention and control can be identified, and the effectiveness of control measures can be monitored. Molecular epidemiologic methods have been used with incredible success in global, national, regional, local, farm-level, and animal-level studies. Now that techniques are becoming increasingly user friendly and affordable, they have started to make their way into veterinary diagnostic laboratories. Although their routine implementation still faces challenges (eg, in terms of cost recovery and turn-around times), it is inevitable that in another few years, molecular methods will be among the routine tools that are used in veterinary epidemiology to promote veterinary public health and to improve production-animal health management.