Airborne transmission of foot-and-mouth disease in pigs: evaluation and optimisation of instrumentation and techniques.

Foot-and-mouth disease (FMD) can be transmitted in a variety of ways, one of which is through virus exhaled into the air by infected livestock. It is clear that where there is close contact there will be a range of possible mechanisms for the transmission of disease from animal to animal, including the airborne route if simple barriers between livestock exist. In transmission of FMD over longer distances, airborne transmission represents a significant challenge to the veterinary services in that the mechanism is essentially uncontrollable if the primary source of the disease is not contained. In the event of an epidemic of FMD, such as the one experienced in the United Kingdom in 2001, it is important for disease control purposes to understand the contribution made to the overall spread of disease by aerosolised virus. This assessment is based on a combination of measurements made in the laboratory and through clinical observations in the field. To date, laboratory measurements have used a number of instruments that were not specifically designed for working with FMD virus or whose performance have not been fully compared and documented. This paper compares four samplers and describes the method by which samples are processed. Overall it is concluded that there is no optimum air sampling instrument which could be successfully employed for all situations but the work provides guidance to those wishing to make measurements in the future and establishes a baseline against which any new samplers can be compared.