At the third meeting of the Office International des Epizooties (OIE) Sub-Commission for Foot-and-Mouth Disease in Southeast Asia in February 1997, it was acknowledged that foot-and- mouth disease (FMD) is still present in most Southeast Asian countries, in particular Bangladesh, Cambodia, Laos, Malaysia, Myanmar, the Philippines, Sri Lanka, Thailand and Vietnam (OIE Press Release 1997). Direct losses equivalent to more than a quarter of the cattle, buffalo and pig production and considerable indirect losses for agriculture due to a shortage of working cattle are the consequences of FMD. Generally, the incubation period for FMD is three to four days, but can range from two to fourteen days (Kitching and Mackay 1995). Up to 80 per cent of ruminants may become persistently infected after recovery from FMD, which means that these carriers can initiate fresh outbreaks (Donaldson 1994a). Immunity to FMD following vaccination is short lived and even vaccinated animals exposed to infection may become carriers. Moreover, even after recovery from infection with one serotype, animals still remain susceptible to infection with any of the other six types (Kitching and Mackay 1995). These factors outline some of the difficulties involved in any attempts of FMD elimination.