The Role of Carrier Animals in the Transmission of Foot and Mouth Disease

Foot and mouth disease (FMD) is a viral infection capable of rapid horizontal spread between infected and susceptible cloven-hoofed animals. In the vast majority of cases transmission occurs following physical or close contact between acutely infected and susceptible individuals: high levels of FMD virus occur in all secretions as well as aerosols derived predominantly from the respiratory tract of animals for 1 to 3 days prior to, and for 7-14 days after, the development of lesions (97, 30, 67, 98, 38, 113). Urine and faeces contain variable but generally lower quantities of virus (67, 114). Less frequently the virus is spread mechanically between infected and susceptible animals by contaminated animal products (e.g. milk and meat), fomites, vehicles or people (67). Rarely, FMD virus is transported over long distances by air-borne aerosols across land (for up to about 10 km) or water surfaces (sometimes hundreds of kms) if suitable climatic and other circumstances prevail (52, 38).