Foot-and-mouth disease in the Americas: epidemiology and ecologic changes affecting distribution.

Foot-and-mouth disease(FMD) was first recorded in South America (SA) circa 1870, in Buenos Aires, Argentina, in Uruguay, and in southern Brazil as a result of the introduction of cattle from Europe during the early days of colonization. Livestock production to trade with neighboring countries was established in the La Plata Region, and the trade of livestock and products with Chile, northeastern and central western states of Brazil, to Peru, Bolivia, and Paraguay spread FMD, which reached Venezuela and Colombia in the 1950s and finally Ecuador in 1961. The traditional forms of livestock husbandry influence the diffusion and maintenance of the FMD virus (FMDV) in different areas. Cattle production in SA depends mainly on a strong relation between cattle-calf operations and fattening operations in a complementary cycle, revealing the vulnerability and susceptibility of these areas to FMDV. Understanding the relationship between time-space behavior of the disease and the forms of production defines the FMD ecosystems, a key concept to elaborating the control/eradication strategies of national FMD eradication programs, which must be modified when trade opportunities between zones of differing sanitary status change. The role of other susceptible species besides bovines, including wildlife, in maintaining and spreading FMDV has been the subject of several studies, but in SA, bovines are so far considered to determine disease presentation. Buffalo (Bubalus bubalis) have been implicated in the spread of the disease between farms in at least one case in Brazil. Sheep are almost on a par with bovine in terms of number, especially in the Southern Cone, but their role in the maintenance of infection is not considered important, possibly owing to rearing practices. Camelid populations in the Andean region do not play an important role in the maintenance of FMD, because of short persistence of infection and low population densities in these species. The importance of wildlife is not clear, but it is accepted that animals are mostly affected as a spinoff during outbreaks in domestic species. Experimentally infected capybaras (Hydrochoerus hydrochoeris hydrochoeris) showed clinical signs and infected other susceptible species, but their role in the maintenance of infection in nature is so far not clear.