A practitioner's primer on foot-and-mouth disease.

Foot-and-mouth disease (FMD) is caused by an RNA virus of the genus Aphthovirus; 7 immunologically distinct serotypes of the virus have been identified. Susceptible species are mainly domestic and wild even-toed ungulates, such as cattle, sheep, goats, pigs, bison, and deer. All body fluids of infected animals can contain the virus and are considered infective. The primary mode of transmission is animal-to-animal transmission through inhalation or ingestion of aerosols containing the virus. The virus can also be spread mechanically by contaminated organic debris and fomites and can survive for 48 hours on human oral and nasal mucosa and be spread to uninfected animals in this manner. There is a rapid progression of clinical signs after an animal becomes infected, and the virus spreads rapidly throughout a herd. Clinical signs include excessive salivation; fever; vesicles and erosions of the oral and nasal mucosa, coronary band, interdigital area, and teats; lameness; sloughing of claws; reluctance to move; anorexia; mastitis; decreased milk production; and abortion or weak newborns. In mature animals, FMD has high morbidity and low mortality rates. Infected animals can become inapparent carriers of the virus.