excessive secretion of stringy or foamy saliva and to drooling, and blisters on the feet that may rupture and cause lameness. Adult animals may suffer weight loss from which they do not recover for several months, as well as swelling in the testicles of mature males, and cows' milk production can decline significantly. Though most animals eventually recover from FMD, the disease can lead to myocarditis (inflammation of the heart muscle) and death, especially in newborn animals. Some infected ruminants remain asymptomatic carriers, but they nonetheless carry the virus and may be able to transmit it to others. Pigs cannot serve as asymptomatic carriers. Subclinical Infection Subclinical (asymptomatic) infections can be classified as neoteric or persistent based on when they occur and whether the animal is infectious. Neoteric subclinical infections are acute infections, meaning they occur soon after an animal is exposed to the FMD virus (about 1 to 2 days) and last about 8 to 14 days. Acute infections are characterized by a high degree of replicating virus in the pharynx. In a neoteric subclinical infection, the virus remains in the pharynx and does not spread into the blood as it would in a clinical infection. Although animals with neoteric subclinical infections do not appear to have disease, they shed substantial amounts of virus in nasal secretions and saliva, so they are able to transmit the FMD virus to other animals. Neoteric subclinical infections often occur in vaccinated animals but can occur in unvaccinated animals as well. Persistent subclinical infection (also referred to as a carrier state) occurs when an animal recovers from an acute infection but continues to have a small amount of replicating virus present in the pharynx. Cattle, buffalo, sheep, and goats can all become carriers, but pigs cannot. Animals can become carriers following acute infections with or without symptoms. Both vaccinated and unvaccinated animals can become carriers. Transmission of the FMD virus from carriers to susceptible animals is considered very unlikely under natural conditions and has not been conclusively demonstrated in field studies. However, in an experiment where virus was collected from the pharynx of carrier cattle and inserted in the pharynx of susceptible cattle, the susceptible cattle became infected and developed characteristic blisters in the mouth and on the feet. This supports the theory that while the likelihood of a carrier spreading FMD is quite low, it is not impossible. It is not fully