Fouth-and-Mouth Disease

• Eradication is considered to be less costly than living with FMD.
• Foot-and-mouth disease (FMD) is a highly contagious viral disease of many wild and domestic cloven-footed mammals and many other animals.
• In swine, the disease is characterized by vesicles on the feet, snout and in the mouth.
• A wide range of wild and domestic animals, especially cloven-footed mammals, are susceptible to FMD.
• Horses are resistant to FMD.
• The disease occurs in most countries with a large livestock population unless those countries have eradicated it and maintained their disease-free status.
• In countries where FMD occurs endemically and pigs are present in large numbers, swine frequently are infected with the disease.
• All age groups are susceptible to FMD.
• An Aphthovirus of the family Picornaviridae causes FMD.
• There are at least seven immunologically distinct types of virus: A, O, C, South African Territory (SAT) 1, 2, 3 and Asian 1.
• Over 60 subtypes of virus have been identified and new subtypes continue to develop.
• Many differ enough antigenically to require preparation of subtype vaccines for their control.
• The antigenic variation of the virus and the limited cross protection among strains has made it impossible to prepare a single vaccine that protects satisfactorily against all strains.
• Effective disinfectants of FMD virus include sodium hydroxide, acetic acid, sodium carbonate and Virkon® (Durvet).
• Virus transmission occurs through respiratory aerosols and direct or indirect contact with infected animals.
• Aerosol transmission of FMD virus over distances as great as 30 miles is believed to occur under certain weather conditions.
• Infected swine are exceptional disseminators of virus.
• FMD virus (FMDV), an aphthovirus of the Picornaviridae family, is capable of infecting a multitude of cloven-hoofed animal species including both ruminants and suids.
• For some virus subtypes, they are able to produce aerosols many times greater in virus concentration than those produced by cattle or sheep.
• They are sometimes referred to as “amplifier hosts” for FMD virus.
• Virus persists for long periods of time in frozen meat products.
• In several notable FMD outbreaks, the index case has been associated with the consumption by pigs of uncooked waste food containing infectious meat scraps.
• Contaminated biologics, including vaccines, have been responsible for outbreaks.
• Foot and mouth disease virus adheres to the mucosa of the respiratory tract, the usual site of virus entry.
• Macrophages are believed to transport virus to secondary sites that include epithelium, mucosa and myocardium.
• In secondary sites, the virus replicates, then a marked viremia develops and the virus infects epithelium at many other sites.
• Within a few days vesicles develop, usually at sites of mechanical stress.
• In swine, common vesicle sites include the snout, mouth, tongue, and especially the feet.
• In cattle, the FMD virus affects the mammary gland epithelium and virus is shed in milk for a prolonged period.
• The lesions of the major vesiculating viral diseases are similar.
• Vesicles develop in the epidermis, and the epithelium over the vesicle soon sloughs.
• Low feed intake can lead to painful tongue and mouth lesions in cattle with FMD.
• Secondary infection occurs on the feet of some swine and leads to chronic lameness.
• Infection in immature sheep and goats can result in death without clinical signs due to heart failure.
• Serologic tests for FMD are used to certify animals for import/export (ie, trade), to confirm suspected cases of FMD, test efficacy of vaccination, and provide evidence for absence of infection.
• Ruptured oral vesicles can coalesce and form erosions but heal rapidly, roughly 11 days after vesicle formation.
• At least 1 g of epithelium should be placed in a transport medium of phosphate-buffered saline (PBS) or equal parts glycerol and phosphate buffer with pH 7.2–7.6.
• Fever of ~40°C is a clinical sign of FMD in cattle.
• The mottled myocardial lesions sometimes are referred to as “tiger-heart” lesions and are useful in diagnosis.
• Clinical signs of FMD in sheep and goats can be largely inapparent.