About the disease
Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-footed domestic and wild animals. It is characterized by fever and vesicular lesions in the mouth, tongue, nostrils, feet, and teeth. Sheep and goats show very mild signs, while pigs act as amplifying hosts, which produce very high concentrations of the virus particle in aerosols. Cattle are indicators of this disease because they generally are the first species to show signs of infection; the lesions are more severe and progress more rapidly than in other animals. The disease affects the integument, respiratory, reproductive, cardiovascular, and urinary systems.
Morbidity reaches almost 100% in susceptible populations. Mortality usually ranges from 1% to 5%, although it may be higher in young animals. Foot-and-mouth disease is a transboundary animal disease with a worldwide distribution. There are various types of FMDV, and strains have been identified in Asia, Africa, and South America.
FMD virus usually enters the host via the respiratory and oral route. Infected animals secrete the virus in all their secretions, so contact and consumption of animal products such as meat, milk, bones, glands, and cheese can spread the disease. The incubation time of the virus is in the range of 2–14 days, depending on the susceptibility of the host and infecting dose. Clinical signs generally develop in 3–5 days. Diseased animals usually recover in 1–3 weeks. Skin lesions usually heal in 7 days after recovery, but secondary bacterial infection may complicate the healing process.
Signs of the disease
- The best-known signs of FMD are fever together with vesicles (blisters) in the mouth, nares, muzzle, hooves, and teats which progress to erosion and sloughing, leading to lameness and anorexia.
- Sticky, foamy, and stringy drooling saliva from the mouth, serous nasal discharge, and decreased milk production.
- Young animals may die without clinical signs, and abortion occurs in pregnant animals.
FMD may be confused with other diseases which show lesions in the mouth. These diseases include vesicular stomatitis, papular stomatitis, bovine viral diarrhea-mucosal disease, malignant catarrhal fever, foot rot, herpes mammillitis, pseudocowpox, rinderpest, bluetongue, contagious ecthyma (orf) in sheep, infectious bovine rhinotracheitis, and chemical and thermal burns.
Treatment and Control
Supportive treatment of infected individuals is warranted. Milking time hygiene is of utmost importance. In areas where FMD is exotic, health care is usually swift and terminal. Drugs are not available to treat FMD, but broad-spectrum antibiotics are intended to control bacterial secondary infection so that the lesions in the mouth and hoofs heal fast.
FMD is a self-limiting disease with a fair prognosis for recovery in 2–3 weeks. The prognosis for young animals is sometimes grave depending on the strains of the virus associated with the disease. Animals vaccinated with the epidemic strains have a good prognosis.
Long-term infection leads to severe loss of production. Sloughing of the hoofs causes secondary bacterial infection and takes a long time to heal. Possibility of tetanus infection through the sloughed hoofs in case of delayed healing.
Strict biosecurity procedures, good animal husbandry practices (e.g., restriction of high-risk visitors, quarantine of high-risk animals and animal products, etc.) aid in the exclusion of FMDV.
Vaccines against FMD are available but cross-protection between different serotypes is limited. Therefore, it is important that the vaccine contain the same subtype of virus as is in the area. This necessitates frequent checking of the serotype and subtype during an outbreak as the FMD virus frequently changes during its natural passage through various species. At the time of the outbreak, ring vaccination with the same strains can protect against a possible epidemic.