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Foot-and-Mouth Disease (FMD) in Animals

Introduction

Foot-and-Mouth Disease (FMD) is a highly contagious viral disease affecting cloven-hoofed animals. It is one of the most economically devastating livestock diseases worldwide due to its rapid spread, severe production losses, and major trade implications. The disease is characterized by fever and the formation of vesicles (blisters) in the mouth, on the feet, and on the teats.

Etiology
Causative Agent

FMD is caused by the Foot-and-Mouth Disease Virus (FMDV), a member of the genus Aphthovirus in the family Picornaviridae.

Virus Characteristics
  • Small, non-enveloped RNA virus
  • Highly resistant in the environment under cool, moist conditions
  • Seven serotypes (O, A, C, SAT1, SAT2, SAT3, Asia1) with multiple subtypes
  • No cross-protection between serotypes
Epidemiology
Species Affected
  • Cattle (highly susceptible)
  • Pigs (important amplifiers of the virus)
  • Sheep and goats (often show mild or subclinical disease)
  • Wild cloven-hoofed animals
Geographic Distribution

FMD is endemic in parts of Africa, Asia, and the Middle East, while many countries maintain FMD-free status through strict control measures.

Transmission
  • Direct contact with infected animals
  • Aerosol transmission (can spread over long distances under favorable conditions)
  • Contaminated fomites (clothing, equipment, vehicles)
  • Ingestion of contaminated feed or animal products
Risk Factors
  • High animal density
  • Movement of animals and animal products
  • Poor biosecurity
  • Windborne spread in suitable climates
Pathogenesis
Entry and Replication

The virus enters the body through inhalation or ingestion and initially replicates in the pharyngeal region.

Viremia
  • Virus spreads via bloodstream to epithelial tissues
  • Localization in areas of friction (mouth, feet, teats)
Lesion Formation
  • Damage to epithelial cells leads to fluid accumulation
  • Formation of vesicles (blisters)
Carrier State

Some animals, particularly cattle, may become carriers, harboring the virus in the pharynx for extended periods.

Clinical Signs
General Signs
  • High fever (40–41°C)
  • Depression
  • Reduced appetite
Vesicular Lesions
  • Blisters in the mouth (tongue, gums, lips)
  • Lesions on feet (interdigital space, coronary band)
  • Lesions on teats and udder
After Vesicle Rupture
  • Painful erosions
  • Lameness
  • Excessive salivation ("drooling")
Species Variations
  • Cattle: severe lesions and lameness
  • Pigs: severe foot lesions, reluctance to move
  • Sheep/goats: mild or subclinical signs
Complications
  • Secondary bacterial infections
  • Myocarditis in young animals ("tiger heart disease")
  • High mortality in neonates
Summary for Practitioners

FMD should be suspected in any outbreak of vesicular disease affecting multiple animals. Rapid reporting is critical, as this is a notifiable disease with serious regulatory implications.

Postmortem Findings
Gross Lesions
  • Vesicles and erosions in mouth and feet
  • Myocardial lesions in young animals (striped appearance)
  • Ulcerations in affected tissues
Microscopic Lesions
  • Degeneration and necrosis of epithelial cells
  • Vesicle formation within epidermis
Diagnosis
Clinical Diagnosis

Based on characteristic vesicular lesions and rapid spread within the herd.

Laboratory Diagnosis
  • PCR for viral RNA detection
  • Virus isolation
  • Serological tests (ELISA)
Differential Diagnosis
  • Vesicular stomatitis
  • Swine vesicular disease
  • Vesicular exanthema
Summary for Practitioners

Laboratory confirmation is mandatory. Immediate quarantine and notification of veterinary authorities are essential upon suspicion.

Treatment
Supportive Care
  • Soft feed and water access
  • Wound care for lesions
  • Prevention of secondary infections
Note

No specific antiviral treatment is available. In many countries, infected animals are culled as part of control strategies.

Summary for Practitioners

Treatment is generally not pursued in outbreak situations due to control policies. Focus is on containment and eradication.

Control and Prevention
Biosecurity
  • Strict control of animal movement
  • Disinfection of equipment and vehicles
  • Controlled farm access
Vaccination
  • Used in endemic regions
  • Requires matching of vaccine to circulating serotype
Eradication Measures
  • Stamping-out (culling infected and exposed animals)
  • Movement restrictions
  • Surveillance and tracing
Summary for Practitioners

Prevention relies heavily on biosecurity and surveillance. In FMD-free countries, rapid response and eradication are key to maintaining disease-free status.

Zoonotic Importance

FMD is rarely transmitted to humans and is not considered a significant zoonotic disease.

Economic Importance

FMD is one of the most economically significant livestock diseases due to production losses, trade restrictions, and costs associated with control and eradication programs.

Summary

Foot-and-Mouth Disease is a highly contagious viral disease of cloven-hoofed animals characterized by vesicular lesions and rapid spread. It has profound economic implications and requires strict control measures, including surveillance, biosecurity, and, in some cases, culling.