Foot and Mouth Disease (FMD)

Master Preventive Medicine – Notes, Case Studies and Practical Insights – with Lomash

Foot and Mouth Disease (FMD)

Syn: Apthous fever, Contagious aptha

It is acute, febrile, highly contagious disease of cloven-footed animals especially of cattle, domestic buffaloes and yaks followed by sheep, goat, swine and all wild ruminants.
It is characterized by initial fever, vesicular eruption and blister-like sores on tongue and lips in mouth, on teat, and between the hooves.
There is focal degeneration of cardiac and skeletal muscles which leads to death in young ones.

Etiology:

FMD virus
+ve sense ss RNA, Genus; Aphthovirus; Family; Picornaviridae
7 different serotypes have been identified serologically as:
- O strain: Oise valley of France (most common in Nepal)
- A strain: Alemand in France (moderate occurrence)
- C strain: Germany (less common in Nepal)
- SAT 1,2,3: South African Territory
- Asia-1: Pakistan in 1954
Virus is sensitive to environmental influence (pH< 5; sunlight) but can survive for long period in freezing temperature.
It can be inactivated at temperature >50°C
It can be destroyed by 2% NaOH, 4% Na₂CO₃ and 0.2% citric acid
It is resistant to iodophore, NH₄ compounds; hypochlorite and phenol

Epidemiology:

Disease was first recorded in 1544 in Europe. Since then it is distributed globally; especially countries of tropical region.
Disease is enzootic in South America, Central Europe and in Ethiopia and Tanzania.
US is free from disease since 1989.
In Asia, disease is widely prevalent in India, Srilanka, Burma and Nepal.
Disease in endemic in Nepal; every year numerous outbreaks is reported. Peak-level occurrence is noted during monsoon and post-monsoon.
Morbidity reaches to 100%, however mortality may be 5% in adults, 75% in suckling pigs and sheep.
Recovered cattle carries virus for 6 months- 2 years and sheep for almost 1-2 months.

Transmission:

Direct contact with infected animals.
Indirect contact with secretions or excretions by infected animals
Disease also transmits through mechanical vectors such as people, equipment, vehicle
Disease transmits through air or water. Virus was reported to travel a distance of >250 km over water and no more than 10 km on land.
All secretions and excretions such as urine, milk, feces, and saliva remain infective.
All fomites such as clothing, harness, mangers, beddings, straws, hay, etc remain infective.

Pathogenesis:

Inhalation/Ingestion of virus
Settle in dorsal surface of soft palate or on lateral wall of pharynx
Invades stratified epithelium of tongue producing primary vesicle.
Virus then multiplies in stratum spinosum where cytolysis takes place giving rise to small cavities developing vesicles.
Virus invades lymph nodes and reaches blood circulation causing viremia.
From bloodstream, virus gets distributed to other epidermal sites but lesion may develop only in areas subjected to physical trauma such as epithelium of mouth, dental pad, feet, and udder where typical lesion is formed.

Clinical Findings:

Cattle and buffalo:

Incubation period= 2-14 days in cattle
Stringy salivation which is profuse and continuous
Depression, anorexia, lameness due to painful vesicles/blisters in skin of lips, tongue, gums, nostrils, coronary band, interdigital spaces and teats.
Rupture of vesicles which leaves areas denuded which may be secondarily infected.
Eroded surface produces quivering and frequent smacking of lips
Animal refuse to eat and drink due to pain in oral mucosa
Emaciation, protrusion of tongue
Heat and swelling of coronet
Udder and teat show vesicles, which cause pain and swelling.
Mastitis, abortion, infertility

Sheep and goat:

Pigs:

PM Findings:

Lesion in ruminal pillar
Heart muscles shows degenerative changes with grey or yellow foci or streaks on myocardium, termed as ‘Tiger-heart disease”.
Vesicles and blisters in tongue, lips, dental pad, gums, hard and soft palate, muzzle, lips, coronary band, snout of pigs, teats and udder, interdigital spaces
Necrosis and edema of stratum spinosum layer of epithelial cells.

Diagnosis:

Based on history and clinical findings
Based on PM findings
Serological test: CFT, ELISA, VNT, PCR, FAT
Animal inoculation test: Materials from vesicles are injected into foot pad of guinea pigs. Appearance of vesicles within 1-7 days indicates positive case.

Differential Diagnosis:

Vesicular Stomatitis In Horses - Ford Veterinary Surgery Center

Treatment:

Prevention and Control:

Restriction of animal movement and surveillance of disease.
Slaughtering of infected, recovered and FMD susceptible contact animals.
Disinfection of premises and all infected animals.
Calf or young animals not allowed to suck milk.
Appropriate disposal or destruction of carcass and all infected animal products/materials.
Eradication: stamping out, quarantine, slaughter and proper disposal of all infected material.
Vaccination of animal in endemic areas;
- FMD Hoechst vaccine (O, A, C and Asia-1 strain)
  - Cattle, buffalo, calves @10 ml, SC
  - Pig, sheep, goat @ 5ml, S/C
  - 1^st vaccination: 3 weeks of age
  - Booster dose: 3 months
  - Revaccination every 6 months
  - Immunity: 6 months
- Raksha- FMD vaccine
  - Primary vaccination: 4 months
  - Booster: 2-4 weeks later
  - Revaccination: Every 6 months
- Animals shouldnot be allowed to drink water from ponds/streams/rivers in case of disease outbreak.
- Movement of people across farms should be restricted.
- In case of outbreak, healthy animals should be attended first, and then affected ones. On attending sick animals, person should wash himself and his clothes with 4% sodium carbonate solution.
- Utensils used for collecting milk should be cleaned with 4% sodium carbonate solution.
- Calves shouldnot be allowed to suckle milk from affected mothers and should not be fed with milk from affected animals.
- Isolation of animals immediately following detection of disease.