Highly contagious disease affecting cloven-hoofed animals, responsible for the outbreak of vesicles and erosion on the buccal mucosa, between the claws and on udders.
Significance
Direct loss:
- High morbidity but low mortality
- Significant loss in milk and meat production
- High cost of disease control measures
Indirect loss:
- Prohibition of animal movement and sale of products
- Obstruction to international commerce (embargo of infected countries)
- Drop in prices
Cloven-hoofed animals:
Domestic: bovines, ovines, caprines, porcines.
Wild: ruminants (cervidae, buffalos) and wild boars.
Man:
Highly resistant. Rare infection occurring through massive exposure.
Asymptomatic affection the most often. Rarely, fever, headache, sore throat and ulcers.
Naked RNA virus from the family Picornaviridae Aphtovirus genus.
7 immunologically distinct serotypes offering no cross-protection: A, O, C, SAT1, SAT2, SAT3, Asia1.
Survives in the outside environment and resists cold but is sensitive to heat and to acid and basic pH. It is destroyed in meat through the maturation process but persists in the spinal cord and lymph nodes.
Incubation period: 2 to 14 days.
Bovines:
• Viremia stage: hyperthermia, exhaustion, inappetence, drop in milk production.
• Stable phase: painful ulcers (vesicles then ulcers)
- in the mouth (tongue, gums, cheeks, palate) leading to dysphagia, chewing and abundant saliva.
- between the claws, responsible for stamping and lameness.
- on the udders (teats)
• Final stage: recovery in 8-15 days, prolonged convalescence and persistence of sequelae (hoof deformation, udder lesions, decreased production). Even recovered animals lose their economic value.
• Complications: weight-loss, secondary bacterial infections, mastitis, claw loss, myocarditis, calf death
Ovines and caprines:
Less severe clinical progression which may go unnoticed except where ovine virus strain tropism induces marked symptoms.
Less marked lesions in the mouth, primarily foot lesions, agalactia, casting, death of young stock.
Porcines:
Fever, loss of appetite, refusal to move.
Sometimes exclusive serious foot lesions, visible easy limping on hard ground.
Groin and teats affected, casting, high mortality among piglets.
No specific treatment is available.
Refer to the legislation and strategy in force in the country concerned.
Sanitary prophylaxis
This is difficult as the virus is highly contagious and resistant and affects numerous susceptible species through various methods of dissemination.
Defensive measures:
Protection of disease-free areas:
- Monitoring and control of animal movements on area borders.
- Prohibition of live animals and animal products from affected countries.
- Quarantine on importation of live animals.
- Prohibition of the use of unsterilized swill.
Offensive measures :
- Isolation and culling of infected animals and susceptible animals having entered into contact with infected animals.
- Destruction of carcasses, litter and products from susceptible animals
- Cleaning and disinfection of premises and equipment + depopulation.
- Controlled human and animal movement.
- Increased monitoring of herds.
- Sterilization of swill.
Medical prophylaxis
Routine vaccination
This strategy is based on the efficacy and harmlessness of the vaccine and requires high vaccinal coverage of the susceptible population.
Combined with a culling and restriction of animal movement policy in the case of an outbreak this strategy limits virus propagation and greatly reduces the number of outbreaks
Strategic vaccination
Strategy employed in countries where prevalence is too high for culling and/or wide scale vaccination to be implemented.
The aim is to limit the impact of the disease by combing strategic vaccination with other measures (monitoring, quarantine, zoning, etc.).
Emergency vaccination
• Covering vaccination for the infected area:
The aim is to reduce the quantity of virus produced by infected animals at the source of the disease (e.g.: pigs) and to limit disease dissemination while waiting for the infected herd to be slaughtered.
• Covering vaccination around the infected area:
The aim is to create a "belt" of vaccinated animals around a source and to limit dissemination of the infection outside this area.
Two types of monovalent or multivalent inactivated virus vaccines exist:
• Vaccine with an aluminium hydroxide - saponin emulsion (ruminants)
• Oil emulsion vaccine (pigs and ruminants)
The vaccine strain is to be chosen according to the strain present in the affected area.