35. Aphthous fever
aka FOOT AND MOUTH DISEASE (only animals)
etiology
viral illness that usually affects infants and children younger than five years old
Picornaviridae, genus Aphthovirus
7 serotypes: A, O, C, SAT1, SAT2, SAT3, and Asia1
inactivated above 50 degrees C
survive in lymph nodes and bone marrow @ neutral pH
residual virus survives in milk products, inactivated by high temp pasteurisation
can persist in contaminated food for cattle
epidemiology
One of the most contagious animal diseases, with important economic losses
Low mortality rate in adult animals
high mortality in young due to myocarditis
Cattle are usually the main host, some strains adapted to pigs, sheep or goats
All wild cloven-hoofed animals are also susceptible, including deer, antelope, wild pigs, elephant, giraffe, and camelids
transmission
Direct contact between infected and susceptible animals
Direct contact of susceptible animals with contaminated objects
Consumption (primarily by pigs) of untreated contaminated meat products
Ingestion of contaminated milk (by calves)
Inhalation of infectious aerosols
Airborne
Humans can harbour FMDV in their respiratory tract for 24–48 hours
incubating and affected animals
Breath, saliva, faeces, and urine; milk and semen
Meat and by-products in which pH has remained above 6.0
rates of carriers in cattle vary from 15–50%
carrier state in cattle usually does not persist for more than 6 months
endemic in parts of Asia, Africa, Middle east and South America
diagnosis
incubation- 14 days
Mortality in general is low in adult animals -1–5%
cattle
pyrexia
anorexia
reduced milk production
grinding of teeth
kicking- caused by vesicles (aphthae) on buccal and nasal mucous membranes and between claws
rupture of lesions leaving erosions after 24h
complications
tongue erosions
hoof deformation
permanent impairment of milk production
myocarditis, death
antigen ELISA test of unruptured vesicle tissue sample
prevention and control
sanitary prophylaxis
animal movement control
quarantine measures
slaughter of infected animals
disinfection of premises
disposal of carcasses, bedding, animal products
medical prophylaxis
inactivated vaccine- standard or higher potency vaccines