42. Foot and mouth disease (aetiology, epidemiology, pathogenesis, clinical signs, post mortem lesions). Flashcards
FMD Occurrence?
FMD Æ NOTIFIABLE DISEASE! ZOONOTIC!
x Highly contagious, spreads quickly, acute, viral cloven-hoofed animals (RU, SU) Æ fever, general symptoms, vesicle
formation, salivation, lameness (Picornaviridae, Aphtovirus)
x Occurrence: previously rapidly spreading epidemics, since 1960s state veterinary medicine measures
and vaccination, substantially reduced number of outbreaks
o Free: North and Central America, Australia, NZ, Japan (recently)
o Sporadic: Europe, rear outbreaks
o Endemic: Turkey, Middle-East, Arabic peninsula, Africa, Asia, South America
Etiology?
Etiology: Picornaviridae, Aphtovirus
o +ssRNA ~ mRNA (short replication time), icosahedral, non-enveloped, 22-25 nm
o Virus shedding starts 9 hrs after infection, very contagious, fastspreading ʹ no time to react!!
o Resistance: good (56C, pH 6.5), shadow, wet-cool sites of the pasture, dirty stall for weeks,
in manure for 40 days, frozen meat, milk powder for months
o CPE (cultivation): after incubation see cell rounding, lysis
o Guinea pig foot scarification (24 hr later vesicles formation), mouse intraperitoneal death within a
few days
o Genotypes, subtypes, strain:
x VP1 (binding, neutralizing antibodies) or complete genome analysis (4 structural
protein total VP1-4)
x 7 serotypes: O and A found worldwide, C israre
x SAT-1, -2, -3: Africa, Arabia
x Asia-1: Asia, Turkey, Middle East
o Several subtypes, no cross protection
o Differential: (guinea pig - cross protection test, CF), VNT, ELISA
Epidemiology?
Epidemiology:
o Susceptibility: ruminants including wild species, pig, guinea pig, hedgehog, dog, human (zoonosis)
o Main hosts: cattle (main reservoir), buffalo (reservoirs)
o Sheep and goat: mild symptoms
o Swine: shedding 1,000-3,000X higher virus than in cattle, but short time
o Spreading: live animal (direct contact, saliva, body fluids, milk, semen), environment,
contaminated feed, water, vehicles, people, (frozen) raw meat, skin, fur,milk
o Long term carrying: tonsils, lymphatic tissue, hoof
o Carriage: sheep, goat, cattle (0.5-3 years), swine and others (few weeks)
o Vaccinated animals can still carry virus and shed
Pathogenesis?
Pathogenesis:
o Infection PO, airborne Æ primary replication in laryngeal, pharyngeal mucosa > viremia > spread
within the body > vesicles on mucosa (mouth, nose, tongue) and skin (teats, feet)
Clinical signs?
Clinical signs: 2-7 days, fever, decreased milk production, depression, high salivation (viscous, frothy)
o Mouth vesicles (bo, goat - severe, sus and sheep - mild): from 2-3 days PI, tattered edge, red
base, bacterial superinfection!!, recovery after immune response
o Feet: severe lameness (Bo, Ov), also loss of hoof - keratin layer (Sus)
Wild animals: mild symptoms
o Myocarditis: young animals (bo, ov, sus), death from heart malfunction
Pathology?
Pathology: vesicles, erosions on mucosa and hoof, pale heart (in young)
