Foot and Mouth Disease Virus (Aphthovirus)

Nereli Isabel G. Agripa4MB

Virology

Order: PicornaviralesFamily: PicornaviridaeGenus: Aphthovirus

• Foot and mouth Disease – Aphthovirus– Cloven-hoofed animals

• Hand, foot and mouth Disease – Coxsackie A virus and Enterovirus 71– Infants and children

I. Virology

A. Structure

• capsid – icosahedral– 4 polypeptides with

(pseudo) T=3 packing. • Diameter = 27-30nm• genome -tightly

packed into the capsid

Figure 1: An electron micrograph of negatively-stained picornavirus particles.

Source: http://www.microbiologybytes.com/virolog

y/3035pics/Picornagif.html

I. Virology

B. Genome• one s/s (+)sense RNA molecule of between 7.2kb (HRV14) to 8.5kb• Picornaviruses:

– Infectious genomic RNA– 5' end = long untranslated region– 3' end = shorter untranslated region – 5' UTR contains the IRES– The rest of the genome encodes a single 'polyprotein’– Both ends of the genome are modified,

I. VirologyC. Replication

Figure 2: Diagram of Picornaviridae replicationSource: http://www.microbiologybytes.com/virology/3035pics/Picorna2.gif

Replication

I. Virology

D. Serotypes– O – A – C – SAT-1 – SAT-2 – SAT-3– Asia-1

II. Signs and Symptoms

• rise in body temperature for 2 to 3 days.• Vesicles that rupture and discharge clear

or cloudy fluid, leaving raw, eroded areas surrounded by ragged fragments of loose tissue.

• sticky, foamy, stringy saliva.• Reduced consumption of feed = painful

tongue and mouth lesions.• Lameness with reluctance to move.• Abortions.• Low milk production (dairy cows).• Myocarditis (inflammation of the

muscular walls of the heart) and death, especially in

newborn animals.

III. MechanismA. Pathogenesis

- Inhalation of airborne virus / infection via alimentary tract or skin lesions

- Primary replication – pharynx- Bloodstream- 3-5 days febrile viraemia- Secondary infection

B. Transmission– Direct or indirect contact – Animate vectors – Inanimate vectors – Airborne, especially temperate zones

IV. DiagnosisIncubation period – 2-14 days

A. Clinical diagnosis

B. Differential diagnosis• Clinically indistinguishable:

– Vesicular stomatitis– Swine vesicular disease– Vesicular exanthema of swine

• Other differential diagnosis:– Rinderpest– Mucosal disease– Infectious bovine rhinotracheitis– Bluetongue– Bovine mammillitis– Bovine papular stomatitis– Bovine viral diarrhoea

C. Laboratory diagnosis– ELISA– Complement fixation

test– Virus isolation

V. Prevention• Sanitary prophylaxis

– border animal movement control and surveillance– Slaughter of infected, recovered, and FMD-susceptible contact

animals– Disinfection of premises and all infected material– Destruction of cadavers, litter, and susceptible animal products in the

infected area– Quarantine measures

• Medical prophylaxis– Inactivated virus vaccine containing an adjuvant.

VI. Epidemiology

• One of the most contagious animal diseases• Low mortality rate in adult animals, • Often high mortality in young = myocarditis

VII. References http://www.cdc.gov/ncidod/dvrd/revb/enterovirus/hfhf.htmhttp://www.oie.int/eng/maladies/fiches/A_A010.HTMhttp://www.microbiologybytes.com/virology/Picornaviruses.html