Bovis ISSN 2398-2993

Foot and mouth disease: the virus

Synonym(s): FMD, aphthovirus

Contributor(s): Veronica Fowler , Tammy Hassel

Introduction

Classification

Taxonomy

  • Order: picornavirales.
  • Family: picornaviridae.
  • Genus: aphthovirus.
  • Species: foot-and-mouth disease virus (FMDV).

Etymology

  • Pico (spanish): very small; rna: RNA; viridae: virus.

Active Forms

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Clinical Effects

Epidemiology

Transmission

  • FMDV is present in secretions such as feces, saliva, nasal fluid, milk, semen and breath and can infect susceptible animals through inhalation, ingestion, skin trauma and contact with mucosal membranes.
  • Cattle, sheep and goats are particularly susceptible to FMDV infection via the respiratory tract, with as little as 10 TCID50 required to initiate infection.
  • In contrast, pigs are relatively resistant to infection via the respiratory tract but instead are more susceptible to infection through ingestion of virus.
  • Other routes of infection have been reported, and include virus entry through abrasions in the skin or mucosal membranes and/or exposure to aerosol or contaminated environments or materials.
  • More recently it has also been identified that live virus can be isolated from lamb fetuses and placenta material, aborted following FMDV infection.

Pathological effects

  • FMD is an acute febrile disease affecting both wild and domesticated cloven-hoofed animals.
  • The disease is characterized by the formation of vesicles in and around the mouth/nasal area and on the coronary bands, except in sheep, where infection is often mild and unapparent which in some cases goes completely undiagnosed. Lesions may also be present on the teats of female cattle.
  • Following infection, the incubation period between infection and the appearance of clinical signs is short, ranging from two to eight days but in some cases has been reported to be as long as 14 days, with the severity of clinical signs being related to infectious dose, species, the level of immunity and the virus strain.
  • Primary virus replication is believed to occur in the lung or pharyngeal epithelium with more emphasis placed on dorsal soft palate which has been shown to support replication of FMDV.
  • The incubation period ranges from 2-14 days.
  • From this point the virus enters the blood circulation, characterized by a viremic phase lasting 3-5 days from which the virus then disseminates into various organs and tissues of the body manifesting as secondary lesions in the mouth, nose, on the coronary bands and occasionally on the teats and udders as a result of infection of the cornified stratified squamous epithelium.

Control

  • There are a number of strategies employed in the control of FMD but the approach undertaken depends on the epidemiological situation and the disease control policy of the country. The control strategies listed below are relevant for countries which are normally disease free.

Control via animal

  • Stringent import and cross-border animal movement controls and surveillance.
  • Vaccination is not used in normally FMD free countries. In FMD endemic countries, vaccination is used to protect the milk yield of dairy cattle.
  • "Stamping out" (culling on infected, 'in-contact' and recovered animals. Culling of susceptible animals which have been present on an infected premises).

Control via environment

  • Strict biosecurity Biosecurity. Infected premises must be thoroughly cleaned and disinfected.
  • Restrictions on animal movements following an outbreak.
  • Control access to livestock to visitors.
  • Control introduction of new livestock.
  • Sureveillance and tracing of potentially infected animals.
  • Appropriate disposal of carcasses and all animal products.

Vaccination

  • There are numerous chemically inactivated vaccines against FMDV.
  • The correct vaccine must be selected based on an antigenic match.
  • Vaccination is not used in countries which are listed as 'FMD free without vaccination' (eg UK).
  • Vaccination is used in regions which are listed as 'FMD free with vaccination' (eg South America).
  • Vaccination is used in regions which are listed as 'FMD endemic' (eg sub-Saharan Africa).

Diagnosis

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Stenfeldt C, Diaz-San Segundo F, de Los Santos T, Rodriguez L L & Arzt J (2016) The Pathogenesis of Foot-and-Mouth Disease in Pigs. Front Vet Sci 3, 41 PubMed.
  • Jamal S M & Belsham G J (2013) Foot-and-mouth disease: past, present and future. Vet Res. 44, 116 PubMed.
  • Knight-Jones T J & Rushton J (2013) The economic impacts of foot and mouth disease - what are they, how big are they and where do they occur? Prev Vet Med 112 (3-4), 161-73 PubMed.
  • Ludi A & Rodriguez L (2013) Novel approaches to foot-and-mouth disease vaccine development. Dev Biol (Basel) 135, 107-16 PubMed.
  • Arzt J, Juleff N, Zhang Z & Rodriguez L L (2011) The pathogenesis of foot-and-mouth disease I: viral pathways in cattle. Transbound Emerg Dis 58 (4), 291-304 PubMed.
  • Parida S (2009) Vaccination against foot-and-mouth disease virus: strategies and effectiveness. Expert Rev Vaccines 8 (3), 347-65 PubMed.
  • Alexandersen S, Zhang Z, Donaldson A I & Garland A J (2003) The pathogenesis and diagnosis of foot-and-mouth disease. J Comp Pathol 129 (1), 1-36
  • Hughes G J, Mioulet V, Kitching R P, Woolhouse M E, Alexandersen S & Donaldson A I (2002) Foot-and-mouth disease virus infection of sheep: implications for diagnosis and control. Vet Rec 150 (23), 724-7 PubMed.
  • Kitching R P (2002) Identification of foot and mouth disease virus carrier and subclinically infected animals and differentiation from vaccinated animals. Rev Sci Tech 21 (3), 531-8 PubMed.
  • Rodriguez L L & Gay C G (2011) Development of vaccines toward the global control and eradication of foot-and-mouth disease. Expert Rev Vaccines 10 (3), 377-87 PubMed.

Organisation(s)

  • OIE - World Organisation for Animal Health.
  • APHA - Animal and Plant Health Agency.

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