Difference between revisions of "Equine Influenza"

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Also known as: '''''Equine Flu'''''
 
  
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== Introduction  ==
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===Subtypes===
 +
*Two subtypes of Equine Influenza have been described:
 +
**H7N7 (Equine 1), which was prevalent in the UK between 1963-1977
 +
**H3N8 (Equine 2), or the European strains, have been circulating since 1965
 +
*Some drift has occurred, causing outbreaks of North-American-like strains of H3N8 in 1998 (EU) and 2003 (South America)
 +
===Pathogenesis===
 +
*Aerosol and fomite transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis
 +
*This manifests a bronchiolitis and serous exudation
 +
*1-3 day incubation period
 +
*Excretion of the virus in nasal secretions peaks at 3-4 days and finishes by 10 days
 +
*Clinical signs:
 +
**Harsh dry cough
 +
**Pyrexia (103-106F)
 +
**Depression
 +
**Loss of appetite
 +
**Enlarged submandibular lymph nodes
 +
*Secondary bacterial infection can follow defective muco-ciliary transport, eg ''Streptococcus zooepidemicus''
  
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There are two subtypes of Equine Influenza described in the world today. These are:
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===Diagnosis===
 +
*Virus isolation: Deep nasal swabs (12 inches) deposited into 10ml of transport medium and transported at 4C
 +
*Antigen detection via ELISA: tests for type A nucleoprotein
 +
*Serology provides a retrospective diagnosis by '''Haemagglutination Inhibition (HI)''':
 +
**Acute and Convalescent (2 weeks post-acute) samples are tested from the same animal
 +
**4-fold increase of HI must be shown to confirm diagnosis
 +
===Control===
 +
*Isolate coughing horses to minimize spread
 +
*Vaccination:
 +
**All vaccines include H7 and varieties of the current circulating strains of H3
 +
**'''Inactivated''' egg-grown vaccine is produced with alhydrogel as an adjuvant
 +
**'''Live''' vaccines using purified haemagglutinin do not require adjuvants
 +
**UK Jockey Club rules regarding timing:
 +
***Horses must be certified as completing a vaccination course of 3 injections at least 8 days prior to racing
 +
***The course consists of a primary inoculation followed by a second within 21-92 days and a third after a further 150-215 days
 +
***Boosters are given annually to maintain immunity, and in the event a year is missed the initial course of three jabs must be repeated
  
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*H7N7 (Equine 1), which was prevalent in the UK between 1963-1977
 
−
*H3N8 (Equine 2), or the European strains, have been circulating since 1965.
 
  
 +
*Causative agent: [[Orthomyxoviridae]]
 +
*[[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|Rhinitis]],
 +
*Pathogenesis:
 +
**Inhalation -> replication in epithelial cells of upper and lower airways (attaches  via haemaglutinin spike and gains entry into cell) -> neuramidase alters efficiency of [[Respiratory System General Introduction - Pathology#Mucociliary escalator|mucociliary apparatus]]
 +
*Sloughing of the affected area
 +
*Severity of signs will depend on dose of virus
 +
*Acute [[Trachea Inflammatory - Pathology#Infectious causes of tracheitis|tracheo]][[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]] with coughing, and fever
 +
*May be accompanied by secondary bacterial infections
 +
*No viraemia
 +
*In severe cases may cause [[Lungs Inflammatory - Pathology#Bronchointerstitial pneumonia|bronchointerstitial pneumonia]]
 +
*Secondary invaders are usually [[:Category:Streptococcus species|''Streptococci'']]
  
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Aerosol and fomite transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis, which then manifests as [[Bronchiolitis|bronchiolitis]] and serous exudation. There is a 1 - 3 day incubation period, with excretion of the virus in nasal secretions peaking at 3-4 days and finishing by 10 days.
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[[Category:Orthomyxoviridae]][[Category:Horse]]
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The disease usually occurs as an outbreak with many horses on the yard becoming infected. The most common age to encounter the disease is around 2 years and stress is a predisposing factor, so this disease is most commonly seen in racing yards.
 
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== Clinical Signs ==
 
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There will be a harsh dry cough with pyrexia (39-41<sup>0></sup>C / 103-106F). The horse will appear generally depressed with a loss of appetite and decreased activity. Submandibular lymph nodes will be enlarged on physical examination. Secondary bacterial infection can follow defective muco-ciliary transport, eg ''[[Streptococcus zooepidemicus]]''.
 
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−
 
 
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== Diagnosis ==
 
−
 
 
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Virus isolation by deep nasal swabs (12 inches) deposited into 10ml of transport medium and transported at 4<sup>0</sup>C. An antigen detection [[ELISA testing|ELISA]] should then be performed. Blood samples for serology should also be taken on day one of the disease (acute phase) and then two weeks later (convalescent stage). A 4-fold increase of haemaglutination inhibition (HI) must be shown to confirm diagnosis.
 
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== Treatment and Control ==
 
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Isolate coughing horses at once to minimize spread and perform thorough disinfection of all shared tack, stables, vehicles, boot and feed buckets. Treat any secondary bacterial infections with suitable antibiotics.
 
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Control for this disease is by [[Vaccines|vaccination]]. All vaccines include H7 and varieties of the current circulating strains of H3. There are strict rules from the Jockey Club regarding timing of vaccinations: Horses must be certified as completing a vaccination course of 3 injections at least 8 days prior to racing. The course consists of a primary inoculation followed by a second within '''21-92 '''days and a third after a further '''150-215 '''days. Boosters are given annually on or before the anniversary of the third injection to maintain immunity, and in the event a year is missed, the initial course of three injections must be repeated.
 
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== References ==
 
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Brown, C.M, Bertone, J.J. (2002) The 5-Minute Veterinary Consult- Equine', Lippincott, Williams &amp; Wilkins
 
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Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool
 
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Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders.
 
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{{review}}
 
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{{OpenPages}}
 
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{{Learning |Vetstream = [https://www.vetstream.com/equis/Content/Disease/dis00586.asp Equine Influenza]}}
 
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[[Category:Orthomyxoviridae]] [[Category:Horse_Viruses]] [[Category:Expert_Review - Horse]] [[Category:Respiratory_Viral_Infections]] [[Category:Respiratory_Diseases_-_Horse]]
 

Revision as of 10:39, 22 May 2010


 This article is still under construction.


Subtypes

  • Two subtypes of Equine Influenza have been described:
    • H7N7 (Equine 1), which was prevalent in the UK between 1963-1977
    • H3N8 (Equine 2), or the European strains, have been circulating since 1965
  • Some drift has occurred, causing outbreaks of North-American-like strains of H3N8 in 1998 (EU) and 2003 (South America)

Pathogenesis

  • Aerosol and fomite transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis
  • This manifests a bronchiolitis and serous exudation
  • 1-3 day incubation period
  • Excretion of the virus in nasal secretions peaks at 3-4 days and finishes by 10 days
  • Clinical signs:
    • Harsh dry cough
    • Pyrexia (103-106F)
    • Depression
    • Loss of appetite
    • Enlarged submandibular lymph nodes
  • Secondary bacterial infection can follow defective muco-ciliary transport, eg Streptococcus zooepidemicus

Diagnosis

  • Virus isolation: Deep nasal swabs (12 inches) deposited into 10ml of transport medium and transported at 4C
  • Antigen detection via ELISA: tests for type A nucleoprotein
  • Serology provides a retrospective diagnosis by Haemagglutination Inhibition (HI):
    • Acute and Convalescent (2 weeks post-acute) samples are tested from the same animal
    • 4-fold increase of HI must be shown to confirm diagnosis

Control

  • Isolate coughing horses to minimize spread
  • Vaccination:
    • All vaccines include H7 and varieties of the current circulating strains of H3
    • Inactivated egg-grown vaccine is produced with alhydrogel as an adjuvant
    • Live vaccines using purified haemagglutinin do not require adjuvants
    • UK Jockey Club rules regarding timing:
      • Horses must be certified as completing a vaccination course of 3 injections at least 8 days prior to racing
      • The course consists of a primary inoculation followed by a second within 21-92 days and a third after a further 150-215 days
      • Boosters are given annually to maintain immunity, and in the event a year is missed the initial course of three jabs must be repeated


  • Causative agent: Orthomyxoviridae
  • Rhinitis,
  • Pathogenesis:
    • Inhalation -> replication in epithelial cells of upper and lower airways (attaches via haemaglutinin spike and gains entry into cell) -> neuramidase alters efficiency of mucociliary apparatus
  • Sloughing of the affected area
  • Severity of signs will depend on dose of virus
  • Acute tracheobronchitis with coughing, and fever
  • May be accompanied by secondary bacterial infections
  • No viraemia
  • In severe cases may cause bronchointerstitial pneumonia
  • Secondary invaders are usually Streptococci
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