Difference between revisions of "Equine Influenza"

Latest revision as of 23:50, 15 June 2016

Also known as: Equine Flu

Introduction

There are two subtypes of Equine Influenza described in the world today. These are:

H7N7 (Equine 1), which was prevalent in the UK between 1963-1977
H3N8 (Equine 2), or the European strains, have been circulating since 1965.

Aerosol and fomite transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis, which then manifests as 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.

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.

Clinical Signs

There will be a harsh dry cough with pyrexia (39-41^0>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.

Diagnosis

Virus isolation by deep nasal swabs (12 inches) deposited into 10ml of transport medium and transported at 4⁰C. An antigen detection 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.

Treatment and Control

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.

Control for this disease is by 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.

References

Brown, C.M, Bertone, J.J. (2002) The 5-Minute Veterinary Consult- Equine', Lippincott, Williams & Wilkins

Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool

Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders.

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Equine Influenza Learning Resources
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-{{unfinished}}
+{{OpenPagesTop}}
+Also known as: '''''Equine Flu'''''
-===Subtypes===
+== Introduction  ==
-*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===
+There are two subtypes of Equine Influenza described in the world today. These are:
-*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
+*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'']]
-[[Category:Orthomyxoviridae]][[Category:Horse Viruses]]
+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.
-[[Category:To_Do_-_Clinical/Viruses]]
-[[Category:Respiratory_Viral_Infections]]
+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.
-[[Category:Respiratory Diseases - Horse]]
+== Clinical Signs ==
+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]]''.
+== Diagnosis ==
+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.
+== Treatment and Control ==
+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.
+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.
+== References ==
+Brown, C.M, Bertone, J.J. (2002) The 5-Minute Veterinary Consult- Equine', Lippincott, Williams &amp; Wilkins
+Knottenbelt, D.C. A Handbook of Equine Medicine for Final Year Students University of Liverpool
+Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) Equine Internal Medicine (Third Edition), Saunders.
+{{review}}
+{{OpenPages}}
+{{Learning |Vetstream = [https://www.vetstream.com/equis/Content/Disease/dis00586.asp Equine Influenza]}}
+[[Category:Orthomyxoviridae]] [[Category:Horse_Viruses]] [[Category:Expert_Review - Horse]] [[Category:Respiratory_Viral_Infections]] [[Category:Respiratory_Diseases_-_Horse]]