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→Equine Influenza
*Some drift has occurred, causing outbreaks of North-American-like strains of H3N8 in 1998 (EU) and 2003 (South America)
*Some drift has occurred, causing outbreaks of North-American-like strains of H3N8 in 1998 (EU) and 2003 (South America)
===Pathogenesis===
===Pathogenesis===
*Aerosol transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis
*Aerosol and fomite transmission infects the epithelium of the upper respiratory tract, resulting in cell necrosis
*This manifests a bronchiolitis and serous exudation
*This manifests a bronchiolitis and serous exudation
*1-3 day incubation period
*1-3 day incubation period
**Loss of appetite
**Loss of appetite
**Enlarged submandibular lymph nodes
**Enlarged submandibular lymph nodes
*Secondary bacterial infection can follow defective muco-ciliary transport, eg ''Streptococcus zooepidemicus''
*For more, see [[Respiratory Viral Infections - Pathology#Equine influenza|here]]
===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 vaccing 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 10 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
*Swine influenza virus in [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]], may progress to [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|pneumonia]] - see [[Respiratory Viral Infections - Pathology#Swine influenza|respiratory viral infections]]
==Swine Influenza==
===Subtypes===
*Avian-like H1 and human-like H3 strains vary in virulence
===Pathogenesis===
*Necrotising bronchiolitis with catarrhal pus
*Barking cough
*Interstitial pneumonia giving consolidation of the lungs and a 'meaty' appearance
*Often associated with bacteria, mycoplasma or immunosuppressive viruses (such as PRRS)
*The virus recycles on farms as litters outgrow maternal antibody at 12 weeks of age
*For more, see [[Respiratory Viral Infections - Pathology#Swine influenza|here]]
===Diagnosis===
*Clinical pneumonia is always suspect
*Serology: retrospective diagnosis by HI
===Control===
*Isolation of premises
*All-in/all-out systems
*Vaccination is not licensed in the UK
*Equine influenza virus in [[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|rhinitis]], see [[Respiratory Viral Infections - Pathology#Equine influenza|respiratory infections]]
==Avian Influenza==
===Subtypes===
*H1-15 and N1-9 have all been isolated
*Highly Pathogenic Avian Influenza (HPAI), caused by H5 and H7 isolates, is also known as Fowl Plague (FP) and is notifiable
**Chinese poultry are currently the main reservoir for H5N1, not wild birds
===Pathogenesis===
*HPAI is defined by:
**Heamorrhages
**Diarrhoea
**Sometimes nervous symptoms
**Sudden death
*H5 spread by feces and infected viscera (kidney/spleen are 100X more infectious than feces)
*H7 and other viruses are carried by 6% of the wild bird population and outbreaks mirror migrating patterns
**This poses significant risk to free-range flocks
===Zoonotic potential===
*A 2003 Dutch outbreak of a pathogenic H7 virus caused widespread conjunctivitis and flu-like symptoms with recovery among poultry workers
*Rural chinese children became infected with H5N1 via aerosol transmission, which was limited to upper respiratory symptoms and did not show horizontal spread
===Control===
*Prevention by proper hygiene and preventing contact with the wild bird population
*Isolation and cull of infected premises
*Firebreak cull in the case of uncontrolled spread
*Vaccination is not currently practiced for the following reasons:
**An eradication policy prevents it
**Vaccination favors the evolution of the virus, which might increase its virulence and drift