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EQUINE INFLUENZA (FLU)

First broadcast on www.provet.co.uk  


This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Flu is a serious disease in horses mainly because it is so highly infectious and because of the devastating effect that it can have on a horses performance

Signs of flu in horses are a cough and a mild fever, but in working horses their athletic performance can be severely affected, so preventative vaccination against the disease is very important, and it is mandatory for many competing horses and ponies such as those competing under Jockey Club Rules.

Like flu in humans and other species one form of the virus that causes flu (in the case of horses it is mainly Orthomyxoviridae Type A virus) has many strains and the different vaccines that are available contain different strains of the virus. 

In the UK the following virus strains are contained in the vaccines listed below *

Vaccine Name Manufacturer Virus Strains in the Vaccine
Duvaxyn IE-Plus Elanco, Eli Lilly
Equine influenza vaccine (inactivated) in suspension for injection
 
Inactivated equine influenza virus, strains:
A/equi-1/Prague/56 15- 18 μg HA*
A/equi-2/Suffolk/89 (European type) 15 - 18 μg HA*
A/equi-2/Newmarket/1/93 (American type) 15 - 18 μg HA*
*Haemagglutinin

 

Duvaxyn IE-T Plus Elanco, Eli Lilly
Combined equine influenza vaccine (inactivated) and tetanus vaccine for veterinary use.
 
IContains inactivated equine influenza virus, strains:
A/equi-1/Prague/56 15 - 18 μg HA*
A/equi-2/Suffolk/89 (European type) 15 - 18 μg HA*
A/equi-2/Newmarket/1/93 (American type) 15 - 18 μg HA*
Tetanus Toxoid 18 Lf (RP≥1.0)**
 

*Haemagglutinin

**Mean potency relative to a reference vaccine of potency ≥150 IU/dose
 
     
Equip F Zoetis UK Limited
Equine Influenza A/Equine/1 Newmarket '77
10 μg
Equine Influenza A/Equine/2 Borlange '91
20 μg
Equine Influenza A/Equine/2 Kentucky '98
1.4 μg
Equip FT Zoetis UK Limited
Equine Influenza A/Equine/1 Newmarket ‘77
10 μg
Equine Influenza A/Equine/2 Borlange ’91
20 μg
Equine Influenza A/Equine/2 Kentucky ‘98
1.4 μg

Immunopurified tetanus toxoid
100 Lf units

 

Equilis Prequenza MSD Animal Health
Equine influenza virus strains:
 

A/equine-2/ South Africa/4/03 - 50 AU1

A/equine-2/ Newmarket/2/93 - 50 AU
1 Antigenic units

 

Equilis Prequenza Te MSD Animal Health
Equine influenza virus strains:

 

A/equine-2/ South Africa/4/03 - 50 AU1
A/equine-2/ Newmarket/2/93 - 50 AU
Tetanus toxoid - 40 Lf2

 

Equilis Resequin MSD Animal Health
For active immunisation of horses and ponies for reduction of respiratory disease caused by equine herpesvirus type 1 (EHV 1), equine herpesvirus type 4 (EHV 4) or equine influenza virus (EIV) of A/equi 1 and the current "American" and "European" strains of A/equi 2.
 

nact. EHV1, strain RAC-H

 

 

 

at least 107.8 TCID50

inact. EHV4, strain 2252
at least 106.5 TCID50
inact. influenza virus, A/equi 1/Prague/1/56
50 μg HA
inact. influenza virus, A/equi 2/Newmarket/1/93 (American-type)
20 μg HA
inact. influenza virus, A/equi 2/Newmarket/2/93 (European-type)
20 μg HA

 

Proteq-Flu Te Merial Animal Health
Active immunisation of horses of 4 months of age or older against equine influenza to reduce clinical signs and virus excretion after infection, and against tetanus to prevent mortality.

Influenza A/equi-2/Ohio/03 [H3N8] recombinant Canarypox virus (vCP2242) ≥ 5.3 log10 FAID50

Influenza A/equi-2/Newmarket/2/93 [H3N8] recombinant Canarypox virus (vCP1533) ≥ 5.3 log10 FAID50

Clostridium tetani toxoid ≥ 30 IU. Adjuvant: Carbomer.

 

* Source NOAH Compendium of Data Sheets for Veterinary Products  2013 Online 

All the viruses in these vaccines are inactivated - which means they should not cause serious signs of flu as a side-effect. These vaccines are also available combined with tetanus vaccine giving protection against the two diseases in one vaccination.

Equine Flu vaccines should be given as follows :

  • Only to healthy horses and ponies
  • To horses and ponies over a certain age (4-5 months) specified by the manufacturers in their data sheets
  • By intramuscular injection
  • The initial course consists of 2 vaccinations 4-6 weeks apart.
  • Repeat vaccines are given 5-7 months and again 12-18 months after the initial course.
  • Thereafter a booster vaccine is advised every 12 months, although horses exposed to the virus may be vaccinated at 6 monthly intervals.
  • Pregnant mares can be vaccinated and it is usually recommended that they be vaccinated 4-8 weeks before the foal is due to be born.

Side-effects and reactions to the vaccine do occur from time to time including :

  • Local swelling at the injection site
  • Abscess formation at the injection site
  • Allergic reactions (rare) - these require emergency treatment by your veterinarian

Unfortunately other viruses can also cause equine influenza, and of course these vaccines do not provide protection - so a vaccinated horse or pony can still develop flu due to other viruses even if it is fully vaccinated.

Like most vaccines there are certain circumstances under which the vaccine may fail to produce an adequate amount of immunity in an individual horse or pony, including the following :

  • If the vaccine has been stored incorrectly
  • If the vaccine has been administered incorrectly
  • The animal has a natural (genetic) resistance to the vaccine
  • The animal (especially young foals) have immunity against the vaccine which they have inherited from the mother
  • The animal has a poor immune system at the time of the vaccination and can't respond properly
  • The animal is too young to mount a good immune response to the vaccine
  • The animal has an infection
  • The animal has poor nutritional status
  • The animal is on drug therapy
  • The animal is under stress

Local circumstances vary, and your veterinarian will advise you about the most appropriate vaccine for your horse or pony, and when best to give the vaccine and boosters.

 

Updated October 2013