Page 37 - March 2005 The Game
P. 37

Your Thoroughbred Racing Community Newspaper The Game, March 2005 37
The Game
Special Advertorial Feature
Health & Nutrition 2005
Influenza in Horses
Drs. Bob Wright and Dan Kenney
Equine influenza is an acute, contagious, respiratory disease caused by two distinct subtypes (subtype 1: H7N7 and subtype 2: H3N8) of influenza A viruses. These are abbreviated to AE-1 and AE-2. In fully susceptible horses, clinical signs include pyrexia (fever) and a harsh dry cough, followed by mucopurulent nasal discharge. In partially immune, vaccinated animals, one or more of these signs may be absent. Characteristically, influenza spreads rapidly in a susceptible population. Influenza is endemic in North America and most of the world. Periodic point explosive outbreaks occur and are quickly spread by a rapidly mobile population of horses. This may be related to the waning of immunity to influenza in the general horse population and/or genetic drift of the virus strain. Only influenza subtype AE-2 has been isolated over the last twenty years worldwide. There are also distinct differences in virus strain lineage between virus isolates in North America and those in Europe. Respiratory
disease outbreaks in groups of horses need to be identified as caused by influenza or one of the other common equine respiratory viruses, such as equine herpesvirus 1 & 4, equine rhinovirus 1 & 2 and equine adenovirus.
The equine influenza strains are not known to cause illness in humans and are classified as AE subtype 1: H7N7 and AE subtype 2: H3N8. These virus strains are different from the strains causing the avian influenza outbreaks of recent years:
• H7N3, which affected poultry in the Fraser Valley of British Columbia in 2004;
• H7N2, which affected poultry in Maryland in 2003 and 2004;
• H5N2, which affected poultry in Texas in 2004;
• HPAI that spread in 2004 to more than ten Asian countries.
Horse Health Risk
The incubation period of equine influenza virus may be as short as 1 to 3 days. Horses can remain infective and shed virus to other horses for up to 10 days in their nasal secretions. A number of factors increase the risk of infection with influenza virus. Horses 1 to 5 years of age are more susceptible to the disease. Those horses with no previous exposure to the virus and/or no previous vaccination to protect them against influenza virus will have a lower immune status and therefore more susceptible to getting an infection. Those horses that are in barns with a lot of in-and- out traffic will have frequent contacts with a large numbers of horses and therefore are more likely to come in contact with the virus. This is much like children bringing home the common cold from school. Sporadic outbreaks of equine influenza occur throughout all horse areas of the world. The virus infection is spread primarily by aerosolized droplets dispersed by coughing. However, the virus can be spread by contaminated equipment (buckets, grooming aids) and contaminated hands. The virus can survive for hours in the environment. Influenza outbreaks can be avoided by;
• preventing entry of the virus into horse groups by quarantining newly arrived horses for at least 14 days and
• appropriate vaccination before exposure.
Vaccination
Equine influenza virus vaccines usually consist of inactivated whole virus subtypes AE-1 and AE-2, or their subunits, with or without adjuvant (to improve immune response). Experts now recommend that the AE-1 component of vaccines should be omitted as no infections with that subtype have been substantiated during the past twenty years.
• Younger horses should receive a primary series of 3 doses of the killed-virus vaccine administered 3-6 weeks apart starting at 6 months of age.
• Revaccination should be at intervals of 3 to12 months depending on age and risk of exposure.
• Revaccination of performance horses should be at intervals of 3 - 4 months.
Using the modified live equine AE-2 influenza vaccine for intranasal administration;
• A single administration protects for at least 6 months.
Regulatory Information
There are no requirements for horses to be vaccinated against equine influen-
za. There are no restrictions for infected horses or horses exhibiting signs of a res- piratory virus from leaving or entering a shows, tracks or other facilities. There are no requirements for horse owners, trainers, grooms or veterinarians to notify any official (provincial, federal or race track) when influenza is suspected.
SEE RECOMMENDATIONS PAGE 38
Using the killed-virus vaccine;
It Takes a lot to be a Winner
Knowledge
Experience
Perseverance Commitment
Brooks (KER) Performance Feeds is very pleased
to congratulate 2004 Sovereign award winning Trainer, Robert Tiller (right) with 2004 top
Assistant Trainer,Tom Lottridge
Robert Tiller has what it takes:
• 3-time Sovereign Award Winner
• 4-time Leading Trainer at Woodbine • Among the top 5 Trainers for
16 consecutive years
• An acknowledged and respected
horseman and conditioner
2004 Sovereign winner Robert Tiller and many other trainers have found that a successful feeding program combines cutting edge research from Kentucky Equine Research, award winning manufacturing from Brooks Performance Feeds and dependable service
from their dedicated dealers:
Bob Peatling’s Triple Crown Feeds Minor Bros. Farm & Country at Fort Erie
Woodbine Racetrack 416-453-7038 905-892-6212 905-658-2559
Phase III
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supplement rich in energy boosting Omega 3 fatty acids
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For more information call:
Brooks Performance Feeds 905-261-8458 905-985-7992 705-928-1288
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