Articles and Information

Equine Flu In The North State

by Dr. Dawn Alves

I am still working on some research about the ID on the strain of flu we are dealing with. If it is a new one or just a resurgence or increased virulence of one that is already included in our vaccines.  Here are some of the issues contributing to this outbreak right now.  Many horses are not kept current on flu vaccinations because most vaccines require multiple vaccinations (2-4) per year to keep immunity up.  Unfortunately there is a big difference between flu vaccines available also as to effectiveness and the number of flu strains each one covers.  There is also a lot of variability based on the amount of antigen in a flu vaccine that contributes to the immunity created.  It is very true that not all vaccines are created equal. Just because it says influenza on the label does not mean it is going to provide your horse with the best or even OK protection.   Also multiple antigen combination vaccines(4 way & 5 way or more) do not create as good of flu immunity.  With these combination vaccines the immune system is challenged by many things at once and in many cases can't concentrate as much as needed on each individual antigen.  Also big combination vaccines have to contain less of each individual antigen so the vaccine is not too reactive(meaning lumps, soreness and sick horses).  It is well documented that the immune system responds well to high antigen density vaccines.  Our routine vaccine program uses a separate rhino-flu vaccine without other things added to get relatively reliable good immune responses without high reactions.   In the case of this particular bout of flu, it seems to be relatively virulent(makes horses pretty sick) and even some "vaccinated" horses are getting it.  Any horses that travel or are exposed to other horses that they don't live with regularly are at risk.  Shows, clinics, trail riding, hospitals and anything else where horses get together are a risk.  The best prevention in a time of outbreak is keep your horse isolated from other horses whenever possible.  Remember this is airborne and spread by nasal secretions and they can spread horse to horse easily when they are in close proximity.  If your horse must be around other unfamiliar horses, use normal precautions to help protect them- no community water troughs or buckets, avoid nose to nose contact, steer very clear from any horses with coughs or runny noses, don't walk down the barn aisle at a boarding facility and pet every horse you pass as you might be the spreader of disease, sick horses should not be moved and should be isolated from others as possible.  So if your horse is as risk of exposure whether it is vaccinated or not, we recommend giving the nasal flu vaccine (flu avert) as soon as possible.  That vaccine seems to be providing the best protection in this outbreak right now.  It provides non- specific local immunity in the nasal passages in 24-48 hours and specific flu immunity by about 3 weeks.  Because it is a nasal vaccine, it approaches the immune system differently than our injectable vaccines and that seems to be the key right now in preventing this flu.

By, Dr. Dawn Alves DVM