Page 33 - NMHBA Summer 2017

“We typically see outbreaks of flu in young horses two to five years old, in training or congregated for racing, showing, etc.”
The influenza virus denudes the epithelium, destroying the cilia and removing that defense mechanism. “The serious cases of influenza are the ones that develop secondary bacterial infection in the lungs (pneumonia),” explains Crisman.
You don’t want the horse exercising, breathing deeply, drawing dust or debris down into airways that cannot fully protect against these particles getting down into the lungs. If you exercise him too soon, you may set him up for a more serious respiratory infection. Many riders, especially those with competition schedules, don’t give the horse enough time.
“We typically see outbreaks of flu
in young horses two to five years old,
in training or congregated for racing, showing, etc. Their job is to perform/make money, and it’s hard to convince people they need to rest a horse this long because the horse feels better after just a week or
so and looks normal. But he’s not,” says Crisman.
Prevention
There are two ways to protect your horse—with vaccination and with attention to biosecurity. “Vaccination is helpful, but it simply puts a protective barrier around the horse for a short period of time. It is not the greatest limiting step for disease prevention,” he says.
“I can’t emphasize enough the importance of biosecurity, but this is
the hardest thing to get people to do.” Keeping new arrivals separate from your other horse for two weeks, quarantine of sick horses, etc., is a good technique to use for biosecurity. “New horses need to
be isolated, checked closely and monitored to make sure they are staying healthy,
with temperature taken twice daily. Also important is submitting nasal swab samples if a horse does get a fever so that we know what it is. There are many diagnostic labs that can help us identify it. Our strategy for treatment and care will be different if it’s herpes or influenza,” he says.
Disinfection is equally important when there is a sick horse, as it ensures the virus is not spread to other horses on shared equipment. Some people just use bleach solutions, but organic matter, such as straw and manure, makes bleach ineffective. “Fortunately, the influenza virus is not very hardy in the environment and, if it is sitting on a surface somewhere, it won’t last a long time. Equine Influenza is primarily spread by nasal secretions from one horse to the mucus membrane of the second horse. It’s not like strangles, which can survive in the environment or in water buckets a lot longer,” says Crisman.
Vaccination can be helpful. For instance, vaccination of mares can help protect their foals. “If a mare is vaccinated during her last trimester, she passes immunity to her foal via colostrum. In this situation, foals will have immunity up to about five or six months of age. If there are other horses on the farm traveling in and out, this could put foals at a higher risk. Depending on exposure risk, some people start vaccinating their foals at five or six months of age, or may wait until they are eight months of age,” he says.
Influenza is a risk-based vaccine. The horses most at risk should be vaccinated three or four times a year. For a backyard
horse that never goes anywhere and might only be exposed unintentionally by an unforeseen encounter with other horses, annual vaccination might or might not be adequate.
“Decisions regarding influenza vaccination should be made by the owner in consultation with his/her veterinarian as to how they will handle vaccination. Influenza is a risk-based vaccine
(rather than one of the core vaccines recommended by the AAEP for every horse), and not very immunogenic,” says Crisman.
“Some of the other vaccines, like tetanus, EEE, WEE and rabies, are highly immunogenic; the body mounts a good
The equine influenza vaccine is a cheap insurance policy and can prevent a large medical bill should the horse become ill.
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