BIOSECURITY:

cell-mediated immunity,” says Green. This formula requires a two-dose series to confer immunity in an unvaccinated horse, followed by boosters every six months.

Any of these products are effective when used as directed. “I think that an intranasal vaccine has some inherent advantages but other vaccine types have their own advantages. The conventional vaccines do work, if you keep the horses regularly boosted,” says Thomas Chambers, PhD, of the University of Kentucky’s Maxwell H. Gluck Equine Research Center, who emphasizes that following up with appropriate boosters is critical the first time a horse is vaccinated: “If you don’t give the follow-up booster shots, you rapidly lose the immunity. There is a lot of data showing this. You need to give the priming dose, and then a few weeks later the booster, which will stimulate the immune protection to an effective level, and then keep up the regular boosters.”

One precaution Keene recommends is to choose a vaccine with the strains that are representative of the viruses that are currently circulating. “Current recommendations from the Expert Surveillance Panel on Equine Influenza are to use a vaccine containing Clade 1 influenza strains [for example, Ohio/03], for those horses within the United States,” he says. “If your horse travels or is exposed to horses traveling internationally, the vaccine should also include a Clade 2 strain [for example, Richmond/07].” The EIV strains contained in an influenza vaccine can be found online or within the product insert, Keene says.

It’s important to remember, however, that a vaccinated horse can still fall ill---if it’s been longer than six months since his last booster, for example, or if he’s exposed to an unusually large quantity of the virus. Still, the vaccination will confer some protection. “A vaccinated horse has many advantages over a nonvaccinated horse if he were to contract the disease,” says Craig. “The first would be a milder, shorter course of disease in the affected animal. He will also shed lower amounts of virus, which will lead to decreased spread of the disease to other horses and improve the overall health of the herd.”

PART OF THE PREVENTIVE STRATEGY

Vaccination is an important preventive measure for equine influenza, but it is only a first step. “Vaccination is helpful, but it simply puts a protective barrier around the horse for a period of time; it is not the greatest limiting step for disease prevention,” says Crisman. “I can’t emphasize enough the importance of biosecurity---keeping new arrivals separate from the main herd for two weeks, quarantine of sick horses, etc.---but this is the hardest thing to get people to do.”

The basic principle of biosecurity is to keep healthy horses separated from those who either are already sick or could potentially be exposed to the virus. The specific steps you need to take depend on your horse’s lifestyle, but here are some basic guidelines.

• Keep frequent travelers separate from “homebodies.” Horses who frequent shows and clinics are more likely to be exposed to viruses they could bring home. It’s especially important to separate the travelers from pregnant mares and foals.

• Quarantine new horses before introducing them to the resident herd. Ideally, you’d have a separate turnout area to keep the new guy apart for a minimum of two weeks to ensure he’s not incubating any illnesses. If you have only one turnout area, you may be able

Even if you don’t have a separate barn to quarantine a sick animal, you can take measures to prevent contact with healthy horses.