Merck Animal Health Study Reveals Equine Influenza on the Rise

Equine influenza virus is one of the leading respiratory diseases in the United States and the number of horses infected has been on the rise1. Since 2008, Merck Animal Health has collected more than 4,700 samples from horses presenting with signs of acute infectious upper respiratory disease and/or acute neurologic disease as part of an ongoing research program. The two leading diagnoses, based on samples submitted from horses of all disciplines and ages across the United States, have been equine herpesvirus-4 and equine influenza virus1.

In an effort to protect horses against these two prevalent respiratory diseases, the United States Equestrian Federation (USEF) will be implementing a rule effective Dec. 1, 2015, mandating that all horses be current (within six months) on their equine influenza virus (EIV) and equine herpesvirus (EHV) vaccines prior to entering a USEF show.

A Step in the Right Direction

Kent Allen, DVM, volunteer chair for the USEF veterinary committee, as well as the drug and medications committees, said the rule change is going to be better for horses and show competitors.

“This rule change and uniformity of rules is going to help us not only better protect our horses against infectious upper respiratory diseases, but it also will improve the welfare of these show horses,” Allen said. “It is important for every owner, as well as the entire USEF organization to ensure that each horse is adequately protected through appropriate vaccination.”

According to Allen, the new rule will be straight-forward and easy for USEF competitors to implement.

“The bottom line is your horse must be current on their equine influenza and equine herpesvirus vaccines by Dec. 1, 2015,” Allen said. “If you maintain this vaccination schedule and obtain appropriate documentation, you will not only comply with the rule, but you also will ensure your horse is adequately protected against these highly contagious respiratory diseases.”

Protecting Your Horse from EIV

Even if you are not competing in USEF shows, EIV should still be a top-of-mind disease concern for all horse owners.

“This highly contagious virus can infect an entire barn of horses in less than 48 hours and it can take weeks to months for each infected horse to completely recover,” says D. Craig Barnett, DVM, Merck Animal Health director of equine veterinary technical services. “Owners and veterinarians alike need to make sure horses at risk for EIV are adequately protected through appropriate vaccination.”

Allen and his staff at Virginia Equine Imaging in Middleburg, Virginia, who specialize in sport horse care, have used the FLU AVERT I.N. vaccine since the product was launched in 1999.

“We know that equine influenza outbreaks happen, especially in high-volume facilities like show grounds, and that is why we trust FLU AVERT I.N. to protect our patients,” Allen said. “We appreciate the vaccine’s long-lasting protection even against various strains of the influenza virus. Based on the research, my practice is convinced FLU AVERT I.N. gives horses a stronger, longer immunity to the influenza virus.”

Another reason Allen prefers FLU AVERT I.N. is the vaccine’s unique intranasal application.

“The athletes in my care need all of their muscles to compete at the highest level,” Allen said. “Any time I can avoid disrupting the muscles they use to compete, I will. I find the intranasal administration of the vaccine to be a superior delivery method.”

The Ideal Vaccine for Horses at Risk

FLU AVERT I.N. has been proven safe and effective in numerous studies, even in horses with compromised immune systems from traveling and/or training2.

“Often times, horses at highest risk for EIV are undergoing times of stress, such as a rigorous showing/training schedule, being transported, or undergoing yearling sale preparation,” Barnett said. “The fact that FLU AVERT I.N. has been tested and proven to be effective, even in these immunosuppressed horses, should give owners and their veterinarians peace of mind that their horse will be protected when vaccinated with FLU AVERT I.N.”

Additionally, FLU AVERT I.N. is the only vaccine on the market that achieves primary immunity from a single dose–even in horses never vaccinated for EIV before, such as late weanlings and yearlings receiving their first influenza vaccine and/or horses with an unknown vaccination history. FLU AVERT I.N. only requires one dose and starts working weeks sooner than other EIV vaccines, which require a minimum of two doses three to four weeks apart. Due to its rapid onset of immunity, FLU AVERT I.N. is recommended in the American Association of Equine Practitioners vaccination guidelines for use in the face of an EIV outbreak.

Effective Against Relevant U.S. Flu Strains

FLU AVERT I.N. continues to prove through clinical research that it provides exceptional protection against clinically relevant influenza strains infecting the United States horse population1,3,4.

“Recently, reports about the lack of effectiveness of EIV vaccines due to changes and mutations in the flu strains infecting our horse population have been on the rise,” Barnett said. “This problem has been challenging and frustrating for veterinarians and owners. However, FLU AVERT I.N. is one option we can count on to be effective against flu strains infecting horses here in the United States. No other equine influenza vaccine provides the same level of protection.”

In addition, a new study conducted at Colorado State University demonstrated how FLU AVERT I.N. stimulates a non-specific, innate immune response at the site of respiratory infections–the upper respiratory tract. This non-specific immune response may help provide some degree of protection against not only EIV, but other respiratory pathogens as well5.

Don’t Leave Home Without It

Influenza is one of the most common and contagious equine respiratory diseases and can lead to significant time away from the saddle. If your horse travels, is in training, shows, races, is young or old and/or comes in contact with other horses that meet the mentioned criteria, then it is at risk for contracting EIV.

“Owners need to be concerned about infectious upper respiratory diseases, especially the most prevalent like EHV-4 and EIV,” Barnett said. “Although they are not typically fatal, they can require significant recovery time and are certainly uncomfortable for the horse.”

Talk to your veterinarian today about protecting your horse with FLU AVERT I.N. To watch an educational video on EIV and FLU AVERT I.N., click here.

1. UC Davis (Nicola Pusterla) & Merck Animal Health. Infectious Upper Respiratory Disease Surveillance Program.
Ongoing Research 2008 – present.
2. Lunn DP, Steve Hussey S, et al. Safety, efficacy, and immunogenicity of a modified-live equine influenza virus
vaccine in ponies after induction of exercise-induced immunosuppression. JAVMA 2001:218(6):900-906.
3. Chambers TM, Holland RE, et. al. A new modified live equine influenza virus vaccine: phenotypic stability, restricted
spread and efficacy against heterologous virus challenge. Equine Vet J. 2001;33(7):630-636.
4. Van de Zande S. Efficacy of Flu Avert IN, a modified live influenza vaccine for horses used in different vaccination
schedules against A/Equi-2/South Africa 04/03 Challenge. Efficacy of Flu Avert / Prequenza, a combined vaccination
schedule against A/Equi-2/Newmarket/05/03 challenge. Patent publication US7601502 B2 October 2009.
5. Landolt GA. Comparison of innate immune responses in equine respiratory epithelial cells to modified-live equine
influenza vaccine and related wild-type influenza virus. Abstract ACVIM 2014.






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