MSD Animal Health Equine is highlighting the results of a study conducted by the company which, it says, proves that Equilis Prequenza offers highly significant protection against viral shedding and the clinical signs of equine influenza (EI).

Current World Organisation for Animal Health (OIE) recommendations are to include a representative strain from each of the two sublineages of equine influenza virus (EIV) - Florida Clade 1 and Florida Clade 2, to deliver optimum protection. 

MSD's study was designed to evaluate the efficacy of Equilis Prequenza, containing whole virus Newmarket/2/93 (European strain) and South Africa/4/03 (Clade1) EIV strains, and an HA canarypox vectored vaccine containing Florida Clade 1 and Clade 2 strains.

Two groups of seven Fjord ponies were vaccinated twice, 4 weeks apart (V1 on day 0 and V2 on day 28).  One group was vaccinated with Equilis Prequenza (MSD AH) and one group with ProteqFlu (Boehringer Ingleheim). The protective antibody response was measured and ponies were challenged, along with six unvaccinated control ponies, by experimental infection with Wexford/14 (a heterologous clade 2 strain), 1 20 days (4.5 months) after V2, and clinical signs and virus shedding monitored. EI serology was measured by single radial haemolysis (SRH) and hemagglutination inhibition (HI).  Clinical signs and virus shedding (measured by qRT-PCR and egg titration) were compared between groups and with controls.

Vicki Farr, BVetMed MRCVS, equine veterinary advisor at MSD Animal Health said: "Following challenge at 120 days after V2 with Wexford/14, this study demonstrates that both vaccines provide a highly significant degree of protection against clinical signs of EI and viral shedding compared to unvaccinated controls. Although the study was not designed to compare the efficacy of the two vaccines, because of practical limitations on the number of animals and hence low power, there was no evidence of any significant differences between these two groups. There was, however, a trend towards slightly lower clinical score on days 4-8 and reduced virus excretion on days 2-5 in the Equilis Prequenza group compared to the HA canarypox vectored vaccine.” 

MSD says Equilis Prequenza offers a broad based approach to immunogenicity by addressing and adapting key areas of an equine influenza vaccine - Matrix-C adjuvant, whole virus antigen and strain; efficacy has been proven through challenge trials and longer term protection confirmed by serology.      

Vicki added: "Equilis Prequenza addresses key factors involved in promoting effective immunogenicity. It combines the demonstrated efficacy against challenge, with a current circulating strain with an established safety profile.  Equilis Prequenza stimulates active immunity against EI providing the reassurance your clients demand. MSD Animal Health is committed to working with equine practices to improve vaccination rates in at-risk horses."

For more information about the trial results contact your MSD Animal Health account manager.

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