Merck Animal Health and Veterinary Experts Partner to Publish Best Practices for Mitigating the Spread of CIV H3N2

Madison, N.J., February 23, 2017 – When an outbreak of canine influenza H3N2 hit several large metropolitan areas in 2015 and 2016, thousands of pets were affected, as were a number of the pet businesses that cared for them. Some of the impacted facilities, such as shelters, kennels, groomers and daycares, were forced to close for weeks. Costs to treat animals and clear the virus from the facilities skyrocketed and businesses suffered lost revenue as the industry worked to understand the virus and how to stop its rapid spread. Within nine months, the virus had spread to more than half the country. Researchers at the University of Wisconsin discovered one of the reasons that canine influenza H3N2 is spreading so quickly- infected dogs can shed the virus for more than 24 days.1
At The Anti-Cruelty Society in Chicago, one sick dog led to an incredibly rapid spread of the disease within the shelter and in the end, 100 of 120 dogs fell ill.2 Given the highly contagious nature of this virus and the possibility of future outbreaks, Merck Animal Health expanded its canine influenza educational initiatives to include best practices that pet businesses can use to help prevent canine influenza from making its way into a facility, as well as what to do if that happens.
“We were able to take the knowledge we had gained from the numerous outbreaks and leverage the expertise of several well-renowned veterinary professionals to develop practical yet important precautionary measures that can be taken to protect the health and well-being of animals and the viability of their respective businesses,” said Melissa Bourgeois, D.V.M., Ph.D., DACVM, Merck Animal Health, who participated in the roundtable discussion to create the recommendations. “While vaccination of at-risk dogs for both strains of CIV is the best first line of defense, education and stringent cleaning protocols are equally critical to effectively managing this virus.”
Some of the key recommendations include:

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  • All dogs should receive vaccinations against core canine infectious diseases.
  • Social dogs are at even greater risk for infectious diseases like canine influenza and pet owners should consult their veterinarian about their risk of disease and vaccination needs.
  • For the best protection, all vaccination series should be finished at least two weeks before visiting a boarding kennel, daycare, training facilities and other events where dogs commingle. This allows time for the immune system to respond.
  • Immediately isolate any dog that shows any signs of infectious disease, such as lethargy, loss of appetite, fever, coughing or diarrhea.
  • Prepare for potential outbreaks by assessing your capacity of care, vaccination recommendations, and sanitation and isolation protocols, as well as educating your staff on these topics.

The recommendations in their entirety were published in the February issue of AAHA Trends Magazine and can be accessed here. The roundtable discussion can be viewed at

About Canine Influenza

Canine influenza virus H3N8 first appeared in the United States in 2003 and since then has been diagnosed in 42 states, most recently in Missouri and Montana. In 2015, a new strain of canine influenza emerged called H3N2, which has already spread to at least 30 states. The H3N8 and H3N2 viruses have different origins and are not closely related; therefore it is important dogs are vaccinated against both strains to ensure they are protected. It has been reported that H3N2 infected dogs produce 10 times more virus than dogs infected with the first strain (H3N8), potentially making it more contagious. H3N2 may be shed for up to 24 days, which is longer than what is seen with H3N8.1 However, both viruses can spread quickly among social dogs. The viruses can be transmitted directly from dog to dog through droplets from sneezing and coughing or indirectly through fomites.

About Merck Animal Health

For over a century, Merck has been a global healthcare leader working to help the world be well. Merck Animal Health, known as MSD Animal Health outside the United States and Canada, is the global animal health business unit of Merck.Through its commitment to the Science of Healthier Animals™, Merck Animal Health offers veterinarians, farmers, pet owners and governments one of the widest range of veterinary pharmaceuticals, vaccines and health management solutions and services. Merck Animal Health is dedicated to preserving and improving the health, well-being and performance of animals. It invests extensively in dynamic and comprehensive R&D resources and a modern, global supply chain. Merck Animal Health is present in more than 50 countries, while its products are available in some 150 markets. For more information, visit or connect with us on LinkedIn,Facebook and Twitter at @MerckAH.
1. Newbury S, et al: Prolonged intermittent virus shedding during an outbreak of canine influenza A H3N2 virus infection in dogs in three Chicago area shelters: 16 cases (March to May 2015), JAVMA, Vol 248, No 9, May 1, 2016.
2. Anti-Cruelty Society of Chicago. Accessed at