Merck and Zoetis line up rival vaccines to fight new strain of dog flu

After an outbreak of canine influenza sickened 1,000 dogs in the Chicago area, 5 of which died, some veterinarians were recommending vaccines made by Merck ($MRK) Animal Health and Zoetis ($ZTS). Problem was, those vaccines were designed to fight the H3N8 strain of the vaccine, which had been prevalent in the U.S. until this year. So vets couldn't promise those vaccines would do much to fight the new strain, H3N2.

Now both companies have stepped forward, just in time for flu season, with vaccines against H3N2. On Nov. 20, Merck announced it had received a conditional license from the USDA to market Canine Influenza Vaccine H3N2--just one week after Zoetis received the same USDA nod for its vaccine. Both of the new vaccines require two doses, administered a few weeks apart.

The new vaccines don't protect against the previously known strain of dog flu, even though that illness is still circulating. So dog owners who want total protection will have to get separate vaccines for H3N8 and H3N2, Merck and Zoetis have said.

Just how serious the threat of dog flu will be this season is a bit of a guessing game. H3N2 was mostly confined to the Midwest, though at the height of the outbreak, veterinarians across the country were voicing concerns the virus would spread. Those worries were heightened by the fact that unlike the older strain of dog flu, this one can spread to cats.

Merck developed its vaccine in collaboration with Cornell University, according to a press release from the company. At first, veterinarians thought the illness they were seeing was merely kennel cough, but Cornell veterinarians tested samples from their noses and throats and discovered the new strain of dog flu, Merck reports.

Edward Dubovi a professor and director of virology at Cornell's Animal Health Diagnostic Center, believes pet owners should seriously consider the new flu shots for their dogs, even if they never vaccinated them against the disease in the past. "Based on experimental studies in Asia and the rate of spread we've observed, I would estimate that H3N2 produces 10 times more virus than H3N8, which makes it far more contagious," Dubovi said.

The quick turnaround on the H3N2 vaccines from Merck and Zoetis isn't surprising, as both companies have been boosting their efforts in preventative health for pets. Zoetis has been shrinking its product portfolio and narrowing its R&D efforts in a bid to cut costs, but it remains dedicated to vaccines, which it demonstrated with its recent $765 million acquisition of Pharmaq, a leading maker of fish vaccines.

And despite rumors that Merck was considering casting off its animal health business, the company recently bulked up its efforts in prevention, announcing earlier this month that it would be buying Harrisvaccines for an undisclosed sum. The USDA has appointed Harrisvaccines to manufacture doses of an avian influenza vaccine for an emergency stockpile.

- here's Merck's press release on canine influenza