May 28, 2015
The Kansas State Veterinary Diagnostic Laboratory has added a canine influenza test designed to differentiate between the common H3N8 and emerging H3N2 strains.
An H3N2 outbreak first reported in Chicago in mid-March has infected more than 1,000 dogs in about a dozen states, killing an estimated 2 to 3 percent of patients.
The laboratory’s H3N2 test was developed at Kansas State University but is not the first. Cornell University’s Animal Health Diagnostic Center and Idexx Laboratories Inc., for example, can confirm whether submitted swabs carry H3N2.
“The test offered by Idexx is a PCR assay,” said Ben Hause, MS, Ph.D., a research assistant professor in the Kansas State University College of Veterinary Medicine. “They run a PCR panel that gives yes/no answers whether the sample is positive for influenza A virus and if positive, whether it’s positive for H3 or N2 or N8. This will tell you whether the sample is positive for influenza and what the subtype is.
“We also screen samples initially by PCR to tell if the sample is positive for influenza A virus,” Hause said. “If positive, we then subtype the virus by sequencing. This will give us the H and N types, but as opposed to the Idexx assay that gives a yes/no result, we have the genetic sequence for the HA/NA genes.
“Influenza viruses mutate rapidly, and there can be significant genetic/antigenic variability within a subtype,” he added. “Sequencing is the best way for us to determine subtype and genetically characterize the virus in finer detail. Sequence information can allow us to predict whether a vaccine will be effective, develop new vaccines or perform epidemiological studies.”
A vaccine is not available for canine H3N2, a strain first identified in Asia in 2006.
“It is still unknown if the vaccine for the H3N8 strain of canine influenza offers cross-protection for this new strain,” said Susan Nelson, DVM, a clinical associate professor at Kansas State’s Veterinary Health Center.
“The main thing is to be vigilant about where you’re taking your dog and watch for signs of illness,” Dr. Nelson said. “This is a disease we’re going to see most often in places where there are groups of dogs, such as doggie day cares, dog parks and boarding facilities.”
Eighty percent of dogs infected with H3N2 display signs such as a cough, fever, nasal discharge, dehydration and lethargy, Kansas State reported. The other 20 percent are symptom-free but remain contagious, Nelson said.
“The vast majority of dogs have a mild form of the disease that lasts for about two to three weeks,” Nelson said. “They will get better with just supportive care. About 10 percent of these dogs can develop pneumonia, which can be fatal.”
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