Dr. Gabriela Landolt

In late February 2011, a jump in cases of respiratory disease in dogs living in and around Durango, Colo., set off alarm bells and created some panic in dog owners concerned about their pet’s health. The outbreak garnered national media attention, and suspicions were raised about a potential epidemic of canine influenza or the possibility of a new virus yet to be described in scientific literature.

Testing at Colorado State University and other laboratories did not pick up canine influenza or H1N1 (some were concerned about this possibility of “swine flu” in dogs). The outbreak most likely was a commonly occurring respiratory infection that took on the look of an epidemic when dogs that regularly attended doggie daycare became infected and ill. Nearly 150 dogs were ill, but all made full recoveries. Lingering questions remain, though, particularly about canine influenza. Dr. Gabriela Landolt, an Assistant Professor in the Department of Clinical Sciences, is hoping her research and that of her colleagues will help answer some of those questions.

“Canine influenza is a problem in Colorado consistently,” said Dr. Landolt. “Through a grant from the Morris Animal Foundation and in collaboration with the ASPCA, we are conducting canine influenza virus surveillance in six humane shelters to see how many dogs that enter and leave the shelters are positive for canine influenza virus or have antibodies directed against the virus in the blood, and what happens to the virus while in the shelter environment.”

Researchers are studying six shelters in Colorado, New York, South Carolina, Florida, Texas and California over a three-year period to determine the levels of canine influenza infection in the shelter dog community. After 18 months of study, early results show a consistent level of canine influenza in Colorado dogs (roughly 8 percent of shelter dogs tested positive for canine influenza virus), with lesser rates in South Carolina, New York, and Florida.

“Unlike in human medicine, we don’t have a centralized surveillance system, so it’s difficult to understand the epidemiology of canine influenza,” said Dr. Landolt. “We hope that this study will give us more data to work with, at least in the shelter community.”

Canine influenza was first isolated in Florida in 2004, with genetic analyses indicating that it began as an equine virus that ended up in dogs. For inexplicable reasons, in the United States the virus has been maintained in dogs and has acquired some consistent changes that have led to the formation of its own lineage. Based on experimental and epidemiological data, dogs also appear to be susceptible to infection when in contact with horses with equine flu. In contrast, horses do not seem to be susceptible to canine influenza.

“The virus has adapted somewhat to dogs, but certainly hasn’t gone as far as it could have,” said Dr. Landolt. “Influenza viruses are not very stable in the environment, so you have to have the right conditions with close contact and closed in spaces to efficiently transmit the virus between dogs.”

Infected dogs fall into three categories: infected with no clinical signs; infected with mild symptoms (fever, cough, lethargy, loss of appetite, and nasal discharge); and a small percent that develop severe disease. These tend to be older or very young animals or animals with pre-existing conditions, particularly lung or heart disease, as well as dogs that are under high stress. Most animals do recover fully.

Dr. Landolt and colleagues recently published a study conducted in dogs that were seen by the Community Practice Service at the Veterinary Teaching Hospital to look at risk factors for canine influenza. The paper, published in the Journal of Internal Veterinary Medicine (November/December 2010), showed that two primary risk factors for canine influenza were doggie daycare and boarding. Similar to human influenza, canine influenza is transmitted more easily in closed spaces. No risk factor was associated with outdoor dog parks. (Seroprevalence and Risk Factors for Canine H3N8 Influenza Virus Exposure in Household Dogs in Colorado E.A. Barrell, H.L. Pecoraro, C. Torres-Henderson, P.S. Morley, K.F. Lunn, G.A. Landolt)

The take-away message for pet owners and veterinarians is that for dogs that get sick with canine influenza, most recover fully. A canine flu vaccine is available and Dr. Landolt recommends it be administered based on risk. If you dog goes to doggie daycare or a boarding facility, the canine influenza vaccine and booster might be a good investment.