Dog owners in Montgomery County, Maryland have been cautioned to look for signs of the highly infectious canine influenza virus. The warning comes after the Maryland Department of Agriculture notified veterinarians on August 21 that the virus had been identified in six dogs – two of which had died. An updated bulletin released on August 29 stated that the total number of identified cases within Montgomery County had risen to at least twenty.
Canine influenza (H3N8) was first identified in 2004 among racing greyhounds in Florida. Quick refresher on influenza: There are three types: influenza A, B, and C. Within influenza A, there are different subtypes that are categorized by the different structure of the proteins on the outside of the virus. The canine influenza virus is closely related to the equine influenza virus subtype H3N8 suggesting that the virus was first transmitted to dogs from horses. Other subtypes of influenza have infected dogs (e.g. H3N2, H5N1, and H1N1). H3N8 is suspected in this instance because, historically, this influenza subtype infects dogs within the United States. Laboratory results confirming the subtype of the virus are pending and should be available in two to three weeks.
Since 2004, canine influenza has been found in 30 states and the District of Columbia. The respiratory virus is highly contagious and spreads through direct contact of aerosolized respiratory secretions or contact with contaminated objects. Because the virus is still relatively new, most dogs have never been exposed, which means that all ages and breeds are susceptible. Twenty percent of infected dogs will remain asymptomatic (or without symptoms), while 80 percent will develop symptoms that include coughing, sneezing, fever, nasal discharge, lethargy, and loss of appetite. While the mortality rate is relatively low (between one and five percent), severe infections may lead to pneumonia and death. Infected dogs, even those that are asymptomatic, shed the virus and remain contagious for seven to ten days. Currently, there is no evidence to suggest that dogs can transmit canine influenza to humans, however due to the constantly changing nature of influenza viruses, H3N8 is being monitored closely.
Dog owners should be on alert for symptoms of canine influenza, and are advised to contact their veterinarians if symptoms develop. Some suggest that owners temporarily avoid places where dogs congregate, such as parks and kennels, as these places increase a dog’s risk for exposure. Montgomery County is keeping its five dog parks open, however signs have been posted that list symptoms of the virus. A vaccine is available, and owners of dogs that attend kennels and parks, or otherwise interact with other dogs, are advised to speak to their veterinarian about the vaccine.