Canine Influenza - An Emerging Concern
By Dr. Leanne Bertani
Canine Influenza has recently become a serious concern among dog fanciers.
The virus was first identified in 2004 as the culprit in a respiratory condition that plagued racing greyhounds in Florida. The Animal Health Diagnostic Center (AHDC) at Cornell has since confirmed that Canine Influenza has reached other states and the non- greyhound canine population. The latest outbreak is in New York, where some boarding kennels have been forced to close temporarily to contain the spread of the virus.
What is interesting about this virus is that it appears to be an H3N8 flu, very similar to the equine (horse) influenza virus. Because it is considered to be an interspecies transmission, the Center for Disease Control is monitoring the outbreak, but officials do not consider the virus to be a public (human) health threat at this time.
The dangerous aspect of the virus in canines is that it initially presents as a common tracheobronchitis ("kennel cough") and may not be respected as the devastating condition it can become. The predominant initial system is a persistent cough, which may continue for 2 to 3 weeks or more. While all forms of tracheobronchitis are theoretically susceptible to secondary bacterial infection, the likelihood of a serious bacterial pneumonia seems to be increased in Canine Influenza. The pneumonia may be accompanied by a sinusitis with purulent nasal discharge and fevers up to 106 degrees Fahrenheit. While the overall fatality rate for all breeds appears to be somewhere around 1%, fatalities may reach 10% or more in puppies, elderly dogs, and those in which treatment has been delayed. In a January outbreak in Florida, 24 greyhounds became clinically ill with the virus; eight of them are said to have died.
At this point in time, the therapy for Canine Influenza is largely supportive, similar to that for other forms of tracheobronchitis. Supportive therapy may include fluid and calorie supplementation, enforced rest, and antibiotics to treat or prevent secondary bacterial infection. Cough suppressants, nebulizers and bronchodilators may be used in selected situations. Hospitalization may be required for dogs with pneumonia or dehydration.
Because fever is thought to help the body fight disease, antipyretics such as aspirin are generally only suggested if the fever is greater than 106 degrees Fahrenheit and does not respond to physically cooling the body. If underlying conditions such as heart failure, respiratory problems or seizures are present, it may be prudent to use antipyretics for more moderate fevers.
While vaccines are available for some types of kennel cough due to bordetella, adenovirus and parainfluenza, there is no vaccine for the Canine Influenza virus available at this writing. If the condition becomes widespread, a vaccine may be formulated in the future. The new flu may be susceptible to antiviral drugs such as amantidine and Tamiflu, but those drugs are not approved for canine use at this time.
Since this is a relatively new pathogen and there is no vaccine available, nearly all dogs are susceptible. The incubation period is only 2 to 5 days, and the transmission rate appears to be high. Veterinarians and immunologists estimate that if one dog in a kennel is affected, the infection will probably be transmitted to nearly all of the rest, even though obvious clinical signs may appear in only 75-80% of the kennel's residents.
For a limited time, the AHDC at Cornell is accepting blood samples at a reduced rate: $20 instead of the normal $50 virus isolation fee. Both acute and convalescent samples are recommended, one at onset and another 2-3 weeks later. In dogs that have recovered from infection, a single sample can determine whether or not the dog was infected with the virus at any time in the past, but will not provide information as to the time of infection. Cornell is also presently accepting lung tissue samples, and those samples, along with throat samples from dogs with high fevers, will be tested for the Influenza virus without charge if accompanied by a case history from your veterinarian. For more details on sample submission, see http://www.diaglab.vet.cornell.edu/news.asp
The take-home message is that we may need to be a little more vigilant about "kennel cough." Don't take coughing dogs to places frequented by other dogs. Keep dams and puppies separated from dogs that are being shown. Wash clothing and change shoes when returning from shows, dog parks or other kennels, particularly if you are in an area where the virus has been confirmed and you have puppies at home. A lower threshold for the decision to prescribe antibiotics for coughing puppies or older dogs may also be indicated.