April 01, 2010
WHAT IS CANINE INFLUENZA?
Canine influenza is a new viral strain called H3N8. The name is derived from the amino acid composition of Hemaglutinin (H) and Neuramindase (N). There are 16 different Hemaglutinin antigens and 9 different Neuramindase antigens. It is a member of the Influenzavirus A genus in the family Orthomyoviridae. All of which is interesting, but unimportant. What is important is that it spreads between dogs only AND is highly contagious. There are two other strains, H3N2 and H5N1. Neither is readily transmitted.
H3N8 has been around the last 40 years as an equine virus, but then something rare occurred. The entire genome transferred itself to dogs. It is now a canine-specific virus. The first documented case was in 2004, but researchers believe it has been around since 1999. It was diagnosed at a greyhound track in Florida and spread quickly through 14 tracks in six states. There are now confirmed cases in 30 states.
WHO’S AT RISK?
It is so highly contagious because it is a new strain. Most dogs do not have an immunity to it. An estimated 80% of dogs coming into contact with it will become infected. Key phrase here is “coming into contact with”. Most of those infected will have a mild case. Approximately 20 to 25% of those will be asymptomatic, but still contagious and a probable fatality rate of 1 to 5%. There is no “season” for it spreads year round. Those dogs highest at risk are those closely congregated, the very young, the very old and the immune-compromised. Scenarios that increase exposure include kennels, doggie daycare, dog parks, breed events, Veterinarian offices and grooming shops. It takes only one dog to infect an entire group.
Its transmitted in the air by coughing and sneezing. By fomites that contaminate surfaces such as tables and doorknobs. And direct contact by licking, nuzzling, petting, people moving between infected and uninfected dogs and shared toys, bedding, water and food dishes.
Incubation is two to five days before the onset of clinical signs. The time the dog is most contagious is before you realize he is infected. They can spread the virus for up to 10 days after symptoms appear. Asymptomatic dogs are just as contagious.
It appears as a dry or moist cough, nasal discharge, low grade fever, lethargy and loss of appetite. Most fatalities occur in undiagnosed dogs. Left untreated it can lead to hemmorrhagic pneumonia.
You cannot diagnosis canine influenza by clinical signs alone. It is often misdiagnosed as kennel cough because it’s difficult to differentiate between other respiratory pathogens. The most reliable test is a blood test done within the first seven days or a throat swab in the first four days.
Since it is a virus, treatment is mostly supportive. Keep your dog well-hydrated, fed a nutritious diet and gives lots of TLC. A cough suppressant may be prescribed. The virus replicates in the respiratory tract and in the nasal lining, which can lead to a secondary bacterial infection. In such circumstances, a broad-spectrum antibiotic is prescribed. Most dogs will recover in two to four weeks.
The virus is easily killed by disinfectants. Examples are quaternary ammonia compounds like Roccal-D, 10% bleach, 1% sodium hypochlorite, 70% ethanol, heated at 56 C/133 F for 30 minutes, irradiate or low pH solutions (2).
Wash your hands before and after handling dogs, after disinfecting equipment and surfaces and before and after leaving pet facilities. Wash clothing normally.
Coughing dogs should not participate in activities where other dogs congregate.
The USDA just approved the first canine influenza vaccine. Like the human vaccine, it may not prevent entirely, but may lessen the severity and duration of the flu. Vaccinated dogs will also have a shorter contagious period.
The best defense, however, is a healthy, well-nourished dog living and playing in a clean environment.
Does all of this sound as if it is the same advice and protocols for the human flu? The precautions we should take for ourselves based on our risk factors is the same for dogs. With one exception. Your coughing dog is nothing to sneeze at. A cough can be an indicator of a serious medical condition that could escalate quickly. Timely veterinary treatment that includes proper testing leads to the correct diagnosis and the right treatment. Afterall, they would do it for us.