Tarheel Tamaskan

CANINE INFLUENZA VIRUS—H3N8

Introduction

Although not widely reported until late in 2005, canine influenza is not a brand new disease: the first recognized outbreak occurred in racing greyhounds in Florida in January of 2004, and the infection may have been present in certain dog populations for a couple of years prior to that. Since its first appearance, canine influenza has been spreading steadily, and has now been found in animal shelters, adoption groups, pet stores, boarding kennels, and veterinary clinics scattered throughout the United States. Although Southern Florida continues to be a high risk area, cases have now been reported in 30 states. Currently, the disease appears to be enzootic (present in a predictable, continuous pattern in an animal community) in the Northeast (New York, the New Jersey corridor and Pennsylvania, especially Philadelphia), Colorado (especially Denver), and Florida.

Although it is likely that canine influenza will continue to spread, at this point it remains relatively uncommon in most areas and should not cause excessive alarm. There is no indication at this time for pet owners to avoid dog parks or other areas frequented by dogs. Prudent precautions are the same as always for prevention of contagious respiratory disease in dogs.

What is canine influenza?

Canine influenza is an enveloped RNA virus. Dogs are the only known susceptible species; there is no evidence at this time that infected dogs pose a risk to humans or other species. Greyhounds are the only breed thus far reported to develop hemorrhagic pneumonia and acute death following infection. There are no other known age or breed risk factors for infection, severe disease or death. Healthy, well vaccinated dogs of all ages may be affected.

Disease course (incubation and recovery)

The incubation period is 2-5 days from exposure to onset of clinical signs. Peak viral shedding occurs 2-4 days post-infection, meaning that dogs may be at their most infectious prior to showing signs of disease. This represents a slightly shorter incubation period than is usually seen with other common causes of canine respiratory disease. In experimentally and naturally infected dogs, viral shedding ceases by 7 days post infection. This relatively short shedding period is typical of influenza infection in other species. Although a percentage of dogs may be subclinically infected as described below, there is no true carrier state for canine influenza. The short shedding period and absence of a carrier state is helpful for shelters trying to minimize disease spread within the shelter and community – it is unlikely that dogs pose a significant infectious risk a week or more after infection.

Clinical signs

When canine influenza first strikes a given population, virtually 100% of dogs will become infected. However, up to ~ 20% will show no signs of disease. Therefore, all exposed dogs must be considered an infectious risk, whether or not they are showing signs of respiratory infection. In most dogs, signs of infection are similar to “kennel cough” from other causes, and may include:

• Mild low-grade fever

• Soft, moist (productive) or dry cough lasting 10-30 days

• Unresponsive to antibiotics or antitussives

• +/- thick, purulent/mildly bloody nasal discharge

After the first week or so of coughing, 10-20% of dogs may progress to a more severe form of infection, including:

• High fever (104-106 F)

• Pneumonia

Death (overall fatality rate varies and is between 1-5% but has been reported as high as 8%)

Is it flu or something else?

There is no way to distinguish canine influenza from respiratory disease caused by other infections based on clinical signs alone. Ultimately, diagnostics should be performed to rule canine influenza in or out. Some factors which raise the suspicion of influenza include:

• History

o Recent introduction of a high risk dog into the shelter population, such as a dog transferred from a canine influenza endemic area, or recent admission of a dog from a boarding kennel or racing track

• Percentage of dogs affected

o Since no dogs will have immunity when influenza first strikes, it is likely that over half the dogs will be infected. If only a few dogs are sick – even if the clinical signs are consistent with flu - it is probably not canine influenza.

• All ages affected

o Puppies are often more severely affected in outbreaks of respiratory disease from other causes, but canine influenza can strike all ages

• Vaccinated dogs affected

o Vaccination provides good protection against canine distemper and moderate protection against other agents of canine respiratory disease. If a high percentage of well vaccinated dogs are severely affected, influenza is more likely

• Possibly more severe signs, more likely fever

• Possibly less responsive to antibiotics

Diagnosis

Testing to confirm canine influenza virus is available at veterinary diagnostic centers. The best test appears to be a paired serology. This means that a blood sample is collected while the dog is sick and the second 2-3 weeks later. However, the dog is contagious immediately after exposure and during the first several days before clinical signs are noted

Transmission

As noted, virus may be excreted for up to three days before clinical signs develop. Once disease is diagnosed, it will be necessary to count back several days to determine which dogs may be at risk from exposure. The virus is shed primarily in respiratory discharge and transmission can be via direct contact, fomites (contaminated objects such as hands, surfaces, clothing, etc.), droplet, and aerosol spread. In a few cases, dog handlers have carried virus home on clothing to infect their own dogs, so a change of clothes between work and home should be routine in any shelter in which canine flu is a concern.

Disinfection

Canine influenza persists < 1 week in the environment. It will be inactivated by most any commonly used disinfectant such as alcohol, bleach, quaternary ammonium compounds, and potassium peroxymonosulfate (e.g. Trifectant ®).

Vaccination

The vaccine, made from killed virus, is intended to aid in the control of disease associated with canine influenza virus infection, type A, subtype H3N8. Canine influenza was first identified as a disease in U.S. dogs in 2004, after an outbreak of respiratory disease in racing greyhounds in Florida. Since then, it has continued to spread and has now been detected in dogs in 30 states and the District of Columbia.

APHIS, through its Center for Veterinary Biologics (CVB), granted the conditional license following the acceptance of data supporting product purity, safety and a reasonable expectation of efficacy. The safety data included the results of studies that evaluated the product under normal conditions, including field safety trials of the size and scope required for full licensure.

Studies indicate that the vaccine can reduce the incidence and severity of lung lesions, as well as the duration of coughing and viral shedding. The product is administered by injection, and is recommended for use in healthy dogs at six weeks of age or older as an aid in the control of disease associated with canine influenza virus infection.

Under the conditional license, the product may be distributed as authorized in each state, and used by, or under the supervision of, veterinarians. During the one-year conditional license period, the CVB will continue to monitor the product’s performance and will evaluate the company’s progress toward full licensure.

APHIS issues conditional licenses in the event of an emergency situation, limited market or other special circumstance. In this case, the special circumstance was the emergence of a new virus for which there were no existing licensed veterinary vaccines.

Treatment

Although there is no specific treatment for canine influenza viral infection at this time, secondary bacterial infection may play a significant role and antibiotics are often indicated. Antibiotics commonly used for treatment of Bordetella bronchiseptica kennel cough, such as doxycycline, Clavamox, or Baytril, are generally not as effective for treatment of secondary infections associated with canine flu. Cephalosporins may be a good choice for treatment of the secondary infections associated with the milder form of disease. Remember that Bordetella is very frequently resistant to Cephalexin, so if a co-infection is suspected, treatment with multiple antibiotics may be indicated. The pneumonia associated with the severe form of disease can be caused by a variety of bacteria including Pasteurella multocida, Staphylococcus intermedius, Streptococcus canis, and Mycoplasma spp. Ideally, a transtracheal wash and culture and sensitivity testing should be performed to choose an antibiotic for treatment of severely ill dogs. If an empirical treatment choice must be made, good choices should include a combination of broad spectrum antibiotics such as a fluoroquinolone + penicillin, either orally if eating or parenterally if inappetant. Supportive care such as IV fluid therapy is of course helpful. Cough suppressants do not tend to be helpful and should be avoided in dogs with a productive cough.

Information for pet owners

Preparation: what pet owners can do now to protect their dog’s health

1. Make sure your pet is following a vaccine schedule as recommended by a veterinarian. Although there is no vaccine for canine influenza, there are vaccinations that decrease the likelihood and severity of other canine respiratory infections. Vaccination against “kennel cough” is generally indicated for dogs at risk for exposure to lots of other dogs, for example dogs that are going to stay at a boarding kennel or doggie day care, participate in agility, dog shows, etc. Vaccines should be given at least a week before exposure, and should be boostered annually.

2. If you board your pet, make sure that the kennel is clean and well maintained, and has a plan for immediately isolating and caring for any dogs that develop signs of “kennel cough” or other disease in a completely separate area (at least 50 feet from healthy dogs or with a separate air supply).

3. Don’t take your pet to dog parks or other places with lots of dogs if he or she has signs of kennel cough or other infectious disease, and for two weeks after recovery.

4. Make sure your pet has current ID tags with your address as well as phone number clearly displayed. This will ensure that the animal can be returned promptly to you in the event of an escape, and will prevent exposure to kennel cough in an animal shelter.

5. Keep your pet in overall good health. Until such time as a vaccine is developed, a strong immune system will be your dog’s best defense against infection.

In Summary

Canine influenza is a newly emerging canine disease. Because it is new, naïve dogs have no natural immunity to it.

Infected dogs shed and spread the virus before the first clinical signs appear.

CIV is easily transmitted by direct contact, cough or sneeze, or via contaminated surfaces.

Cases have been reported in veterinary clinics, shelters, boarding and grooming facilities, and all types of multiple dog facilities.

CIV progresses to pneumonia in up to 20% of cases and is fatal in up to 8%.

The vaccine is provided as a subcutaneous injection (under the skin) given 2-4 weeks apart with a one dose annual revaccination recommended.

It is recommended for all dogs that are vaccinated for Bordatella

For dogs that visit places where multiple dogs interact and socialize such as shelters, pet stores, boarding and grooming facilities, doggie daycare facilities, dog shows and trials, veterinary clinics and kennels.

Our Policy

Are we going to require this vaccine for all of our patients? Absolutely not. We feel that each animal’s lifestyle and travel history impact the decision of whether to vaccinate or not. If you have questions regarding whether this vaccine is right for your pet, please discuss it with staff and doctor. We do feel, however, that it is important to let our clients know about this emerging disease and guide them through healthy lifestyle choices for their dog.