Update on Newly Emerging Canine Flu Virus

Canine Influenza has garnered a great deal of attention in the national press recently, but it appears to have had a minimal impact on Texas to date.  Dr. Gayne Fearneyhough, Head of Diagnostic Services and Informatics at the Texas Veterinary Medical Diagnostic Laboratory, had the following to say on the subject:

“The issue has settled down now, but for a few days the press was working hard to make a sensational issue of it.  We still have not had any cases identified in Texas since last year, and those cases were only in racing animals.  So, the risk appears minimal to pet animals at the current time.  We are working on a Serology test that would be useful in identifying animals exposed to the virus.  We also have a rapid screening test and a molecular test that may be of value, but they have not been validated for this purpose.”

“Bottom line:  This does not appear to be a major health issue for Texans or their animals.  However, an influenza virus jumping to another species is very interesting, and with the increasing concerns for the potential for a human influenza pandemic, this is certainly of interest to researchers.”

While not currently a problem, canine influenza is certainly something that veterinarians in Texas should be aware of and continue to carefully monitor.  Dr. Tom Lester, Head of the Virology Section at TVMDL, recently issued the following information for veterinarians:

Newly emerging Canine Flu Virus:

Reports of a new virulent strain of canine influenza (canine flu) have recently been circulating in the popular press.

An H3N8 strain of influenza virus previously associated with horses was isolated in 2004 from greyhounds at a racetrack in Jacksonville, FL, and subsequently found at other racetracks in Florida, Massachusetts, Arizona, West Virginia, Wisconsin, Texas, and Iowa.

Like most influenza, the incubation period is 2-5 days, transmission can occur by aerosol, fomites, and/or contact. The symptoms are similar to “kennel cough” with the exception of high fever >105, leukopenia, and nasal discharge.  Morbidity approaches 80% with mortality between 1-10%.  Signs may last for 2-3 weeks depending somewhat on secondary bacterial infection.  The virus is sensitive to antiviral drugs specific for influenza A viruses; none of these have been approved for use in dogs.

Gross lesions include extensive hemorrhage in the lungs, mediastinum, and pleural cavity.  Histologically a tracheitis, bronchitis, broncheolitis, and suppurative pneumonia are observed.  Additionally, the epithelial lining of the airway lumen are infiltrated by neutrophils and macrophages.

Influenza infection is suspected, we suggest collecting serum samples (acute and convalescent, paired samples), respiratory swabs, and/or transtrachael washes for isolation.  Tissues (fresh and fixed) on postmortem cases should include lungs, tracheas, and regional lymphatics.  Fresh tissues for isolation should be collected as aseptically as possible, chilled to 4 degrees C (refrigerate), and shipped on ice packs, overnight, as soon as possible.

For additional information on canine influenza, please see the Centers for Disease Control and Prevention’s Media Briefing on Canine Influenza at:

http://www.cdc.gov/od/oc/media/transcripts/t050926.htm