Canine Influenza

Prancer - photo courtesy of Chris Meraz

Historically dogs had not been considered as one of major host species for influenza A virus. Such a belief was drastically changed once a report of greyhounds in a racing track compound contracting with influenza A virus highly similar to H3N8 Equine Influenza Virus (EIV) was made in 2004 in the United States. Since then, the virus named “Canine Influenza Virus (CIV)” was able to sustain in a variety of dog breeds and had steadily spread through the US, becoming an important respiratory pathogen for dogs. While H3N8 CIV continued to circulate in the US, another CIV derived from H3N2 Avian Influenza Virus (AIV) was reported in 2007 in Korea. The H3N2 CIV infection has been limited to Southeast Asia, primarily Korea, China and Thailand. In 2015, this new strain of CIV was detected during respiratory disease outbreaks in US Midwestern states such as Illinois, Wisconsin, Indiana, Ohio and Iowa. So, two strains of CIV, which genetically and antigenically distinct, are present in US canine populations today. Both strains of CIV have been demonstrated to be pathogenic to dogs under experimental conditions, causing acute respiratory disease and be transmissible from infected dogs to comingled dogs. Therefore, CIV infection should be on your differential list for canine respiratory diseases. Clinicians should be aware that H3N2 CIV can also infect and cause the disease in cats.

The Iowa State University Veterinary Diagnostic Laboratory (ISUVDL) is offering laboratory tests for both strains of CIV. At present, PCR-based assays are the primary routine tests for rapid detection of viral genome in samples. Sequencing is performed for further characterization (e.g., subtype) of the virus in samples. PCR assays for quickly differentiating between H3N8 and H3N2 in samples are under development. Virus isolation tests can be performed when necessary. Good sampling is essential for accurate results since influenza is a rapidly progressing disease. Nasal swabs, tracheal swabs or tracheal washes from acutely affected animals with fever, inappetence, lethargy and nasal secretion should be submitted for virus detection. Use synthetic swabs with plastic shafts and submit in a liquid, not a gel-based, transport media such as saline (0.5ml) or a commercial transport media provided with the swab. Samples collected from dogs exhibiting coughing may not be optimal for virus testing. Samples of lung, and mid- to distal trachea, both formalin-fixed and fresh, can also be collected from deceased dogs for testing. All these samples except formalin-fixed tissues should be shipped chilled for better preservation of the virus. Prior exposure to the virus can be documented by antibody testing which requires serum submission. Please note interpretation of serology results has the most diagnostic significance if both an acute (drawn as close to appearance of clinical signs as possible) and convalescent sample (drawn 2-3 weeks after the acute sample) are submitted.

The following tests are available:

Test Fee     Sample of choice
PCR (screening and subtyping) $40 Swabs, tracheal washes, fresh tissues
HI test (H3N8 CIV) $10 Serum
Influenza NP ELISA $5 Serum
Virus isolation $25 Swabs, tracheal washes, fresh tissues


For more information or any questions, contact:

Dr. Kyoungjin Yoon (,
Dr. Phil Gauger (,
Dr. David Baum (
or diagnosticians at the ISU VDL (515-294-1950).

More Information:

Additional information can be found at the AVMA website
Factsheet from CFSPH