Appropriate Samples for Detecting the Presence of Canine Influenza Virus

As with most viral diseases, there are several ways to determine the role of a virus in a clinical event. While there is a tendency to want a single sample type that will work in all cases, the reality is that this is not possible. The list of possible tests is:

1. Canine Influenza Virus HI test ($22.70 per sample) At present, the most reliable way to diagnose canine influenza virus infections is by serological tests. The direct link be‐tween canine influenza virus and a clinical event is through the collection of acute and convalescent serum samples. The first sample is collected at the first presentation of the patient and then 2‐3 weeks later. Serum can be separated from the clot and held in the refrigerator until collection of the second sample. Samples can be shipped overnight without cold packs or 2‐day delivery with cold packs. For animals that have recovered from a case of "kennel cough", a single serum sample can determine whether the animal has been infected with canine influenza virus at some point in the past. As this is a relatively new pathogen of dogs, we do not expect to find a high sero prevalence in unaffected dogs.
2. PCR test for Canine Influenza ($38.00 per sample) At present, the most reliable way to directly detect the virus is through a PCR test on either swabs (nasal swabs preferred) or respiratory tissue. A generic PCR test that detects the highly conserved matrix gene is the test of choice. While we are currently looking for the H3N8 virus, a test unique to this virus would miss a potential influenza infection caused by another flu strain such as H5N1. Broad screening tests are to be used whenever possible in surveillance programs.
3. Isolation of canine influenza virus is a relatively unreliable way to confirm the infection. The reason for this is not clear, but the timing of the sample collection may be the main culprit. Experimental infections have shown that nasal swabs are nearly twice as successful in isolating the virus as nasopharyngeal swabs taken at the same time on the same animal. We continue to encourage the submission of samples for virus isolation because it is essential to track the genetic changes that are occurring in the virus as it makes its way through the dog population. Samples that are submitted for PCR detection of the virus that are test positive will be automatically set for Virus Isolation at no additional cost.

Note: All dogs that cough are not infected with canine influenza virus. The standard respiratory pathogens of dogs have not gone away. One should always consider a complete diagnostic work‐up that would include cultures for bacteria and mycoplasma. Check our Test & Fee Manual for sample submission information and fees.

Submission forms for the Animal Health Diagnostic Center (AHDC) can be found on the submission page.

Canine Influenza Virus FAQs

What samples should be collected from a sick dog to detect the influenza virus?

Within 5 days of clinical onset: Use PCR and hold serum

• Nasal and Pharyngeal swab-place in red top tube with a few drops of saline
• Clot tube to hold for antibody titer if needed

10 days or more since clinical onset: Use serology to detect antibodies

• serum sample (red-topped blood collection tube; separate and save serum, hold at refrigeration temperatures).
• A convalescent sample 10 days after presentation (=/>20 days after onset) should be collected
• Both samples can be submitted for Influenza A antibody titers

If the dog has been sick between 5 and 10 days: Use a combination of PCR and serology

• Collect both samples above
• Hold the serum and submit the swab for Influenza A PCR
• Submit serum after collection of convalescent sample

What tests can be performed at Cornell?

Influenza A PCR

Canine influenza PCR, which will identify any influenza A virus, including H3N8 and H3N2 strains.
For more comprehensive testing, request the Canine Respiratory PCR Panel which tests for most common respiratory pathogens found in dogs, including influenza A.

• All Influenza positive samples will be further characterized. Results will be provided on an addended report within 3-5 days of the original result in most cases. Some positive samples may require additional sequence analysis. This may take several weeks to complete.
• All samples with positive influenza tests will be further characterized, with typing results available in most cases within a few days of the original result. Some samples may need additional testing to determine the strain type involved. If this is the case, clients will be notified and results will be provided as soon as possible. No additional fees are charged for virus typing.

Influenza A serology

Canine Influenza HI test (HI stands for hemagglutination inhibition). This test detects antibodies against influenza viruses.

• Samples are tested for antibodies to H3N2 and H3N8 viruses
• There may be limited cross reaction.
• Dogs previously vaccinated with a canine influenza vaccine may have a titers, but these are typically low.
• Dogs recovered from an influenza infection will have a higher titer.

How should the samples be shipped to the lab?

We recommend shipping for next day to expedite Canine influenza PCR testing. If samples are in transit for several days, they will still be suitable for PCR testing. If virus isolation may also be requested, next day delivery is important.

Serum samples for Canine Influenza HI testing should be shipped with freezer packs for next day delivery if the serum is still in a tube with the clot. If the serum has been separated and chilled, it can be placed in an insulated mailer and shipped via most routine priority mail or courier delivery services without freezer packs and will be suitable for testing on arrival.

MD-WEB-001-V01 5/25/2018