Which horses need to be sampled?
- Any unvaccinated horse with typical influenza signs
- Vaccinated horses with non-specific respiratory signs
- Unvaccinated in-contact horses
Both nasopharyngeal swabs and paired bloods not less then 14 days apart can be used for diagnosis.
When to sample
Nasopharyngeal swabs: to maximize the chances of obtaining sufficient virus samples need to be taken no longer than 2-3 days after clinical sings first appear. If it is too late to swab the affected horse it can still be fruitful to take swabs from in contact animals as shedding begins before clinical signs.
Paired plain bloods: can be taken further into the disease process because they can still pick up antibody change even if virus excretion is too low detect with a swab. To obtain a meaningful diagnosis two samples not less than two weeks apart are always required.