Strangles Testing: All You Need To Know
Strangles testing can sometimes be a bit of a minefield, especially with the different tests available. Hopefully this guide can help highlight the pros and cons of each type of test, and when they are best used.
1.Swab - (Nasopharyngeal PCR)
Just like a COVID-19 test, this involves passing a (very large) cotton swab up the nasal cavity.
Pros: It is relatively easy and non-invasive to perform. At the lab, they will be looking for bacterial DNA, which lets us identify if an active infection is present.
Cons: Active infections can be missed if the bacteria are only in the guttural pouches, and not in the nasal cavity.
When we will recommend this test: If we are coming to see a horse with signs consistent with Strangles, and there is a large volume of mucous/snot.
2.Bloods - (Serum ELISA)
This test looks for antibodies to Strangles bacteria in the bloodstream.
Pros: It is very easy to perform, and is generally the cheapest form of testing.
Cons: It only identifies that a horse has had exposure, which could have been up to six months previously. Antibodies only indicate a normal immune response following exposure, and will last in the bloodstream for a long time, meaning they don’t necessarily indicate current infection.
When will we recommend this test: Because of the shortfalls of this test, we will not commonly recommend its use for diagnostic purposes. It is commonly requested by external parties prior to movement of horses, however we are unable to diagnose a current infection without further testing via a guttural pouch wash.
3. Guttural pouch wash - (Guttural pouch PCR)
The guttural pouches are two sacs that sit at each side of the back of a horse’s head, and are where Strangles bacteria will sit if there is a current or persistent infection. Therefore, getting a sample from these pouches is the most definitive method of ruling out a current Strangles infection. We could send the sample for ‘culture’ - where the lab will try to grow the bacteria from the sample. However this takes several days and isn’t completely reliable. The quickest, and easily most reliable test is via a PCR reaction, which just looks for the presence of bacterial DNA in the sample.
Pros: This is gold-standard testing which provides a definitive answer whether there is or isn’t a current Strangles infection. It is by far the most reliable test and very rarely provides inaccurate answers.
Cons: Because it requires specialist equipment and is a relatively specialist skill to perform competently, it has an associated increased cost.
Overall, a swab is generally used if we have lots of nasal discharge and a high suspicion of strangles. A blood test is a cheap and fairly quick way to identify horses who haven’t been exposed to Strangles in the last six months, however if you get a positive result (approx 25% of horses), you will likely need to have a guttural pouch wash performed to ascertain the true Strangles status of your horse, costing more time and money. A guttural pouch wash is the quickest, most reliable route to understanding the Strangles status of your horse, but with a higher cost.
All of the above procedure options are available to book via our team on 01323 815120. If you have any queries about any of the above information, or want to discuss anything regarding Strangles testing, please do not hesitate to contact us.