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Hi dr.O
I’m looking to import a horse from Portugal where Piro is very common. I’m from Canada so the horse needs to test negative to piro to be imported.
My question is about testing and interpreting results: I see that some tests are considered « negative » if the horse scores below 40, and positive if it scores above 40. However I don’t understand how a horse can be considered negative if some level of antibodies are detected?
Knowing that the disease can go silent and come back with stress, isn’t that a big risk to consider a horse negative when the value is not « 0 »?
Also, are there any tests that can tell if a horse is an asymptomatic carrier of the disease? How can we know for sure that a horse does not represent a risk of being a carrier? Thank you -
Hello clauee,
Most of your questions are answered by the fact that serological tests don’t perfectly detect antibodies that are only caused by the presence of the disease you are testing for. These tests cross-react with other antibodies or in some disease’s antibodies may form during exposure, but this individual resisted the disease. Perhaps there are related organisms that don’t persist but cross-react. Then there are the individuals who were infected and then successfully treated (B caballi) but the antibodies persist. There is no test that anybody would claim is 100% specific for the presence of infection but currently, the most accurate test would be PCR where they look for pieces of the organism’s DNA. Cornell runs this test I believe.
DrO
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