I have been noticing a number of products advertised on Television that
prevent canine heartworm infection. However, they all warn that the dog
should be tested for heartworm BEFORE taking the product.
Is there a biological reason for not giving the preventive medication to a
dog already infected with heartworm? Or, is it simply a marketing ploy to
avoid an owner claiming that the medication did not prevent the heartworm
infection?
Regards
Terry
