Quote:
Originally Posted by EarthAngel  I have a question as to why I need to have the heartworm test done once a year when my Yorkie who is 1 yr. 5 mos. old and a Boxer who is 1 yr. old have been on it since they were able to get it? I still have no idea why they need to get retested before getting their next prescription of Heartguard. If anyone can tell me I'd appreciate it. |
Just like bacteria developes a resistance to antibiotics, worms mutate and develop a resistance to drugs. That is another reason why yearly tests are so important.