[anonymous]

@ Lora J
Whatever method you decide to use for a heartworm/flea/tick/Lyme preventives, I just wanted to stress the importance of routine testing.
“Using a single test, your veterinarian can check for any combination of the following diseases, including all of them: heartworm disease, Lyme disease, ehrlichiosis, and anaplasmosis”.
“SNAP” testing refers to a group of quick, convenient, blood tests that can be performed at your veterinarian’s office. There are various SNAP tests for different purposes:
SNAP Heartworm RT Test—screens for heartworm infection
SNAP 3Dx Test—simultaneously screens for heartworm disease, Lyme disease, and ehrlichiosis
SNAP 4Dx Test—simultaneously screens for heartworm disease, Lyme disease, ehrlichiosis, and anaplasmosis.
above 2 paragraphs are excerpts from: http://www.vetstreet.com/care/heartworm-disease-lyme-disease-ehrlichiosis-anaplasmosis-snap-testing-in-dogs

I once had 3 dogs test negative for Lyme in April, when one showed symptoms in September I had them retested. All 3 were positive for Lyme.
It is important when this happens to start the antibiotic protocol ASAP
Good luck.