It is said that if the dog has no symptoms, not to treat, as the dog has been exposed to the disease but does not have it. However, when I get a count of over 300 on a C-6 I can not take the chance not to treat and end up with kidney failure. The laboratories will say to treat on a C-6 greater than 30.
I have had my 3 with lyme at one time or another, one tested positive 3 years in a row (she was the 300 cnt on C-6). She never had any symptoms but I treated again the last time and she finally tested negative.
My vet consulted with my girls' internal specialist and he recommended to treat her even with no symptoms and it finally did the job.
My oldest girl is the only one that ever had symptoms and her first treatment did the job and she has tested negative every year since.