Ticks are usually harmless, but large ones seem to imply that is has been there for some time now. You might want to check both your dogs, THOROUGHLY, for more ticks. On the dog you found the big tick on, look for where it might have been, and see if the possible area the tick might have been is swollen, because ticks are known for carrying diseases, such as lime disease. If you do find a swollen, infected area you should call a vet ASAP.
-Hope this helps!!!

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Pet Care