

Found an engorged tick on our dog while wearing her seresto collar. Should I be concerned the collar is defective? Or are exceptions expected?
First time poster here! I wanted to know if anyone else has been in this situation.
We've been using seresto collars for our dogs for years now, and just recently replaced them for the usual 8 month cycle. It's been a few weeks since they've had the new ones on, but today we discovered an engorged tick on one of them.
We're not entirely sure how long it might have been on her, but we're concerned since we were under the impression that the collar was to kill off a tick through contact before it can latch on. But after removal the tick was still alive and well (prior to burning 🔥)
Is it possible the collar we had on her is defective? Or is this something that just has a rare chance of happening?
EDIT: Thanks for all the replies everyone! I'm the dogs' uncle and was posting this to help assuage my sisters worries. I appreciate all the affirmations that the collar was not going to offer 100% protection.
We aren't able to do the ingestibles as many people kindly suggested due to other health concerns unfortunately. But we'll see our options when we can see the Vet and double check to make sure she's disease free (she has gets the annual shots, but better safe than sorry). Really grateful to all the folks who chimed in to help!