Stanley is 1 (maybe 13mo, it's not super clear). I got him from a rescue in October 2023

AmStaff/ pit bull terrier 41lbs Male neutered

I took him to the Vet in May 2024. I thought he had his vaccines finished but I couldn't provide all of those records so we got all the shots. We also started heartworm preventative (my ignorance is acknowledged- I shouldn't have waited)

We've been back 4 times since for various reasons, and just recieved word that microfilaery (sp?) Was found in his blood. We just came back from the second blood draw today.

They suggested I reach out to the shelter since this can be very pricey, and I did without much hope. However, I got back a very judgey response, essentially claiming it's my fault for being a poor owner.

Now, I accept my part of the blame. But from my research, could this infection even have happened in the time I had him? From oct-april we had a pretty brutal winter (not many mosquitos), and the incubation period before it can be seen on tests is 5-7months, correct?

Tldr: is the shelter possibly responsible? Could they have really had him on preventatives, then my time without was the infection window?