Should I be worried about my Dogs STDs?

I recently had to travel to Grimsby to help my mate move his caravan and stayed over for a couple of nights. While I was gone I let my good mate Andrew dog sit because I couldn't take the canine over with me. After getting my dog back it seemed a bit shook up and wasn't eating much so after a couple weeks of this behavior I took It to the vets. The results came back yesterday and my dog has contracted Chlamydia and 2 types of Gonhorrea. This has worried me quite a lot because there are no other dogs In my friend Andrews area and Andrew has been getting treatment for his sex addiction for the last two years (he used to sleep with 3 escorts a week) I don't want to think the worst of my good friend but could it have been possible that it was him who gave my dog the STDs? I hate to think it could be true but it wouldn't be out of character from him. Any suggestions on how I could confront Andrew would be appreciated thanks in advance.