Am I way off base?

 You're totally not off base. I wouldn't take my dogs around. Nothing is 100%. It's very, very unlikely for an adult dog that's been vaccinated to get parvo, but... Why bring the germs back with you?

 Exactly what I was thinking!! I knew I wasn't a nervous nelly!!

No, I wouldn't.  Even if the likelihood is small, if you go there you can spread it around other places, and some puppy who hasn't been vaccinated yet....

When a dog we pulled for a rescue was diagnosed with whip worms and kennel cough, I didn't bring my dogs to the training club for two weeks.  They were healthy and haven't got whip worms (I use monthly Interceptor, bi-annual kennel cough vaccinations, and have done fecals), but I didn't want them possibly spreading it on to dogs who weren't on Interceptor, weren't up to date on kennel cough vaccines, or had weaker immune systems. 

I wouldn't bring my dog, and I wouldn't even step foot there.  No sense in tracking anything back home.

tiffy

BFs aunt, a BYB, had a litter of pups that got parvo, 1 died and the others got to the vet in time and were treated.

Yeck, I wouldn't even let the BF in your house wearing shoes he wore at his aunt's home (unless he bleached the bottom of the shoes).  It is so easy to spread parvo!!  You would feel terrible if a friend with a puppy visited your home and got parvo because your BF tracked it into your home.

I wonder how much the aunt breeds.  It is hard to get rid of parvo and her yard may harbor it for up to 2 years.

BF has not been over there since the end of May. Lets put it this way, she has 1 male and 5 females, you guys figure it out. I have a very hard time keeping my mouth shut. 

tiffy

I have a very hard time keeping my mouth shut. 

Some "innocent" comments re Parvo might help a little.  Here are some examples, but they may not fit the aunt's breeding situation.

• "Do you plan to replace the sod in your yard?" 
• "Boy, I bet all that bleaching was a real pain.  Oh, you haven't bleached the entire house, too?  Aren't you afraid that you tracked it inside?"  
• "Do you think they picked up Parvo at the vet's?  I heard that some breeders won't even let their young pups touch anything at the vet's except for a towel they bring from home and the vet's hands."

The worse you make Parvo clean up sound, the longer she may wait for another litter.  You might be able to keep a few litters from being bred.

For the sake of future pups, you also might want to clue the aunt in on using the Neopar vaccine for Parvo (designed for high risk pups).  On the other hand, the more litters she loses the more likely she is to stop breeding.  Hard choice!

Sounds like a bad situation. I wouldn't take my own dog there.