While parasites are extremely common in young puppies we do everything in our power to prevent infestation in our adult dogs and in our yard to prevent the spread to our puppies, our children and ourselves!!
Not all doggie parasites can spread to people, and the most common "Large Roundworm" is harmless to humans, but there are some sorts that can infect you and your family, so it is more important to pay attention to your pup's health (and her poop) than you might think!
To date none of our adult dogs or puppies bred here have ever tested positive for any kind of parasite, ever. Now that can change in a heartbeat, and does not necessarily mean I'm doing something unsanitary. We do have several neighbors that don't believe in keeping their dogs in their yards, and these dogs just LOVE to come over here to poop. (Thanks) We also have lots of dogs and visitors to our property. While we work very hard to keep the puppies' yard section clean and free of strange dogs it just isn't always possible to prevent everything! We hope we will contnue to see negative fecals on all our animals and those reports from our new puppy owners as well.
Some parasites are transmitted via mosquitos and I do my best to keep their numbers down.
We don't have standing water or stagnant water, puddles, etc on the yard so I can't imagine any puppy or dog here can contract giarrdia or Leptospirosis. While we do have ticks I keep the pups in areas where we don't generally see ticks and I check them thoroughly daily and have never *knock on wood* pulled a tick off any of the dogs. (Plus Lyme disease generally is transmitted from nymph deer ticks around August and takes around 12-24 hours of a tick being attached to actually transmit the spirochete)
We do treat our yard regularly with an awesome product that is made of garlic, believe it or not, and it works better than every poison and nasty toxic substance on the market. This stuff, called "Yard Barrier" is really a life-saver. We buy it by the case, so if you'd like to try it out let us know and you can buy one of our bottles. Otherwise you can find it on Amazon, and through many other dealers around. This stuff is truly amazing and it is safe and it makes my yard smell like an Italian resturant for about 1 evening. :-) The smell dissapates after that, so no worries there. I guess "vampires" (like mosquitos and ticks and biting flies) really do hate garlic!
So, the answer to your question is, we believe that it is very unlikely that your pup will go home with parasites of any kind. However, since they are common and can be picked up anywhere you might go with your pup after you leave here you should talk to your vet about having standard "worming" treatments (which we do start here as a preventative) and possibly having a fecal test done if you're seeing any watery stools with your little guy.
Hope that helps!