I don’t manage horses myself, as horses have been on full board. One barn wormed only as necessary…tested and then wormed for what shows up, like I do with dogs. The other worms everyone, proactively, on a regular schedule.
For the dogs, I don’t worm proactively because 1) the cost of the wormer
2) I don’t think it’s necessary as they so rarely get worms (barring a brand new, wormy, rescue dog!). Horses are out eating grass, and whatever might be on it all day, much higher risk for picking up worm eggs than a house pet dog. My dogs eat kibble and canned food and not much off the ground outside.
We had a long term flea problem a few years ago at our old house…it was the cleaning ladies! They’d vacuum a house down the street, infested with fleas, and then come vacuum ours :(. It took me a while to figure it out, when I did I made them use my vacuum instead of theirs. It took months and months to get those fleas off our pets and out of our house. Partly because I wouldn’t “bomb” due to a young child. Elbow grease with several times a day vacuuming mostly and daily laundry, ugh. Capstar if we visited anyone else, so we didn’t bring live fleas with us, and Advantix II on all pets. Only one dog got tapes, only once, though, so I don’t think fleas are a guarantee of tape worms. The worms were very obvious, they are easy to see, unlike hooks or something. When I saw the tapes from the one dog in her stool, I took fecals in for everyone, she was the only one. Go figure.
Unless there are symptoms of parasites, I only bring a fecal in once a year for each dog. Adult dogs have pretty much NEVER had worms, other than that one tape incident. Puppies sometimes do. Puppies come with some from Mom sometimes, and they eat weird stuff off the ground that adult dogs are too smart to eat ;). And, immature immune system leaves them open to all kinds of stuff.
I did worm everyone, several times, when we had a young puppy from a hoarder’s yard…she was infested with EVERYTHING and it took a while to clean her up. Because she wasn’t house trained and was having accidents for a while (plus loose stools from worms), I figured that the chances were high enough that the other pets could pick it up off the floor, that I’d worm everyone when I wormed her.