A. Global Worming.... (so sorry)
Now, on to more serious stuff! First things first, and possibly most importantly, before blindly routinely treating dogs every month or quarter for worms that they may or (probably) may not have, please consider spending the money that you would pay for worming tablets on a faecal worm test instead. Then treat the dog for worms if they are present.
The faecal worm test* checks for the presence of roundworms, tapeworms and coccidia and involves collection of a little fresh poo collected over 5 days (keep refrigerated), posted off to a lab and the results come back very quickly. I have just gone through the process and it could not be simpler. Your vet should happily provide the collection tube and give you the results. It costs about CHF60. Assuming the worst, you need to treat for worms. You should take advice from your vet on what is best for your dog.
Signs that dogs may have worms include: diarrhoea and/or vomiting, fever, scooting/licking rear end (scooting can also indicate other issues), reluctance to eat, lethargy, dull coat, mucus coated stools, worms or “rice bodies” in poo. If you notice any of the above, speak to your vet, it would be a good idea to get a worm test done. Otherwise you could consider routinely testing annually.
If you decide to do preventative worm treatment throughout the year, perhaps because your dog is a scavenger (especially if he eats snails, slugs, fox poo or other animal poo), you live in a high risk area for worms and/or you'd rather not do routine faecal tests, here are some natural anti-helminthics (worm preventers) to consider:
*For heart/lung worm testing, a blood test is required. Incidence is low in Switzerland, I suggest discussing with your vet if you have specific concerns.