Hi Leri,
Not stating that they have worms or that you should worm.
However, most livestock has a certain amount of worms, a count of <100 is classed as low level and does not require treatment, as the count increases (possibly by re-ingesting eggs passed in dung or by "infected" earthworms) then the need to worm with a chemical based wormer increases.
Verm X is a good product, but acts mainly as a method of clearing the animals gut of worms by them passing out in droppings. However, if the pig (or other animal) is in constant contact with those droppings then the re-ingestion risk is higher.
The only sure way to know is by a worm egg count (will post today), then worming, if necessary, using a suitable wormer and ensuring you have a good system in place for rotating pens / paddocks - as you can see from the link I posted some species of worms can lay dormant in the soil for a considerable period.
You said earlier that the pigs were bred by you - but you must have got your original stock somewhere so even though your ground may never have housed pigs, you may or may not have brought them in with the stock.
Thanks