We use an injectable solution for all parasites - internal and external - which is about 46 euros for 50 mls. The last bottle we bought was 150 euros for 200mls so worth it to us will so many pigs. It can also be used on sheep, goats and (with a very faint wisper because the vet told us not to spread it around), the dogs as well. The dogs have to be done monthly but the pigs, goats and sheep we do four monthly, although on virgin ground it should not be necessaryh to repeat the treatment earlier than six monthly.
Kate