Some gp experts advocate that the piggies should be wormed every 6 months,alternating with Panacar and Ivermectin.
Panacur is a sheep wormer which is effective against intestional worms,but these are very rare in gps.
Ivermectin is an antiparasitic which kills external mites.
I only use Ivermectin if a piggy has mites which I cannot get rid of with GGs shampoos and melts.These generally do work.
I do not use Panacur because my pigs live indoors and do not have access to grass which may have been contaminated by foxes,dogs etc.
I also strongly beleive that the use of anthelmintics and pesticides as a routine precaution,could result in the worms and mites becoming resistant to these drugs.A lot of the drugs used in the treatment of malaria have been used as prophylactics by travellers,and this has resulted in the drugs becoming inefective.
This is my personal opinion and I know some forom members will disagree with me,and in the end of course,it iis up to individual owners to do what they think is best for their pigs.