Having contact with a LIVE pig does not cause Tumá. Pig is only ritualy impure for Jews when it's dead. Besides, these purity laws about contact with Tuma does not apply when there is no Temple, except in case a Jew would want to ascend the permitted areas of Har Habayt. In that case he would need to go to Mikve if he had been in contact with a dead pig. For Gentiles it's Hallachically allowed to eat pork providing there is no health risk. But a gentile can choose to avoid impure food if he wishes.
Anyway it's not convenient for a Jew to have a pig or dog as a pet at home becuase Jewish law forbids Jews to allow a pig, a dog or a person of the opposite sex to pass between two Jews. Likewise a Jew must not walk between two pigs, two dogs or two persons of the oppsoite gender.
But, in case of any doubt, please consult an Orthodox Rav. I am not expert on Hallacha.