MADISON, Wis. (AP) – Wisconsin will require import permits for pigs entering the state starting March 1st to make sure they are free of a problem virus.   The virus is Porcine Reproductive and Respiratory Syndrome. Officials say it can cause reproductive failure in breeding stock and respiratory illness in young pigs.  Industry groups estimate the virus costs more than $600 million each year.  Pork producers and veterinarians disclose the PRRS status of pigs when acquiring the permit. They also must submit a certificate of veterinary inspection online.