Second, as Carlos suggested, build trust along the entire value chain with information and conversation. This is basic public relations and community building. However, this will take time. Take some lessons from the BSE (Bovine Spongiform Encephalopathy ) press that hit the beef industry;http://www.ers.usda.gov/Publications/ERR34/ has some information on how BSE announcements effected beef purchases.
Third, look for opportunity to leverage economic information to help strengthen production / management processes for the long term. See Ag Economist Dennis DiPietre blog for more info http://www.swinecast.com/DennisDiPietreBlog.
Again, there is no quick fix to marketing against a steady stream of FUD. This is a great case of building trust and community _before_ issues arrive. That way, when FUD does hit, you can help educate and reduce FUD within your community / value chain (Now there's an article: "Turn Your Value Chain into a Community!").
Quick comment on what Carlos said about email "I think that one of the options we have is 'email marketing' to reinforce pork's image among the public": Email marketing is only one tool among many. You have a message to convey and email can help deliver it. However, some of the people that need information may not be in your email lists but in your partner's email lists. Provide those partners with a set of informational tools they can share. Also, look where your audience gets their information. Web sites, social networks, regular media; develop a plan that will carry your message through those channels to your audience.