Reporting from Mexico City -- With the death toll climbing, Mexican authorities at the center of an international swine flu epidemic struggled Monday to piece together its lethal march, with attention focusing on a 4-year-old boy and a pig farm. ... The boy lived near a pig farm run by a U.S.-Mexican company, Granjas Carroll, in the municipality of Perote, in Veracruz state on the Gulf of Mexico. He contracted the disease on April 2, Cordova said, one of a group of residents who came down with what was at the time labeled a particularly bad case of the flu....