In the coastal jungle of Vera Cruz state, bulldozers chewed their way last week through rain forests and matted vines. They were clearing a path across the waist of Mexico for an 800-mile-long fence. Its purpose: to check the northward spread of aftosa (foot-&-mouth disease), which had already infected about one-sixth of Mexico's 13 million head of cattle and brought nightmares to Texas ranchers.
Other U.S.-aided attempts to wipe out aftosa by killing all infected and exposed cattle had bogged down against the iron-hard resistance of the Mexican campesinos (TIME, Dec....