Abhorrent Siren by John Baltisberger

Something is mutating the aquatic wildlife on the South Texas border, making the animals larger, hungrier, and more vicious. Something is mutating the people of Texas, turning them into cannibalistic monsters driven by their basest instincts to feed, nest, and reproduce. Something approaches San Antonio, shaking the earth with each step, driving the mutating power forth and poisoning everything it comes across. Something...abhorrent. An extreme horror novel from the author of War of Dictates and Blood & Mud