One of the most lethal poisons ever used in the West's war on predators may be staging a comeback. President Richard Nixon banned Compound 1080 in 1972 following its widespread misuse and the death of untold numbers of birds, animals and even humans. Now the Texas Department of Agriculture wants the EPA to allow its use on an emergency basis to control rabies in 43 counties. Officials of the New Mexico Environment Department and wildlife activists say if the EPA grants the request, other states may follow Texas' lead. For more information, call Pat Wolff at New West Research 505/466-1661. To comment on the proposal by Sept. 23, write the EPA , Office of Pesticide Programs, 401 M Street, SW, Washington, DC 20460 or send a fax to 703/308-8369.