A survey of 560 Procambarus clarkii conducted during the late spring of 1998, 1999, and 2005 indicated that, within Louisiana, U.S.A., Allocorrigia filiformis infected the antennal glands of crayfish from roadside ditches and swamps primarily in the bottomland hardwood and cypress vegetation region. Infections were absent from Louisiana's marsh and prairie regions, as well as from eastern Texas, U.S.A., but extended northward into the Lower Mississippi River Valley, including the delta areas of Arkansas, Kentucky, Mississippi, Missouri, and Tennessee, U.S.A. Prevalence of infection was 0% at 38 localities but ranged from 15.8 to 100% at 22 other localities.