At Southern Methodist University campus about 6 miles south of Taos, New Mexico,, we recovered tetrathyridia of Mesocestoides in five Peromyscus maniculatus in the summers of 2008 (3 of 129, 0.023%), 2009 (0 of 98, 0%), 2010 (1 of 112, 0.008%), 2011 (0 of 88, 0%), and 2012 (1 of 86, 0.011%). Tetrathyridia from the body cavity of one of the five infected mice were injected into the peritoneal cavity of laboratory white mice, Mus musculus. Our later examination of the laboratory mice revealed heavy infections of tetrathyridia continuing to reproduce asexually. Here we provide important new information on the prevalence of asexuality among tetrathyridia and underscore the need for further study of this variation among metacestodes of this cosmopolitan genus.