ABSTRACT
The developmental cycle of a new species of Sarcocystis (S. neotomafelis) was investigated. Cysts obtained from the muscle fibers of the woodrats were given orally to 19 laboratory newborn kittens, 5 pups and 5 crotalids. Infection developed only in newborn kittens. Macrogametes, microgamonts and immature oocysts were observed principally in the jejunum. Immature oocysts were detected at 6-21 post infection days. Based on morphological observations made by light and electron microscopy, and repeating transmission experiments, S. neotomafelis is described as a new species. Also the prevalence of cysts and the statistical frequency of sarcocystosis according to location and hosts's sex are given. This is the first species described in Mexico, and also the first report for Neotoma.