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Updated: Aug 12, 2026

Diagnosis of Ecto- and Endoparasites in Laboratory Rats and Mice
Published on: September 6, 2011
Sarcocystis sigmodontis n. sp. from the cotton rat (Sigmodon hispidus)
1Veterinary Research Laboratory, Montana State University, Bozeman 59717.
Abstract:
Sarcocystis sarcocysts were found in 3 of 4 cotton rats (Sigmodon hispidus) from Atlanta, Georgia. Sarcocysts were several centimetres long and were present only in skeletal muscles. The sarcocyst wall appeared thin (less than 1 micron), with minute projections in the light microscope. By transmission electron microscopy, the sarcocyst wall had 0.6-1.0 x 0.21-0.36-micron villar protrusions without microtubules. The metrocytes were 6.5 x 3.8 micron, and the bradyzoites were 8 x 2.7 micron. The sarcocysts were not infectious for dogs and cats. The parasite was named Sarcocystis sigmodontis because it differed from all sarcocysts in rodents.
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