Brian C. Faulkner and Robert L. Lochmiller
Department of Zoology, 430 Life Sciences West, Oklahoma State University, Stillwater, OK 74078.
Few published reports exist concerning the distribution of Eimeria species infecting the hispid cotton rat, Sigmodon hispidus (1,2). In the present note we report the first records of Eimeria species infecting cotton rats in Oklahoma. The Eimeria were obtained from cotton rats collected April 24th, 1996 in a Johnsongrass (Sorghum halapense)-dominated field on the western edge of the city of Stillwater, Payne County, Oklahoma (N 36°7'7.0" W 97°7'20.5").
A total of 30 cotton rats were trapped with Sherman live traps and returned to the laboratory where they were maintained in polystyrene cages with wood-shaving bedding. Animals were provided water ad libitum during their confinement, and after being confined for approximately 24 hours, were released back at the trapping area. Fecal pellets produced during confinement were removed and processed as per Wilber et al. (3). The samples were maintained in K2Cr2O7 solution for two weeks due to the long (11 -12 days) sporulation time of Eimeria tuskegeensis (1). Two replicate coverslips were prepared for each sample and each coverslip was examined for oocysts using an Olympus light microscope at 100× magnification. Individual cysts were measured under oil immersion with a calibrated ocular micrometer at a magnification of 1000 ×.
A total of 4 species of coccidia were obtained, all from the genus Eimeria (Table 1). All 4 species have been previously described by Barnard et al. (1) in Alabama and by McAllister et al. (2) in Texas. Twenty-one of the 30 animals captured (70%) were hosts for at least one species of Eimeria. Of these, 15 hosts were infected with one Eimeria species and six were infected with two. None of the animals sampled were found to be infected with Isospora masoni, which has been reported previously in cotton rats from Alabama (4). Furthermore, none of the cotton rats were found to harbor the Eimeria sp., Isospora sp., or Adelina sp., which have also previously been reported in cotton rats in Alabama (1). However, these are not believed to be true parasites of cotton rats (1), so their absence in cotton rats in Oklahoma was most likely due to the lack of true hosts of these Eimeria species in the area. This report represents a significant northern range extension for the four species of Eimeria which we detected in our survey.
The authors thank Dr. Sidney Ewing, Oklahoma State University, Department of Infectious Diseases and Physiology, for his assistance in the identification of the coccidia species found in this survey. The authors also thank the National Science Foundation (Project No. IBN-9318066) and the United States Air Force Office of Scientific Research for the funding which made this project possible.
1. Barnard, W.P., Ernst, J.V., and Dixon, C.F., Coccidia of the cotton rat, Sigmodon hispidus, from Alabama. J. Parasitol. 60, 406-414 (1974).
2. McAllister, C.T., Upton, S.J., Planz, J.V., and DeWalt, T.S., New host and locality records of coccidia (Apicomplexa: Eimeridae) from rodents in the southwestern and western United States. J. Parasitol. 77, 1016-1019 (1991).
3. Wilber, P.G., Hanelt, B., Van Horne, B., and Duszynski, D.W., Two new species and temporal changes in the prevalence of eimerians in a free-living population of Townsend's ground squirrels (Spermophilus townsendii) in Idaho. J. Parasitol. 80, 251-259 (1994).
4. Upton, S.J., Lindsay, D.S., Current, W.L., and Ernst, J.V., Isospora masoni sp. n. (Apicomplexa:Eimeridae) from the cotton rat, Sigmodon hispidus. Proc. Helminthol. Soc. Wash. 52, 60-63 (1985).
Received: 1997 Mar 21; Accepted: 1997 Jun 24