Abstract: Objective To establish and analyze the morphological parameters of the oocysts of Cryptosporidium muris for defining their morphological change. Methods Oocysts were collected from KM mice（immunodepressed by dexamethasone for 10 days） and examined with modified acid-fast staining. Images of 1 190 oocysts were acquired by photograph system. The length, width, perimeter, area and equivalent diameter of the oocysts were obtained by computer digital image processing system and analyzed by SPSS software (Version 11.0). Result The average length of the oocysts was 5.93 μm， ranging from 3.36 μm to 8.51 μm in 95% confidence interval of them. The average width was 4.96 μm, ranging from 3.26 μm to 6.66 μm in 95% confidence interval of them. The average perimeter was 18.03 μm and the average area was 16.08 μm2. Conclusion Data obtained from the computer system are objective and precise, offering scientific foundation for measuring the oocysts and for identifying Cryptosporidium spp.

Key words: Cryptosporidium muris, Oocyst, Digital image processing, Morphological parameter