Abstract
Growth activities for Cryptosporidium parvum causing aquatic infections have been evaluated by such methods as in vitro excystation test or DAPI/PI staining test, and a direct infectivity has evaluated finally by animal infection test. As to their methods, various proposals have made for the animals used and the evaluation criteria. In this method, we proposed a method of quantitatively evaluating the infectivity of C. parvum from the changes in the number of oocysts excreted in feces with the passage of time by using mice with severe combined immunodeficiency disease (SCID) . As a result of applying this method to oocysts with and without ozonation treatment, we could evaluate the infectivity and its reductive effect. Also, we could reduce the number of animals used to one-quarter to three-quarter or so of the usual number, without killing the experimental animals. Furthermore, we conducted in vitro excystation test, and compared and discussed the results with that of the animal experiment test.
