Data reported here addressed: (i) the parameters necessary for a routine assessment of the two successive stages of the disease (body weight gain, parasitemia time course, CSF parasite counts), (ii) the changes in NO concentration occurring in the course of the neurological disease and the related NOS activity, as well as the identification of the cell types in which the cerebral NO-pathway changes take place. The gene discussed is NOS1; the disease is parasitic infectious disease.