Trypanosoma congolense. 3. Serological responses of experimentally infected cattle.
Abstract A complement fixation (CF) test for the diagnosis of Trypanosome congolense infection in cattle was developed and compared with the indirect fluorescent antibody (IFA) test. Serological investigations were made with cattle immunized with irradiated T. congolense and challenged with untreated T. congolense. Trypanosomal antibodies were demonstrated by the CF test. The results indicated good specificity and sensitivity between the CF method and the IFA test. The CF test also afforded easier reading of results than the IFA test; however, antigen preparation was more difficult in the former. The serological responses detected by the IFA and CF test appeared to be influenced by early variations of parasitemia, although no correlation appeared to exist between titer and parasitemia at later stages of the infection. Antibodies were detected in animals which received injections of irradiated T. congolense prior to challenge with viable organisms.
Comparative studies on the laboratory diagnosis of experimental Trypanosoma congolense infection in sheep.
Comparative studies on the laboratory diagnosis of sheep experimentally infected with T. congolense were carried out by parasitological and serological methods during a period of 53 weeks. Trypanosomes were most numerous in the first weeks after inoculation, when they were detectable by all three parasitological tests: the wet mount preparation, the haematocrit centrifuge technique, and the mouse inoculation test. In the later stages of the infection, trypanosomes were observed intermittently by the HCT until 34 weeks, and were detected by the mouse inoculation throughout the experimental period. The immunolysis test andthe complement fixation test showed positive reactions starting from two weeks up to 30-35 weeks and 40-45 weeks respectively, while the titres of the indirect fluorescent antibody test and the non-specific immunoconglutination tests persisted at a high level throughout the infection. The effect of a trypanocidal drug was best detected by the IK test.
An Essay on the Nature and Significance of the Normative Nature of Economics
It is conventional in economics to distinguish between the normative and the positive. The normative has to do with goodness and badness, and with what ought and ought not to be done;1 and the positive has to do with objective description and/or explanation, with what is and with what is necessary given some normative end. The normative has to do with desirability; the positive has to do with truth (in the sense of either descriptive accuracy or serviceability of a means to a given end).2