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.
Hill country sheep production. I. The influence of age, flock, and year on some components of reproduction rate in Romney and Border Leicester × Romney ewes.
Data from 7,091 straightbred Romney and Border Leicester × Romney ewes grazed at the Whatawhata Hill Country Research Station over the period 1959 to 1967 have been used to obtain estimates of flock and age-of-ewe effects on reproduction rate and its components and of year-to-year variation. The ewes were from six groups: a Romney control (RCR) flock, a Romney flock in which ewes were mated either to Romney (RER) or to Border Leicester rams (REB), and flocks of first-cross (F1), second-cross (F2), and third-cross (F3) Border Leicester × Romney ewes mated to first-cross Border Leicester × Romney rams. The ewes' ages at lambing varied from 2 to 5 years and no selection was practised. The ratio of number of lambs weaned per ewe present at lambing increased from the RCR (0.84) to the F1 (1.07), then declined with interbreeding to the F2 (0.92) and further to the F3 (0.87) ewes. Similar changes were evident for the percentage of ewes lambing, of multiple births, and of lambs surviving to weaning. Over...