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.
Diurnal Variation in the Concentration of Trypanosoma congolense in the Blood-Vessels of the Ox's Ear
Summary (1) It can be shown that the normal distribution of T. congolense within the blood vessels of its mammalian host is most uneven, the concentration being much higher in capillaries than in arteries and veins. (2) In the ear the average concentration of trypanosomes throughout the vessels is inversely proportional to the amount of blood passing through in unit time, i.e., to the temperature. (3) This is reflected in blood-smears made from the ear veins, there being usually many more trypanosomes in the early morning than at midday. (4) Advantage of this knowledge should be taken in routine diagnostic procedures, and also when using blood-smears to measure the trypanocidal action of drugs.
Experimental infections with African trypanosomes. IV. Immunization of cattle with gamma-irradiated Trypanosoma rhodesiense.
Abstract Cattle immunized with gamma-irradiated Trypanosoma rhodesiense were protected against a challenge inoculation of unirradiated trypanosomes given 1 wk later. These animals were still resistant when rechallenged after 8 mo and some residual immunity persisted for 14 mo after immunization. Animals which had undergone self-cure after infection were resistant when challenged 14 mo later. No resistance was observed in animals challenged with a heterologous strain of T. rhodesiense. The infections observed in unprotected bovines were of a mild nature. Leukopenia and fever were common early in the course of infection, but no anemia was evident at any time.