East Coast Fever immunisation trials in Uganda: field exposure of zebu cattle immunized with three isolates of Theileria parva.
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Biomedical subjects
Publications and source records attributed to J Robson.
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Identification by means of the blood incubation infectivity test (BIIT) of 159 Trypanosoma brucei subgroup strains recently isolated from non-human hosts in the Lambwe Valley, Kenya, has defined the distribution in these hosts of both T. brucei and T. rhodesiense in an endemic sleeping sickness area. The presence of a small third group strongly suggestive of a population intermediate between these two species has also been revealed for the first time.Repeated testing of a number of these strains has shown marked consistency in the results. Strains identified by the BIIT as T. rhodesiense have been isolated for the first time from a reedbuck and a sheep. There appears to be direct relationship between the local prevalence rates of T. rhodesiense in non-human reservoirs and the incidence of sleeping sickness in man.
A preliminary survey of 2 073 domestic animals in the Lambwe Valley, Kenya, showed a 7.4% rate of infection with Trypanosoma congolense and T. vivax. In comprehensive surveys covering 6 384 domestic stock, pathogenic trypanosomes were found in 17.0% of cattle, 5.0% of sheep, and 2.1% of goats. Adults were more often infected than young animals, and males more often than females. T. congolense was the trypanosome most frequently diagnosed, followed by T. vivax and the T. brucei subgroup. T. theileri was also found. The examination of wet blood films in the field as a means of diagnosing trypanosome infections was shown to be valueless. More infections were detected in peripheral blood films than in systemic blood films, but both should be examined. An examination of smears of glandular fluid is essential for the diagnosis of T. vivax in cattle, while mouse-inoculation tests are necessary for the diagnosis of the T. brucei subgroup. The detection of T. vivax was improved by the high-speed centrifugation of blood samples in capillary tubes.
The results of recent field studies on the capillary agglutination test (CAT), a simple and rapid test for detecting trypanosomal antibodies in livestock, are described. The test promises to be valuable in determining the degree of trypanosomal challenge experienced by closed and settled herds of cattle.
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The authors describe a simple test (the blood incubation infectivity test) by which Trypanosoma brucei (sensu stricto) may be differentiated from T. rhodesiense without recourse to human volunteers. The method consists in incubating the strain of trypanosome under test for 5 hours at 37 degrees C in vitro in human blood, followed by observation of the effect of this procedure on the strain's infectivity to rats.Thirteen strains of T. rhodesiense were investigated; in each, the ability to infect rats was retained after incubation. In all 6 strains of man-tested T. brucei, it was destroyed.The consistency of the results with proven strains suggests very strongly that the blood incubation infectivity test provides a valid means of differentiating these parasites.
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