The irradiation of . II. The immunogenicity of irradiated blood parasites for intact cattle and splenectomised calves |
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Authors: | IG Wright DF Mahoney GB Mirre BV Goodger JD Kerr |
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Institution: | 1. CSIRO, Division of Animal Health, Long Pocket Laboatories, P.B.No.3, P.O., Indooroopilly, Quensland, Australia 4068.;2. CSIRO, Division of Mathematics and Statistics, Long Pocket Laboratories, P.B.No.3, P.O., Indooroopilly, Queensland, Australia 4068. |
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Abstract: | Intraerythrocytic forms of were exposed to 350 Grays (Gy) γ irradiation and were then injected intravenously into intact two and three year old Hereford steers. One of 15 steers died on initial infection and subsequently six steers were given a virulent heterologous challenge three weeks after recovery; all six animals were highly immune. The remaining eight animals were kept under quarantine conditions for 10 months and were then challenged with a different virulent heterologous strain of . Seven of eight were highly immune, but one animal died. Subsequently a further 12 steers were injected intravenously with 1 × 108 irradiated organisms. All showed only mild transient clinical signs. After 12 months quarantine in a tick-free area these animals were then challenged with a virulent heterologous strain and all 12 were shown to be highly immune. Irradiation reduced the infective dose from 1 × 108 to 2.5 × 103 parasites. These parasites multiplied at the same rate, and achieved the same maximum parasitaemia as the parent non-irradiated strain, but the disease produced by them was not severe. A dose of 2.5 × 103 non-irradiated paasites was lethal to all of the four animals which received it. It was concluded that irradiation had produced a predominantly avirulent parasite population. |
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