The irradiation of [formula omitted]. II. The immunogenicity of irradiated blood parasites for intact cattle and splenectomised calves

• Published in: Veterinary immunology and immunopathology Vol. 3; no. 6; pp. 591 - 601
• Main Authors: Wright, I.G., Mahoney, D.F., Mirre, G.B., Goodger, B.V., Kerr, J.D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.1982
• ISSN: 0165-2427; 1873-2534
• DOI: 10.1016/0165-2427(82)90042-3

Intraerythrocytic forms of B. bovis 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 B. bovis . Seven of eight were highly immune, but one animal died. Subsequently a further 12 steers were injected intravenously with 1 × 10 8 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 × 10 8 to 2.5 × 10 3 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 × 10 3 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.