Abstract:
An attempt was made to attenuate Cowdria ruminantium by irradiation of the nymphal stage of
its tick host, Amblyomma hebraeum. The irradiated nymphae were homogenized and serial dilutions
of the resultant suspension were injected intravenously into heartwater-susceptible sheep. No attenuation
could be demonstrated but the results indicate that progressively more micro-organisms will be
destroyed the higher the irradiation dosage applied, and that dosages between 20 and 30 kilorad
apparently prove fatal to all the pathogenic organisms.
