Field experience with heartwater (Cowdria ruminantium) in cattle.

Observations are reported on 2743 animals immunised against heartwater since 1958. The methods of immunisation and control of reactions are discussed. This procedure is not without risk and 0,83% of the animals died in spite of treatment. Bos indicus breeds appear to have a greater resistance to heartwater and are relatively easy to immunise. Of the Box taurus breeds the South Devon, the Jersey and the Charolais seem to be particularly susceptible. Older animals and pregnant cows are considered to be in the high risk category.