1. It has been confirmed that the immunity in sheep following recovery
from infection comprises a short period of premunition, followed by a period
of gradually decreasing sterile immunity.
2. Infection during the period of sterile immunity again initiates the
cycle premunition, sterile immunity.
3. Circulating virus is detectable in the peripheral circulation of
immune sheep following reinfection, whether a demonstrable reaction is
produced or not.
4. Up to a period of four years after recovery - the limit of the experiment -
the residual immunity is sufficient to protect against fatal infection
in sheep under laboratory conditions.
5. The significance of these findings and their relation to the problem
of the control of heartwater are discussed.
The articles have been scanned in colour with a HP Scanjet 5590; 300dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.