Investigations on the natural and acquired resistance of cattle to artificial infection with Cowdria ruminantium
du Plessis, J.L.; Bezuidenhout, J.D.
Journal of the South African Veterinary Association 50(4): 334-338
1979
ISSN/ISBN: 1019-9128 PMID: 553974 Document Number: 143876
Sixty cattle, artificially immunized against C. ruminantium, were challenged 3, 6, 12 and 24 months later. Levels of conglutinin were determined in pre-immunization serum samples. There appeared to be a relationship between the pre-infection levels of conglutinin and the susceptibility of the animals to heartwater. At the time of immunization 31 out of 60 cattle (51.6%) with levels in the low-titre range (1:10-1:160) showed a typical febrile response, whereas 29 (48.4%) with conglutinin levels in the high-titre range (1:320 and higher) were either fully or partially resistant. Except for 2 animals that developed mild febrile reactions when they were challenged 2 years after artificial immunization, all the cattle were fully resistant to challenge with C. ruminantium-infected sheep blood. Hence cattle can retain their immunity to heartwater for at least 2 years in the absence of reinfection.