Title page for ETD etd-0609103-140047


Type of Document Dissertation
Author Baudena, Marie Alexandra
Author's Email Address abaude1@lsu.edu
URN etd-0609103-140047
Title Equine Immunity to Cyathostome Infections
Degree Doctor of Philosophy (Ph.D.)
Department Veterinary Microbiology & Parasitology (Veterinary Medical Sciences)
Advisory Committee
Advisor Name Title
Thomas R. Klei Committee Chair
David W. Horohov Committee Member
H. Wayne Taylor Committee Member
James E. Miller Committee Member
Bryan T. Rogers Dean's Representative
Keywords
  • equine
  • horse
  • parasite
  • small strongyles
  • cyathostomes
  • immunity
Date of Defense 2003-05-22
Availability unrestricted
Abstract
To study the protective responses of cyathostome-infected ponies, two challenges were performed employing animals with different histories of exposure to these parasites. The hypothesis developed and to be tested in these experiments was that ponies that had longer exposure to cyathostome contaminated pastures would express acquired resistance to infection. The assumption behind this hypothesis was that helminth-na´ve ponies infected with cyathostomes would eliminate the infection using only innate immune responses. Whereas previously exposed ponies would eliminate the infection with acquired immune responses, and these would be more effective in ponies with longer exposure to cyathostomes. Thus, helminth-na´ve animals would acquire the largest number of worms, followed in decreasing order by young and then adult ponies.

Two types of challenges were used: an experimental infection with 150,000 cyathostome infective third stage (L3) given over a period of 5 days, and the natural acquisition of infection by grazing a cyathostome contaminated pasture for 7 weeks. The natural challenge was performed to confirm the data obtained with the experimental challenge, therefore to validate its use.

The parasitological data recovered showed that ponies with acquired resistance to cyathostome infections had reduced total number of worms, of developing larvae, luminal fourth stage larvae, adult parasites and of cyathostome species. The acquisition of resistance was also observed as elevations in the hypobiotic larvae numbers and of intestinal mast cells, intestinal and peripheral eosinophils, and antibody responses. These responses were consistent with increases in Th2 type cytokines, principally IL-4.

The data obtained suggest that the immune mechanisms of resistance developed in ponies with acquired protection to cyathostome are slow to develop and are targeted against each parasite stage present in the host. These results warrant further research in the area, especially in the difference between immune mechanisms of helminth na´ve ponies and animals with short exposures to cyathostome contaminated pastures.

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