Fasciola hepatica
infection causes significant clinical disease in ruminants. Current control methods, based on flukicidal drugs, are becoming less useful because of resistance in fluke populations. Vaccination would be a viable alternative, but as yet no
vaccine to protect ruminants against liver fluke
infection has been commercialised. Adjuvants can be used to enhance and promote protective immune responses by
vaccines. In previous vaccination trials, we have observed a distinct adjuvant effect, or a degree of protection, in animals administered adjuvant alone in the absence of any specific F. hepatica
antigen. Understanding this effect will be important for continuing efforts to develop
vaccines effective against fasciolosis. This study investigated the effects of three adjuvants (
Quil A, Freund's Incomplete and
TiterMax Gold) on the course of experimental F. hepatica
infection in 6-month-old sheep (n=33). At completion of the trial, all animals were necropsied to determine fluke burden and fluke weight.
Quil A administration led to a significant reduction in faecal egg count (P<0.0001) and significantly higher parasite-specific serum antibody activity for all isotypes measured (P<0.01). This suggests that
Quil A, which promotes a Th1 response, may be useful as an adjuvant in anti-Fasciola
vaccines. Furthermore, it reinforces the results of our previous studies indicating that enhanced Th1 responsiveness to
vaccine antigens is required to achieve protection against challenge by F. hepatica.