An oral Vibrio vaccine for salmonids was developed.
The vaccine was produced by spray coating lyophilized
formalin-killed whole cells of Vibrio anguillarum (VA LS 1-
74) onto non-pareil sugar beads. Then methacrylic acrylic
acid copolymer (Eudragit L-30D) was applied as an enteric
protective coating.
Using x-ray radiographic techniques, it was found that
large particles (> 1.1 mm) remain in the fish stomach for
more than 2 hours before they would enter the pyloric caeca.
The pyloric sphincter which has an opening of 0.94 mm, acts
as barrier to prevent the passage of large food particles in
the stomach to the pyloric caeca. Based on this information
non-pareil sugar beads of 18-20 mesh or smaller should be
used as the vaccine carriers. A 15% (w/w) Eudragit L-30D
coating is needed to provide enteric protection of the
vaccine loaded sugar beads of 18-20 mesh size. Lower levels
of coating resulted in the bead breaking down in the stomach
and releasing contents prior to entering the pyloric caeca.
Since the lymphoid tissues are diffuse throughout the whole
GI tract, it may not be necessary to target a vaccine to
deliver antigens to a specific area of the intestinal tract,
but only protect the antigens from gastric fluids.
In vitro dissolution studies indicate that 10% VA LS 1-
74 loading was sufficient for rapid vaccine release (42%
released in 30 minutes) and a 15% Eudragit L-30D coating was
suitable for providing protection against stomach acid. The
vaccine product used in vivo studies contained 10% VA LS 1-
74 and 15% Eudragit L-30D on non-pareil sugar seeds of 18-20
mesh size.
Coho salmon were given the vaccine orally, and 30 days
afterward a live challenge test was performed. There was no
significant difference in the survival rates in a live
bacteria challenge test with the positive control (83.3%)
and test (80.3%) groups. Both had higher survival rates
than the no vaccine fed control group. The serum and
mucosal antibody levels to Vibrio were significantly higher
(p<0.01) in the test group (19700 units/ml) than the other
two groups (2530 units/ml in the positive control group and
617 units/ml in the negative control group). The antibody
titer appears to be a better indicator for vaccine efficacy
than survival rate of live bacteria challenge tests.
The oral Vibrio vaccine developed is effective, and the
technique to protect the antigen can be applied to other
antigens or proteins for oral delivery producing an
economical pathway for mass vaccination of fish. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37467 |
| Date | 13 December 1990 |
| Creators | Wong, George Kaon |
| Contributors | Christensen, John M. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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