p crude LPS 005 05 mg into ayu Following challenge mortalities among the

P crude lps 005 05 mg into ayu following challenge

This preview shows page 392 - 394 out of 594 pages.

workers injected i.p. crude LPS (0.05-0.5 mg) into ayu. Following challenge, mortalities among the vaccinates and controls were 0% and 86.7%, respectively. Similarly, O-antigen preparations induced an immune response following injection in a wide range of fish species, including ayu, carp, Japanese eel, Japanese flounder, rainbow trout and red sea bream (Nakamura et al, 1990). Incorporating purified 43 kDa OMP of Aer. hydrophila in FCA and a booster 3 weeks later (without FCA) led to a demonstrable immune response and protection against challenge by V. anguillarum in blue gourami (Trichogaster trichopterus) (Fang et al., 2000). Devel- opment of live attenuated vaccines have been tried, with some success (Norquist et al, 1989; 1994). A field trial with a live attenuated V. anguillarum vaccine (VANIOOO) involved bathing 10 g rainbow trout in a dose equivalent to 1 x 10^ cells/ml for 60 min at 9°C in brackish water. Following a natural challenge, 68% of the unvaccinated controls succumbed compared with 14% of the vaccinates (Norquist et al., 1994). Interestingly, these workers considered that the live vaccine protected against both furunculosis and vibriosis. However, there may be problems with regulatory auth- orities regarding Hcensing for fisheries use. To date, most of the vaccine development programmes have concentrated on bivalent products, containing cells of V. anguillarum and V. ordalii (e.g. Nakai et al., 1989b). At various times, these have been applied to fish by injection (of dubious practicaHty for masses offish), on food (oral administration), by bathing/immersion, by spraying, and by anal and oral intubation. The evidence has shown that oral application, perhaps the most convenient method, fares least successfully. Indeed, comparative vaccine trials have produced a wealth of information. For example, Baudin-Lauren9in and Tangtrongpiros (1980) reported cumulative percentage mor- talities among experimental groups of fish as follows: Unvaccinated controls 33.8% Oral-vaccinated fish 31.7% Immersion-vaccinated group 2.1% Group vaccinated by injection 1.4% Similar findings, although generally more favourable for orally administered vac- cines, were pubhshed by Amend and Johnson (1981) and Home et al. (1982). Thus, Amend and Johnson (1981) revealed the following mortahties in vaccinated salmonids:
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374 Bacterial Fish Pathogens Unvaccinated controls 52% Oral-vaccinated fish 27% Immersion-vaccinated group 4% Spray-vaccinated fish 1 % Group vaccinated by injection 0% This compares with the work of Home et al. (1982), who reported mortalities of: Unvaccinated controls 100% Oral-vaccinated fish 94% Immersion-vaccinated group 53% Group vaccinated by injection 7% In a detailed examination of the effects of oral administration of formalin-inactivated vaccines in chinook salmon, Fryer et al. (1978) noted that maximal protection followed the feeding of 2 mg of dried vaccine/g of food for 15 days at temperatures even as low as 3.9°C. An important corollary was the observation that longer feeding regimes did not result in enhanced protection. This should be considered if prolonged durations of vaccination, via the oral route, are advocated. The reason for the
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