Naraid Suanyuk and Akkarawit Itsaro

pp. 143 - 149

Abstract

Streptococcus iniae infections are becoming an increasing problem in aquaculture and have been reported worldwide
in a variety of fish species. Our previous study showed that S. iniae infection in tilapia Oreochromis sp. and Asian sea bass
Lates calcarifer cause serious damage in fish farm in Thailand. To prevent streptococcosis caused by S. iniae, a formalinkilled vaccine was applied in red tilapia Oreochromis niloticus x O. mossambicus by injection, immersion and oral vaccination. At 1 week post vaccination, levels of antibody titer and some blood parameters response to different routes of administration were significantly different. The best disease resistance was found in the group injected with vaccine plus β-(1,3/1,6)–
glucan with the relative percent survival (RPS) of 95.12% followed by pure vaccine injection (RPS = 80.49%), immersion
(RPS = 41.46%) and oral vaccination (RPS = 9.75%).
No difference in blood parameters of tilapia after vaccination for 4 weeks was observed. However, antibody titer of
the group received vaccine plus β-(1,3/1,6)–glucan and vaccine alone were significantly higher than the other groups. RPS of
fish at week 4 post vaccination showed the same trend as the highest disease resistance recorded in the group injected with
vaccine plus β-(1,3/1,6)–glucan (RPS=76.00%) which significantly differ from vaccine alone (RPS=54.00%). Immersion and
oral vaccination showed less effect on disease protection at week 4 post vaccination. The result from the present study
indicated that formalin-killed S. iniae vaccine provided excellent efficacy against S. iniae infection in tilapia by intrapertoneal injection and tilapia by intrapertoneal injection and -(1,3/1,6)–glucan increased the effectiveness of vaccine produced from S. iniae. -(1,3/1,6)–glucan increased the effectiveness of vaccine produced from S. iniae.