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Title: Parasitism affects vaccine efficacy against Streptococcus iniae in Nile tilapia

item Shoemaker, Craig
item MARTINS, MAURICO - University Of Santa Catarina
item Xu, Dehai

Submitted to: European Association of Fish Pathologists
Publication Type: Abstract Only
Publication Acceptance Date: 5/12/2015
Publication Date: 9/6/2015
Citation: Shoemaker, C.A., Martins, M.L., Xu, D. 2015. Parasitism affects vaccine efficacy against Streptococcus iniae in Nile tilapia [abstract]. European Association of Fish Pathologists. p. 182.

Interpretive Summary:

Technical Abstract: Tilapia culture worldwide is estimated to be US$ 5 billion and is important to domestic and global food security. Parasites and bacteria co-occur in both extensive and intensive production of tilapia. The effect of parasitism on vaccine performance in fish is little studied. The objective of this study was to determine if parasitism of tilapia affected vaccine efficacy. Antibody level and survival of Nile tilapia vaccinated with a modified Streptococcus iniae bacterin were compared among non-parasitized fish, fish parasitized by Trichodina heterodentata and Gyrodactylus cichlidarum, and fish parasitized by T. heterodentata, G. cichlidarum and Ichthyophthirius multifiliis (Ich). Among vaccinated fish, fish free from parasites (Trichodina, Gyrodactylus and Ich) had the highest antibody level (0.43, SE=0.14). Significantly (p < 0.05) lower anti-S. iniae antibody was noted in parasitized vaccinated fish (0.30, SE=0.08). Among the vaccinated treatments post challenge, fish parasitized by Trichodina, Gyrodactylus and Ich showed the lowest survival (80.0%, SE=10.0), significantly (p<0.05) lower than vaccinated fish free from parasites (97.5%, SE=2.5) or parasitized by Trichodina and Gyrodactylus (95.0%, SE=5.0). Following challenge with S. iniae, non-vaccinated fish free from parasites showed higher survival (47.5%, SE=2.5) than non-vaccinated fish parasitized by Trichodina and Gyrodactylus (37.5%, SE=2.5). Non-vaccinated fish parasitized by all 3 parasites showed the lowest survival (27.5%, SE=2.5) post challenge. Relative percent survival (RPS) demonstrated a decrease in vaccine performance for the group of fish that were parasitized with Trichodina and Gyrodactylus and Ich. RPS was 72% compared to 95 and 92%, respectively, in the other vaccinated treatments following challenge. This study demonstrated a reduction in vaccine performance in parasitized tilapia and highlights the importance of monitoring or controlling parasite levels in the aquaculture setting. Limiting parasitic infection should be considered in fish health management as a strategy to enhance vaccine effectiveness.