Location: Aquatic Animal Health Research
2011 Annual Report
Another goal of this agreement is to determine effects of parasitism on fish susceptibility to pathogenic bacteria, including the impact of parasitism on fish immune function against pathogens. ARS scientists conducted studies to demonstrate that parasitism in fish increased infection and mortality following exposure to pathogenic bacteria. The mechanical injury from the parasite apparently provided a portal of entry for the bacterium. There is no information on the effects of parasitism on the vaccine efficacy against bacteria in cultured fish. ARS scientists and a visiting scientist from Brazil conducted studies to determine whether parasitism influenced vaccine efficacy against Streptococcus iniae (a gram positive bacteria) in Nile tilapia. The study results demonstrated a reduction in vaccine performance in fish infected by parasites compared to non-parasitized fish. A decrease in antibody levels, red blood cell and white blood cell counts were observed in the parasitized vaccinated fish. This study highlights the importance of monitoring parasite infections in the aquaculture to optimize vaccine efficacy. The prevention of parasite infection in fish not only reduced the direct damage by parasites but also reduces fish mortality due to bacterial infection and enhances fish immune protection against pathogens.
A site visit by two ARS scientists in September 2010, provided discussion for the collaborative research in fish health. ARS scientists presented seminars “Fish vaccines against Streptococcus iniae in tilapia”, “Fish vaccines against Aeromonas hydrophila in channel catfish” and “Infection by Ichthyophthirius enhanced tilapia susceptibility to Streptococcosis” for approximate 30 research scientists and graduate students. Scientists of ARS and the cooperators have also had discussions by phone and e-mails to plan collaborative research in fish health and monitor the progress of this project.