ARS | Publication request: Parasitism enhances susceptibility to bacterial infection in tilapia

Submitted to: Global Aquaculture Advocate
Publication Type: Popular Publication
Publication Acceptance Date: February 4, 2011
Publication Date: March 1, 2011
Citation: Xu, D., Shoemaker, C.A., Klesius, P.H. 2011. Parasitism enhances susceptibility to bacterial infection in tilapia. Global Aquaculture Advocate. March/April 28-29.

Technical Abstract: Gyrodactylus is a small elongate monogenetic parasite that mainly lives on the skin and gills of freshwater fish. Gyrodactylus causes mechanical injuries on fish epithelium that can lead to fish mortality under crowded conditions. Streptococcus iniae is a severe bacterial pathogen and the economic losses caused by this bacterium in aquaculture worldwide are estimated to be over US $150 million annually. In tilapia production facilities, it has been observed that parasites and bacteria co-infected tilapia and led to fish mortality. No information was available on the effect of Gyrodactylus parasitism on S. iniae infection in tilapia. A study was conducted to evaluate whether tilapia infected with Gyrodactylus were more susceptible to S. iniae. Results of this study demonstrated that parasitism in tilapia with Gyrodactylus increased infection and mortality following exposure to S. iniae. The mechanical injury from the parasite apparently provided a portal of entry for the bacterium. The information in this study is important for fish health management to minimize fish loss. The prevention of parasite infection in fish not only reduced the direct damage by parasites but also reduces fish mortality due to bacterial infection.