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Title: Naturally infected channel catfish (Ictalurus punctatus) concurrently transmit Ichthyophthirius multifiliis and Edwardsiella ictaluri to naive channel catfish

Author
item Xu, Dehai
item Shoemaker, Craig
item ZHANG, QIZHONG - Guangzhou University
item Klesius, Phillip

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2012
Publication Date: 11/26/2012
Citation: Xu, D., Shoemaker, C.A., Zhang, Q., Klesius, P.H. 2012. Naturally infected channel catfish (Ictalurus punctatus) concurrently transmit Ichthyophthirius multifiliis and Edwardsiella ictaluri to naive channel catfish. Aquaculture. 376-379:133-136.

Interpretive Summary: Bacterium Edwardsiella ictaluri and parasite Ichthyophthirius multifiliis (Ich) are two common pathogens of catfish which cause major losses to catfish aquaculture. The objective of this study was to expose naive channel catfish to naturally infected fish that carried Ich and E. ictaluri to provide clinical evidence for transmission of two pathogens. This study demonstrated that co-infections increase the severity of infectious diseases and lead to higher mortality comparing to fish infected by a single pathogen. The results showed that fish naturally coinfected with Ich and E. ictaluri could concomitantly transmit both pathogens to naive fish. The results are important for fish farmers and health managers to understand the potential ability of parasites to vector bacterial disease. Parasites introduced via wild fish or fish from other farms could concomitantly involve the introduction and/or transmission of microbial disease agents. Precaution is needed to thoroughly examine fish prior to shipment or purchase to prevent the spread of aquatic animal pathogens.

Technical Abstract: There is no information available whether fish naturally coinfected with Ichthyophthirius multifiliis (Ich) and Edwardsiella ictaluri can concurrently transmit both pathogens to naive fish. The objective of this study was to expose naive channel catfish (Ictalurus punctatus) to naturally infected fish that carried Ich and E. ictaluri to provide clinical evidence for transmission of both pathogens. Three tanks of fish were exposed to naturally coinfected fish and two tanks were utilized as mock-infected controls in each of the two trials. In trial I, 34 out of 60 fish (56.7%) exposed to two infected fish per tank died at day one. All remaining fish (100%) died two days post exposure. Of the dead fish, all showed heavy Ich infection and E. ictaluri was isolated from the kidney of 50% of the dead catfish. In trial II, the cumulative mortality in fish exposed to 2 coinfected fish per tank was less than 20% during days 1-7 post exposure. Most of the fish died from 8 to 14 days post exposure to the coinfected fish. Ninety-six % of the fish were positive for both Ich and E. ictaluri in trial II. The results demonstrated that fish naturally coinfected with Ich and E. ictaluri could concomitantly transmit both pathogens to naive fish. In aquaculture management, precaution is needed to thoroughly examine fish prior to shipment or purchase to prevent the spread of aquatic animal pathogens.