Association of red‐mark syndrome with a Rickettsia‐like organism and its connection with strawberry disease in the USA |
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| Authors: | M Metselaar K D Thompson R M L Gratacap M J L Kik S E LaPatra S J Lloyd D R Call P D Smith A Adams |
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| Institution: | 1. Aquatic Vaccine Unit, Institute of Aquaculture, University of Stirling, UK;2. Department of Pathobiology, Pathology, University of Utrecht, The Netherlands;3. Clear Springs Foods, Inc., Buhl, ID, USA;4. Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA;5. Intervet Schering‐Plough Animal Health, Aquaculture Centre, Saffron Walden, Essex, UK |
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| Abstract: | Red‐mark syndrome (RMS), a disease seen mostly in rainbow trout, Oncorhynchus mykiss, is of unknown aetiology. The research presented here indicates the presence of an intracellular bacterium in RMS‐affected fish. A positive reaction was observed using immunohistochemistry (IHC) with skin lesions, liver, kidney and spleen of affected fish sampled from several locations within the United Kingdom using two different polyclonal antisera raised against Piscirickettsia salmonis. The same reaction was also seen with a number of different anti‐P. salmonis monoclonal antibodies (MAbs). A disease with similar clinical signs to RMS, referred to as strawberry disease (SD), has been reported in the USA. A Rickettsia‐like organism (RLO) has recently been associated with SD based on analysis of 16S rDNA sequences. Using the same panel of anti‐P. salmonis antibodies used to screen the RMS samples, similar staining was obtained in tissue of SD‐affected fish by IHC. A polymerase chain reaction (PCR) using RLO‐specific primers was also performed on RMS‐affected fish from the United Kingdom, and the samples were positive for the RLO 16S rRNA sequence. These findings suggest that the same aetiological agent may be responsible for RMS in the United Kingdom and SD in the USA. |
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| Keywords: | immunohistochemistry Piscirickettsia salmonis rainbow trout red‐mark syndrome Rickettsia‐like organism strawberry disease |
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