Proceeding of Veterinary and Animal Science Days 2015, 15th- 17th July, Milan, Italy 

HAF © 2013 

Vol. II, No. 1s  ISSN: 2283-3927 

   

 

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CORRESPONDING AUTHOR 

Alessandra Cafiso,  

alessandra.cafiso@unimi.it 

 

 

ABSTRACT  
Red mark syndrome (RMS) is a chronic skin disease of unknown aetiology affecting farmed rainbow trout Oncorhynchus 

mykiss in Europe that causes single or multiple bright red skin lesions. Histological analysis showed acute inflammation in the 

area of the skin suggesting a bacterial infection. No aetiological agent has been unequivocally identified, although the 

involvement of a single transmissible agent has been suggested. The 16S rDNA of a bacterium belonging to the family 

Midichloriaceae (Rickettsiales) was found in association with RMS skin lesions.  

In this work, we present a novel specific method for absolute quantification of the midichloriacea associate d with RMS in O. 

mykiss, based on a quantitative PCR approach. The qPCR method was tested on healthy skin, on lesions when present and on 

organ samples (heart, liver, spleen, intestine, and kidney) from ten fish. Our work shows, for the first time, that the 

midichloriacea is present not only in skin lesions but also in organs of affected fish. Further studies are needed to prove 

whether this bacterium is actually involved in the pathology. 
 

 

 

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Lloyd S.J., LaPatra S.E., Snekvik K.R., Cain K.D., and Call D.R. 2011. Journal of Fish Diseases 34:701–709. 

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Montagna M., Sassera D., Epis S., Bazzocchi C., Vannini C., Lo N., Sacchi L., Fukatsu T., Petroni G., and Bandi C. 2013. Applied 

and Environmental Microbiology 79:3241–3248.  

Molecular evidence for a bacterium of the 

family Midichloriaceae (order Rickettsiales) 

in skin and organs of the rainbow trout 

Oncorhynchus mykiss affected by red mark 

syndrome 

A. Cafiso
1
, C. Bazzocchi

1
, U. McCarthy

2
 

1 
Department of Veterinary Science and Pubblic Health, Università degli 

Studi di Milano, Via Celoria 10, 20133 Milan, Italy 

2 
Marine Scotland Science, Marine Laboratory, Aberdeen, Scotland