In the Mediterranean, species like sea bream are showing pathological symptoms never described before in this region. We are referring specifically to skin ulcers or red lesions. This “new disease” is causing a significant decline in sea bream populations in the Mediterranean. Thus, this project is focused on expanding the knowledge of this disease.

Electron and optical microscopic studies have shown that the rash is associated to an intracellular bacterium that follows the same intracellular multiplication patterns as some known Chlamydias.

A polyclonal antibody was obtained, capable of detecting the intracellular organisms both by immunoblot and indirect immunofluorescence in infected cellular cultures and spleen and kidney smears of fish affected by the rash.

The intracellular bacterium was isolated and cultivated on CHSE-214 (salmon) cells, and the infected cells showed signs of cytopathology with cell death occurring 24 h after infection. The liquid medium used for the cultures remained transparent and there were no signs of extracellular bacterial growth.

The secondary cultures on new cell cultures allowed the growth and establishment of the bacterium.

Parasites likes Eimeria or Phylloameba only appeared in isolated cases. These were considered to be products of the diversity of the different pathologies of the samples.

According to the information obtained from the infected fish, the authentic rash seems to be related to the presence of a “Rickettsia-like” intracellular bacterium observed in all the samples under electron microscope, possibly a new species included within the group currently known as “Parachlamydias”.

The project’s final report includes recommendations for the development of future work to obtain definitive results based on these initial results.