THE USE OF CONJUGATED EFFECT OF THE BACTERICIDAL TREATMENT FOR YERSINIOSIS IN RAINBOW TROUT

Liliana Athanasopoulos, Veta Nistor, Elena Mocanu, Magdalena Tenciu, Maria C. Chioveanu, M.D. Popa

Abstract
   Enteric red mouth disease (ERM) or yersiniosis, is an infectious and contagious disease, that is wildly spread across the world. In Romania, trout culture is facing this serious disease that causes a high mortality among fish population, varying between 10 and 60%.
   The etiologic agent of the disease is the virulent bacterium Yersinia ruckeri, from the Enterobacteriaceae family. This bacterium is considered strictly pathogenic, although it can survive a few months in water and sediments. The sources of infection can be the ill fish, carriers of the pathogen, that spread the bacteria in the water through their excrements of the poorly maintained ponds, water and sediment, farm equipment, bird excrements, some mammals. The predominant factors leading to yersiniosis disease are poor fish rearing conditions (accumulations out of the accepted limits for organic substances, nitrates, oxygen deficit, presence of periphyton etc.) combined with adaptive stress. When the poor conditions lead to an immunity loss of the fish and the disease sets in.
   Purpose of this paper is to find new treatments that act simultaneous internally on the pathogen inside the trout through administration of antibiotics in food, but also externally by destroying the residual bacteria found in mud and periphyton, through administration of non-toxic disinfectants, which does not cause side effects to the antibiotic medication.
   The work method consists in applying the same antibiotic treatment in the two ponds (B2, B3) under identical growth conditions and density, selected from the same batch of trout yersiniosis, with the difference that in the B3 pond, oral administration of medication was cumulated with long term peracetic acid baths.
   The diagnosis of Yersinosis was based on the identification of the first symptoms of the disease and was confirmed by microbiological examination and the treatment was based by sensitivity tests which decided the type of administered antibiotic.
   Rresults were quantified by monitoring mortalities in the two ponds and shows that in the B3 pond where the trout was treated with antibiotic and disinfectant, the recorded mortality is 3.18 % lower.
   The current experiment, using an antibiotic treatment administered orally, combined with a general disinfectant, administered in the water,peracetic acid, reduced the rainbow trouts mortality caused by Yersiniosis.

Key words: Yersiniosis, treatment, antibiotic, peracetic acid