“Effect of disinfectants on water quality and colonization of fish by infectious organisms (7009)”

EFFECT OF DISINFECTANTS ON WATER QUALITY AND COLONIZATION OF FISH BY INFECTIOUS ORGANISMS

Parasites and bacteria are common causes of disease and may be one of the factors slowing down the current development of aquaculture. Preventive water disinfection eliminates dangerous pathogens and residual disinfectant concentrations should be used to treat fish for external parasitic and bacterial diseases.

The effects of two disinfectants – peracetic acid (PAA) and hydrogen peroxide (H₂O₂) on the hydrochemical properties of water and the parasitic and bacterial load on the skin and gills of carp are described in this paper. Three groups (n=6) of common carp (Cyprinus carpio) were exposed to PAA (1.5 mg·l^-1) and H₂O₂ (5 mg·l^-1) applied daily for a duration of 4 days. The test was triplicated. After exposition, bacterial and parasitological examinations of the gills and skin were conducted using bacteriological smear and microscopy of tissue scrapes. Hydrochemiacal parameters were measured before and after the trial. Parasitological and bacterial load of the skin and gills was classified into five categories and subsequently statistically evaluated using the Mann Whitney test.

Parasitological examination revealed a statistically significant (P<0>) effect of PAA on Trichodina sp. These parasites were eliminated on the skin and on the gills of the fish from PAA group. No other statistically significant differences were mentioned among group tested.

Semiquantitative bacteriological examination revealed a statistically significant reduction (P<0>) in the bacterial load of skin in both PAA and H₂O₂ exposed groups. Conversely, there was no statistically significant difference in the bacterial load of gills.

The results show that the application of PAA and H₂O₂ in the tested concentrations for four days has antibacterial effect, while PAA showed also antiparasitic effects.

1. Zusková, Eliška, South Bohemian University in České Budějovice, Presenter