Abstract: This paper aims to find new methods of laboratory investigations to identify the early stages of parasitic diseases in fish, to reduce mortality and improve disinfecting treatments. Hematology is used in ichthyopathology worldwide, especially in the case of infectious-contagious diseases, but we suggest studying the appropriateness of their widespread use in our country, extending them in the case of parasitic diseases with serious prognosis, to quantify the precise equivalence between the anatomical-pathological changes determined by the degree of fish infestation (resulting from the microscopic examination) and the physio-pathological ones expressed by the biochemical changes (shown by blood tests) that occur in the fish body, in various stages of a parasitic disease. The usefulness of performing a blood analysis, as a precision factor in paraclinical investigations, allows to determine the exact stage of the disease on which the effect of the disinfection treatment shows maximum efficiency and will also reveal the modality in which stocking densities of fish are influencing the immunity mechanism of the fish. From all the parasitic diseases we have chosen a protozoan Ichthyophthirius multifiliis (Fourchet 1876) infestation, which has a mortality of 50-90% on fish, due to a faster propagation rate, an aggressive behavior, it attacks the host tissue, penetrating deep into the subepithelial- skin and gills, thus achieving protection against chemotherapeutic substance used in the treatment, demonstrating the need to treate the disease in the early stages, when the parasite may be destroyed. The experimental results show that the degree of infestation is growing directly proportional to the stocking density, and inversely proportional with the size and immunity of the fish (the immunological parameters are increased by immunoglobulin M), the serological parameters (erythrocytes increase the hematocrit, hemoglobin and the total protein serum decrease), and the biochemical parameters (glucose, ALT and AST) increase due to the stress, disease state and the successive treatments. This study highlights how large losses in the fish farm sector can be effectively decreased, by using new, accurate analysis tools. The losses are caused by parasitic diseases that rapidly evolve and sometimes can be aggravated by the cumulative effect of adaptive stress, as frequent expression of technological errors, that act negatively on the defense mechanisms of fish. By correlating the results of hematologic analysis with those of the clinical and regular microscope examinations, the fish health can be monitored, through the growth period or in the case of biological material transfer from a fish farm to another, aiming to reduce the fish mortality by 89-98%.

: fish, ichthyopathology, diagnosis, haematological analyses

biology

Presentation: poster