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Monogenean parasites and their effect on the expression of Toll-like receptor genes in Abramis brama x Rutilus rutilus hybrid system

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Year of publication 2017
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description Infection by monogeneans (the gill and skin helminths), can cause severe health problems in fish, especially those living in aquaculture. In response to parasite infection, multiple immunological processes are initiated. An important process associated with the immune response to infection is an expression of immune genes, which can adapt immune response against particular parasites. The understanding of immune genes expression and gene modulation by parasitic infection can bring additional information on the fish immune system. Subsequently, new methods to control parasitic infections might be established [1]. In our study, we aimed to determine the effect of infection by monogenean parasites on the expression of genes encoding Toll-like receptors (TLR2 and TLR21), a crucial component of fish innate immune system, in the fish lymphatic organs (spleen and head kidney) and gills (i.e. site of infection of the studied monogenean parasites). Abramis brama, Rutilus rutilus, and their hybrids collected from Hamry reservoir (N=10 for each group) were dissected and their parasites were determined. Monogenean parasites represented the most abundant group of parasites in studied fish. Differences in parasitic load between fish groups, as well as differences in expression of studied TLR genes in organs and between fish groups, were analyzed using Kruskal-Wallis test. The effect of monogenean abundance on the expression of TLRs was analyzed by general linear model (GLM) using the fish group as a covariate. The associations between the abundance of each monogenean species and expression of TLRs in the selected organ were analyzed using Pearson correlation. The parasitic load differed between fish groups. A. brama had a significantly higher abundance of monogenean parasites in comparison with R. rutilus and hybrids. The analysis of gene expression showed a significantly higher TLR21 expression in the spleen of A. brama than in remaining groups. Additionally, a significant effect of monogenean abundance and fish group on TLR21 expression in the spleen was supported by GLM analysis. In case of TLR2, a significant difference in its expression in the head kidney was revealed between R. rutilus and hybrids. Expression of TLR2 and TLR21 in remaining tissues did not differ significantly between fish groups. However, in A. brama significant negative correlation was observed between the abundance of Dactylogyrus wunderi (the second most abundant monogenean parasite detected in our study) and expression of TLR21 in gills. Our findings imply that infection by monogenean parasites has an effect on the expression of TLR genes in studied fish. However, the effect of other parasite groups besides Monogenea on the level of TLR expression cannot be excluded. Therefore, an experimental study involving infection by single monogenean parasite species is further needed in order to confirm these findings.
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