Ecological factors associated with parasite Ichthyophthirius multifiliis gene abundance in the aquatic environment：novel clues for ecological control of Ichthyophthiriasis

Abstract

Abstract Background Ichthyophthirius multifiliis is considered one of the most harmful parasite, which can invade various economic freshwater fish. It can cause great economic losses to the aquaculture and ornamental fish industries. Until today, there is no efficient drug or vaccine to control this disease. The classic triangle disease model suggests that the occurrence of a disease is the result of interactions between the host, environment and pathogen. Here we aim to explore the relationship between the environmental I. multifiliis’s genes abundance and ecological factors. Results Based on shotgun metagenomics sequencing technology, the relationship between biotic factors and I. multifiliis’s genes abundance was analyzed. We found that there has a significant negative correlation between Bacteria genes abundance and I. multifiliis’s genes abundance, a significant positive correlation between Archaea genes abundance and I. multifiliis’s genes abundance. When exploring the effects of physicochemical factors on the plankton community and I. multifiliis’s genes abundance between different health condition groups, it was found that nitrate was the most correlated factor with differences in the plankton community between groups; In ponds outbroken Ichthyophthiriasis, nitrate concentrations were significantly negatively correlated with I. multifiliis’s genes abundance. In the analysis of nitrogen cycle related functional genes, the abundance of both nitrogen cycle related and nitrate metabolism related functional genes were found to be higher in the ponds without outbreaks of Ichthyophthiriasis. Finally, significant different plankton (genus level) between groups were also analyzed, as well as the contribution of species associated with nitrate metabolism. Conclusions Our study identified microbiological and physicochemical factors that maybe associated with Ichthyophthiriasis. This survey can provide clues for future efficient ecological control of Ichthyophthiriasis.