Abstract
Myxozoans are a diverse group of cnidarian parasites, including important pathogens in different aquaculture species, without effective legalized treatments for fish destined for human consumption. We tested the effect of natural feed additives on immune parameters of common carp and in the course of a controlled laboratory infection with the myxozoan Sphaerospora molnari. Carp were fed a base diet enriched with 0.5% curcumin or 0.12% of a multi-strain yeast fraction, before intraperitoneal injection with blood stages of S. molnari. We demonstrate the impact of these treatments on respiratory burst, phagocytosis, nitric oxide production, adaptive IgM+ B cell responses, S. molnari-specific antibody titers, and on parasite numbers. Both experimental diets enriched B cell populations prior to infection and postponed initial parasite proliferation in the blood. Curcumin-fed fish showed a decrease in reactive oxygen species, nitric oxide production and B cell density at late-stage infection, likely due to its anti-inflammatory properties, favoring parasite propagation. In contrast, multi-strain yeast fraction (MsYF)-fed fish harbored the highest S. molnari-specific antibody titer, in combination with the overall lowest parasite numbers. The results demonstrate that yeast products can be highly beneficial for the outcome of myxozoan infections and could be used as effective feed additives in aquaculture.
Highlights
Myxozoans are cnidarian endoparasites with reduced morphology and commonly a two-host life cycle, usually including fish as vertebrate hosts
Experimental evidence showed that feeding with yeast-derived β-glucans decreases the number of effect had previously notshasta been studied we investigated how Ceratomyxa parasite stagesin inmyxozoan rainbow trout parasites
We investigated how curcumin, a parasiticidal agent with known anti-inflammatory activity and a multi-strain yeast fraction (MsYF), an immunomodulator, influence the innate and adaptive immune responses of common carp and whether the effect translates into a reduction in the number of proliferative blood stages of S. molnari and specific antibodies raised against it
Summary
Myxozoans are cnidarian endoparasites with reduced morphology and commonly a two-host life cycle, usually including fish as vertebrate hosts. Some of the most severe fish diseases caused by myxozoans include proliferative kidney disease and whirling disease in salmonids [1,2], proliferative gill disease in channel catfish [3] and emaciation disease caused by Enteromyxum spp [4,5]. With the increase of water temperatures, epidemiological models predict spreading of myxozoans into new geographic regions and disease outbreaks [7]. A northwards migration trend of Tetracapsuloides bryosalmonae was confirmed by several records of disease outbreaks from European territories [8,9,10,11] and recent reports exist of massive fish mortalities from natural habitats such as the Yellowstone river [12,13]. In Central Europe, rising water temperatures have been associated with
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