The effect of dietary immunostimulants on the susceptibility of common carp (Cyprinus carpio) to the white spot parasite, Ichthyophthirius multifiliis

Dietary supplementation of Chinese herbal medicines enhances the immune response and resistance of rainbow trout (Oncorhynchus mykiss) to infectious hematopoietic necrosis virus

Rainbow trout is a widely farmed economical cold-water fish worldwide, but the prevalence of infectious hematopoietic necrosis virus (IHNV) presents a severe risk to the aquaculture industry, resulting in high mortality and huge economic losses. In this study, the impacts of different concentrations (0, 10, 20, and 30 g/kg) of Chinese herbal medicine mixture (CHMM) on the immune response and resistance of rainbow trout to IHNV infection were evaluated. The results show that CHMM noticeably increased (P < 0.05) T-SOD, CAT, AST, ALT, ACP, and AKP activities and decreased MDA content. NF-κB, TNF-α, IFN-β, IL-1β, JAK1, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while SOCS2 expression was downregulated (P < 0.05). Following infection with IHNV, feeding rainbow trout with varying amounts of CHMM resulted in noticeably increased (P < 0.05) T-SOD, ACP, and AKP activities and significantly decreased (P < 0.05) MDA content and AST and ALT activities. TNF-α, IFN-β, IL-1β, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while the expressions of JAK1 and SOCS2 were downregulated. The expression level of the IHNV G protein gene at a dosage of 20 g/kg was notably lower than that of the other CHMM feeding groups. This study provides a solid scientific basis for promoting CHMM as an immunostimulant for boosting antiviral immunity in rainbow trout.

Efficacy of dietary live or heat-killed Bacillus subtilis in goldfish (Carassius auratus) infected with Ichthyophthirius multifiliis

BACKGROUND

The beneficial effects of Bacillus subtilis on growth, immune response, and disease resistance against various diseases in different fish species have been proved. However, there are no data concerning this probiotic effect on skin mucosal immunity in fish infected with Ichthyophthirius multifiliis (Ich). Ich has a high mortality rate in both edible and ornamental fish and consequently is concerned with heavy economic losses.

OBJECTIVES

Thus, we assessed the efficacy of live and heat-killed B. subtilis on skin immunity and histopathology in goldfish (Carassius auratus) infected with Ich.

METHODS

Goldfish (144 fish, 2.38 g average weight) were stocked in nine glass tanks each in three replicates. Fish were fed 10⁹ CFU g^-1 live or heat-killed B. subtilis for 80 days.

RESULTS

Probiotic administration in both viable and non-viable forms could enhance the growth performance in goldfish. Probiotic therapy also reduced the density of the parasite and histopathological level on skin and gill tissues of the treated fish. Real-time polymerase chain reaction analysis showed a higher expression of lysozyme and tumour necrosis factor-α in the treated groups compared to the control group.

CONCLUSIONS

These data demonstrated the beneficial effect of B. subtilis as probiotic and paraprobiotic on growth performance and disease resistance to Ich infestation in goldfish.

Effects of dietary Astragalus Propinquus Schischkin polysaccharides on growth performance, immunological parameters, antioxidants responses and inflammation-related gene expression in Channa argus

The present study investigated the effects of dietary Astragalus Propinquus schischkin polysaccharides on growth, immune responses, antioxidants responses and inflammation-related genes expression in Channa argus. Channa argus were randomly divided into 5 groups and fed 5 levels diets of A. propinquus schischkin polysaccharides (0, 250, 500, 1000 and 2000 mg/kg) for 56 days. The results showed, dietary A. propinquus schischkin polysaccharides addition can increase the final body weight, weight gain and specific growth rate, decrease the feed conversion ratio of Channa argus. And dietary A. propinquus schischkin polysaccharides supplementation can increase the levels of serum superoxide dismutase, catalase, glutathione peroxidase, lysozyme, complement 3, complement 4, immunoglobulin M and alkaline phosphatase, decrease the levels of serum malondialdehyde, cortisol, aspartate aminotransferase and glutamic-pyruvic transaminase. Furthermore, dietary A. propinquus schischkin polysaccharides can decrease the gene expression levels of interleukin-1β, interleukin-, tumor necrosis factor-α and nuclear factor-κB, increase the gene expression levels of glucocorticoid receptor in liver, spleen, kidney, intestine. To sum up, dietary A. propinquus schischkin polysaccharides can accelerate growth, enhance immune responses and antioxidants responses, regulate inflammation-related genes expression in Channa argus and the optimum amount is 1000 mg/kg.

Serine protease inhibitors of the whirling disease parasite Myxobolus cerebralis (Cnidaria, Myxozoa): Expression profiling and functional predictions

Here, we studied the expression pattern and putative function of four, previously identified serine protease inhibitors (serpins) of Myxobolus cerebralis, a pathogenic myxozoan species (Cnidaria: Myxozoa) causing whirling disease of salmonid fishes. The relative expression profiles of serpins were determined at different developmental stages both in fish and in annelid hosts using serpin-specific qPCR assays. The expression of serpin Mc-S1 was similar throughout the life cycle, whereas a significant decrease was detected in the relative expression of Mc-S3 and Mc-S5 during the development in fish, and then in the sporogonic stage in the worm host. A decreasing tendency could also be observed in the expression of Mc-S4 in fish, which was, however, upregulated in the worm host. For the first time, we predicted the function of M. cerebralis serpins by the use of several bioinformatics-based applications. Mc-S1 is putatively a chymotrypsin-like inhibitor that locates extracellularly and is capable of heparin binding. The other three serpins are caspase-like inhibitors, and they are probably involved in protease and cell degradation processes during the early stage of fish invasion.

Susceptibility-related differences in the quantity of developmental stages of Myxobolus spp. (Myxozoa) in fish blood

Here, we investigated the early development of two closely related myxozoan parasites, the highly pathogenic Myxobolus cerebralis, the causative agent of the whirling disease in salmonids, and Myxobolus pseudodispar, a common, non-pathogenic parasite of cyprinids. The aim of our study was to examine under in vivo laboratory conditions whether fish blood is involved in the intrapiscine development of the two parasite species and investigate if there is dissimilarity between the parasite infection intensity in blood and if it varies in terms of host susceptibility and parasite pathogenicity. Highly susceptible, less susceptible and non-susceptible hosts were involved. Blood samples were taken 1 day, 1 week and 1 month post exposure to M. cerebralis and M. pseudodispar, respectively. The prevalence and infection intensity was estimated by parasite-specific quantitative real-time PCR. Although previous findings assumed that M. cerebralis might escape from host immune system by migrating via peripheral nerves, our experimental results demonstrated that M. cerebralis is present in blood during the early stage of intrapiscine development. For the non-pathogenic M. pseudodispar, the highest infection prevalence was found in the original host, common roach Rutilus rutilus, whereas the highest infection intensity was detected in rudd Scardinius erythrophthalmus, a “dead-end” host of the parasite. The presence of M. pseudodispar developmental stages in the blood of both susceptible and non-susceptible cyprinids suggests that the susceptibility differences remain hidden during the early stage of infection. Our findings supply further evidence that host specificity is not determined during the early, intrapiscine development involving the vascular system. Furthermore, we found remarkable differences in the infection dynamics of the two parasite species examined, possibly due to their distinct pathogenicity or variations in adaptive capabilities to immune components in host blood.

β-Glucan and Parasites

Immunosuppression caused by parasitic infections represents the foremost way by which the parasites overcome or escape the host’s immune response. Glucan is a well-established natural immunomodulator with the ability to significantly improve immune system, from innate immunity to both branches of specific immunity. Our review is focused on the possible role of glucan’s action in antiparasite therapies and vaccine strategies. We concluded that the established action of glucan opens a new window in treatment and protection against parasitic infections.