Probiotics Modulate Tilapia Resistance and Immune Response against Tilapia Lake Virus Infection

Abstract

Tilapia lake virus (TiLV) causes an emerging viral disease associated with high mortality and economic damage in tilapia farming around the world. The use of probiotics in aquaculture has been suggested as an alternative to antibiotics and drugs to reduce the negative impact of bacterial and viral infections. In this study, we investigate the effect of probiotic Bacillus spp. supplementation on mortality, viral load, and expression of immune-related genes in red hybrid tilapia (Oreochromis spp.) upon TiLV infection. Fish were divided into three groups, and fed with: control diet, 0.5% probiotics-supplemented diet, and 1% probiotics-supplemented diet. After 21 days of experimental feeding, the three groups were infected with TiLV and monitored for mortality and growth performances, while organs were sampled at different time points to measure viral load and the transcription modulation of immune response markers. No significant difference was found among the groups in terms of weight gain (WG), average daily gain (ADG), feed efficiency (FE), or feed conversion ratio (FCR). A lower cumulative mortality was retrieved from fish fed 0.5% and 1% probiotics (25% and 24%, respectively), compared to the control group (32%). Moreover, fish fed with 1% probiotic diet had a significantly lower viral load, than those fed with 0.5% probiotic and control diet at 5, 6, 9, and 12 days post infection-challenge (dpc). The expression patterns of immune-related genes, including il-8 (also known as CXCL8), ifn-γ, irf-3, mx, rsad-2 (also known as VIPERIN) showed significant upregulation upon probiotic treatment during the peak of TiLV pathogenesis (between 9 and 12 dpc) and during most of the study period in fish fed with 1% probiotics-supplemented diet. Taken together, these findings indicate that dietary supplementation using Bacillus spp. probiotics may have beneficial effects to strengthen tilapia immunity and resistance against TiLV infections. Therefore, probiotic treatments may be preventively administered to reduce losses caused by this emerging viral infection in tilapia aquaculture.

Weight-dependent susceptibility of tilapia to tilapia lake virus infection

“…The positive effects of probiotics was highlighted in a recent study, which showed that probiotic supplementation with Bacillus spp. in tilapia feed improved fish survival while reducing the TiLV load in the organs of fish (Waiyamitra et al, 2020).…”

Dietary supplementation withBacillusspecies improves growth, intestinal histomorphology, innate immunity, antioxidative status and expression of growth and appetite‐regulating genes of Nile tilapia fingerlings

“…Probiotics include bacteria, yeast and filamentous fungi, which can be used individually or in mixtures or consortia (Ringø et al, 2020). Several studies have shown that enrichment of Nile tilapia diet with probiotics enhanced growth (Elsabagh et al, 2018;Khunrang et al, 2021;Silva et al, 2021;Tachibana et al, 2021), boosted immunity (Kord et al, 2021;Kuebutornye et al, 2020) and protected from infections (Aly et al, 2008;Cavalcante et al, 2020;Liu et al, 2021;Mohammadi et al, 2021;Ramos et al, 2017;Tan et al, 2019;Waiyamitra et al, 2020). Similarly, the use of probiotics showed positive effects in shellfish (Abdel-Tawwab et al, 2020;Butt et al, 2021;Kesselring et al, 2019;Knipe et al, 2021;Ringø, 2020;Vargas-Albores et al, 2017), rainbow trout (Al-Hisnawi et al, 2019) and common carp (Yanbo & Zirong, 2006;Zaheri-Abdehvand et al, 2018).…”

Assessing the effect of probiotics on tilapia lake virus‐infected tilapia: Transmission and immune response

“…An ordinary one-way analysis of variance (ANOVA) with Tukey's multiple comparisons test was applied to the statistically significant difference at p < .05. Significances for cumulative mortality, viral loads or immune gene expressions were set at p < .05 during the TiLV infection (Waiyamitra et al, 2020). Results of statistical analyses of each experimental data adopted from Waiyamitra et al (2020) are shown and compared in Table S1.…”

“…Significances for cumulative mortality, viral loads or immune gene expressions were set at p < .05 during the TiLV infection (Waiyamitra et al, 2020). Results of statistical analyses of each experimental data adopted from Waiyamitra et al (2020) are shown and compared in Table S1.…”