Filtration, concentration and detection of salmonid alphavirus in seawater during a post-smolt salmon (Salmo salar) cohabitant challenge

Currently, the prevalence of salmonid alphavirus (SAV) in Norwegian Atlantic salmon farms is largely surveyed via sacrificing fish and sampling of organ tissue on a monthly basis. However, a more cost-efficient, straightforward, rapid, reliable, reproducible and animal welfare friendly method based on the detection of SAV in water could be considered as an alternative method. In the present study, such a method was developed and optimized through a 6 wk cohabitant challenge trial, using post-smolt Atlantic salmon Salmo salar L challenged with high or low doses of SAV subtype 3 (SAV3). Tank water and tissue samples from cohabitant fish were collected at 16 time points. SAV3 was concentrated from the water by filtration, using either electronegative or electropositive membrane filters, which were subsequently rinsed with one of 4 different buffer solutions. SAV3 was detected first in tank water (7 d post-challenge, DPC), and later in cohabitant fish organ tissue samples (12 DPC). The electronegative filter (MF-Millipore™) and rinsing with NucliSENS® easyMAG® Lysis Buffer presented the best SAV3 recovery. A significant positive correlation was found between SAV3 in the tank water concentrates and the mid-kidney samples. Based on these results, detection of SAV3 in filtrated seawater is believed to have the potential to serve as an alternative method for surveillance of SAV in Atlantic salmon farms.

The Role of Nile Tilapia (Oreochromis niloticus) in the Life Cycle of Toxocara spp.

The present study aimed to experimentally assess Nile tilapia as potential paratenic host of Toxocara spp. A total of 15 Nile tilapia (Oreochromis niloticus) were fed with 300 embryonated Toxocara canis eggs by oral gavage, while five others of the control group received distilled water. The fish were individually analyzed at 16, 24, 48, 72, and 240 h after inoculation. Water contamination was assessed, and tissue migration by liver, gastrointestinal tract (GIT), eyes, and central nervous system. A murine model was used as the paratenic host for egg infectivity assessment. Eggs and larvae were found in plastic tank water and fish GIT, ranging from 23 to 86% per fish. Eggs and larvae were recovered from the tank water (76.3%) and fish GIT (23.7%). The counting of eggs and larvae observed was negatively correlated with number of eggs and larvae in the water tank (rho = −0.698, p = 0.003). Shedding of embryonated eggs was first detected at 16 and up to 240 h, with significant egg and larvae yield decrease on water-shedding (p = 0.001) and in the GIT (p = 0.007). Although no T. canis larva was recovered in fish tissues, egg infectivity after fish GIT transit was experimentally confirmed by mice assessment. In conclusion, despite shedding viable embryonated eggs through the gastrointestinal tract, tilapias may not play a role as a suitable paratenic hosts for Toxocara spp., posing low risk of zoonotic transmission by fish meat consumption.

Effect of feed pellet size and tank water level on growth performance in juvenile pikeperch, Sander lucioperca (L.), reared in a recirculating system

Three 28-day experiments were performed to assess the impact of two sinking feed pellet sizes (0.5–1.0 and 0.9–1.6 mm for experiment I, 0.9–1.6 and 1.3–2.0 mm for experiment II, and 1.3–2.0 and 1.6–2.4 mm for experiment III) and two tank water levels (0.50 and 0.65 m) on the growth performance of juvenile pikeperch of different mean initial body weights in experiment I, II, III respectively (1.1 ± 0.1 g, 5.1 ± 0.2 g, 16.6 ± 0.5 g) at different ages (67, 102, and 137 days post hatch). Two-factor analysis of variance showed that the growth of pikeperch was positively correlated with feed pellet size in experiment I, both feed pellet size and water level in experiment II, and water level in experiment III. The feed pellet sizes of 0.9–1.6 and 1.3–2.0 mm at body weights of 1.1 g and 5.1 g, respectively, are recommended to promote more efficient pikeperch growth rates. In the case of pikeperch with a body weight of 16.6 g, the feed pellet size was less important than the tank water level.

Disinfection of Tank Water Using Biogenic Silver Nanosilica as Anti-Microbial Agents in Jeddah City

The need for clean water is becoming urgent all over the world. The risk of microbial contamination of drinking water and its growing ability under poor nutritional conditions occur frequently and existing water management systems do not efficiently eliminate these micropollutants. The major goal of this research is to analyze and test the drinking water quality at random locations in Jeddah City and to investigate the integration of polyurethane foam coated nano-silica silver nanoparticles (NSAgNPs) into the water purification system. The study was conducted in Jeddah city at random intervals during August to December 2020. Twenty-five samples (n = 25) of drinking water (tank water) were collected from different locations in Jeddah. The water samples were found contaminated with E. coli, Klebsiella pneumoniae. and the most prevalent yeast species was Candida albicans. The multi-drug resistance isolates were positively identified by PCR amplification of 16S rDNA gene fragments. The antimicrobial activity of nano-silica silver nanoparticles (NSAgNP) was analyzed and their optimal concentrations that remove potentially harmful microbes were determined. The cytotoxicity of NSAgNPs by Sulforhodamine B colorimetric (SRB) assay against breast adenocarcinoma cell line (MCF-7) showed no cytotoxic effect at concentrations ≤100 µg/mL. The 50% growth inhibition concentration (IC 50) of NSAgNPs after 72 h was 35.8 µg/mL. The excellent performance of NSAgNPs can be attributed to the capping surface functional groups and smaller particle size 8.931 nm, as verified by TEM. In conclusion, the purified water obtained by using 100 mg/L NSAgNPs is free from microbial contaminants and completely safe to drink. We recommend the integration of biosynthesized foam coated silver nanoparticles with water purification system to achieve the desired final water quality.

Conflict in commons: collective action and institutions

Common pool resources (CPRs) are safe-guards and foundation for rural livelihood especially for the developing nations like India. Cooperation is needed to conserve CPRs due to its very features. Community institutions sometimes face conflicts to conserve commons cost-effectively. But, conflicts may simultaneously help and hamper the local governance of commons. For empirical verification, we have conducted a primary survey on 419 users of canal water, community forest and tank water in 11 CPRs dependent villages from West Bengal, India. We observed positive relations between conflict and collective action in conservation of commons. This finding seems to be conflicting with the notion that, conflict undermines collective action and therewith the potential for sustainability. We examined and found that successful informal communities are more conflictive and at the same time cooperative than formal one. The occurrences of supply, demand and policy side conflicts and conflict resolution methods are also not significantly different between formal and informal institutions. Therefore, conflict and informal institution have some positive impact for the successful conservation. We suggest that authorities have to study the nature and types of conflicts before implementing rules and institutional arrangements thereafter. Keywords – collective action, institutions, commons, conflicts, conservation

Piscirickettsia salmonis shedding and tissue burden, and hematological responses during cohabitation infections in chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar

Background Salmonid rickettsial septicemia is an emergent and geographically widespread disease of marine-farmed salmonids caused by infection with the water-borne bacterium Piscirickettsia salmonis. Very little is known about the route, timing, or magnitude of bacterial shedding from infected fish. Methodology/principal findings A cohabitation challenge model was used to assess shedding from chum Oncorhynchus keta, pink O. gorbuscha and Atlantic salmon Salmo salar. Infections in donor fish were established by intraperitoneal injection of P. salmonis. Naïve recipients were cohabitated with donor fish after which cumulative percent morbidity and mortality (CMM) was monitored, and bacterial burdens in kidney and in tank water were measured by qPCR. All donor fish died with mean days-to-death (MDD) among species ranging from 17.5 to 23.9. Among recipients, CMM ranged from 42.7% to 77.8% and MDD ranged from 49.7 to 56.4. In each trial, two peaks of bacterial DNA concentrations in tank water closely aligned with the MDD values of donor and recipient fish. Bacterial tissue burden and shedding rate, and plasma physiological parameters were obtained from individual donors and recipients. Statistically significant positive correlations between the shedding rate and P. salmonis kidney burden were measured in donor pink and in donor and recipient chum salmon, but not in donor or recipient Atlantic salmon. In Atlantic salmon, there was a negative correlation between kidney bacterial burden and hematocrit, plasma Ca++ and Mg++ values, whereas in infected chum salmon the correlation was positive for Na+ and Cl- and negative for glucose. Conclusions A dependency of bacterial shedding on species-specific patterns of pathogenesis was suggested. The coincidence of bacterial shedding with mortality will inform pathogen transmission models.