Norovirus Persistence in Oysters to Prolonged Commercial Purification

Depuration is generally the main treatment employed for bivalve mollusks harvested from contaminated sites. Commercial depuration has demonstrated to be effective for removal of bacterial pathogens, although it probably provides only limited efficacy against human enteric viruses. We evaluated the quantitative reduction of norovirus (NoV) genogroups I and II in naturally contaminated oysters after 1, 4, and 9 days of depuration. The process was conducted in an authorized depuration plant, and NoV concentration was determined by RT-qPCR according to ISO 15216-1:2017 method. Regardless of the NoV genogroup, our results showed no significant reduction in NoV concentration after 1 day of depuration. Higher mean reduction (68%) was obtained after 4 days of treatment, while no further increase was observed after 9 days. Overall, reduction was highly variable, and none of the trials showed statistically significant reduction in NoV RNA concentration at the end of each depuration period. Indeed, NoV concentration remained high in 70% of samples even after 9 days of depuration, with values ranging between 4.0 × 102 and 2.3 × 104 g.c./g. These results indicate that an extension of commercial depuration time does not appear to be effective for reducing or eliminating NoV in oysters.

Environmentally relevant levels of four psychoactive compounds vary in their effects on freshwater fish condition: a brain concentration evidence approach

Background The aquatic environment has been contaminated with various anthropogenic pollutants, including psychoactive compounds that may alter the physiology and behavior of free-living organisms. The present study focused on the condition and related mortality of the juvenile chub (Squalius cephalus). The aim of the study was to test whether the adverse effects of the antidepressants sertraline and citalopram, the analgesic tramadol and the illicit drug methamphetamine, on fish condition exist under environmentally relevant concentrations and whether these effects persist after a depuration period. Innovative analyses of the fish brain concentrations of these compounds were performed with the aim to show relationship between compound brain tissue concentration and fish condition. Methods The laboratory experiment consisted of 42 days of exposure and a subsequent 14-day depuration period with regular monitoring of the condition and mortality of exposed and control fish. Identical methodology, including individual brain concentration analyses for the tested compounds, was applied for all substances. Additional study on feeding under sertraline exposure was also conducted. The feeding was measured from the 28th day of the exposure, three times in a week, by observation of food intake during 15 minutes in social environment. Results The effects of particular psychoactive compounds on chub condition varied. While sertraline induced a lower condition and increased mortality, the effects of methamphetamine were inverse, and tramadol and citalopram had no significant effect at all. Individual brain concentrations of the tested compounds showed that the effects of sertraline and methamphetamine on fish condition were increased with brain concentration increases. Additionally, the food intake was reduced in case of sertraline. In contrast, there was no relationship between tramadol and citalopram brain tissue concentration and fish condition, suggesting that the concentration-dependent effect is strongly compound-specific. Methamphetamine was the only compound with a persistent effect after the depuration period. Our results demonstrate the suitability of the brain concentration evidence approach and suggest that changes in fish condition and other related parameters can be expected in freshwater ecosystems polluted with specific psychoactive compounds.

Kinetics of polychlorinated biphenyls in Bactrian camels

The study aimed to determine the accumulation and depuration of polychlorinated biphenyls (PCBs) in Bactrian camels. Four lactating, two-humped camels (Camelus bactrianus) received 0.8 mg PCBs (1.3 μg/kg body weight) daily for 56 days. Then, the depuration of the animals was monitored for the next 4 months. Milk, blood and hump fat of the camels were sampled every 2 weeks and analyzed. Body weight increased significantly, from approximately 550 to 613 kg, by the end of the study. The fat mass in the humps initially decreased (-2.3 kg, P<0.05) then increased at the end of the depuration period (+2.0 kg, P<0.05). At the end of the exposure period, the concentrations of the indicator PCBs were 1.6 mg/g hump fat, 0.85 mg/g milk fat and 0.56 mg/L blood serum, i.e., ten times over the background level. The concentrations in the hump fat decreased significantly during the depuration period, for congeners 28, 52, 101 and 118, but did not vary appreciably for the heavily chlorinated congeners 138, 153 and 180. The apparently stable concentrations of the heavier congeners may be an artifact of the reduced fat mass in the humps during the first part of the depuration period, combined with fat mobilization, which may mask the reduction of stored PCBs. PCB concentrations in the milk and blood were not significantly reduced during the depuration periods, as they represent the outflow of PCBs from the pool stored in the humps and have a weak affinity for lipophilic compounds, respectively. Therefore, it should be recommended to avoid the consumption of raw fat from camel hump in polluted areas because this organ would easily bioaccumulate organic pollutants during an exposure and store it over an extended period. PCB contaminants in milk would reflect the intensity of the outflow from the stored pool, and it would take a longer time in camels than in other ruminants to obtain safe food after the exposure of the animals to persistent organic pollutants.

TiO2 nanoparticles intake by fish gill cells following exposure

Engineered nanomaterials such as nanoparticles (NPs) are increasingly being used for commercial purposes in products within medicine, electronics, sporting goods, tires, textiles and cosmetics. They comprise diverse types of materials from metals, polymers, ceramic to biomaterials and have been defined as particles with at least one dimension in the order up to 100 nm1. The higher toxicological potential of NPs is mostly due to their small size, wide surface, increase of their chemical reactivity and biological activity and the capacity to generate free radicals. NPs also can have the ability to penetrate trough the biological barriers and to move easily through the biological systems. Therefore, is mandatory to assess the toxicity of these nanomaterials, since their industrial production and uses will also result in releases to the environment with unclear consequences.The aim of the present work is to evaluate the toxicity of titanium dioxide (TiO2) NPs on gill gluthatione-S-transferase activity (GST), lipid peroxidation and on structure of the gills of two freshwater fish species (Carassius auratus and Danio rerio). Suspensions of TiO2 NPs, with an average size of 21 nm, were prepared using distillate water and then ultrasonicated (10 min, 35 KHz). The suspensions were added to 10L of tap water in exposure tanks, to obtain nominal concentrations (0.01; 0.1; 1, 10; 100 TiO2 mg/L). The test fish, C. auratus (N=144) and D. rerio (N=80), were randomly distributed by 6 exposure tanks and an additional tank with clean tap water was used as control. Fish were sampled after 7, 14, and 21 days. Six fish from both species were left for depuration in clean tap water during 14 days and then sacrificed. The GST activity was determined by following the procedure described by Habig et al. and lipid peroxidation was measured based on the Thiobarbituric Acid Reactive Species method. The tissues were processed essentially according to Martoja and Martoja for light microscopy (LM). For transmission electron microscopy (TEM) the samples were fixed sequentially in glutaraldehyde, osmium tetroxide and uranyl acetate, dehydrated in ethanol and embedded in Epon-Araldite according to standard procedures. The histological and ultrastructural observations were performed using a Leica-ATC 2000 microscope and a JEOL 100-SX electron microscope respectively.The results show a significant increase of GST in gills tissues for C.auratus exposed to 10 and 100 mg/L TiO2 NPs and a decrease following the depuration period. With respect to D. rerio a significant increase was observed in fish exposed to 1, 10 and 100 mg/L TiO2 NPs. Lipid peroxidation are in agreement with GST results but showing a significant increase for fish (C.auratus and D. rerio) exposed to concentrations of 0.1 TiO2 mg/L NPs and higher. Usually, the oxidative stress caused by exposure to TiO2 NPs is attributed to hydroxyl radicals (OH) generated by photochemical (UV/vis) processes but it may be also related to specific properties of TiO2 NPs such as size, surface area and solubility that can influence the degree of toxicity. The results from LM observations (Fig. 1) showed that exposure to TiO2 NPs affected gill tissues, with changes being detected in both fish species exposed to 0.1 TiO2 mg/L NPs and higher which is in accordance with biochemical results. Changes include different degrees of hyperplasia (from low to complete fusion of lamellae). The TEM analysis revealed that TiO2 NPs were internalized by gills epithelial cells accumulating in vacuoles inside these cells (Fig. 2). After the depuration period it was observed that the capability for gills to recover was not complete. The results show a strong response to oxidative stress caused by exposure to TiO2 NPs, possibly because they are in direct contact with the exposure medium and function as a first barrier against external aggression. However, the gills changes observed following exposure and a partial recover after depuration suggest that TiO2 NPs may cause deleterious effects in fish gills compromising fish homeostasis.The authors acknowledge the funding by Fundação para a Ciência e Tecnologia through grant PTDC/CTM/099446/2008 and through project no. PEst-C/EQB/LA0006/2011 granted to Requimte.

Effects of feeding on waterborne silver uptake and depuration in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss, ~50 g) were exposed to 0.1 µM AgNO3 in ion-poor water (Ca ~300 µM, pH ~7, 13°C) with or without being fed 2% of their body weight daily. Gills, plasma, livers, and bile were sampled after 4 h, 24 h, and 1 week. Feeding did not alter Ag uptake by trout, and did not prevent decreases in plasma Na and Cl caused by Ag. To study Ag depuration, trout were exposed to 0.1 µM AgNO3 for one week and then were placed in Ag-free, ion-poor water with or without being fed 1% of their body weight daily. Plasma Ag decreased over the 15-day depuration period (elimination rate, ke = 0.085 day–1), but there were no effects of feeding on Ag depuration. There were no physiological differences between fed and unfed fish except for slightly higher plasma glucose concentrations and higher condition factors in fed fish by the end of the Ag depuration period. Thus, once Ag has entered a fish, subsequent elimination (e.g., from the plasma) is not affected by food-related processes such as biliary excretion or increased metabolic rate, or by external factors like food debris in the water.