Microcosm environment models for studying the stability of adenovirus and murine norovirus in water and sediment.

Microcosms are useful tools for understanding the survival and fate of enteric viruses in aquatic environments. This study set out to determine the stability of infectious enteric viruses in an aquatic environment using a laboratory scale microcosm. Sediment and overlaying water were collected from a lagoon and inoculated with known concentrations of recombinant adenovirus (AdV-GFP) and murine norovirus (MNV-1). Infectious particles of these viruses were measured using fluorescence microscopy (AdV-GFP) or the plaque assay method (MNV-1), over 85 days in two different conditions: under natural sunlight and in fully darkened environments. The time required to reach one log reduction in viral titres (T90) of viable viruses in a natural condition microcosm for AdV-GFP and MNV-1 was shorter than in a dark condition microcosm. There was also a negative correlation between the temperature and infectivity of these viruses in both water and sediment samples. Considering that microcosms aim to mimic natural environment conditions and that AdV-GFP and MNV-1 are excellent surrogates for measuring the infectivity of the respective viruses strains, the results presented here have the potential to be applied in future health hazard studies and also would be useful for future climate scenarios.

Spatial distribution of enteric viruses and somatic coliphages in a Lagoon used as drinking water source and recreation in Southern Brazil.

This study aimed to evaluate the contamination level of the Peri Lagoon, the main freshwater reservoir of Santa Catarina Island, Southern Brazil, for human adenovirus (HAdV), hepatitis A virus (HAV), rotavirus species A (RVA), and somatic coliphages (SOMCPH). Viruses were also investigated in sediments and their sensitivity against natural sunlight was analysed by studying their spatial distribution in different depths of the water column. A total of 84 water samples and 48 sediment samples were examined by qPCR or RT-qPCR. Infectivity of HAdV and SOMCPH was determined and quantified by plaque assay method. A sum of 64% and 48% of water and sediment samples were positive for HAdV, respectively. RVA was present in 33% and 18% of water and sediment samples, and 25% of water samples were positive for HAV. HAdV were infectious in 76% of water and 83% of sediment samples that were positive by qPCR. SOMCPH could be detected in 42% and 18% of water and sediment samples, respectively. The data pointed a variation of viruses' prevalence according to the different water column depths. These results demonstrated that water sources and sediments contaminated by human wastes could play an important role in the recontamination of water columns harvested for further treatment or used for recreational purposes. These data can be of great value for future risk assessment analysis.

Settling and survival profile of enteric pathogens in the swine effluent for water reuse purpose.

The present study evaluated the pathogens persistence and settling profile in swine effluent. We determined the enteric pathogens settling characteristics, their survival and inactivation profile in swine effluent (for water reuse purpose) and in sludge (generated after aerobic treatment - during secondary settling process). The study was performed in laboratorial-scale and in full-scale (manure treatment plant). Enteric viruses and enteric bacteria were used as biomarkers. Results showed that these enteric pathogens were significantly reduced from swine effluent during secondary settling process, and enteric viruses removal was correlated with the suspended solids decantation. The design of secondary settlers can be adapted to improve pathogens removal, by diminishing the solids loading rate per area and time, ending in higher hydraulic retention times.

Utility of specific biomarkers to assess safety of swine manure for biofertilizing purposes.

Swine production is an important economic activity in Brazil, and there is interest in the development of clean production mechanisms to support sustainable agro-industrial activities. The biomass derived from swine manure has good potential to be used as a biofertilizer due to its high nutrient concentration. However, the land application of manure should be based on safety parameters such as the presence of pathogens that can potentially infect animals and people. This study was designed to assess the presence of porcine circovirus-2 (PCV2), porcine adenovirus (PAdV), rotavirus-A (RV-A) and Salmonella spp. in liquid manure, as well the infectivity of two genotypes of circovirus-2 (PCV2a and PCV2b) present in liquid manure. Three swine farms were evaluated: 1) a nursery production farm (manure analyzed before and after anaerobic biodigestion), 2) a grow-finish production farm (analyzed before and after anaerobic biodigestion), and 3) a second grow-finish production farm (raw manure-affluent). PCV2, PAdV and RV-A were present before and after anaerobic biodigestion (either affluent or effluent) at all farms. Salmonella spp. were detected at farm 1 (affluent and effluent) and farm 3 (raw manure-affluent) but not farm 2 (affluent and effluent). When the ability of the anaerobic biodigestion process to reduce viral concentration was evaluated, no significant reduction was observed (P>0.05). Both the PCV2a and PCV2b genotypes were detected, suggesting viral co-infection in swine production. The results revealed infectious PCV2 even after anaerobic biodigestion treatment. The presence of Salmonella spp. and enteric viruses, especially infectious PCV2, in the final effluent from the anaerobic biodigester system suggests that the process is inefficient for pathogen inactivation. Due to the prevalence and infectivity of PCV2 and considering the successful use of molecular methods coupled to cell culture for detecting infectious PCV2, we suggest that this virus can be used as a bioindicator in swine manure treatment systems to check the efficiency of pathogen inactivation and ensure the production of safe biofertilizers from swine manure.