A semi-nested RT-PCR assay for detection of norovirus in rat fecal samples

A novel dual-mode aptasensor based colorimetry and electrochemical detection of norovirus in fecal sample

Norovirus is a leading cause of acute gastroenteritis in humans. This paper presents the development of a novel dual-mode aptasensor for detecting norovirus using colorimetry and electrochemical methods. The initial colorimetric method utilizes gold nanoparticles (AuNPs) and sodium chloride to establish a positive correlation between the concentration of norovirus in a solution and the absorbance ratio A650/A520. The naked eye can detect concentrations as low as 0.1 μg/mL, corresponding to a Ct value of 33 (2.2 copies/μL, CT = 34.102-3.2185·lgX), allowing for qualitative and semi-quantitative analysis. For more accurate trace analysis, a gold electrode is modified with a thiol-modified aptamer and closed with 6-Mercapto-1-hexanol. After incubation with norovirus, the virus specifically binds to the aptamer, causing changes in its spatial structure and distance from the electrode surface. These changes can then be detected using electrochemical square wave voltammetry (SWV). Under optimal reaction conditions, the peak current from SWV exhibits a strong linear relationship with the logarithm of norovirus concentrations between 10-9 μg/mL and 10-2 μg/mL. The regression equation Y = 14.76789 + 1.03983·lgX, with an R2 value of 0.987, accurately represents this relationship. The limit of detection was determined to be 1.365 × 10-10 μg/mL. Furthermore, the aptasensor demonstrated high specificity for norovirus in fecal samples, making it a promising tool for detecting norovirus in various sample types.

Genome characterization, prevalence and tissue distribution of astrovirus, hepevirus and norovirus among wild and laboratory rats (Rattus norvegicus) and mice (Mus musculus) in Hungary

Rodents including rats are reservoir of several pathogens capable of affecting human health. In this study, faecal and different organ specimens from free-living Norway rats (Rattus norvegicus) (N = 18) and faecal samples from laboratory rodents (rats N = 21 and mice N = 20) collected from different geographic areas in Hungary between 2017 and 2020 were investigated by viral metagenomics and conventional RT-PCR methods. The complete genome of three different RNA viruses, rat astrovirus, rat norovirus and rat hepevirus were characterized and analysed in detail. Rat norovirus was detected in faecal (17.6%, 3/17) and kidney (7.1%, 1/14) samples; rat astrovirus in faecal (23.5%, 4/17) and spleen (13.3%, 2/15) samples, and rat hepevirus in 43% to 67% the faecal, liver, kidney, lung, heart, muscle, brain and blood samples from Norway rats, respectively. Rat norovirus was also identifiable in 5% (1/21) of laboratory rats and rat astrovirus in 40% (8/20) of faecal samples from laboratory mice. Co-infections were found in 28% (5/18) wild Norway rats. The highest RNA viral load of astrovirus (1.81 × 108 copy/g) and norovirus (3.49 × 107 copy/g) were measured in faecal samples; while the highest RNA viral load of hepevirus (1.16 × 109 copy/g) was found in liver samples of Norway rats, respectively. This study confirms the wide geographic distribution and high prevalence of astrovirus, norovirus and hepevirus among wild rats in Hungary with confirmation of different organ involvement of as well as the detection of norovirus and astrovirus in laboratory rats and mice, respectively. This finding further strengthens the role of rodents in the spread of viral pathogens especially infecting human.

First report of norovirus sequences isolated from raccoon dogs in mainland China

Noroviruses can infect humans and a wide variety of other mammalian hosts, causing varying degrees of diarrhea. In this study, two novel norovirus genomes were identified for the first time in farmed raccoon dogs, designated as raccoon dog noroviruses BUCT-K1 and BUCT-K4. Neither the farmers nor the raccoon dogs had symptoms (e.g., diarrhea) at the time of sample collection. We collected 14 stool samples from two farms, and 85.7% (12/14) of the samples were norovirus positive by RT-PCR. The two norovirus genomes have the highest identity to Dog/Z7/19/CH, suggesting that the norovirus might have been transmitted from dogs to raccoon dogs. Genomic and evolutionary analyses indicated that different directions of evolution occurred following the spread of the norovirus to the raccoon dogs. This study has increased knowledge of norovirus-infected animal species and has provided additional information on the norovirus family.