Subclinical hepatitis E virus infection in laboratory ferrets in the UK.

Ferrets are widely used for experimental modelling of viral infections. However, background disease in ferrets could potentially confound intended experimental interpretation. Here we report the detection of a subclinical infection of ferret hepatitis E virus (FRHEV) within a colony sub-group of female laboratory ferrets that had been enrolled on an experimental viral infection study (non-hepatitis). Lymphoplasmacytic cuffing of periportal spaces was identified on histopathology but was negative for the RNA and antigens of the administered virus. Follow-up viral metagenomic analysis conducted on liver specimens revealed sequences attributed to FRHEV and these were confirmed by reverse-transcriptase polymerase chain reaction. Further genomic analysis revealed contiguous sequences spanning 79-95 % of the FRHEV genome and that the sequences were closely related to those reported previously in Europe. Using in situ hybridization by RNAScope, we confirmed the presence of HEV-specific RNA in hepatocytes. The HEV open reading frame 2 (ORF2) protein was also detected by immunohistochemistry in the hepatocytes and the biliary canaliculi. In conclusion, the results of our study provide evidence of background infection with FRHEV in laboratory ferrets. As this infection can be subclinical, we recommend routine monitoring of ferret populations using virological and liver function tests to avoid incorrect causal attribution of any liver disease detected in in vivo studies.

Test performance data demonstrates utility of a cattle DIVA skin test reagent (DST-F) compatible with BCG vaccination.

Bacillus Calmette-Guérin (BCG), an attenuated strain of Mycobacterium bovis (M. bovis), is the lead candidate vaccine for control of bovine tuberculosis (TB) in cattle. However, BCG vaccination sensitises cattle to bovine tuberculin, thus compromising the use of the current bovine TB surveillance tests. To address this, we have developed a diagnostic skin test that is not compromised by BCG vaccination and is able to detect BCG vaccinated animals that subsequently develop bovine TB following exposure to M. bovis. Building on previous work using 'in house' formulated protein cocktail reagents, we herein present test performance data for a single fusion protein (DST-F) containing the mycobacterial antigens ESAT-6, CFP-10 and Rv3615c formulated as a 'ready to use' reagent by a commercial manufacturer. Our results demonstrate that, unlike tuberculin reagents, a diagnostic skin test using DST-F maintained high specificity in BCG vaccinated animals. Furthermore, the DST-F skin test demonstrated a high relative sensitivity in identifying M. bovis infected animals, including those where BCG vaccination failed to prevent bovine TB pathology following experimental exposure to M. bovis. The DST-F is currently undergoing field trials in Great Britain to support its licensure and commercialisation.

Intranasal Infection of Ferrets with SARS-CoV-2 as a Model for Asymptomatic Human Infection.

Ferrets were experimentally inoculated with SARS-CoV-2 (severe acute respiratory syndrome (SARS)-related coronavirus 2) to assess infection dynamics and host response. During the resulting subclinical infection, viral RNA was monitored between 2 and 21 days post-inoculation (dpi), and reached a peak in the upper respiratory cavity between 4 and 6 dpi. Viral genomic sequence analysis in samples from three animals identified the Y453F nucleotide substitution relative to the inoculum. Viral RNA was also detected in environmental samples, specifically in swabs of ferret fur. Microscopy analysis revealed viral protein and RNA in upper respiratory tract tissues, notably in cells of the respiratory and olfactory mucosae of the nasal turbinates, including olfactory neuronal cells. Antibody responses to the spike and nucleoprotein were detected from 21 dpi, but virus-neutralizing activity was low. A second intranasal inoculation (re-exposure) of two ferrets after a 17-day interval did not produce re-initiation of viral RNA shedding, but did amplify the humoral response in one animal. Therefore, ferrets can be experimentally infected with SARS-CoV-2 to model human asymptomatic infection.