Evidence of antibodies against SARS-CoV-2 in wild mustelids from Brittany (France)

In the French region of Brittany, mainly in the department of the Cotes dArmor, during the first semester of 2021, seropositivity for SARS-CoV-2 was detected in five wild mustelids out of 32 animals tested. Anti-SARS-CoV-2 IgG against at least four out of five recombinant viral proteins (S1 receptor binding domain, nucleocapsid, S1 subunit, S2 subunit and spike) were detected using automated western blot technique in three martens (Martes martes) and two badgers (Meles meles). An ELISA test also objectified seropositivities. Although the 171 qPCRs carried out on samples from the 33 mustelids were all negative, these preliminary results (observational study) nevertheless bear witness to infections of unknown origin. The epidemiological surveillance of Covid-19 in wildlife must continue, in particular with the tools of efficient serology.

Automated Western immunoblotting detection of anti-SARS-CoV-2 serum antibodies.

ELISA and chemiluminescence serological assays for COVID-19 are currently incorporating only one or two SARS-CoV-2 antigens. We developed an automated Western immunoblotting as a complementary serologic assay for COVID-19. The Jess Simple Western system, an automated capillary-based assay was used, incorporating an inactivated SARS-CoV-2 lineage 20a strain as antigen, and IgT detection. In total, 602 sera were tested including 223 from RT-PCR-confirmed COVID-19 patients, 76 from patients diagnosed with seasonal HCoVs and 303 from coronavirus-negative control sera. We also compared this assay with the EUROIMMUN(R) SARS-CoV-2 IgG ELISA kit. Among 223 sera obtained from RT-PCR-confirmed COVID-19 patients, 180/223 (81%) exhibited reactivity against the nucleocapsid and 70/223 (31%) against the spike protein. Nucleocapsid reactivity was further detected in 9/76 (14%) samples collected from patients diagnosed with seasonal HCoVs and in 15/303 (5%) coronavirus-negative control samples. In the subset of sera collected more than 2 weeks after the onset of symptoms, the sensitivity was 94% and the specificity 93%, the latter value probably reflecting cross-reactivity of SARS-CoV-2 with other coronaviruses. The automated Western immunoblotting presented a substantial agreement (90%) with the compared ELISA (Cohens Kappa=0.64). Automated Western immunoblotting may be used as a second line test to monitor exposition of people to HCoVs including SARS-CoV-2.