Evaluation of the antiviral effect of chlorine dioxide (ClO2) using a vertebrate model inoculated with avian coronavirus

Background The need for safe and effective antiviral treatments is pressing given the number of viral infections that are prevalent in animal and human populations, often causing devastating economic losses and mortality. Informal accounts of anecdotal use of chlorine dioxide (ClO 2 ), a well-known disinfectant and antiseptic, in COVID-19 patients has raised concern about potential toxicity, but also raises the question that ClO 2 might elicit antiviral effects, a possibility that has never been examined in vivo in any animal model. Here, we challenged the hypothesis that ClO 2 decreases the viral load and virus-induced mortality in a vertebrate model. For this, we determined viral load, virus-induced lesions and mortality in 10-day old chick embryos inoculated with 10 4 mean EID 50 /mL of attenuated Massachusetts and Connecticut avian coronavirus (IBV) strains. Results The ClO 2 treatment had a marked impact on IBV infection. Namely, viral titres were 2.4-fold lower and mortality was reduced by half in infected embryos that were treated with ClO 2 . Infection led to developmental abnormalities regardless of treatment. Lesions typical of IBV infections were observed in all inoculated embryos, but severity tended to be significantly lower in ClO 2 -treated embryos. We found no gross or microscopic evidence of toxicity caused by ClO 2 at the doses used herein. Conclusions Our study shows that ClO 2 could be a safe and viable way of treating and mitigating the effects of avian coronavirus infections, and raises the possibility that similar effects could be observed in other organisms. Graphical abstract