Defra and the Joint Biosecurity Centre (JBC) have presented a paper on the risk of SARS-CoV-2 infections in rodents occurring from exposure to humans.
The paper was presented on 8 April 2021 and focused on answering three crucial questions:
- What is the likelihood of Covid-19 remaining viable in the environment and wastewater such that a rodent could become infected?
- What is the likelihood that a variant of concern (VOC) of Covid-19 could infect a rodent and produce sustained population-level transmission?
- What is the likelihood that a human is exposed to an infectious dose of the virus through contact with rodents via pest control, waste management or wastewater management?
The paper outlines that there is significant potential for key risk factors to occur and have been observed to occur in controlled conditions.
However, there is a high degree of uncertainty that these can occur in the wild.
The most significant gap in knowledge flagged in the report is whether the rodents that do contract a strain of Covid-19 that is of concern to humans, can pass it to one another (creating a reservoir) and then further passing it on to people.
This would be particularly concerning to occupational workers, such as pest professionals.
What are the risks for Covid-19 transmission via rats?
The government report outlines that the risk of Covid-19 remaining in such levels as to be infectious in waste is very low (>1%).
However, if a Covid-19 strain could survive long enough in waste, then the likelihood of a human-to-rodent crossover is high (66-90%), given the considerable interaction between rodents and potentially contaminated human waste.
The level of contact between humans and rats which could potentially lead to new cases is very low for the general population and restricted mainly to occupational exposure [for example, pest professionals].
The executive report states:
“The level of contact between humans and rats which could potentially lead to new cases is very low for the general population and restricted mainly to occupational exposure [for example, pest professionals].
“The potential for this to lead to an outbreak (where human-to-human transmission occurs) will depend on the immune status of the population, the vaccine efficacy and level of circulating variants”.
Authors suspect that any Covid-19 strain which moves human-to-rodent would adapt rapidly to a rodent-to-rodent transmission and therefore be highly unlikely to move back to a rodent-to-human transmission.
Much of the report admits a high level of uncertainty - however, this should not stop us seriously considering the impacts of the report.
Should we be concerned by the report findings?
The paper clarifies that if a viable transmission route is identified, there will be a medium risk to professionals working in proximity to rodents and waste (10-66% or one case a fortnight).
While the findings haven’t been proved with any degree of certainty, we should still keep the report in mind.
Measures you can take to minimise potential transmission:
- Employ safe systems of work around rodent carcasses, including their removal and disposal
- Ensure that you have appropriate PPE and use it correctly at all times
- Identify contamination pathways, including direct and indirect contact with rodents, particularly in high-risk environments such as around food and biological waste.
Final thoughts
As an industry, we’ve been working with infectious and commutable diseases for a long time.
Although this link between rodents and Covid-19 is undoubtedly alarming, many (if not all) of the risk mitigation measures will already be standard practice for pest professionals.
BPCA will continue to monitor any new data or studies linking pests and Covid-19.
Got more questions about Covid and keeping your team safe?
Our technical team are on hand to help members with any of their concerns. Contact us today.
technical@bpca.org.uk