In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), was detected in Wuhan, China, and the risk to global human health was quickly identified. The risks that COVID-19 poses to human health are clear but data concerning the risk to wildlife is lacking.
Following the discovery of a closely related betacoronavirus in a horseshoe bat in eastern Asia, bats have been a prominent focus; nevertheless, empirical research to directly quantify the harm that SARS-CoV-2 poses to bats is limited.
Background
The first risk assessment to evaluate the risk of SARS-CoV-2 transmission from people to North American (NA) bats was undertaken in April 2020. The risk assessment revealed a small chance of transmission during summer work activities based on the best available evidence and largely relying on expert judgment. Following that evaluation, further information and data became available, such as bat viral challenge tests, which helped to clarify the dangers of human-to-bat transmission and led to a second risk assessment in the fall of 2020.
In May 2021, COVID-19 vaccinations were relatively widespread, which potentially reduced the level of viral shedding among humans.
In a recent paper published in The Wildlife Society, risk assessments for research, survey, monitoring, management (RSM), wildlife rehabilitation (WR), and wildlife control (WC) were updated.
The study
The authors first verified that earlier research’s structural features of decision structuring were still applicable to agencies contemplating summer bat operations, and then they updated the probability of susceptibility estimations for little brown bats (LBB). Finally, during summertime RSM, WC, and WR operations, the risk of SARS-CoV-2 human-to-bat transmission was re-evaluated, and the effectiveness of new and current risk mitigation techniques was assessed.
What did they do?
The framework featured a varied range of US state and federal decision-makers, which included many of the aims and management options under consideration at the time. Changes can occur to the framing of a decision over time, which may result in variations in the structure of the problem and resulting models. As a result, the authors reassessed the initial decision framing for spring and summer work with the initial decision-makers from the original research to revise the summer risk assessment.
Employees handling bats, workers in close proximity to bats in a shared enclosed environment, and workers in close proximity to bats but not in a shared enclosed space were used to create the RSM infection risk model.
Bat handling and employees in close contact with bats but not in a shared enclosed environment were used to create the WR infection risk model. Bat handling and workers in close proximity to bats but not in a shared enclosed environment were used to generate the WC infection risk model.
Findings
The predicted median chance of susceptibility to LBB was 0.44, assuming a sufficient dosage of SARS-CoV-2 for each bat infection. A follow-up expert elicitation determined that the median probability of susceptibility was 89% lower and had less uncertainty after the collection of fresh information. New information, such as the homology of human and bat angiotensin-converting enzyme 2 (ACE2) receptors, was used to revise the estimate.
When the authors reanalyzed the infection risk models, they discovered an 87–88% reduction in the predicted number of infected bats per 1,000 bats encountered when compared to the previous findings. According to prior research, the median number of bats infected per 1,000 during RSM activities was calculated to be 6.96.
Utilizing revised probability of susceptibility estimations, the authors discovered that the median number of bats infected was fewer than one per 1,000, an 88% reduction from the earlier estimate. The median number of bats infected per 1,000 in WR interactions was lowered from 13.03 to 1.56, representing an 88% drop in the median value. The median number of bats infected per 1,000 in WC contacts was lowered from 3.72 to 0.47, a drop of 87%.
Across all three encounter types, the findings indicate that the median number of SARS-CoV-2 infected bats per 1,000 encountered reduced by 65–67%. Furthermore, when compared to previous research, the new estimate decreased by 88–89%. Across encounter types, the median estimate for vaccination decreased by 86–88%. Risks decreased by 98–99% when COVID-19 testing and immunization were administered together.
Implications
The long-term effects of SARS-CoV-2 in agricultural or wild animals, as well as their propensity to function as reservoir hosts, are unknown. As seen by the advent of the highly transmissible Omicron variant in humans, viruses rapidly mutate, recombine, and evolve in host species.
It’s unclear how emerging strains alter wildlife’s vulnerability to the virus. To lower the risk of future zoonotic transmission, generalizable risk mitigation methods guided by One Health could be effective across a variety of human-animal interactions.
As pathogens advance and so does the understanding of them, decision analysis can be used to drive more specific risk assessments and guide organizational choices about human-wildlife interactions.
