In a recent article published on the bioRxiv * prepress server, the researchers looked at whether Mexican free-tailed bats were a reservoir of coronavirus 2 (SARS-CoV-2) for severe acute respiratory syndrome.
Study: Experimental infection of Mexican free-tailed bats (Tadarida brasiliensis) with SARS-CoV-2. Image credit: Rudmer Zwerver / Shutterstock
Fund
SARS-CoV-2, which emerged from Asian wild bats, has caused the 2019 Coronavirus Disease Pandemic (COVID-19). Numerous concerns about the virus’s ecology remain unresolved when the pandemic enters its third year.
It is crucial to understand how SARS-CoV-2 interacts with wildlife, such as whether 1) American wildlife can serve as a viral reservoir; 2) SARS-CoV-2 can genetically adapt to new hosts and become more virulent; or 3) the virus can affect the health of wild populations, especially endangered or threatened species.
In particular, concern has been expressed that SARS-CoV-2 is spreading to new hosts and infecting bats and other wildlife species in North America. Large colonies of Mexican free-tailed bats (Tadarida brasiliensis (TABR)) are found in the southern United States (USA), often in populated regions. As a result, they may come into contact with SARS-CoV-2 through infected people. Because they are migratory species, this species can carry SARS-CoV-2 to or from South and Central America if they are susceptible to it.
About the study
In the present study, researchers experimentally infected wild-type TABR with SARS-CoV-2 to assess reservoir possibility, susceptibility, population effects of infection between this species, and virus adaptability to a likely new host.
The team performed reverse transcription-polymerase chain reaction (RT-PCR) assessments of fecal material collected from the TABR prior to the viral challenge. They used quantitative RT-PCR (qRT-PCR) examination of oral and rectal swabs to assess SARS-CoV-2 excretion after experimental inoculation of bat virus.
A competitive enzyme-linked immunosorbent assay (cELISA) was used to detect SARS-CoV-2 antibodies. The scientists monitored for clinical signs of SARS-CoV-2 infection during the three-week study duration among the animals. They also performed histopathological and postmortem examinations.
In addition, immunohistochemistry was used to find the SARS-CoV-2 antigen in sections of the rostral lung, nasal cavity, heart, liver, spleen, pancreas, small and large intestine, stomach. and the brain of a total of 14 simulated and experimentally inoculated. bats. In addition, the authors performed qRT-PCR analyzes of tissues collected from control bats and infected with SARS-CoV-2.
Results and discussions
Overall, the results of the study indicated that five of the ten bats inoculated with SARS-CoV-2 oronasally developed the infection and emitted a moderate amount of virus orally for six to 18 days after the viral challenge. . Prior to the completion of the study, all five animals mounted an immune reaction, seroconverted, and cleared the virus with no obvious signs of disease. In addition, the team found no evidence of virus transmission in uninoculated co-hosted TABR.
The inoculum titer used, i.e., 105 tissue-mediated infectious dose (TCID50) / dose, was probably close to the 50% infectious dose for TABR, as five of the ten inoculated bats, or 50 %, were infected with viruses. However, the highest viral concentration excreted by infected bats was between 103 and 104 equivalents of TCID50 / ml. Therefore, SARS-CoV-2 contact transmission between TABRs would be unlikely from these data.
The way the researchers maintained the bats during the challenge phase was another potential explanation for why there was no viral transfer between TABRs. In the wild, TABR is housed in large colonies in anthropogenic and natural structures such as caves, bridges and culverts. An infected bat and an uninoculated bat were placed in one-meter3 cages for this research. Bats were not forced to cluster as densely in this relatively large area as they would in a natural place, perhaps preventing the spread of the virus.
The study also found an absence of viral elimination through the digestive tract, in addition to the obvious lack of transmission. The authors found no virus evidence in the digestive tract of any bats or in rectal swabs, including infected bats.
Another observation was that SARS-CoV-2 infection in TABR did not appear to have any detrimental impact on health. Although it was uncertain whether infected wild bats would impair the ability to provide maternal care, seek food, or perform other vital activities, the research results suggest that TABR populations were probably not at risk for the COVID-19 pandemic. .
Conclusions
Current findings showed that although TABR was vulnerable to SARS-CoV-2 infection, it may not lead to mortality among infected wild TABR populations. However, the transmission of SARS-CoV-2 from TABR to or from humans and other animal species is a definite possibility that needs further research for proper definition. The team noted that crucial follow-up research would involve accurately estimating the SARS-CoV-2 infectious dose at TABR.
Current data from the study were beneficial to wildlife biologists, bat rehabilitators, cave recreationists, and the general public if they interact with Mexican free-tailed bats or enter caves or other resting environments. of bats.
* Important news
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guided by clinical practice / health-related behavior, or treated as established information.
Magazine reference:
- Jeffrey Hall, Erik Hofmeister, Hon Ip, Sean Nashold, Ariel Leon, Carly Malave, Elizabeth Falendysz, Tonie Rocke, Mariano Carossino, Udeni Balasuriya, Susan Knowles. (2022). Experimental infection of Mexican free-tailed bats (Tadarida brasiliensis) with SARS-CoV-2. bioRxiv. two: