Background: Like most pathogens that infect human, the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) is highly suspected to originate from wildlife. Indeed, the connexion to bats has been extensively discussed. This diversified group, accounting for 20% of living mammals species, has been recognized to harbor a great diversity of alpha and betacoronaviruses, some of which being very close to the SARS-CoV. Unfortunately, the ways and modalities of transmission from bats to other mammals remain currently unknown and more globally, the ecology of coronaviruses in wildlife is poorly described. One key point of the cycle of airborne or fomite-dispersed viruses is their ability to survive outside their host and to persist in potentially deleterious environment before reaching the next host. Concerning SARS-CoV, and considering the viral load detected in feces by molecular methods, it has been hypothesized that feces could act as fomites in a fecal-oral transmission model based on comparison with other most studied coronaviruses such as gastro-enteritis associated coronaviruses infecting human, pig or carnivores.
Here we address basic questions on SARS-CoV survival in insectivorous bat feces that can be determinant for the virus evolution in nature by having incidence on the spill-over, the ways of transmission and the capacity for bats to act as passive vectors. This also contributes to evaluate the infectious status of bat guano that is exploited and distributed as high quality fertilizers in many countries such as Thailand. Moreover, data on virus survival may facilitate the isolation of wild-type viruses.
Methods: The persistence kinetic of SARS-CoV in droppings was evaluated by titration on VeroE6 cells. The viral ultrastructure was monitored by electron microscopy. The genome presence and degradation was investigated by qRT-PCR and standard RT-PCR on several genes.
Results: The contact with bat feces induced several modifications of the ultrastructure of the virus associated with a dramatic loss of titer while the genome remained detectable and relatively preserved.
Conclusion: This study demonstrates that solutes contained in insectivorous bat feces render its unsuitable fomites for SARS-CoV, making the fecal-oral route unlikely to account for transmission of SARSr-CoV in this group. Alternatively, transmission to carnivores may have occurred through predation behavior.