Selective replication and vertical transmission of Ebola virus in experimentally infected Angolan free-tailed bats

The natural reservoir of Ebola virus (EBOV), agent of a zoonosis burdening several African countries, remains unidentified, albeit evidence points towards bats. In contrast, the ecology of the related Marburg virus is much better understood; with experimental infections of bats being instrumental for understanding reservoir-pathogen interactions. Experiments have focused on elucidating reservoir competence, infection kinetics and specifically horizontal transmission, although, vertical transmission plays a key role in many viral enzootic cycles. Herein, we investigate the permissiveness of Angolan free-tailed bats (AFBs), known to harbour Bombali virus, to other filoviruses: Ebola, Marburg, Taï Forest and Reston viruses. We demonstrate that only the bats inoculated with EBOV show high and disseminated viral replication and infectious virus shedding, without clinical disease, while the other filoviruses fail to establish productive infections. Notably, we evidence placental-specific tissue tropism and a unique ability of EBOV to traverse the placenta, infect and persist in foetal tissues of AFBs, which results in distinct genetic signatures of adaptive evolution. These findings not only demonstrate plausible routes of horizontal and vertical transmission in these bats, which are expectant of reservoir hosts, but may also reveal an ancillary transmission mechanism, potentially required for the maintenance of EBOV in small reservoir populations.


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Since wild-caught animals with large individual variance and imprecise age determination must be used for this experiment, the number of animals per experimental group would have to be very high for a valid statistical evaluation.Therefore, we compromised sample size and included a minimum of 3 animals per variable (time points) within cohorts (6 animals per group).This was not possible for 2 groups.At least 2 technical replicates were included for downstream analyses.The comparison between the number of infected and non-infected animals was planned to be statistically analysed using Fisher's exact test, and the comparison of viral load in the organs was planned to use two way repeated measures ANOVA.In accordance with the planned statistical analyses, the initial sample size estimation per group was as following: Randomization Animals were randomly assigned to groups separately by sex, to allocate at least one female per cohort.

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Investigators were not blinded for the following analyses (clinical observations, clinical measurements and collection of shedding samples).Blinding is not possible to follow up clinical progresion of individual animals and due to safety protocols within the BSL4.Analysis of samples was not blinded.This was deemed unnecesary for sample processing (e.g.qPCR, serology and titration) for the data collection and analyses.
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