Experimental Inoculation of Egyptian Fruit Bats (Rousettus aegyptiacus) with Ebola Virus

Abstract

Colonized Egyptian fruit bats (Rousettus aegyptiacus), originating in South Africa, were inoculated subcutaneously with Ebola virus (EBOV). No overt signs of morbidity, mortality, or gross lesions were noted. Bats seroconverted by Day 10-16 post inoculation (p.i.), with the highest mean anti-EBOV IgG level on Day 28 p.i. EBOV RNA was detected in blood from one bat. In 16 other tissues tested, viral RNA distribution was limited and at very low levels. No seroconversion could be demonstrated in any of the control bats up to 28 days after in-contact exposure to subcutaneously-inoculated bats. The control bats were subsequently inoculated intraperitoneally, and intramuscularly with the same dose of EBOV. No mortality, morbidity or gross pathology was observed in these bats. Kinetics of immune response was similar to that in subcutaneously-inoculated bats. Viral RNA was more widely disseminated to multiple tissues and detectable in a higher proportion of individuals, but consistently at very low levels. Irrespective of the route of inoculation, no virus was isolated from tissues which tested positive for EBOV RNA. Viral RNA was not detected in oral, nasal, ocular, vaginal, penile and rectal swabs from any of the experimental groups.

Keywords: Ebola virus; Egyptian fruit bat; experimental inoculation; seroconversion; shedding; tissue tropism.

Figure 1

Individual (●) and mean (solid line) IgG levels in 24 Egyptian fruit bats inoculated subcutaneously with Ebola virus (EBOV) in a serial euthanasia study. Results for anti-EBOV IgG antibody by enzyme-linked immunosorbent assay are shown as percent positivity (PP) of ELISA positive internal control serum. ELISA cut-off value of 36.7 PP (dashed line). The values in brackets indicate the number of individual bats sampled on a particular day post inoculation.

Figure 2

Individual and mean IgG levels in Egyptian fruit bats inoculated intraperitoneally (▲, dotted line; n = 5) and intramuscularly (●, solid line; n = 6) with Ebola virus (EBOV) in a serial euthanasia study. Results for anti-EBOV IgG antibody by enzyme-linked immunosorbent assay are shown as percent positivity (PP) of ELISA positive internal control serum. ELISA cut-off value of 36.7 PP (dashed line). The values in brackets indicate the number of individual batssampled on a particular day post inoculation.