Isolation of Angola-like Marburg virus from Egyptian rousette bats from West Africa

Marburg virus (MARV) causes sporadic outbreaks of severe Marburg virus disease (MVD). Most MVD outbreaks originated in East Africa and field studies in East Africa, South Africa, Zambia, and Gabon identified the Egyptian rousette bat (ERB; Rousettus aegyptiacus) as a natural reservoir. However, the largest recorded MVD outbreak with the highest case–fatality ratio happened in 2005 in Angola, where direct spillover from bats was not shown. Here, collaborative studies by the Centers for Disease Control and Prevention, Njala University, University of California, Davis USAID-PREDICT, and the University of Makeni identify MARV circulating in ERBs in Sierra Leone. PCR, antibody and virus isolation data from 1755 bats of 42 species shows active MARV infection in approximately 2.5% of ERBs. Phylogenetic analysis identifies MARVs that are similar to the Angola strain. These results provide evidence of MARV circulation in West Africa and demonstrate the value of pathogen surveillance to identify previously undetected threats.


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A total of 435 Rousettus aegyptiacus bats were collected as a part of a joint filovirus surveillance effort in Sierra Leone. Of these, 11 tested positive for marburgvirus RNA. Virus isolates were obtained and phylogenetic analysis identified Gabon and Angola-like marburgvirus strains circulating in R. aegyptiacus bat populations in Sierra Leone.
The research sample is 435 Rousettus aegyptiacus bats captured at four locations. These bats were collected opportunistically as part of a larger filovirus surveillance effort in Sierra Leone. The samples consisted of adult males (n=99), adult females (n=109), juvenile males (n=95), and juvenile females (n=132).
Sample size was not determined statistically. The bats were collected opportunistically as part of a larger filovirus surveillance effort in Sierra Leone. This sample size represents the the total number of Rousettus aegyptiacus collected during this surveillance effort at the time of the writing of this manuscript.
The capture data (species identification, sex, age) were collected by field teams. These data are collected by measuring, weighing, and visually or by dichotomous keys, identifying the bat. Sexual identification is done by looking for external sexual characteristics. Bat species field identifications were confirmed on select MARV positive bats using mtDNA barcoding of the cytochrome b and cytochrome oxidase subunit 1 mitochondrial genes by laboratory teams. Diagnostic testing data, virus sequence data, and phylogenetic output were all performed by laboratory teams.
Rousettus aegyptiacus collection occurred as part of a larger surveillance effort beginning in January 2016 and is currently ongoing. Sampling occurs during the dry seasons and based on the availability of personnel, for a duration of 2 -23 days. For this manuscript, sampling occurred on the following dates: Jan. 14-25 2016; 30 Jan. -22 Feb. 2017, 23 Oct. -12 Nov. 20176 and 12 Dec. 2017;25 Sept. -16 Oct. 2018.
No data were excluded from the analysis.
For the statistical analysis, the Pearson's chi-squared tests were successfully repeated. Sequence generation from the identical sequences were successfully repeated. Phylogenetic analysese were successfully repeated. Diagnostic results were successfully repeated and confirmed through testing of additional tissues. This is not relevant to our study. We are describing the findings of a filovirus surveillance effort.
Blinding is not relevant to our study. We are describing the findings of a filovirus surveillance effort.
Fieldwork was performed at night, typically in the absence of rainfall. Nighttime temperatures in Sierra Leone run between 22/24°C . Sierra Leone is tropical so humidity levels are typically high. Mist netting for bats occured in forested areas, usually near cave openings.
All animal sampling and sample exporting was performed with permission from the Ministry of Agriculture, Forestry, and Food Security, with approval of both the Institutional Animal Care and Use Committees (IACUC) at the University of California, Davis (protocol number: 16048) and the CDC (protocol number: 2943AMMMULX). All captures were identified prior to sampling to identify any threatened and endangered species.
This study created only a minimal and short term disturbance at the trapping locations. This disturbance was minimized by trapping these locations only up to twice per year using trapping bouts of less than 3 weeks duration. Rousettus aegyptiacus are listed on the IUCN red list website (https://www.iucnredlist.org/search?query=rousettus%20aegyptiacus&searchType=species) as a stable species of least concern.