Bas-Congo tibrovirus

Bas-Congo tibrovirus (BASV) is a poorly characterized rhabdovirus discovered in the blood of a patient who survived a severe illness resembling hemorrhagic fever[1]. The virus was named after the former Democratic Republic of Congo province of Bas-Congo (now Kongo Central). BASV was discovered using next-generation sequencing and attempts to isolate the virus were not successful. BASV RNA has only been detected in one individual and its role as a human pathogen has not been established[2].

Bas-Congo tibrovirus
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Negarnaviricota
Class: Monjiviricetes
Order: Mononegavirales
Family: Rhabdoviridae
Genus: Tibrovirus
Species:
Bas-Congo tibrovirus
Synonyms
  • Bas-Congo virus

Discovery

In the spring of 2009, two teenagers living in Mangala, a small village located in the western-most province of the Democratic Republic of Congo, developed a severe illness with symptoms that included: fever, headache, abdominal pain, mouth and nasal bleeding, hematemesis, and bloody diarrhea. Both of the teenagers died within days of developing symptoms[1]

More than a week later, a 32-year-old nurse who cared for the two teenagers, fell ill. His symptoms were similar to the two teenagers: nasal, ocular, and oral bleeding; hematemesis and bloody diarrhea. He was provided supportive care and recovered. A blood sample was collected and subjected to next-generation sequencing. Analysis revealed the presence of a novel rhabdovirus, BASV, that was similar to other members of the poorly characterized tibrovirus genus[1].

Disease Association

BASV was present in the blood of the infected individual at more than 1 million RNA copies/mL of plasma, suggesting an active infection[1].

Although next-generation sequencing is a powerful tool for detecting novel viruses, it does not unambiguously establish BASV as the cause of the patient’s illness. Indeed, other experts have suggested that BASV is not the cause of the patient’s illness and noted that an outbreak of Shigella was occurring in the area at the same time[2].

Genome

The complete BASV genome is not available. An 11,892 bp genome has been reported[3], which is likely 95% - 98% complete. The BASV genome consists of the five typical rhabdovirus genes (N, P, M, G and L), as well as three open reading frames of unknown function (U1, U2, and U3).

Replication

Little is known about the replication lifecycle of BASV however, it is assumed to be similar to other rhabdoviruses. Research into the virology of BASV has been hindered because live replicating virus is not available.

Incidence and Prevalence

Little is known about the incidence or prevalence of BASV. BASV antibodies were detected in the infected patient, as well as a close contact who did not show any symptoms of disease[1]. A serosurvey of 50 randomly selected blood donors in the Kasai-Oriental Province in the Democratic Republic of Congo did not detect any positive samples[4]. This province, however, is approximately 2,000 kilometers from the town where BASV was first detected.

Transmission

The natural reservoir and route of transmission of BASV are unknown. A machine learning algorithm designed to predict animal reservoirs and arthropod vectors suggests the natural host may be cattle and the insect vector a biting midge[5]. This prediction is consistent with what is currently known about the transmission cycle of other tibroviruses.

Relationship to Other Rhabdoviruses

Phylogenetic analysis of the polymerase protein (L) revealed indicates that BASV is most closely related to members of the tibrovirus genus[6]. There are eight known tibroviruses, including BASV [7]. Four tibroviruses have been isolated from biting midges (Culicoides), three from humans, and one from a healthy steer. With the exception of Bas-Congo, none of the other tibroviruses have been associated with any disease. Experimental infection of cattle with various tibroviruses does not produce any symptoms of disease[8].

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References
  1. Grard G, Fair JN, Lee D, et al. A novel rhabdovirus associated with acute hemorrhagic fever in central Africa [published correction appears in PLoS Pathog. 2016 Mar;12(3):e1005503] [published correction appears in PLoS Pathog. 2017 Sep 7;13(9):e1006583]. PLoS Pathog. 2012;8(9):e1002924. doi:10.1371/journal.ppat.1002924
  2. https://science.sciencemag.org/content/bas-congo-virus-not-established-pathogen
  3. https://www.ncbi.nlm.nih.gov/nuccore/NC_043067.1
  4. Steffen I, Liss NM, Schneider BS, Fair JN, Chiu CY, Simmons G. Characterization of the Bas-Congo virus glycoprotein and its function in pseudotyped viruses. J Virol. 2013;87(17):9558–9568. doi:10.1128/JVI.01183-13
  5. S. A. Babayan et al., Predicting reservoir hosts and arthropod vectors from evolutionary signatures in RNA virus genomes. Science 362, 577-580 (2018)
  6. Walker PJ, Firth C, Widen SG, et al. Evolution of genome size and complexity in the rhabdoviridae. PLoS Pathog. 2015;11(2):e1004664. Published 2015 Feb 13. doi:10.1371/journal.ppat.1004664
  7. https://talk.ictvonline.org/ictv-reports/ictv_online_report/negative-sense-rna-viruses/mononegavirales/w/rhabdoviridae/802/genus-tibrovirus
  8. Cybinski, D. H., St. George, T. D., Standfast, H. A. & McGregor, A. Isolation of tibrogargan virus, a new Australian rhabdovirus, from Culicoides brevitarsis. Veterinary Microbiology 5, 301–308 (1980)
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