Wüstenschiff

HEPATITIS VIRUSES: FOUND IN BATS
********************************
A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

Date: Fri 18 Oct 2013
Source: Virology Blog [edited]
http://www.virology.ws/2013/10/18/hepat ... s-in-bats/


Hepatitis B viruses in bats
---------------------------
Hepatitis B virus (HBV) is a substantial human pathogen. WHO estimates that there are now 240 000 000 individuals chronically infected with HBV worldwide, of which 25 percent percent will die from chronic liver disease or hepatocellular carcinoma. The hepatitis B virus vaccine is highly effective at preventing infection. Because there are no known animal reservoirs of the virus, it is believed that HBV could be globally eradicated. The recent finding of HBV in bats raises the possibility of zoonotic introduction of the virus.

Serum and liver biopsies from 3080 bats from Panama, Brazil, Gabon, Ghana, Germany, Papua New Guinea, and Australia were screened for HBV-like sequences by polymerase chain reaction (PCR). 10 positive specimens were found from 3 bat species: _Uroderma bilobatum_ from Panama, and _Hipposideros cf. ruber_, and _Rhinolophus alcyone_ from Gabon. The complete viral genome sequence was determined for 9 of the positive specimens. Phylogenetic analysis revealed that the bat viruses form 3 different lineages, and that each virus differs by at least 35 percent from known hepadnaviruses. The virus from _H. cf. ruber_ has been named roundleaf bat HBV, while those from _Rhinolophus_ and _Uroderma_ have been named horseshoe bat HBV, and tent-making bat HBV.

Viral DNA in the liver of _Hipposideros_ bats was found to be higher than in other organs or serum. Some lymphocyte infiltration was observed in the liver of these animals, as well as deposits of viral DNA within hepatocytes. These observations indicate that the bat HBV viruses likely replicate in the bat liver and cause hepatitis.

Serological studies revealed that hepadnaviruses are widespread in Old World bats: antibodies against bat hepadnaviruses were detected in 18 percent of hipposiderid bats and 6.3 percent of rhinolophid bats. An important question is whether these 3 bat hepadnaviruses can infect human cells. Only tent-making bat HBV could infect primary human hepatocytes, which occurred via the human HBV cell receptor, sodium taurocholate cotransporting polypeptide. However serum from humans that had been immunized with HBV vaccine did not block infection of human hepatocytes with this virus.

These observations show that viruses related to human HBV are replicating in the liver of bats. Earlier this year (2013) another hepadnavirus was identified in long-fingered bats (_Miniopterus fuliginosus_) in Myanmar. The complete genome sequence was obtained and virus particles were observed in bat liver tissues. The finding of hepadnaviruses in bats raise many interesting questions. The 1st is whether human HBV originated by infection with bat HBV, either by consumption of bat meat or another mode of transmission. How long ago this occurred is not known. It has been suggested that HBV has been in humans for at least 15 000 years. Some avian species contain avihepadnaviral sequences integrated into their genome, indicating that these viruses originated at least 19 million years ago. These findings also raise many questions about the pathogenesis of hepadnaviral infection in bats, including the mode of transmission (in humans, the virus is transmitted by exposure to blood, for example, by injection or during childbirth), and whether chronic infections can occur as they do in humans.

Finally it is interesting to consider the zoonotic potential of tent-making bat HBV, which can infect human cells. Because bat hepadnaviruses are genetically distinct from HBV, current serological and nucleic acid screening programs would not detect human infections. The authors suggest that human and non-human primate sera from areas in which these bat viruses were isolated should be screened using assays that detect the bat hepadnaviruses. Without such information we do not know if these viruses currently infect humans.

[Byline: Vincent Racaniello]

--
Communicated by:
Faruku Bande
<bandeyabo@yahoo.com>

[Bats are found on all continents except Antarctica. Bats also are being increasingly recognized as reservoir hosts for viruses which can cross species barriers to infect humans and other domestic and wild mammals. Whereas other mammals, such as certain species of rodents (order Rodentia) and carnivores (order Carnivora), may possess traits in common with species of bats, such as the ability to hibernate, no group of mammals shares the full suite of attributes that make bats unique. Of the more than 4600 recognized species of mammals, 925 (about 20 percent) are bats [see CH Calisher et al: Bats: Important Reservoir Hosts of Emerging Viruses. Clin Microbiol Rev. 2006 July; 19(3): 531-45. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1539106/].

Bats evolved early and have changed relatively little in comparison with mammals of other taxa. Although the fossil record of bat evolution is incomplete, a recent analysis of 17 nuclear genes dated the origin of chiropterans to the Eocene period (52 to 50 million years ago), coincident with a significant rise in global temperature. 3 major microchiropteran lineages were traced to Laurasia and a 4th to Gondwana. The correspondingly ancient origins deduced for certain zoonotic viruses maintained in bats, such as the henipaviruses and lyssaviruses, suggest a long history of cospeciation [species evolving in parallel]. It appears that the hepadnaviruses can now be added to this list of viruses with ancient origins in bats.

Viruses that evolved with bats may have used, for replication, cellular receptors and biochemical pathways which are conserved in mammals that evolved later and which underwent radiation in later geological periods. If so, these conserved cellular receptors and pathways could enhance the capacity for transmission of bat-associated viruses to other mammals.

Transmission from bats of viruses causing highly pathogenic disease has been demonstrated for rabies virus and related lyssaviruses, Nipah and Hendra viruses, and inferred for SARS-CoV-like virus of bats. Other viruses, such as certain alphaviruses, flaviviruses and bunyaviruses, may infect bats via arthropods, but it is not clear whether bats are important reservoir hosts for these viruses.

Further research will be required to establish the relationship of the hepadnaviruses present in bats to the hepatitis B virus currently responsible for human disease. - Mod.CP

Photos of the bats mentioned:
_Uroderma_bilobatum_
http://lh3.ggpht.com/-h8p7xOSqS38/SPt4H ... obatum.jpg
_Hipposideros_:
http://www.uvm.edu/~jdecher/Hipposideros.JPG
_Rhinolophus alcyone_
http://farm9.staticflickr.com/8384/8485 ... ac7b52.jpg
- Mod.JW]

Forscher lassen Hepatitis B-Virus auferstehen
Virologen der Unis Bonn und Gießen entdecken neues Fledermausvirus, das auch Menschen infizieren könnte
17.09.2013 - Uni Bonn

Die Hepatitis B zählt zu den verbreitetsten gefährlichen Viruserkrankungen weltweit. Wissenschaftler des Bonner Universitätsklinikums und der Universität Gießen haben in Proben einer Gelbohr-Fledermaus ein Virus entdeckt, das mit dem Hepatitis B-Erreger eng verwandt ist und das Potential besitzt, Leberzellen des Menschen zu infizieren. Die Forscher stellten fest, dass die herkömmliche Hepatitis B-Impfung gegen dieses Virus nicht wirkt. Die Ergebnisse werden in der aktuellen Ausgabe der Proceedings of the National Academy of Sciences (PNAS) vorgestellt ... mehr

Gruß
Birgitt