Tuesday, October 23, 2012

Virology Journal: Ebola Virus In Chinese Bats


Common pipistrelle (Pipistrellus pipistrellus) – Credit Wikipedia


# 6655


We are ten months into 2012, and so far it has been a pretty good year for Chiroptologists (scientists that study bats). 


While bats are often associated with diseases like rabies and histoplasmosis, over the past year we’ve seen bats linked to at least five exotic disease outbreaks around the globe and one rather unexpected discovery. 


In January we watched as Nipah Claimed 5 Lives in Bangladesh. Nipah, and its close cousin Hendra from Australia, are bat borne viruses that occasionally jump to humans (or other mammals) and can spark outbreaks.


Nipah, you may recall, was used as the basis for the fictional MEV-1 virus in the movie Contagion last year (see The Scientific Plausibility of `Contagion’).



Although no human cases are involved, last February the CDC announced the unusual discovery of a novel flu strain in little yellow-shouldered bats (Sturnira lilium) captured at two locations in Guatemala.(see A New Flu Comes Up To Bat).

While common in waterfowl, this was the first time that influenza had been detected in bats.


In July we saw an outbreak of Ebola Sudan in western Uganda (see Uganda: Ebola Sudan And A Timely Dispatch From The EID Journal), followed in August by an outbreak of Ebola-Bundibugyo in the Democratic Republic of the Congo (see WHO: DRC Ebola Update).


The natural reservoir for Ebola viruses are believed to be fruit bats of the Pteropodidae family, although the virus in humans is usually linked to the consumption of infected bushmeat (considered an intermediate host).  


In early September, we learned of the discovery of two cases of a novel coronavirus out of the Middle East, and once again a bat host is considered likely (see Coronavirus `Closely Related’ To HK Bat Strains).


And only last week, news emerged of a Marburg Virus outbreak in Uganda, which is still ongoing (WHO Update on Marburg Virus In Uganda). 


A close cousin to Ebola, Marburg is also believed carried by fruit bats of the Pteropodidae family, which can pass the virus on to other intermediate hosts, or directly to humans.


There are currently five known strains of the Ebola virus - Ebola-Zaire, Ebola-Sudan, Ebola-Reston, Ebola-Ivory Coast and Ebola-Bundibugyo – which along with the Marburg virus make up the family Filoviridae.


Of these, only Ebola-Reston – found in the Philippines – does not cause illness in humans. It is pathogenic in non-human primates, and has been found to infect pigs, which gives scientists some cause for concern.


Ebola Reston is also the only ebolavirus known to circulate outside of Africa.


That is . . . until now.


We’ve a new open access study, published this month in the Virology Journal, that has found evidence suggesting that Ebola viruses are circulating in Chinese bats, although the exact strain involved isn’t clear.



Serological evidence of ebolavirus infection in bats, China

Junfa Yuan, Yuji Zhang, Jialu Li, Yunzhi Zhang, Lin-Fa Wang and Zhengli Shi


The genus Ebolavirus of the family Filoviridae currently consists of five species. All species, with the exception of Reston ebolavirus, have been found in Africa and caused severe human diseases. Bats have been implicated as reservoirs for ebolavirus. Reston ebolavirus, discovered in the Philippines, is the only ebolavirus species identified in Asia to date. Whether this virus is prevalent in China is unknown.


In this study, we developed an enzyme linked immunosorbent assay (ELISA) for ebolavirus using the recombinant nucleocapsid protein and performed sero-surveillance for the virus among Chinese bat populations. Our results revealed the presence of antibodies to ebolavirus in 32 of 843 bat sera samples and 10 of 16 were further confirmed by western blot analysis.


To our knowledge, this is the first report of any filovirus infection in China.


While researchers were able to detect cross-reactive antibodies to two types of Ebola viruses (Zaire and Reston), identification of the exact EBOV strain in China was not possible.  The author’s write:


The unsuccessful identification of ebolavirus-related genes in the samples is likely attributable to the often low-level of virus replication, the similarly transient nature of the infection in bats or the sequence mismatch of the PCR primers used and the target sequence of the potential unknown ebolavirus genomes.



Until the late 1990s, little thought was given to bats as reservoirs of epidemic diseases. Outbreaks of Nipah in Malaysia in 1998 - which lead to  265 cases of acute encephalitis and more than 100 deaths (cite) – put bats suddenly under the spotlight. 


Four years later - after the SARS outbreak in China - the SARS coronavirus was detected in horseshoe bats in China (cite), solidifying bats as important reservoirs of emerging infectious diseases. 


Since then scientists have discovered an increasing array of viral diseases that are carried by bats, although in many cases in isn’t clear how big a threat they actually pose to humans.


None of this is meant to demonize bats, as we are surrounded by a great many different hosts of zoonotic diseases.


Still, the CDC offers some sage advice when it comes to avoid coming in contact with bats.


 Take Caution When Bats Are Near

Photo: Bats

Bats play an important role in our ecosystem. However, they are also associated with diseases deadly to humans. Learn how you can stay safe when bats are near.

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