Common pipistrelle (Pipistrellus pipistrellus) – Credit Wikipedia
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Several months ago in a blog called Virology Journal: Ebola Virus In Chinese Bats, we looked at the first evidence suggesting that Ebola viruses are circulating among bats in China, although the exact strain involved wasn’t clear.
Researchers were able to detect cross-reactive antibodies to two types of Ebola viruses (Zaire and Reston), but identification of the exact EBOV strain in China was not possible.
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).
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 a close cousin - the Marburg virus - make up the family Filoviridae.
Of these, only Ebola-Reston – found primarily in the Philippines – does not cause illness in humans.
Up until recently, Ebola Reston was the only ebolavirus thought to circulate outside of Africa.
Today, the CDC’s EID JOURNAL published a Dispatch that describes the seroprevalence of cross reactive antibodies against Ebola in bats tested in Bangladesh. A few excerpts, but follow the link to read the dispatch in its entirety.
Volume 19, Number 2—February 2013
Dispatch
Ebola Virus Antibodies in Fruit Bats, Bangladesh
Kevin J. Olival , Ariful Islam, Meng Yu, Simon J. Anthony, Jonathan H. Epstein, Shahneaz Ali Khan, Salah Uddin Khan, Gary Crameri, Lin-Fa Wang, W. Ian Lipkin, Stephen P. Luby, and Peter Daszak
Abstract
To determine geographic range for Ebola virus, we tested 276 bats in Bangladesh. Five (3.5%) bats were positive for antibodies against Ebola Zaire and Reston viruses; no virus was detected by PCR. These bats might be a reservoir for Ebola or Ebola-like viruses, and extend the range of filoviruses to mainland Asia.
<SNIP>
Conclusions
Our study provides evidence of Ebola virus infection in wildlife from mainland Asia and corroborates the observation that filoviruses are harbored across a much larger geographic range then assumed (2). Preferential reactivity to ZEBOV suggests exposure to an Ebola virus that is distinct from REBOV, the only filovirus currently found in Asia. We consider the likelihood of cross-reactivity with MARV as low because there is only a 35% aa identity between nucleoprotein genes of REBOV/ZEBOV and MARV. However, we cannot rule out co-infection with multiple filoviruses.
An interesting side note, one of the authors listed on this dispatch is Professor Ian Lipkin, director of Columbia University’s Center for Infection and Immunity in New York.
Dr. Lipkin served as technical advisor for the 2011 film Contagion, and created the fictional MEV-1 bat virus used as the movie’s viral villain (see The Scientific Plausibility of `Contagion’).
Our knowledge of the diseases carried by bats has expanded considerably since the early 1990s. Up until that time, the primary concern was rabies.
During the 1990s – two new bat-borne viruses emerged - Nipah and Hendra - both henipaviruses of the family Paramyxoviridae.
The Hendra virus was first isolated in 1994 after the deaths of 13 horses and a trainer in Hendra, a suburb of Brisbane, Australia. A stable hand, who also cared for the horses, was hospitalized, but survived.
Over the past 18 years 40 outbreaks of Hendra virus – all involving horses – have been reported in Australia. Four human fatalities have been linked to the virus as well.
The debut of Nipah was in Malaysia in 1998, where the virus first jumped from bats to local swine herds, probably via bat droppings into the swine’s environment or food. From there, it jumped to humans, resulting in 265 cases of acute encephalitis and more than 100 deaths (cite).
This first human outbreak was initially thought to be due to Japanese encephalitis, and so precautions around pigs were delayed for nearly two months, allowing the virus to spread.
Over the past decade, Nipah has sparked a number of small outbreaks across Southern Asia, although the most intense activity has been centered around Bangladesh.
Nipah/Hendra Virus & Fruit Bat Home Range – WHO
The most notorious of the emerging bat-viruses has been SARS-CoV (coronavirus), which sparked an epidemic in 2002-2003 that infected roughly 8,000 people around the globe, killing nearly 800.
Which explains why so much interest has been paid to the detection last year of a handful of novel coronavirus infections in the Middle East (see WHO Coronavirus Update).
And perhaps most surprisingly of all, early in 2012 we learned about a new strain of influenza found in an unusual host: bats (see A New Flu Comes Up To Bat).
This discovery adds an H17 flu subtype, and a new host species, suddenly making all of the textbooks and slide presentations on influenza out of date.
In 2007 a PNAS article called A previously unknown reovirus of bat origin is associated with an acute respiratory disease in humans, told of a 39 year old man infected when a bat flew into their Malaysian home. More than a week after he was placed in isolation, two other members of his family came down with the same illness, suggesting H-2-H transmission.
The authors of that report wrote:
Bats, probably the most abundant, diverse, and geographically dispersed vertebrates on earth, have recently been shown to be the reservoir hosts of a variety of zoonotic viruses responsible for severe human disease outbreaks, some with very high mortality.
While most researchers expect the next pandemic to come from a swine or avian source, other species – like bats – are increasingly being looked to as significant reservoirs of dangerous zoonotic pathogens.
All of which makes studies, like this one today, of particular interested to researchers.
