Bats: Friend or Foe?

Bats often suffer from a negative public image, condemned as flying vermin and carriers of disease but they are critical elements of all terrestrial biotic communities. They help control insects, reseed cut forests and pollinate plants that provide food for humans and other species. Their guano (excrement) is also used as a fertiliser and for manufacturing soaps, gasohol (an automobile fuel) and antibiotics.

However, bats are recognised as a significant source of zoonosis – the spread of infectious diseases from animals to humans. Some of the human pathogens bats are known to transmit include Hendra virus, Nipah virus and rabies virus. They have also been linked to the transmission of SARS and Ebola viruses. Currently 75 percent of emerging infectious diseases are zoonoses.  In the UK the only known zoonotic disease associated with bats is rabies, specifically, European Bat Lyssavirus type 2 (EBLV2). However, EBLV2 has only been found in 11 bats in the UK despite over 12,000 bats having been tested and rabies has only been associated with one human case in the UK.

A team of researchers led by Dr. Reed Shabman of the J. Craig Venter Institute and Prof. Christopher Basler of the Icahn School of Medicine at Mount Sinai, New York, have discovered a novel gammaherpesvirus – named bat gammaherpesvirus 8 (BGHV8) – from the cells of the cave bat Myotis velifer incautus using next-generation DNA sequencing technologies.

The researchers were looking at tumour cells taken from the wing of an adult female microbat found in a cave in Texas. They were DNA sequencing the genetic material from these cells to better understand bats’ immune response to infection. What they discovered was quite surprising. They noticed that a large number of the genes sequenced weren’t in fact bat genes but were genes related to the herpes viruses. Further investigation revealed they had discovered a previously unknown virus – BGHV8. Using next-generation DNA sequencing technology they were able to construct a full-length genomic map of BGHV8.

Dr. Shabman said, “This is the first replicating bat gammaherpesvirus that’s been isolated. Most labs just have bits and pieces of a virus.”

The team were able to assemble nearly 130,000 base pairs of the BGHV8 genome and demonstrated that the virus was capable of infecting isolated human lung and human liver cells. However, most herpes viruses are relatively harmless and animal-to-human transmission of herpes virus is very rare.

Prof. Basler said, “A big question is why bats are repeatedly associated with infections that transfer to humans. We have very few tools to study bats’ immune responses to viruses. This natural bat virus is actually going to prove to be useful in understanding and probing how bats respond to natural infections and microorganisms that can cause disease.”

This discovery allows a better understanding of the bat viral reservoir and may help scientists devise methods to prevent future bat-borne disease outbreaks in the human population.