Halloween is right around the corner, so we continue our coverage of one of the most notable creatures of the season: bats. Previously we covered vampire bats and their role in spreading rabies to humans and livestock in South America. Considering how bats appear to be vectors for both Ebola and rabies this made left me wondering what other viruses bats carry.
Many animals carry some sort of virus that belong to the Orthomyxoviridae family which is broken into three classes A, B, and C. Classes B and C primarily infect humans while class A infects a range of hosts including birds, mammals, and reptiles. However, no Orthomyxoviridae virus has been found in bats, or so we thought. In October researchers from Maryland and Kanas discovered a new flu virus that can be transmitted between bats and in doing so discovered a new lineage of the Orthomyxoviridae family and a potential new pandemic flu.
Influenza is a negative sense RNA virus consisting of 7-8 segments allowing it to recombine during infection and create new combinations of RNA segments. Multiple types of influenza can infect a host cell simultaneously allowing strains of flu from different hosts to recombine in novel ways. This ability to be infected with different types of influenza viruses is why there are new outbreaks of the flu every year and why the virus has the potential to become a global pandemic if the correct reassortment happens.
Bats carry many diseases such as Coronaviruses, Filoviruses, and Henipaviruses, but as stated earlier, no Orthomyxoviridae have been previously found. While trying to sequence genomes the researchers found influenza-like RNA sequences in tissue cultures. However, when these sequences were introduced into cell cultures they did not replicate efficiently. The researchers then synthetically altered the surface protein structure and re-infected cell and animal models. The virus reproduced efficiently in the cell and mice models with high mortality among the mice; thus showing that the virus can reproduce in traditional flu hosts. The researchers indicated that the bat virus does not have the same surface proteins that influenza A and B contain. This lack of ability to infect the same cells shows high cell specificity that results in a limitation of the cell types that influenza A and bat influenza can infect. Finally, the genetic differences that are seen in the bat influenza virus indicate that they are a distant relative of the current influenza types, thus potentially making them a new branch of the Orthomyxoviridae family tree.
The difficulty in growing the bat viruses in traditional cells without modification indicates that the virus does not have the necessary surface proteins to enter cells. However, after synthetic modification the bat virus was very lethal in host cells and animal models. This indicates that the bat virus is only distantly related to the influenza A and B types that circulate currently. Therefore, the risk of reassortment between flu viruses is small and there is a smaller risk of a global pandemic.
In conclusion, bats harbor many viruses and make great Halloween decorations but they pose little risk for a global pandemic of zombie apocalyptic proportions and are great for the environment. So, make sure you thank the next bat that you see and we will continue our coverage of our winged friends next week.