Bats threatening or threatened

Prof. Vikram Misra, Dept. of Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Canada

Many people are terrified of bats! When you mention bats their thoughts turn to vampires and other mysterious creatures of the night. Much of this is because we know very little about bats. In reality, they are amazing animals that are critical for environmental health. In the millions of years that bats have been around, they have evolved unique adaptations to their unique lifestyles and the pathogens they encounter. They also have much to teach us.

In recent years several viruses that appear to cause no overt disease in their natural bat hosts have spilled over into people and other animals causing serious and often fatal disease. My laboratory wants to answer two questions about bats and their viruses – Why don’t their viruses make bats get sick? And – Why do bat viruses spillover to other animals? We have discovered that like humans bats respond to viral infections with an antiviral innate response but unlike humans and other animals they seem to actively suppress inflammation. Since an overblown inflammatory response is often responsible for pathology and for making the effects of viral infection much worse, this may explain why people get very sick with diseases like SARS, MERS and Ebola but bats, infected with similar viruses don’t. We have also discovered that bats seem to have relatively harmonious relationships with some viruses and that these viruses cause low level, asymptomatic persistent infections. However, this relationship can be disturbed by stress, such as that caused by a fungal infection that is currently killing bats in North America. Stress appears to cause an increase in viral replication. If environmental and other stressors similarly upset virus-bat relationships it may explain why spillover events are often accompanied by deforestation and bat habitat destruction.