Emerging infections at the human-animal interface
Infectious diseases, especially ones that emerge from wildlife, have always fascinated me. When I started my PhD in 2014, the ebola virus outbreak was wreaking havoc in West Africa. Soon after, I became interested in studying neglected wildlife virus reservoirs and understanding how these viruses co-exist with their wildlife hosts. Bats play an essential role in our ecosystem, but recent studies have also identified that bats can carry many viruses that cause serious disease in humans and agricultural animals. Over the last 5 years, I have studied and discovered unique aspects of the bat immune system that enable them to co-exist with viruses. Understanding how bats can live with these viruses without developing disease may one day enable us to design better therapeutics for other mammals, such as humans.
Of all emerging infections, 75% have an animal original. Viruses like rabies can be detected in animals like raccoons, skunks, foxes, and bats to name a few; all of which can be found in an urban environment. So how do we protect ourselves? Multiple government websites have recommendations on how to keep rabies at bay. Routes of exposure to rabies often involve direct contact with animals. So, if you come in contact with one of these animals, contact local animal services; if you have been bitten, seek medical attention immediately. You can also learn whether there have been cases of rabies detected in wildlife in your province, through a look-up service on the Public Health Agency of Canada’s (PHAC) website. Even if you are exposed to the rabies virus, a vaccine exists, so there is nothing to worry about as long as you are vaccinated before symptoms set in.
There are other pathogens that make the jump from animals to humans, and cause serious disease. Nipah is an example of a virus that jumped from fruit bats to humans in Bangladesh. Nipah virus infections causes respiratory disease and acute encephalitis in humans. Although there is no vaccine or treatment for this virus, policy changes and altered traditional practices have played a huge role on controlling outbreaks. In Bangladesh, Nipah virus spreads through contaminated date palm sap, a traditional drink that is consumed by the locals, fresh and unpasteurized. Bats love the drink too! So when farmers put their pots up on the trees to harvest date palm sap, the bats fly in to drink out of the pots, contaminating the drink in the process. In addition to research into understanding the molecular mechanisms of disease, a lot of work has been put into identifying intervention strategies to combat the spread of disease. Simple practices like covering the sap collection pots with bamboo skirts have been successful in keeping bats out.
Closer to home in Canada, Lyme disease is an emerging problem. Lyme disease spreads through the bites of black-legged ticks (Ixodus scapularis) that carry the causative bacteria. In the wild, Lyme disease is maintained by deer, rodents and other small mammals. Hikers should be watchful when venturing into ungroomed trails. It is always a good idea to check yourself for ticks after spending time in tall grass, shrubs, and bushes. A buddy system to check each other for ticks is recommended. Guidelines on how to remove a tick can be found on government websites. Not all ticks carry or transmit these bacteria, but it doesn’t hurt to check for ticks and remove them after an exciting hike!
Emerging infections continue to pose a threat and as humans encroach upon forests, we will continue to come in contact with wildlife and potentially the bugs that are carried by them. Be watchful of what animals you come in contact with and when in doubt, get in touch with the appropriate authorities. Although studies often identify pathogens in wildlife, the chances of encountering an infected animal and acquiring the pathogen is relatively low.
Dr. Arinjay Banerjee (Ph.D.) is a member of the STAN Board of Directors.
This article reflects his personal opinion and not that of his employer or STAN