Using mud to prevent pandemics
‘Pandemic’ is a word that conjures up terrifying images of a devastating disease outbreak spreading across human populations, leaving the surviving communities in tatters. We tend to visualize pandemics in the distant past, such as the notorious ‘Black Death’ (caused by a bacterium called Yersinia pestis) that ravaged medieval Europe; however, more recent disease outbreaks such as the Spanish Flu, SARS (Severe Acute Respiratory Syndrome), and Ebola should remind us that the potential for pandemics remains to this day. If we dig a little deeper, we should also remind ourselves that diseases with pandemic potential occur in non-human species as well, with wildlife often playing a key role in transmitting these diseases. A note on terminology: in animals, pandemics can be referred to as ‘panzootics,’ and diseases that pass from animals to humans are called ‘zoonoses.’
A recent example is from 2014/2015, when North America saw a wave of bird flu—a viral disease also known as ‘avian influenza’ or ‘AI’—that spread through domestic poultry barns across the continent. The virus responsible for the 2014/15 outbreak likely originated from Korea, where it hitched a ride across the Pacific Ocean to Alaska through a migrating duck or goose and merged (via a process called ‘re-assortment’) with a North American virus. Once in North America, migrating waterfowl carried the virus across the continent where it could infiltrate into poultry barns. The subsequent panzootic caused substantial impact with 16 barns infected and approximately 325,000 birds euthanized in British Columbia and Ontario. In the United States, over 48 million poultry birds from 223 barns were euthanized to try to contain further spread of the virus.
What can be done to prevent these sorts of animal or human pandemics? The key lies in appropriate surveillance, when human and animal health officials examine many samples, on the lookout for bacteria or viruses that are likely to cause an outbreak. Bird flu has many different circulating strains—just like seasonal human influenza—however, certain strains are more likely to cause disease in poultry (i.e. H5 or H7). Wild waterfowl typically carry these different strains without showing signs of disease, which means it is difficult or expensive to collect samples from enough birds to give a clear picture of which viral strains are in circulation during a given year or season. Luckily, we can overcome this hurdle because wild birds shed AI virus in their feces. This means that mud from wetlands where birds gather—and defecate—contains traces of the different AI strains carried by many different birds. Thus testing wetland mud for AI gives us a more complete surveillance picture than by using traditional AI surveillance techniques.
The CWHC BC node at the BC Ministry of Agriculture partnered with the BC Centre for Disease Control to determine how best to implement this new, genomic-based approach for the detection and characterization of AI in wetland mud into BC and Canadian AI surveillance programs. The Genomic Analysis of Wetland Sediment as a Tool for Avian Influenza Surveillance and Prevention is a two-year project that takes place in the lower mainland of BC. The project will compare AI viral “footprints” in wetland mud to AI viruses detected in hunted and live-caught wild waterfowl. Implementing this mud-based AI detection approach into Canadian AI surveillance programs is expected to improve our ability to detect, predict, and prevent future AI pandemics.
The project is supported through a combined partnership from agencies including Genome BC, the Canadian Wildlife Health Cooperative, the Canadian Food Inspection Agency (CFIA), Investment Agriculture Foundation of BC, the Sustainable Poultry Farming Group, and the Governments of Canada and British Columbia through Growing Forward 2, a federal-provincial-territorial initiative.
Author: Michelle Coombe