Migratory birds unfairly blamed for spreading disease

MIGRATORY animals are often blamed for the global spread of diseases, but a study by a researcher at Deakin University’s Waurn Ponds campus has shown their role may be less significant than previously thought.

Alice Risely, a PhD candidate in Deakin’s School of Life and Environmental Sciences, said the recently-published study of migratory shorebirds (on which she was the lead researcher) showed the species were exceptionally good at resisting invasion from ingested microbes.

“In humans, travelling increases our risk of getting ill, because we come into contact with many new microbes that our immune system has never encountered before.

“So we wanted to work out if migrants are also more susceptible to these potentially disease-causing microbes as they travel to new locations, or if they’ve adapted to this risk.”

The study looked at the gut bacteria of migratory shorebirds, which undergo some of the longest and fastest migrations in the animal kingdom.

“We found that the migratory shorebirds we studied were exceptionally good at resisting invasion from ingested microbes, even after just having flown thousands of kilometres,” Ms Risley said.

“Birds that had just returned from migration (during which they stopped in many places in China, Japan, and South East Asia), didn’t carry any more species of bacteria than those that had stayed around the same location for a year.

She said migratory animals were notoriously hard for ecologists to track and test for infections because of the vast areas they occupy.

“With the rate of zoonotic diseases (pathogens that jump from animal hosts to humans) on the rise, migratory animals have been under increasing scrutiny and suspicion of aiding the spread of avian influenza viruses (bird flu), Lyme disease, and even Ebola.

“Billions of animals fly, swim and walk around the globe every year on their seasonal migrations, but there is in fact surprisingly little direct evidence that these animals are frequently spreading pathogens long distances.”