Rising sea levels, melting glaciers, more intense rainstorms and more frequent heat waves are among the planetary woes that may come to mind when climate change is mentioned. Now, two University of Michigan researchers say an increased risk of avian influenza transmission in wild birds can be added to the list.
Population ecologists Pejman Rohani and Victoria Brown used a mathematical model to explore the consequences of altered interactions between an important species of migratory shorebird and horseshoe crabs at Delaware Bay as a result of climate change.
They found that climate change could upset the carefully choreographed interactions between ruddy turnstone shorebirds and the horseshoe crabs that provide the bulk of their food during the birds' annual stopover at Delaware Bay, a major estuary of the Delaware River bordered by New Jersey to the north and Delaware to the south.
Climate change-caused disruptions to the well-timed interplay between the birds and crabs could lead to an increase in the avian influenza infection rate among ruddy turnstones and resident ducks of Delaware Bay, the researchers found. Because Delaware Bay is a crossroads for many bird species traveling between continents, an increase in the avian infection rate there could conceivably help spread novel subtypes of the influenza virus among North American wild bird populations, according to Rohani and Brown.
Their findings were published online Aug. 29 in the journal Biology Letters.
"We're not suggesting that our findings necessarily indicate an increased risk to human health," said Rohani, a professor of ecology and evolutionary biology, a professor of complex systems and a professor of epidemiology at the School of Public Health.
"But every single pandemic influenza virus that has been studied has included gene segments from avian influenza viruses. So from that perspective, understanding avian influenza transmission in its natural reservoir is, in itself, very important."
Avian influenza refers to infection with bird flu Type A viruses. Those viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species.
Avian flu viruses do not normally infect humans. However, sporadic human infections with avian flu viruses have occurred. Since 2003, for example, more than 600 cases-including more than 300 deaths-of human infection with highly pathogenic avian influenza A H5N1 have been reported worldwide, according to the World Health Organization.
Delaware Bay, which hosts many resident bird species as well as the hundreds of thousands of migratory birds that gather to feed on horseshoe crab eggs, is known as a hot spot for avian influenza virus. Infection levels in ruddy turnstones, which stop at Delaware Bay each May during their northbound migration to breeding grounds in the Arctic after wintering in South America, have been found to be exceptionally high.