By Stuart Layt
Australia is one of a series of global hotspots researchers have identified as central to the spread of a debilitating disease in birds.
An international team, including Australian researchers, has been investigating the spread of avian malaria around the world.
The disease is very similar to the type of malaria that affects humans, although the avian form cannot be caught by humans. It is, however, spread the same way – by mosquitoes transferring blood-borne parasites.
University of Queensland ecologist Nicholas Clark, one of the authors of the research, said the team compiled a data set of 53,000 wild birds, giving researchers a clear picture of how the disease was spread.
“It allows us to understand what sort of bird species might be susceptible, because infection rates vary across bird species, but also which areas seem to be hotspots,” Dr Clark said.
“Australia has areas that have quite high infection rates, and they correspond to areas that also see rates of mosquito-borne diseases in humans, so north Queensland and subtropical regions around south-east Queensland.”
The researchers also identified hotspots across Europe and North America, with the highest rates worldwide recorded in parts of Saharan Africa and the Arabian Peninsula.
Avian malaria affects between 13 per cent and 14 per cent of bird species worldwide. It is believed to have been spreading in some parts of the world for years but can have a significant impact on populations that have not built up a resistance to it.
The researchers point to the example of Hawaii in the late 1800s to early 1900s, where the disease was introduced and caused a third of the 55 known species of Hawaiian honeycreepers to become extinct.
Research co-author Konstans Wells, from Swansea University in Britain, said the spread of the disease across regions of the world was very complex.
“Since each bird species is unique in its ecological niche and is differently exposed to disease-transmitting insects during breeding and migration, infection risks are not the same for different bird species,” Dr Konstans said.
“For example, long-distance migrating birds were more likely to be infected in some continents but less likely in others.”
In many cases, humans are the cause of the spread, having transplanted bird species carrying the parasites as well as the mosquitoes that spread the disease.
Dr Clark said the growing effects of climate change were also causing the spread, as birds change their migration habits and species are pushed out of their natural range by rising temperatures.
“If the climate changes as it’s expected to over the next few decades, that could allow the mosquitoes to move to areas where they’ve never been before,” he said.
“Hawaii is seeing this. As it gets warmer the mosquitoes can move higher up the mountains than they used to, and the birds that live high up are being exposed for the first time.”
He said the disease also threatened efforts to repopulate wild species using captive breeding programs because those birds would have no resistance.
“There are a lot of birds around the world that have lived in areas that haven’t had these parasites, and there’s a real concern what happens to them,” he said.
The research has been published in the journal Global Ecology and Biogeography.