Migrating birds typically pack light for their seasonal journey. But scientists at the University of Georgia recently confirmed their luggage includes a potentially devastating disease, avian malaria. The mosquito-borne disease has nearly wiped out a bird population in Hawaii in the last three years. Learning more about the range and distribution of the disease will help with conservation efforts, especially for vulnerable or island species in other parts of the world.

The research, published in Integrative Zoology, examines the relationship between migrating birds and different environments impacted by climate change. The study revealed bird migration has a strong influence on the spread of the parasites that cause the disease. Researchers also discovered that changes in climate could affect the spread by altering migration patterns or impacting the presence or absence of mosquitoes.

“Avian malaria has been around for a long time,” said lead author Carlos Molinero, a doctoral candidate in the Odum School of Ecology. “It is difficult to know the distribution of the parasites that cause the disease, so we are trying to figure out where they are and why they are there.”

Mosquitoes, the primary carrier for avian malaria, arrived on the Hawaiian island chain in the early 1900s, but changes in climate have made an impact, especially in these types of climates. Warmer temperatures in higher elevations are facilitating the spread of the disease, threatening several of the endemic bird populations that didn’t have the necessary immunity. 

The team of Odum School researchers took a new analytical approach, comparing different regions with similar ecosystems known as ecoregions. The method, ecoregion pairwise analysis, had not been used before with wildlife disease analysis, according to Molinero.

“Since we have a lot of data available on avian malaria on a global scale, it was the perfect system,” he said.

MalAvi is a public database that collects data, including geographical information, on malaria parasites that infect birds. Comparing regions instead of individual birds helped researchers spot patterns in the disease distribution that could be missed if they focused on a single species. The researchers created indexes comparing the types of parasites, migratory birds and non-migratory birds that different regions share. Out of 814 global ecological regions, avian malaria parasites were found in 246 or roughly 30 percent. North America, South America, Europe and Africa showed lots of different parasite types.

“We saw what we expected,” said Molinero. “Similar malaria lineages [parasites] are found in two faraway places, thousands of miles apart. We expected the migratory bird community to be partially responsible for that.”

Many of the regions were connected by a designated flyway, a flight path used by large numbers of migrating birds. One example highlighted avian parasite hotspots in Peru and Tanzania, Mozambique, Malawi and Zambia. These areas overlap with the Central and Pacific Americas flyways in Peru, and the Black Sea-Mediterranean flyway and West Asian-East African flyway in Africa.

“There is a figure [representing the data] in our report showing regions with similarities and straight lines drawn between them,” he said. “The lines match up perfectly with the flyways.” 

But climate change is shifting those bird migration patterns and mosquito habitats, either increasing or decreasing their overlap. More overlap means higher disease transmission risks, while less overlap may reduce it. Other birds are shortening or stopping migrations, which could limit long-distance disease spread but increase local transmission. Warmer temperatures also let mosquitoes expand into new areas, including higher elevations.

“Most locations connected by migratory birds share parasites that show evidence of infecting non-migratory birds too, which suggests efficient onward transmission following migration,” said Andrew Park, professor of  disease ecology with a joint appointment in the Odum School and UGA’s College of Veterinary Medicine.

Beyond avian malaria, this new analytical method can be utilized in studying other diseases like influenza and ectoparasites. It can also help guide future conservation and management practices—including vaccinations—in established hotspots where species may not have the proper immunity, Molinero said.

“We hope to replicate what was done with avian malaria and see if other parasite types have the same patterns where migratory birds are also moving them around the world.”

Co-authors include doctoral candidate Christian H. Brown and alumni Timothy L. Odom (PhD ’25) and Daniel C. Suh (PhD ’24).