Researchers make concerning discovery about spread of avian malaria

Nearly every species of forest bird in Hawaiʻi can pass avian malaria on to mosquitoes, helping the deadly disease persist across the islands.

What's happening?

A team led by the University of Hawaiʻi at Mānoa analyzed samples from over 4,000 birds spanning Kauaʻi, Oʻahu, Maui, and Hawaiʻi Island. The parasite behind avian malaria, Plasmodium relictum, was detected at 63 of 64 sites they tested.

According to the study, published in the journal Nature Communications, native honeycreepers and introduced species were both able to infect southern house mosquitoes, the main species that spreads the disease. Even when the pathogen was barely detectable in a bird's blood, it was enough to infect a mosquito.

The team found that infected birds remain contagious over months, sometimes years, through low-level infections. That prolonged, simmering phase of infection is what drives the bulk of transmission across the state, according to the study.

"Avian malaria has taken a devastating toll on Hawaiʻi's native forest birds, and this study shows why the disease has been so difficult to contain," Christa M. Seidl, mosquito research and control coordinator for the Maui Forest Bird Recovery Project, told ScienceDaily.

"When so many bird species can quietly sustain transmission, it narrows the options for protecting native birds and makes mosquito control not just helpful, but essential."

Why is avian malaria in Hawaiʻi concerning?

The parasite targets red blood cells. That breakdown can trigger organ damage and severe anemia. For the ʻiʻiwi, a scarlet honeycreeper, the infection kills roughly 90% of those affected. The ʻakikiki, a Kauaʻi honeycreeper, has vanished from its natural habitat, with avian malaria cited as the main cause.

As temperatures climb, mosquitoes are pushing into higher-altitude forests that once gave native birds a safe place to live. As those safe zones disappear, almost no mosquito-prone area on the islands is free from the disease.

"We often understandably think first of the birds when we think of avian malaria, but the parasite needs mosquitoes to reproduce and our work highlights just how good it has gotten at infecting them through many different birds," Seidl said.

What's being done about avian malaria in Hawaiʻi?

The Maui Forest Bird Recovery Project belongs to Birds, Not Mosquitoes, a coalition of universities, government agencies, nonprofits, and private-sector organizations working to cut mosquito numbers on the islands.

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If you want to help, consider donating to Hawaiian bird conservation organizations like the Maui Forest Bird Recovery Project. 

Meanwhile, it's important to reduce your carbon footprint to slow the rising temperatures that push mosquitoes into new territory, whether that means switching to clean energy at home or flying less.

Contact your elected officials and voice support for policies that fund wildlife disease research and habitat protection.

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