The Scourge of Avian Malaria

Mosquito-borne illness is pushing endangered birds to the brink....

Mosquito-borne illness is pushing endangered birds to the brink

Hawai‘i’s native birds face an array of threats. Habitat loss due to humans. Invasive plants. Invasive animals, particularly rats, cats, and mongoose.

But there is one invasive species, in particular, that is pushing many native birds to the brink, if they haven’t already rendered them extinct: the mosquito. 

Scarlet Hawaiian honeycreepers are particularly susceptible to avian malaria. Courtesy Flickr / USFWS

Ear-buzzing, blood-sucking, disease-spreading denizens of dusk, they’re now a (grudgingly) accepted part of Hawaii’s ecosystem.

But it wasn’t always so. Prior to the 19th century, Hawai‘i was mosquito-free. According to the state Department of Health, the first batch arrived in 1826, likely breeding in casks stowed in ships (though a persistent myth tells a more compelling, if less plausible story of a sailor who, jilted by a Hawaiian girl, intentionally unleashed the insects out of spite).How they got here is an interesting historical footnote. But they’re here, spreading avian malaria.

What is Avian Malaria? 

As with other varieties of malaria, it’s a mosquito-borne disease, first found in Hawai‘i in the 1940s. More specifically, it’s a species of protozoan parasite. It’s spread by the Southern House mosquito, a species that needs warm temperatures to survive. That has generally prevented it from infecting birds that live at higher elevations below the “mosquito zone” (roughly below 5,000 feet).

However, per a report by the Pacific Island Ecosystems Research Center, “Hawai‘i is rapidly warming due to climate change, allowing malaria-vectoring mosquitoes to establish populations in increasingly higher elevation forests which threatens the remaining native bird populations.”

The disease enters the bloodstream and reproduces, causing lethargy, appetite loss, and, in certain cases, death. Humans can’t contract it—hence the “avian” modifier—but it’s a growing threat to some of our dwindling feathered friends.

An array of endemic species have been affected, from the Hawaiian honeycreeper to the Maui Parrotbill (kiwikiu). Per a report from the U.S. Geological Survey, “Malaria infections are highest at low elevations and over 90 percent of infected scarlet Hawaiian honeycreepers (ʻiʻiwi) die from this disease.”

Is There a Solution? 

A strategy promoted by the Birds, Not Mosquitos Project—a collaborative effort between state and federal agencies—is to release male mosquitoes infected with a common bacteria called Wolbachia. When they mate with females, it renders their eggs unviable. Essentially, as the project describes it, it’s “mosquito birth control.”

Not everyone likes that idea. A state Board of Agriculture decision to approve the plan drew protestors to the streets in January, demanding the County put the brakes on the plan, claiming it hadn’t been adequately studied. At present, it’s set to commence on Maui in 2024.

Certainly, the history of introducing one species to curb or eliminate another (or for sport) doesn’t always work out as planned. See axis deer or the aforementioned mongoose, to name just two. 

But these native birds are precious. Their calls and flashing colors help define the island. And once they’re gone, they’re gone. 

Jacob Shafer

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