Overview

Photo: USDA

Avian malaria in Hawai'i is caused by the protozoan parasite, Plasmodium relictum. In birds, this parasite infects peripheral red blood cells and internal tissue such as liver, spleen, bone marrow and brain cells. It was first introduced to Hawaii in exotic birds kept by settlers, but it was not until the introduction of the southern house mosquito (Culex quiquefasciatus) in 1826 that it could spread. Hawaii’s native birds succumbed quickly because they have no resistance to the disease. Avian malaria has contributed to the extinction of at least 10 native bird species in Hawaii, and threatens many more. Many native birds can no longer breed in their historic breeding grounds at lower elevations because of avian malaria, forcing them to breed in higher elevations where food and cover may be scarce. Exotic bird species are resistant to the disease, but serve as reservoirs. The spread of mosquitoes is enhanced by the feeding habits of feral pigs which uproot native vegetation creating depressions in the soil which collect rainwater thereby allowing mosquitoes to breed.

Birds Affected

I’iwi and other Hawaiian honeycreepers; Alala; Maui Parrotbill; Newell’s Shearwater; ‘Elepaio.

Control

Reduction or elimination of mosquito larval habitat is the most effective form of mosquito control. In agricultural and residential areas, objects that hold standing water should be removed. Management of the disease in wet forest areas requires the eradication of feral pigs.