Avian malaria

Avian malaria is a parasitic disease of birds.

Etiology

Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in tropical regions. There are several other species of Plasmodium that infect birds, such as Plasmodium anasum and Plasmodium gallinaceum, but these are of less importance except, in occasional cases, for the poultry industry. The disease is found worldwide, with important exceptions. Usually, it does not kill birds. However, in areas where avian malaria is newly introduced, such as the islands of Hawaii, it can be devastating to birds that have lost resistance over evolutionary time.

Vector

Its main vector in Hawaii is the mosquito Culex quinquefasciatus, which was introduced to the Hawaiian islands in 1826. Since then, avian malaria and avian pox together have devastated the native bird population, resulting in many extinctions. Hawaii has more extinct birds than anywhere else in the world; just since the 1980s, 10 unique birds have disappeared.

Virtually every individual of endemic species below 4000 feet in elevation has been eliminated by the disease. These mosquitoes are limited to lower elevations, below 5,000 feet, by cold temperatures that prevent larval development. However, they appear to be slowly gaining a foothold at higher elevations and their range may be expanding upwards. If so, most remaining Hawaiian land birds may become at risk to extinction.

Most of the Hawaii islands have a maximum elevation of less...
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