Avian malaria

Avian malaria
Scientific classification
Domain:	Eukaryota
(unranked):	Alveolata
Phylum:	Apicomplexa
Class:	Aconoidasida
Order:	Haemosporida
Family:	Plasmodiidae
Genus:	Plasmodium
Species:	P. relictum and others of the genus

Avian malaria is a parasitic disease of birds, caused by parasite species belonging to the genera Plasmodium and Hemoproteus (phylum Apicomplexa, class Haemosporidia, family Plasmoiidae). The disease is transmitted by a dipteran vector including mosquitoes in the case of Plasmodium parasites and biting midges for Hemoproteus. The range of symptoms and effects of the parasite on its bird hosts is very wide, from asymptomatic cases to drastic population declines due to the disease, as is the case of the Hawaiian honeycreepers. The diversity of parasites is large, as it is estimated that there are approximately as many parasites as there are species of hosts. Co-speciation and host switching events have contributed to the broad range of hosts that these parasites can infect, causing avian malaria to be a widespread global disease, found everywhere except Antarctica.

Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in all parts of the world apart from Antarctica. 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 Hawaiʻi, it can be devastating to birds that have lost resistance to the parasites over time.

Avian malaria is a vector-transmitted disease caused by protozoa in the genera Plasmodium and Haemoproteus; these parasites reproduce asexually within bird hosts and both asexually and sexually within their insect vectors, which include mosquitoes (Culicidae), biting midges (Ceratopogonidae), and louse flies (Hippoboscidae). The blood-parasites of the genus Plasmodium and Haemoproteus, encompass an extremely diverse group of pathogens with global distribution. The large number of parasite lineages along with their wide range of potential host species and the pathogen’s capacity for host switching makes the study of this system extremely complex. Evolutionary relationships between hosts and the parasites have only added complexity and suggested extensive sampling is needed to elucidate how global cospeciation events drive disease transmission and maintenance in various ecosystems. In addition to this, the parasite’s ability to disperse can be mediated by migratory birds and thus increases variation in prevalence patterns and alters host-parasite adaptation processes. Host susceptibility is highly variable as well and numerous efforts have been made to understand the relationship between increased prevalence and host traits such as nesting and foraging height, sexual dimorphism or even incubation time length. So far, the effects of this disease in wild populations is poorly understood.

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