Plasmodium vaughani is a parasite of the genus Plasmodium subgenus Novyella.

Like all Plasmodium species P. vaughani has both vertebrate and insect hosts. The vertebrate hosts for this parasite are birds.

The parasite was first described by Novy & MacNeal in 1904.

The length of the asexual cycle is 24 hours.

Trophozoites: Ring forms are unusual. The trophozoite is usually irregular in outline. The nucleus is small and there may be a single clear outgrowth of the cytoplasm. One ot two small pigment granules may be seen. These forms are found in mature and polychromatic erythrocytes.

Schizonts: These are usually found in a polar or sub polar position within the host cell but may be found anywhere within the cell. They are found in mature or polychromatic erthrocytes. Mature forms meaure 2.3 to 5.4 microns in width and 1.5 to 4.4 microns in length. They are irregular in shape but tend to be round or ovoid. Within each schizont are 4-8 merozoites. These are usually arranged in a fan like fashion but may occur at random. A transparent globule may be present along with one to three pigment granules. The host nucleus is not normally displaced.

Gametocytes: The macro- and microgametocytes are very similar except for size in this species. They are elongated, possess 2-24 (usually 10) pigment granules which may be found in clumps and are usually found in mature erythrocytes. The nucleus is pale, compact and central in position. The gametocyte usually lies along the host cell nucleus but young gametoctyes may adhere to the host cell membrane. The host nucleus is not normally displaced. They are 8.0 to 13.7 microns in length and 1.2 to 2.8 microns in width.

Asexual replication appears to occur in three ways:

(1) by repeated binary fission of the chromatin with eventual splitting of the cytoplasm

(2) by the splitting of an elongate parasite into merozoites having a bead-like arrangement

(3) by the similar breaking-up of a ring-shaped form with a resulting ring of merozoites

This species is second only to Plasmodium relictum in its frequency of occurance.

This species is found in Alaska, Colombia, New Hebrides, New Brunswick, Nigeria and Pakistan.

• Culex pipiens

Known hosts for this species include the blackbird (Agelaius phoenicius), the goldfinch (Carduelis carduelis), the blue jay (Cyanocitta cristata), the yellow warbler (Dendroica petechia), the robin (Erithacus rubecula), junco (Junco hyemalis hyemalis), the red-billed leiothrix (Leiothrix lutea), the bullfinch (Loxigilla violacea), house sparrow (Passer domesticus), the weaver (Ploceus cucullatus), the canary (Serinus canaria), the pigeon (Streptopelia senegalensis), eastern meadowlark (Sturnella magna), starling (Sturnus vulgaris) black-faced grassquit (Tiaris bicolor), white-eyed thrush (Turdus jamaicensis) and American sparrows (Zonotrichia species).

• P. vaughani merulae

• P. vaughani tenuis

• P. vaughani vaughani