Plasmodium ashfordi

Plasmodium ashfordi is a species of the genus Plasmodium subgenus Novyella.

Like all species in this genus it has both vertebrate and insect hosts. The vertebrate host are birds.

Description
This species was first described in 2007 by Valkiunas et al.

The parasite infects erythrocytes.

The influence of trophozoites on the morphology of infected erythrocytes is not marked. The parasite nucleus is small, usually terminal in position or with chromatin concentrated along the outer periphery of trophozoites. One or two small (<1 µm in diameter) vacuoles are frequently present in the cytoplasm.

Ring forms are not characteristic.

The trophozoites are usually found in mature erythrocytes but may be seen in polychromatic erythrocytes during heavy infections. They are variable in shape, usually irregular in outline. Outgrowths extending beyond the main body of the trophozoites are absent. Fully grown trophozoites usually possess one or two minute brown pigment granules which are usually terminal in position and located close to each other.

The meronts are fan-like and contain 7 - 8 merozoites (range: 4 - 10). They measure ~5.0 micrometres (range:3.3-6.2) in length, 2.2 micrometres in width (range: 1.7-3.1) and 9.4 square micrometres (range: 5.4-12.2) in area. The pigment granules occupy 0.8-1.3 square micrometres in area.

Fully grown gametocytes occupy positions lateral to the nuclei of infected erythrocytes. They are elongated in form and irregular in outline from the earliest stages of their development. The influence of gametocytes on the morphology of infected erythrocytes usually is not pronounced, but nuclei of some infected erythrocytes may be slightly displaced laterally.

The parasite nucleus is diffuse and its boundaries are difficult to discern. The chromatin may be positioned anywhere in the gametocyte, which is a rare feature for macrogametocytes of avian hemosporidians. Pigment granules are roundish or oval in form, clumped together into a prominent group usually located terminally or occasionally subterminally. Because of this clumping, the number of pigment granules and their size are difficult to determine.

Macrogametocytes are found only in mature erythrocytes even during heavy parasitemia. They measure 9.7 micrometres (range: 7.1 - 12.3) long, 2.3 micrometres (range: 1.9 - 2.8) in width and 21.2 (range: 13.1 - 30.6) square micrometres in area. The cytoplasm is coarsely granular in appearance and usually lacks vacuoles.

The microgametocyte are 9.7 micrometres (range: 7.6 - 12.0) long, 2.2 micrometres (range: 1.6 - 2.6) in width and 19.8 (range: 13.5 - 25.1) square micrometres in area. Compared with the macrogametocytes, their nuclei are relatively compact - a rare feature for avian hemosporidians. The nuclei are located centrally or subcentrally.

Geographical location
This species is found in Europe and probably in Africa.

Clinical features and pathological effects
The organism was isolated from great reed warblers (Acrocephalus arundinaceus).