These include gamebirds (Galliformes), waterfowl (Anseriformes), raptors (Accipitriformes, Falconiformes, Strigiformes), pigeons and doves (Columbiformes), and perching birds or songbirds (Passeriformes).

The genus Halterium was created by the French parasitologist Alphonse Labbe for a species he observed with gametocytes in erythrocytes, with pigment granules, and halter-shaped when fully formed.

A second species in this genus was described in 1909 by Johnston and Cleland who found pigmented gametocytes in the blood of the Australian tortoise Chelodina longicollis.

He followed the opinions of Wenyon, Hewitt and DeGiusti and suggested that all these parasites belonged to the one species — Simondia metchnikovi.

Levine and Campbell in 1971 moved all the species in Simondia and Haemocystidium into Haemoproteus, an opinion that was followed by subsequent authors.

The genus Haemocystidium was resurrected again by Telford in 1996 when he described three new species of protozoa in geckos from Pakistan.

For instance, many DNA sequences have been identified for Haemoproteus in birds around the world in recent years, leading to new knowledge about the previously unknown diversity of this parasite in different regions.

[3] The species infecting avian hosts have been divided into two subgenera — Haemoproteus and Parahaemoproteus — a division proposed in 1965 by Bennett et al..

Although the majority are parasites of the Columbiformes, some species from this subgenus have also been reported in the Charadriiformes, Pelecaniformes and Suliformes.

The oocysts rupture and release numerous sporozoites that invade the salivary gland and serve as a focus of subsequent infection for another host once the insect takes its next blood meal.

The organisms occupy the majority of the cytoplasm, leaving the light magenta, finely granular, pink nucleus centrally located.

The gametocytes have five basic forms: Pigment granules are refractile and yellow to brown in colour.

Experimental infection of turkeys with H. meleagridis resulted in lameness, diarrhea, depression, emaciation, anorexia and occasionally anemia.

Importantly, new records of Haemoproteus are discovered constantly and should still be monitored for effects on host condition.

Instead the larvae hatch in utero, are fed internally by "milk glands," and pass through three morphological stages before being deposited to pupate.

The concept of a "one host-one species" was originally used in the taxonomy of this genus as it appears that the parasites are at least moderately host specific.

The avian species known to be infected are listed below: Order Accipitriformes Family Accipitridae A 2024 study found that the Haemoproteus species from accipitrid birds formed a distinct clade, found in these birds only and which might be classified into a separate subgenus or even genus.

urbanensis Sachs 1953 and Haemoproteus zasukhini Burtikashvili 1973 are considered to be synonyms of H. passeris Kruse 1890.