Haemoproteus is a genus of alveolates that are parasitic in birds, reptiles, and amphibians. Its name is derived from Greek: haima 'blood' and Proteus, a sea god that had the power to assume various shapes. The name Haemoproteus was first used in the description of H. columbae in the blood of the pigeon Columba livia by Walther Kruse in 1890. This was also the first description of this genus. Two other genera—Halteridium and Simondia—are now considered to be synonyms of Haemoproteus. The protozoa are intracellular parasites that infect the erythrocytes. They are transmitted by blood-sucking insects including mosquitoes, biting midges (Culicoides), louse flies (Hippoboscidae) and horse-flies ("tabanids", "tabanid flies"). Infection with this genus is sometimes known as pseudomalaria because of the parasites' similarities with Plasmodium species. Within the genus there are at least 173 species, 5 varieties and 1 subspecies. Of these over 140 occur in birds, 16 in reptiles and 3 in amphibia: 14 orders and 50 families of birds are represented. These include gamebirds (Galliformes), waterfowl (Anseriformes), raptors (Accipitriformes, Falconiformes, Strigiformes), pigeons and doves (Columbiformes), and perching birds or songbirds (Passeriformes).
Taxonomy and systematics
Evolution The earliest known fossil is of a Haemoproteus-like organism (Paleohaemoproteus burmacis) was found in the abdominal cavity of a female biting midge trapped 100 million years ago in amber found in Myanmar.
Taxonomic history The first description of this genus was in 1890 by Kruse, who described H. columbae in the blood of the pigeon Columba livia. McCallum in 1897 showed that the process of exflagellation was part of sexual reproduction in these parasites and thought it probable that the same process occurred in Plasmodium. The first record of a haemoproteid parasite in a reptile was by Simond in 1901 who gave it the name H. metchnikovi. The Sergent brothers in 1906 showed that the ectoparasitic fly Pseudolynchia canariensis was the vector of H. columbae. Aragao in 1908 demonstrated the schizogonic stages of H. columbae in the endothelial cells of the lungs of nestling pigeons infected by the bite of infected Pseudolynchia. It was generally believed that transmission of the parasites was by regurgitation during a blood meal until Adie showed that the parasites develop in the salivary glands in a fashion analogous to that of Plasmodium in mosquitoes. 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. This genus was soon subsumed into the genus Haemoproteus. The genus Haemocystidium was created to give a name to the haemoproteid of a gecko belonging to the genus Hemidactylus in Sri Lanka by Castellani and Willey in 1904. 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. These species were transferred to Haemoproteus in 1926 by Wenyon. The genus was resurrected by Garnham in 1966 when he created a new generic name — Simondia — for the haemoproteids of chelonians. He followed the opinions of Wenyon, Hewitt and DeGiusti and suggested that all these parasites belonged to the one species — Simondia metchnikovi. He retained the name Haemocystidium for the haemoproteids of lizards. A different genus of vectors was identified in 1957 by Fallis and Wood when they identified H. nettionis in Culicoides downesi Wirth and Hubert in Ontario, Canada. 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. This genus like those of many protozoa may be further modified once additional DNA sequences are available. 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.
Subgenera The species infecting avian hosts have been divided into two subgenera — Haemoproteus and Parahaemoproteus — a division proposed in 1965 by Bennett et al.. These may be distinguished as follows: Haemoproteus: Vectors are hippoboscid flies (Hippoboscidae). Exflagellation does not occur below 20 degrees Celsius. Mature oocysts have diameters greater than 20 micrometres. The average length of the sporozoites is less than 10 micrometres. One end of the sporozoite is more pointed than the other. Although the majority are parasites of the Columbiformes, some species from this subgenus have also been reported in the Charadriiformes, Pelecaniformes and Suliformes. Parahaemoproteus: Parasites of birds other than the Columbiformes. Vectors are biting midges (Ceratopogonidae). Exflagellation occurs below 20 °C (68 °F). Mature oocysts have diameters less than 20 micrometres. The average length of the sporozoites is greater than 10 micrometres. Both ends of the sporozoite are equally pointed. While it was previously thought that Haemoproteus was limited to doves and related species, species in this genus have been isolated from frigatebirds.
Species list
Life cycle
The infective stage is the sporozoite which is present in the salivary glands of the vector. Once the vector bites a new host, the sporozoites enter the blood stream and invade endothelial cells of blood vessels within various tissues including those of the lung, liver and spleen. Within the endothelial cells, the sporozoites undergo asexual reproduction becoming schizonts. These in turn produce numerous merozoites which penetrate the erythrocytes and mature into either female gametocytes (macrogametocytes) or male gametocytes (microgametocytes). Gametocytes can then be ingested by another blood-sucking insect where they undergo sexual reproduction in the midgut of the insect to produce oocysts. 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.
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