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| Genus: | Haemoproteus
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Haemoproteus aegnithidaede | |
Haemoproteus is a genus of protozoa that are parasitic in birds, reptiles and amphibians. The genus created was by Kruse in 1890. Its name is derived from Greek: Haima - blood and Proteus - a sea god who had the power of assuming different shapes. Three other genera - Halteridium, Haemocystidium 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, louse flies (Hippoboscidae) and biting midges (Culicoides).
Within the genus there are 133 species, 5 varieties and 1 subspecies. Of these 114 occur in birds, 16 in reptiles and 3 in amphibia: 14 orders and 47 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).
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.
The earliest known fossil is of a Haemoproteus like organism was found in the abdominal cavity of a female biting midge trapped 100 million years ago in amber and found in Myanmar.[1]
Pigment granules are refractile and yellow to brown in colour.
Infections with most Haemoproteus species appear to produce subclinical infections.
Post-mortem findings include enlargement of the spleen, liver and kidneys. These organs may appear chocolate-brown due to hemozoin deposition. Cytologic imprints may reveal schizont-laden endothelial cells. Some species of Haemoproteus will also form large, cyst-like bodies within the skeletal muscles that resembling those seen with Sarcocystis species infections.
Experimental infection of turkeys with Haemoproteus meleagridis resulted in lameness, diarrhea, depression, emaciation, anorexia and occasionally anemia.
Muscovey ducks infected with Haemoproteus nettionis suffered lameness, dyspnea and sudden death.
Pigeons infected with Haemoproteus columbae had enlarged gizzards.
In other avian species, anemia, anorexia and depression have been reported occasionally.