Hepatocystis is a genus of parasitic protozoa transmitted by midges of the Culicoides

Culicoides

Culicoides is a genus of biting midges in the subfamily Ceratopogonidae. Around 500 species of Ceratopogonidae are at present placed in the genus and this is split into many subgenera. Several species are known to be vectors of various diseases and parasites which can affect animals.-Notable...

 genus. Hosts include Old World primates, bats

Bats

A bat is a flying mammal in the Chiroptera order.Bats may also refer to:-Films:*Bats , starring Lou Diamond Phillips and Bob Gunton*Bats: Human Harvest -Groups:...

, hippopotamus

Hippopotamus

The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...

 and squirrels. This genus is not found in the New World. The genus was created by Miller in 1908.

The type species is Hepatocystis kochi.

There are currently 25 recognised species in this genus.

History

The first observation of malaria in bats dates to the end of the 19th century when Dionisi described gametocytes in the blood of a bat in 1988.
The type species of this genus (Hepatocystis kochi) was described by Laveran in 1899 from the blood of a primate and he named it Plasmodium kochi.

Life cycle

The protozoa are transmitted by the bite of the insect vector. The sporozoites migrate to the liver where they typically form merocysts within the liver paranchema. These may also develop in the spleen and lungs. Macroscopically these may appear as white to gray nodular foci within the tissue. These lesions within these organs are characterized by well-circumscribed focal fibrosis, accumulation of eosinophils and histiocyte

Histiocyte

A histiocyte is a cell that is part of the mononuclear phagocyte system . The mononuclear phagocytic system is part of the organism's immune system...

s, hamorrhage or hamosiderosis with the loss of normal architecture.

The cystlike exoerythrocytic schizonts are found within the merocysts. These found around the edges of the merocytes in huge numbers. The central core of the cyst consists of a non cellular granular material.

Released merozoites either invade other hepatocytes or erythrocytes. Within the erythrocytes the merozoites first become ring forms, then trophozoites and finally gametocyte

Gametocyte

A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called spermatocytes, and female gametocytes are called oocytes....

s. The gametocytes are huge and fill the entire erythrocyte. Like those of Plasmodium

Plasmodium

Plasmodium is a genus of parasitic protists. Infection by these organisms is known as malaria. The genus Plasmodium was described in 1885 by Ettore Marchiafava and Angelo Celli. Currently over 200 species of this genus are recognized and new species continue to be described.Of the over 200 known...

 and unlike those of Hepatozoon

Hepatozoon

Hepatozoon is a genus of Apicomplexan protozoa which incorporates over 300 species obligate intraerythrocytic parasites. Species have been described from all groups of tetrapod vertebrates, as well as a wide range of haematophagous arthropods, which serve as both the vectors and definitive hosts of...

 their nuclei are Feulgen negative. Haemozoin may be found within the erythrocytes.

Infected erythrocytes are then taken up when the insect vector feeds on the host.

Within the vector the sporogonic cycle lasts between 5–6 days. The oocysts develop in the haemocoele chiefly in the head near the brain and eye.

Pathology

The mature merocysts are visible to the naked eye on the hepatic surface. These appear as raised, grayish-white to translucent foci with a central accumulation of fluid. Multiple, depressed areas of fibrosis with calcification representing healed lesions may also be found.

Microscopically the liver cysts have an irregular central space filled with faintly eosinophilic, acellular, flocculent material. Surrounding this is a peripheral rim of myriad, round, lightly basophilic merozoites which measure ~1.0–2.0 mm in diameter. The cysts themselves are delineated by a thin, convoluted, eosinophilic, hyaline capsule. A significant inflammatory response to the merocysts may or may not be present. If a reaction is present, it is typically granulomatous with an admixture of eosinophils and lymphocyte

Lymphocyte

A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...

s.

The first appearance in the blood is normally two months after infection. The only stage seen in the blood are gametocytes. These double in number for the first three days and mature. Having reached maturity, they gradually decline in number and normally disappear after a month. Secondary episodes may occur at variable intervals.

The early gametocytes consist of minute dense spots of chromatin with a tiny loop of cytoplasm. As the parasite grows, the chromatin tends to spread in a semicircle or into multiple dots. There is no stippling of the erythrocyte.

Mature gametocytes are larger than a normal erythrocyte stain poorly compared to other protozoa. In both male and female gametocytes, the nucleus consists of two portions.

The macrogametocyte is a steel blue color measuring 9.5 micrometres in diameter. The nucleus has a pale pink area with dense chromatin in the middle and is much smaller than that of the microgametocyte.

The microgametocyte stains less densely, is biscuit-colored and measures 9.0 micrometres in diameter. The nucleus is a large, oval, pale pink area occupying one-third to one-half of the parasite.

Clinical features

In endemic areas, the incidence can range from 24 to 75% in nonhuman primates.

Although infection with Hepatocystis does not normally cause fever it may cause anaemia in the host.

Some versions of the Duffy antigen

Duffy antigen

Duffy antigen/chemokine receptor also known as Fy glycoprotein or CD234 is a protein that in humans is encoded by the DARC gene....

 have been associated with protection from Hepatocytis infection in yellow baboons (Papio cynocephalus).

Host records

Primates and bats are the most commonly identified host of these parasites.

H. bouillezi, H. cercopitheci, H. kochi and H. simiae infect Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

n monkeys.

H. semnopitheci and H. taiwanensis infect Oriental monkeys.

These species may lie in different phylogenetic clades but this is not yet known.

Hosts where parasite species is known

H. bainae - Cantor's roundleaf bat (Hipposideros galeritus)

H. bouillezi - mona monkey (Cercopithecus mona)

H. brosseti - Franquet's epauletted fruit bat (Epomops franqueti)

H. carpenteri - hammerhead bat (Hypsignathus monstrosus)

H. cercopitheci - De Brazza's monkey (Cercopithecus neglectus) and greater spot nosed monkey (Cercopithecus nictitans).

H. epomorphori - fruit bat (Epomorphorus gambianus)

H. garnhami - greater short nosed fruit bat (Cynopterus sphinx)

H. hippopotami - hippopotamus (Hippopotamus amphibius)

H. hipposideri - large leafnosed bat (Hipposideros armiger terasensis).

H. kochi - African green monkeys (Cercopithecus aethiops), black mangabey (Cercocebus aterrimus), black crested gibbon (Hylobates concolor)

H. levinei - grey-headed flying-fox (Pteropus poliocephalus)

H. muuli - Berdmore's ground squirrel (Menetes berdmorei)

H. perronnae - Angola

Angola

Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...

n fruit bat (Lissonycteris angolensis), little collared fruit bat (Myonycteris torquata),

H. pteropi - bat (Cynopterus bracyotis), Horsefield's fruit bat (Cynopterus horsfieldi), bat (Pteropus colinus), common flying fox (Pteropus edwarsii), spectacled flying fox (Pteropus conspicillatus), fruit bat (Pteropus geddiei), black flying fox (Pteropus gouldi), grey-headed flying fox (Pteropus poliocephalus), little red flying fox (Pteropus sacpulatus)

H. rhodiani - bat (Hipposideros galeritus)

H. simiae - chacma baboon (Papio ursinus)

H. semnopitheci - crab eating macque (Macaca irus), Sunda Island leaf monkey (Presbytis aygula)

H. taiwanensis - Formosan rock macque (Macaca cyclopis)

H. vassali - squirrel (Callosciurus flavimanus)

Parasite species unknown

red bellied tree squirrel (Callosciurus erythraeus)

lesser short nosed fruit bat (Cynopterus brachyotis)

fruit bat (Cynopterus horsfieldi)

bare backed fruit bat (Dobsonia moluccense)

Ethiopia

Ethiopia

Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...

n epauletted fruit bat (Epomophorus labiatus)

large leafnosed bat (Hipposideros armiger terasensis)

diadem leaf nosed bat (Hipposideros diadema)

white cheeked gibbon (Hylobates concolor)

Formosa

Formosa

Formosa or Ilha Formosa is a Portuguese historical name for Taiwan , literally meaning, "Beautiful Island". The term may also refer to:-Places:* Formosa Strait, another name for the Taiwan Strait...

n macaque (Macaca cyclopis)

southern pig tailed macque (Macaca nemestrina)

long winged bat (Miniopterus schreibersii)

olive baboon (Papio anubis)

yellow baboons (Papio cynocephalus)

Formosan giant flying squirrel (Petaurista grandis)

orangutan (Pongo pygmaeus)

black flying fox (Pteropus alecto)

small flying fox (Pteropus hypomelanus)

horse shoe bat (Rhinolophus) species

Vectors

Known vectors belong to the genus Culicoides

Culicoides

Culicoides is a genus of biting midges in the subfamily Ceratopogonidae. Around 500 species of Ceratopogonidae are at present placed in the genus and this is split into many subgenera. Several species are known to be vectors of various diseases and parasites which can affect animals.-Notable...

. Species of the genus Streblidae

Streblidae

Streblidae are flies in the superfamily Hippoboscoidea, and together with their relatives the Nycteribiidae are known as "bat flies". They are winged or wingless ectoparasites of bats, and often have long legs...

 may also be able to act as vectors but this is not yet certain.

• H. brayi - Culicoides nubeculosus and Culicoides variipennis

• H. kochi - Culicoides adersi Ingram and Macfie 1923

• H. levinei - Culicoides nubeculosus