Hematozoa is a subclass of

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

of the

Apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. T ...

clade. Well known examples include the ''

Plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a vert ...

'' spp. which cause

malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...

in humans and Theilera which causes theileriosis in cattle. A large number of species are known to infect

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s and are transmitted by

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

vectors. The pattern in which Haematozoa infect a host cell depends on the genera of the blood parasite. ''Plasmodium'' and ''Leucozytozoon'' displace the nucleus of the host cell so that the parasite can take control of the cell where as ''Hemoproteus'' completely envelops the nucleus in a host cell. Infections of haematozoa can have adverse fitness effects on certain species. Species that have been isolated or have not been exposed to the infection have been found to be especially vulnerable to

pathogenic In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

effects. The infection effects can persist in avian host species through long-distance migrations. Blood parasites that have been studied were found to be transmitted by

hematophagous Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice by certain animals of feeding on blood (from the Greek words αἷμα ' "blood" and φαγεῖν ' "to eat"). Since blood is a fluid tissue rich in nutritious p ...

(bloodsucking)

dipteran Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...

(insect) vectors that have life stages in both aquatic and aerial environments.

Plasmodium

'', a genus consisting of over 170 species, infects mammals, reptiles, birds, and amphibians. Blood parasites of the ''Plasmodium'' genus cause

, which most commonly infect vertebrates with only four strains known to infect humans. Species of blood parasites that infect humans include ''Plasmodium falciparum, Plasmodium vivax, Plasmodiun ovale,'' and ''Plasmodium malariae''. The parasites are transmitted through malaria infected mosquitos which inject

sporozoites Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

, the parasite's infective cells, into human hosts. When injected, sporozoites migrate to the liver where they replicate and rupture to increase the spread of the parasitic infection inside the host. The study of ''Plasmodium'' parasites has been significant in serving the role as a model organism for human malaria research. Similarities in pathological effects of parasites on avian hosts have been found in parasites infected with malaria in humans by transmission of

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

bites.

Theileria

Theileria ''Theileria'' is a genus of parasites that belongs to the phylum Apicomplexa, and is closely related to ''Plasmodium''. Two ''Theileria'' species, ''T. annulata'' and ''T. parva'', are important cattle parasites. ''T. annulata'' causes tropical ...

'' is a haematozoan parasite, mainly found in coastal areas, that is transmitted by ''Haemaphysalis longicornis'' ticks that emerged from the Eastern hemisphere. Cases of ''Theileria orientalis'' were recently found in the Eastern United States in 2017 where cattle in Virginia presented symptoms concurrent with the parasite. However, further investigation identified the tick to be prevalent in the United States as early as 2010, with eight other states along the coast detecting this parasite. The ''Theileria orientalis'' parasite, like other haematozoa, infect erythrocytes, causing chronic anemia resulting in illness and death of cattle. Infections by the tick parasite induce symptoms such as anemia, jaundice, and anorexia in cattle. Cattle imported from prevalent ''Theileria orientalis'' areas are often quarantined from a naïve herd to prevent the spread of the parasite to susceptible cattle. Identification of ''Theileria orientalis'' is achieved by the sequencing of blood samples to identify two key features of the parasite, a small ribosomal subunit and a major piroplasm surface protein.

Avian infections

Avian haemosporidians include the ''Plasmodium, Haemoproteus, and Leucocytozoon'' genera. Avian species can have mixed infections in which multiple genera of haemosporidians are involved, which provides additional challenges in identification of the haemosporidian. Avian haemosporidians are expressed globally with the exception of polar regions. They are mainly found in wet tropical climates, which provide easy transmission of haematozoan infections. Avian species serve adequate hosts that transmit haematozoa during migratory periods, which increases fitness of the parasite. Avian species that exist in large flocks, such as

Waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which in ...

, are adequate hosts and easily transmit the infection due to close proximity in flocks. Symptoms of avian haemosporidians include anemia, weight loss, and mortality. Haemosporidian parasites are detected by highly sensitive and specific PCR techniques as well as microscopic examination. The parasites are important to understand the infections and strategies to prevent further transmission of the parasite.

References

{{Reflist Eukaryotic microbiology

Plasmodium

Theileria

Avian infections

See also

References