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Coccidia (Coccidiasina) are a subclass of microscopic,
spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...
-forming, single-celled
obligate intracellular parasite Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. Types of parasites There are two main types of intracellular parasites: Facultative and Obligate. Facultative intracellular par ...
s belonging to 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. Th ...
n class
Conoidasida Conoidasida is a class of parasitic alveolates in the phylum Apicomplexa. The class was defined in 1988 by Levine and contains two subclasses – the coccidia and the gregarines. All members of this class have a complete, hollow, truncated ...
. As obligate intracellular parasites, they must live and reproduce within an
animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
cell. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa. Infection with these parasites is known as
coccidiosis Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in ...
. Coccidia can infect all mammals, some birds, some fish, some reptiles, and some amphibians. Most species of coccidia are species-specific in their host. An exception is '' Toxoplasma gondii'', which can infect all mammals, although it can only undergo sexual reproduction in cats. Depending on the species of coccidia, infection can cause fever, vomiting, diarrhea, muscle pain, and nervous system effects and changes to behavior, and may lead to death. Healthy adults may recover without medication—but those who are immunocompromised or young almost certainly require medication to prevent death. Humans generally become infected by eating under-cooked meat, but can contract infection with ''T. gondii'' by poor hygiene when handling cat waste.


Taxonomy

The class is divided into four orders, which are distinguished by the presence or absence of various asexual and sexual stages: *Order
Agamococcidiorida Agamococcidiorida is an order within the subclass Coccidia of the phylum Apicomplexia. All members of this order are parasitic protozoa. They are found in marine annelids. Taxonomy Two families are recognised in this order. Life cycle Bot ...
Levine-1979 *Order
Eucoccidiorida The Eucoccidiorida are an order of microscopic, spore-forming, single-celled parasites belonging to the apicomplexan class Conoidasida. Protozoans of this order include parasites of humans, and both domesticated and wild animals including birds. ...
Léger & Duboscq-1910 *Order Ixorheorida Levine-1984 *Order
Protococcidiorida Protococcidiorida is an order within the subclass Conoidasida of the phylum Apicomplexia. All members of this order are parasitic protozoa. The order was created by Kheisin in 1956. The species in this order infect annelids. There are five ...
Kheisin-1956 The order Eucoccidiorida is divided into two suborders. These two groups differ in their sexual development: syzygy for
Adeleorina ''Adeleorina'' is a suborder of parasites in the phylum Apicomplexa. History Léger proposed this taxon in 1911. The first species identified was '' Dactylosoma ranarum'' by Lankester (1871) in a frog in Europe. It was initially called ''Unduli ...
and independent gametes for
Eimeriorina Eimeriorina is a suborder of phylum Apicomplexa. All species in this clade are homoxenous or facultatively homoxenous. Merogony, gamogony and oocyst formation all occur within the same host. The hosts may be vertebrates or invertebrates. Erro ...
. The first suborder, Adeleorina, comprises coccidia of invertebrates and the coccidia that alternate between blood-sucking invertebrates and various vertebrates; this group includes '' Haemogregarina'' and ''
Hepatozoon ''Hepatozoon'' is a genus of Apicomplexa alveolates 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 arthropod ...
''. There are seven families in this suborder. The second suborder, Eimeriorina, comprises coccidia of a variety of coccidia many of form cysts. A number of genera, including ''
Toxoplasma ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as ...
'' and ''
Sarcocystis ''Sarcocystis'' is a genus of protozoan parasites, with many species infecting mammals, reptiles and birds. Its name is dervived from Greek ''sarx'' = flesh and ''kystis'' = bladder. The lifecycle of a typical member of this genus involves two ...
'', infect vertebrates.


Coccidiosis


Transmission

Infected animals spread spores called oocysts in their stool. The oocysts mature, called sporulation. When another animal passes over the location where the feces were deposited, it may pick up the spores, which it then ingests when grooming itself. Mice may ingest the spores and become infected. When another animal eats the mouse, it becomes infected. Some species of coccidia are transmissible to humans, including
toxoplasma ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as ...
and
cryptosporidium ''Cryptosporidium'', sometimes informally called crypto, is a genus of apicomplexan parasitic alveolates that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (intestinal cryptos ...
.


Infection

Inside the host, the sporulated oocyst opens, and eight sporozoites are released. Each one finds a home in an intestinal cell and starts the process of reproduction. These offspring are called merozoites. When the cell is stuffed full of merozoites, it bursts open, and each merozoite finds its own intestinal cell to continue the cycle.


Symptoms of infection

As the infection continues, millions of intestinal cells may become infected. As they break open, they produce a bloody, watery diarrhea. This can cause dehydration, and can lead to death in young or small pets. Coccidian infections display symptoms mainly from the digestive tract including diarrhea, inflammation, intestinal pain or damage, vomiting, and irregular nutrition. These can lead to weight loss or reduced growth development, anemia, exhaustion, and even death in severe cases.


Diagnosis and treatment

Coccidiosis can be diagnosed by finding oocysts in fecal smears. In early stages of the disease, there may be very few oocysts being shed, and a negative test does not rule out the disease. Coccidiosis is most commonly treated through the administration of
coccidiostat A coccidiostat is an antiprotozoal agent that acts upon Coccidia parasites. Examples include: * Amprolium * Arprinocid * Artemether * Clazuril * Clopidol * Decoquinate * Diclazuril * Dinitolmide * Ethopabate * Halofuginone * Lasalocid * ...
s, a group of medications that stop coccidia from reproducing. In dogs and cats, the most commonly administered coccidiostat is sulfa-based
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
s. Once reproduction stops, the animal can usually recover on its own, a process that can take a few weeks, depending on the severity of the infection and the strength of the animal's immune system.


See also

*
Cryptosporidium ''Cryptosporidium'', sometimes informally called crypto, is a genus of apicomplexan parasitic alveolates that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (intestinal cryptos ...
(the organism) and
Cryptosporidiosis Cryptosporidiosis, sometimes informally called crypto, is a parasitic disease caused by ''Cryptosporidium'', a genus of protozoan parasites in the phylum Apicomplexa. It affects the distal small intestine and can affect the respiratory tract i ...
(the resulting disease) *
Toxoplasma ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as ...
(the organism) and Toxoplasmosis (the resulting disease) *
Cyclospora cayetanensis ''Cyclospora cayetanensis'' is a coccidian parasite that causes a diarrheal disease called cyclosporiasis in humans and possibly in other primates. Originally reported as a novel pathogen of probable coccidian nature in the 1980s and described i ...
(the organism) and
Cyclosporiasis Cyclosporiasis is a disease caused by infection with ''Cyclospora cayetanensis'', a pathogenic protozoan transmitted by feces or feces-contaminated food and water. Outbreaks have been reported due to contaminated fruits and vegetables. It is not ...
(the resulting disease) * List of parasites (human) *
Zoalene Dinitolmide (or zoalene) is a fodder additive for poultry, used to prevent coccidiosis infections. It is sold under trade names such as Coccidine A, Coccidot, and Zoamix. Dinitolmide is usually added to feed in doses of 125 ppm (preventive ...
, a fodder additive for poultry, used to prevent infections from coccidia *
Ponazuril Ponazuril ( INN), sold by Merial, Inc., now part of Boehringer Ingelheim, under the trade name Marquis® (15% w/w ponazuril), is a drug currently approved for the treatment of equine protozoal myeloencephalitis (EPM) in horses, caused by coccidia ...
, a drug used to treat protozoan infection in large animals that has shown effectiveness at treating coccidiosis in shelter puppies and kittens


References


Further reading

* Describes using live-parasite vaccine versus a monoclonal antibody to block the sporozoite from invading a host's cell. *


External links

* * * * * {{Taxonbar, from=Q1147204 Conoidasida Dog diseases Cat diseases Animal diseases Veterinary protozoology SAR supergroup subclasses