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Cryptosporidium muris.jpg
Cryptosporidium muris oocysts found in human feces.
Scientific classification Red Pencil Icon.png
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Apicomplexa
Class: Conoidasida
Order: Eucoccidiorida
Suborder: Eimeriorina
Family: Cryptosporidiidae
Genus: Cryptosporidium
Tyzzer, 1907

Cryptosporidium andersoni
Cryptosporidium bailey
Cryptosporidium bovis
Cryptosporidium cervine
Cryptosporidium canis
Cryptosporidium cuniculus
Cryptosporidium ducismarci
Cryptosporidium fayeri
Cryptosporidium felis
Cryptosporidium fragile
Cryptosporidium galli
Cryptosporidium hominis
Cryptosporidium marcopodum
Cryptosporidium meleagridis
Cryptosporidium molnari
Cryptosporidium muris
Cryptosporidium parvum
Cryptosporidium ryanae
Cryptosporidium saurophilum
Cryptosporidium serpentis
Cryptosporidium suis
Cryptosporidium ubiquitum
Cryptosporidium viatorum
Cryptosporidium wrairi
Cryptosporidium xiaoi


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 cryptosporidiosis), sometimes with a persistent cough (respiratory cryptosporidiosis). [1] [2]

Treatment of gastrointestinal infection in humans involves fluid rehydration, electrolyte replacement, and management of any pain. As of January 2015, nitazoxanide is the only drug approved for the treatment of cryptosporidiosis in immunocompetent hosts. [3] Supplemental zinc may improve symptoms, [3] particularly in recurrent or persistent infections or in others at risk for zinc deficiency. Cryptosporidium oocysts are 4–6  μm in diameter and exhibit partial acid-fast staining. They must be differentiated from other partially acid-fast organisms including Cyclospora cayetanensis .

General characteristics

Cryptosporidium causes cryptosporidiosis, an infection that may present as a diarrhoea, sometimes with a persistent cough in immunocompetent hosts.[ clarification needed ] [1] Other apicomplexan pathogens include the malaria parasite Plasmodium and the toxoplasmosis parasite Toxoplasma . Unlike Plasmodium, which transmits via a mosquito vector, Cryptosporidium does not use an insect vector, and is capable of completing its lifecycle within a single host, resulting in cyst stages that are excreted in feces or through inhalation of coughed on fomites and are capable of transmission to a new host. [1] [4] [5]

A number of Cryptosporidium species infect mammals. In humans, the main causes of disease are C. parvum and C. hominis (previously C. parvum genotype 1). C. canis, C. felis, C. meleagridis, and C. muris can also cause disease in humans. [4]

Cryptosporidiosis is typically an acute, short-term infection, can be recurrent through reinfection in immunocompetent hosts, and become severe or life-threatening in immunocompromised individuals. In humans, it remains in the lower intestine and may remain for up to five weeks. [4] The parasite is transmitted by environmentally hardy cysts (oocysts) that, once ingested, exist in the small intestine and result in an infection of intestinal epithelial tissue. [4] Transmission by ingestion or inhalation of coughed on fomites is a second, less likely route of infection. [1]

The genome of Cryptosporidium parvum, sequenced in 2004, was found to be unusual amongst eukaryotes in that the mitochondria seem not to contain DNA. [6] A closely related species, C. hominis, also has its genome sequence available. [7]

Life cycle

Life cycle of Cryptosporidium spp. Cryptosporidiosis 01.png
Life cycle of Cryptosporidium spp.

Cryptosporidium has three developmental stages: meronts, gamonts and oocysts. [8] They reproduce within the intestinal epithelial cells. [9] The Cryptosporidium spore phase (oocyst) can survive for lengthy periods outside a host. It can also resist many common disinfectants, including chlorine-based disinfectants. [10]

Water treatment and detection

Many treatment plants that take raw water from rivers, lakes, and reservoirs for public drinking water production use conventional filtration technologies. Direct filtration, which is typically used to treat water with low particulate levels, includes coagulation and filtration but not sedimentation. Other common filtration processes including slow sand filters, diatomaceous earth filters, and membranes will remove 99% of Cryptosporidium. [11] Membranes and bag- and cartridge-filter products remove Cryptosporidium specifically.

Cryptosporidium is highly resistant to chlorine disinfection; [12] but with high enough concentrations and contact time, Cryptosporidium inactivation will occur with chlorine dioxide and ozone treatment. In general, the required levels of chlorine preclude the use of chlorine disinfection as a reliable method to control Cryptosporidium in drinking water. Ultraviolet light treatment at relatively low doses will inactivate Cryptosporidium. Calgon Carbon-funded research originally discovered UV's efficacy in inactivating Cryptosporidium. [13] [14]

One of the largest challenges in identifying outbreaks is the ability to verify the results in a laboratory. The oocytes may be seen by microscopic examination of a stool sample, but they may be confused with other objects or artifacts similar in appearance. [15] Most cryptosporidia are 3–6 μm in size, although some reports have described larger cells. [15]

Boiling is believed to be the safest option for water contaminated by Cryptosporidium. [16] [17]


Exposure risks

Dealing with stabilized compost - i.e. composting material that has gone through the phases where micro-organisms are digesting the organic matter and the temperature inside the composting pile has reached temperature up to 50-70ºC - poses very little risk as these temperatures kill pathogens and even make oocysts unviable. [20]

Like many fecal-oral pathogens, the disease can also be transmitted by contaminated food, poor hygiene or turning compost in a local compost site. Testing of water, as well as epidemiological study, are necessary to determine the sources of specific infections. Cryptosporidium typically does not cause serious illness in healthy people. It may chronically sicken some children, as well as adults exposed and immunocompromised. A subset of the immunocompromised population is people with AIDS. Amongst homosexuals who have AIDS, insertive anal sex is an increased risk factor. [21] Analingus and oral-genital sex after anal-genital sex are known transmission routes. [22]

Other transmission routes include exposure to laboratory specimens. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Apicomplexa</span> Phylum of parasitic alveolates

The Apicomplexa 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. The organelle is an adaptation that the apicomplexan applies in penetration of a host cell.

<i>Toxoplasma gondii</i> Type of protozoan parasite

Toxoplasma gondii is a parasitic protozoan that causes toxoplasmosis. Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals, but felids are the only known definitive hosts in which the parasite may undergo sexual reproduction.

<span class="mw-page-title-main">Cryptosporidiosis</span> Parasitic disease

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 in both immunocompetent and immunocompromised individuals, resulting in watery diarrhea with or without an unexplained cough. In immunosuppressed individuals, the symptoms are particularly severe and can be fatal. It is primarily spread through the fecal-oral route, often through contaminated water; recent evidence suggests that it can also be transmitted via fomites contaminated with respiratory secretions.

In medicine, public health, and biology, transmission is the passing of a pathogen causing communicable disease from an infected host individual or group to a particular individual or group, regardless of whether the other individual was previously infected. The term strictly refers to the transmission of microorganisms directly from one individual to another by one or more of the following means:

<span class="mw-page-title-main">Coccidia</span> A subclass of protists

Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within an animal cell. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa.

<span class="mw-page-title-main">Natural reservoir</span> Type of population in infectious disease ecology

In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and reproduces, or upon which the pathogen primarily depends for its survival. A reservoir is usually a living host of a certain species, such as an animal or a plant, inside of which a pathogen survives, often without causing disease for the reservoir itself. By some definitions a reservoir may also be an environment external to an organism, such as a volume of contaminated air or water.

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 severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.

<i>Cryptosporidium parvum</i> Species of single-celled organism

Cryptosporidium parvum is one of several species that cause cryptosporidiosis, a parasitic disease of the mammalian intestinal tract.

Wilderness-acquired diarrhea is a variety of traveler's diarrhea in which backpackers and other outdoor enthusiasts are affected. Potential sources are contaminated food or water, or "hand-to-mouth", directly from another person who is infected. Cases generally resolve spontaneously, with or without treatment, and the cause is typically unknown. The National Outdoor Leadership School has recorded about one incident per 5,000 person-field days by following strict protocols on hygiene and water treatment. More limited, separate studies have presented highly varied estimated rates of affliction that range from 3 percent to 74 percent of wilderness visitors. One survey found that long-distance Appalachian Trail hikers reported diarrhea as their most common illness. Based on reviews of epidemiologic data and literature, some researchers believe that the risks have been over-stated and are poorly understood by the public.

<i>Cyclospora cayetanensis</i> Species of single-celled organism

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 in the early 1990s, it was virtually unknown in developed countries until awareness increased due to several outbreaks linked with fecally contaminated imported produce. C. cayetanensis has since emerged as an endemic cause of diarrheal disease in tropical countries and a cause of traveler's diarrhea and food-borne infections in developed nations. This species was placed in the genus Cyclospora because of the spherical shape of its sporocysts. The specific name refers to the Cayetano Heredia University in Lima, Peru, where early epidemiological and taxonomic work was done.

The 1993 Milwaukee cryptosporidiosis outbreak was a significant distribution of the Cryptosporidium protozoan in Milwaukee, Wisconsin, and the largest waterborne disease outbreak in documented United States history. It is suspected that The Howard Avenue Water Purification Plant, one of two water treatment plants in Milwaukee at the time, was contaminated. It is believed that the contamination was due to an ineffective filtration process. Approximately 403,000 residents were affected resulting in illness and hospitalization. Immediate repairs were made to the treatment facilities along with continued infrastructure upgrades during the 25 years since the outbreak. The total cost of the outbreak, in productivity loss and medical expenses, was $96 million. At least 69 people died as a result of the outbreak.

<span class="mw-page-title-main">Portable water purification</span> Self-contained, easily transported units used to purify water from untreated sources

Portable water purification devices are self-contained, easily transported units used to purify water from untreated sources for drinking purposes. Their main function is to eliminate pathogens, and often also of suspended solids and some unpalatable or toxic compounds.

<span class="mw-page-title-main">Nitazoxanide</span> Chemical compound

Nitazoxanide, sold under the brand name Alinia among others, is a broad-spectrum antiparasitic and broad-spectrum antiviral medication that is used in medicine for the treatment of various helminthic, protozoal, and viral infections. It is indicated for the treatment of infection by Cryptosporidium parvum and Giardia lamblia in immunocompetent individuals and has been repurposed for the treatment of influenza. Nitazoxanide has also been shown to have in vitro antiparasitic activity and clinical treatment efficacy for infections caused by other protozoa and helminths; evidence as of 2014 suggested that it possesses efficacy in treating a number of viral infections as well.

Cryptosporidium hominis, along with Cryptosporidium parvum, is among the medically important Cryptosporidium species. It is an obligate parasite of humans that can colonize the gastrointestinal tract resulting in the gastroenteritis and diarrhea characteristic of cryptosporidiosis. Unlike C. parvum, which has a rather broad host range, C. hominis is almost exclusively a parasite of humans. As a result, C. hominis has a low zoonotic potential compared to C. parvum. It is spread through the fecal-oral route usually by drinking water contaminated with oocyst laden feces. There are many exposure risks that people can encounter in affected areas of the world. Cryptosporidium infections are large contributors of child death and illness in heavily affected areas, yet low importance has been placed on both identifying the species and finding more treatment options outside of nitazoxanide for children and AIDS patients.

<span class="mw-page-title-main">Protozoan infection</span> Parasitic disease caused by a protozoan

Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. They are usually contracted by either an insect vector or by contact with an infected substance or surface and include organisms that are now classified in the supergroups Excavata, Amoebozoa, SAR, and Archaeplastida.

<span class="mw-page-title-main">Eukaryotic Pathogen Database</span>

The Eukaryotic Pathgen Database, or EuPathDB, is a database of bioinformatic and experimental data related to a variety of eukaryotic pathogens. It was established in 2006 under a National Institutes of Health program to create Bioinformatics Resource Centers to facilitate research on pathogens that may pose biodefense threats. EuPathDB stores data related to its organisms of interest and provides tools for searching through and analyzing the data. It currently consists of 14 component databases, each dedicated to a certain research topic. EuPathDB includes:

Cryptosporidium muris is a species of coccidium, first isolated from the gastric glands of the common mouse. Cryptosporidium does originate in common mice, specifically laboratory mice. However, it also has infected cows, dogs, cats, rats, rabbits, lambs, and humans and other primates.

<span class="mw-page-title-main">Feline zoonosis</span> Medical condition

A feline zoonosis is a viral, bacterial, fungal, protozoan, nematode or arthropod infection that can be transmitted to humans from the domesticated cat, Felis catus. Some of these diseases are reemerging and newly emerging infections or infestations caused by zoonotic pathogens transmitted by cats. In some instances, the cat can display symptoms of infection and sometimes the cat remains asymptomatic. There can be serious illnesses and clinical manifestations in people who become infected. This is dependent on the immune status and age of the person. Those who live in close association with cats are more prone to these infections. But those that do not keep cats as pets are also able to acquire these infections because of the transmission can be from cat feces and the parasites that leave their bodies.

Cryptosporidium varanii is a protozoal parasite that infects the gastrointestinal tract of lizards. C. varanii is often shed in the feces, and transmission is primarily via fecal-oral route. Unlike Cryptosporidium serpentis, C. varanii does not colonize the stomach, but rather the intestines of most infected lizards, such as geckos. An exception to this rule are monitor lizards, as gastric (stomach) lesions have been found in those species. Oocysts of lizard Cryptosporidium are larger than the snake counterpart.

Cryptosporidium serpentis is a protozoal parasite that infects the gastrointestinal tract of snakes. Sporated oocysts of C. serpentis are intermittently shed in the feces, and transmission is primarily via fecal-oral route. C. serpentis is a gastric parasite, primarily colonizing the stomach. Unlike mammalian Cryptosporidium - that is usually self-limiting - C. serpentis remains chronic and in most cases, eventually lethal in snakes once an animal has become symptomatic. However, recent advancements in detection have led to the identification of healthy carrier animals some of which have thus far remained in good health for years and cast doubt on previous assumptions about the lethality of the parasite, though it remains to be seen how many carriers will remain healthy and for how long as most such animals are euthanized immediately. Cryptosporidiosis infection has been documented in a variety of snake species worldwide, such as North American Corn snakes and Australian Taipans, both free-living and captive. Necropsy examinations of expired captive snakes infected with C. serpentis note characteristic gastric mucosal hypertrophy that, in time, narrows the gastric lumen, resulting in classic symptoms of repetitive regurgitation and anorexia. Due to the enlargement of the stomach lining, a noticeable midbody bulge can be palpable and commonly visible. Frequent mucoid stools have been reported. However, some snakes will display no external symptoms at all throughout their lifetime, yet still remain infectious to counterparts.


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Further reading