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Cryptosporidium spp. (Pathogen)

Organism:
This organism belongs to the coccidia, is a true pathogen, and causes cryptosporidiosis.  The round oocysts measure 4-6 µm and are most commonly found in fecal specimens. What was previously called Cryptosporidium parvum and was thought to be the primary Cryptosporidium species infecting humans is now classified as two separate species, C. parvum (mammals, including humans) and C. hominis (primarily humans).  Differentiation of these two species based on oocyst morphology is not possible.

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Life Cycle:
Intestine, oocysts passed in feces, are immediately infectious, survive in the environment, and are transmitted via contaminated food and/or water.  Extraintestinal infections can occur in the gall bladder, lungs, liver, and pancreas, primarily in severely immunocompromised patients.
Internal autoinfection occurs, particularly in the compromised patient; immunocompetent patients tend to self cure over a period of a few weeks.

Acquired:
Fecal-oral transmission via oocyst form; contaminated food and water

Epidemiology:
Worldwide, primarily human-to-human transmission, also animal-to-human transmission

Clinical Features:
Intestinal: Intermittent diarrhea (5-10 watery, frothy bowel movements per day), nausea, low-grade fever, abdominal cramps, anorexia; some may have relatively few symptoms.
Extraintestinal:  Immunocompromised patients cannot self-cure; the illness is chronic and becomes progressively worse, and the sequelae may be a major factor leading to death.
Once the primary infection has been established, the immune status of the host plays a very important role in determining the length and severity of the illness.

Clinical Specimen:
Intestinal:  Stool, examination of mucosal surface (biopsy)
Extraintestinal:  Fluids, biopsy specimens

Laboratory Diagnosis:
Intestinal:  Ova and Parasite examination (concentration ONLY); from concentrate sediment, (500 x g for 10 min) modified acid-fast stains are performed.  Fecal immunoassays are also available (FA, EIA, immunochromatographic cartridges).   Multiple fecal examinations may be required to recover the organisms, particularly if the stools are formed; there is a direct relationship between the stool consistency and the number of oocysts present (diarrhea = more oocysts).
Extraintestinal:  Modified acid-fast stains
Tissue:  Found at all levels of the intestinal tract, with the jejunum being the most heavily infected site.  Routine H&E staining is sufficient to demonstrate the organisms.  Under regular light microscopy, the organisms are visible as small (~1 – 3 µm) round structures aligned along the brush border (intracellular, but extracytoplasmic and found in parasitophorous vacuoles).

Organism Description:
Oocyst:  Round oocysts, containing 4 sporozoites.  However, sporozoites are not always seen in every oocyst; the oocysts are immediately infectious when passed (even if sporozoites are not visible).
Tissue:  Oocysts (~1 – 3 µm) can be seen aligned along the brush border (intracellular, but extracytoplasmic and found in parasitophorous vacuoles).

Laboratory Report:
Cryptosporidium spp.oocysts

Treatment: 
Garcia, L.S. 2007.  Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, D.C.
Although a number of drugs have been tested, none are totally effective.

Control:
Improved hygiene, adequate disposal of fecal waste, adequate washing of contaminated fruits and vegetables; prevention of human-animal contact, particularly cattle