View source for Cryptosporidium hominis

*A member of the [[Cryptosporidium]] which causes diarrheal disease in humans
*Similar to [[Cryptosporidium parvum]] which typically infects cows, but can also infect humans

==Background==

===Microbiology===

*Protozoan parasite in the genus [[Cryptosporidium species|''Cryptosporidium'']]

===Epidemiology===

*Infects humans, but can also infect cows, mice, gnotobiotic pigs, and rarely other species
*Transmitted fecal-oral via environmental contamination (such as recreational water), and can be spread person-to-person
**Outbreaks are most commonly associated with drinking water, even when properly treated
**Daycares (more common than [[Giardia]])
**Also seen with petting zoos and cider
**Higher rates of transmission in MSM
*Resistant to chlorination and can survive in the environment up to 6 months
*In developing countries, primarily affects children less than 5 years
*In developed countries, primarily affects adults, related to travel
**Causes 2-6% of traveller's diarrhea

===Life Cycle===

*Host ingests an '''oocyst''' (needing as few as 10 to cause disease)
*The oocyst excyst in the stomach and proximal small bowel, releasing four '''sporozoites'''
*Sporozoites bind to the intestinal epithelial cells and becomes vacuolized by the host cell membrane
*In the '''parasitophorous vacuole''', they reproduce asexually into further sporozoites, which divide into '''type I meronts'''
*The type I meronts mature and release motile '''merozoites'''
*The merozoites again attach to the intestinal epithelial cells
*Merozoites then either reproduce asexually, as above, or sexually
**Sexual reproduction involves a '''macrogamont''' and '''microgamont''', which form a '''zygote'''
**The zygote develops into an oocyst which contains four sporozoites
*Oocysts may be involved in auto-inoculation (if thin-walled) or environmental contamination (if thick-walled)

===Pathophysiology===

*Infection activates nuclear factor kappa B (NF-κB), which activates a large response
*Infection results in increased permeability of the intestinal mucosa
*T-cells are involved, with chronic infection in patients who are CD4-deplete

==Clinical Manifestations==

*Incubation period [[Usual incubation period::7 days]] (range [[Incubation period range::1 to 30 days]])

===Immunocompetent adults===

*Associated with waterborne outbreaks, travel, animal contacts, or child contacts
*Watery (to mucoid) diarrhea and malabsorption, more lower bowel symptoms
*May also have abdominal cramping, nausea or vomiting, and fever
*Lasts 5 to 14 days, but up to 100
*However, recurs in about 40% and can become an intermittent or chronic diarrhea similar to irritable bowel syndrome

===Childhood diarrhea===

*Causes about 10-15% of acute childhood diarrhea in developing countries
*Presents with watery diarrhea, cramps, and nausea and vomiting
*May also have fever, cough, dyspnea, and foul-smelling stool
*Can turn into chronic diarrhea and malabsorption

===People living with HIV===

*Most cases are asymptomatic or mild and self-limited
*Chronic infection more common in HIV with CD4 <150, lasting up to 6 months
*May also involve extraintestinal cryptosporidiosis, such as biliary or respiratory disease

===Other immunocompromised patients===

*May present similarly to HIV
*Includes solid organ transplant, hematopoietic stem cell transplant, and hyper-IgM syndrome

==Diagnosis==

*Stool microscopy
**Seen on modified acid-fast staining (70% sensitive)
**Can do immunofluorescence as well (more sensitive)
*Stool antigen
*PCR

==Management==

*For immunocompetent hosts, supportive care, including fluids and antimotility agents like loperamide, is generally adequate
*In immunocompetent hosts: [[Is treated by::nitazoxanide]] 500 mg p.o. twice daily for 3 days
**Not approved in Canada, needs SAP
*In severely immunocompromised patients, may not be curable without reversing immunosuppression
**Can treat with [[nitazoxanide]] 500 to 1000 mg p.o. twice daily for 14+ days
*Other medications
**[[Paromomycin]] likely inferior to nitazoxanide
***Dose is 500 mg p.o. three to four times daily for 14 days
**[[Macrolides]] likely ineffective
**[[Rifaximin]] and [[albendazole]] need more study

== Further Reading ==

* Treatment of human intestinal cryptosporidiosis: A review of published clinical trials. Int J Parasitol. 2021;17:128-138: doi:[https://doi.org/10.1016/j.ijpddr.2021.09.001 10.1016/j.ijpddr.2021.09.001]{{DISPLAYTITLE:''Cryptosporidium hominis''}}
[[Category:Protozoa]]
[[Category:Gastrointestinal infections]]