Cryptosporidium hominis: Difference between revisions

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Cryptosporidium hominis
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* A member of the [[Cryptosporidium species]] which causes diarrheal disease in humans
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*A member of the [[Cryptosporidium]] which causes diarrheal disease in humans
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*Similar to [[Cryptosporidium parvum]] which typically infects cows, but can also infect humans
   
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==Background==
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{{DISPLAYTITLE:''Cryptosporidium hominis''}}
  
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===Microbiology===
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*Protozoan parasite in the genus [[Cryptosporidium species|''Cryptosporidium'']]
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===Epidemiology===
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*Infects humans, but can also infect cows, mice, gnotobiotic pigs, and rarely other species
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*Transmitted fecal-oral via environmental contamination (such as recreational water), and can be spread person-to-person
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**Outbreaks are most commonly associated with drinking water, even when properly treated
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**Daycares (more common than [[Giardia]])
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**Also seen with petting zoos and cider
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**Higher rates of transmission in MSM
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*Resistant to chlorination and can survive in the environment up to 6 months
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*In developing countries, primarily affects children less than 5 years
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*In developed countries, primarily affects adults, related to travel
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**Causes 2-6% of traveller's diarrhea
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===Life Cycle===
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*Host ingests an '''oocyst''' (needing as few as 10 to cause disease)
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*The oocyst excyst in the stomach and proximal small bowel, releasing four '''sporozoites'''
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*Sporozoites bind to the intestinal epithelial cells and becomes vacuolized by the host cell membrane
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*In the '''parasitophorous vacuole''', they reproduce asexually into further sporozoites, which divide into '''type I meronts'''
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*The type I meronts mature and release motile '''merozoites'''
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*The merozoites again attach to the intestinal epithelial cells
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*Merozoites then either reproduce asexually, as above, or sexually
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**Sexual reproduction involves a '''macrogamont''' and '''microgamont''', which form a '''zygote'''
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**The zygote develops into an oocyst which contains four sporozoites
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*Oocysts may be involved in auto-inoculation (if thin-walled) or environmental contamination (if thick-walled)
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===Pathophysiology===
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*Infection activates nuclear factor kappa B (NF-κB), which activates a large response
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*Infection results in increased permeability of the intestinal mucosa
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*T-cells are involved, with chronic infection in patients who are CD4-deplete
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==Clinical Manifestations==
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*Incubation period [[Usual incubation period::7 days]] (range [[Incubation period range::1 to 30 days]])
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===Immunocompetent adults===
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*Associated with waterborne outbreaks, travel, animal contacts, or child contacts
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*Watery (to mucoid) diarrhea and malabsorption, more lower bowel symptoms
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*May also have abdominal cramping, nausea or vomiting, and fever
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*Lasts 5 to 14 days, but up to 100
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*However, recurs in about 40% and can become an intermittent or chronic diarrhea similar to irritable bowel syndrome
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===Childhood diarrhea===
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*Causes about 10-15% of acute childhood diarrhea in developing countries
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*Presents with watery diarrhea, cramps, and nausea and vomiting
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*May also have fever, cough, dyspnea, and foul-smelling stool
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*Can turn into chronic diarrhea and malabsorption
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===People living with HIV===
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*Most cases are asymptomatic or mild and self-limited
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*Chronic infection more common in HIV with CD4 <150, lasting up to 6 months
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*May also involve extraintestinal cryptosporidiosis, such as biliary or respiratory disease
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===Other immunocompromised patients===
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*May present similarly to HIV
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*Includes solid organ transplant, hematopoietic stem cell transplant, and hyper-IgM syndrome
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==Diagnosis==
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*Stool microscopy
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**Seen on modified acid-fast staining (70% sensitive)
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**Can do immunofluorescence as well (more sensitive)
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*Stool antigen
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*PCR
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==Management==
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*For immunocompetent hosts, supportive care, including fluids and antimotility agents like loperamide, is generally adequate
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*In immunocompetent hosts: [[Is treated by::nitazoxanide]] 500 mg p.o. twice daily for 3 days
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**Not approved in Canada, needs SAP
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*In severely immunocompromised patients, may not be curable without reversing immunosuppression
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**Can treat with [[nitazoxanide]] 500 to 1000 mg p.o. twice daily for 14+ days
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*Other medications
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**[[Paromomycin]] likely inferior to nitazoxanide
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***Dose is 500 mg p.o. three to four times daily for 14 days
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**[[Macrolides]] likely ineffective
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**[[Rifaximin]] and [[albendazole]] need more study
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== Further Reading ==
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* 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:Protozoa]]
 
[[Category:Gastrointestinal infections]]
  
[[Category:Gastrointestinal infections]]

Latest revision as of 10:17, 30 August 2023

Background

Microbiology

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 7 days (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: 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

Further Reading

  • Treatment of human intestinal cryptosporidiosis: A review of published clinical trials. Int J Parasitol. 2021;17:128-138: doi:10.1016/j.ijpddr.2021.09.001
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