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


== Background ==
==Background==


=== Microbiology ===
===Microbiology===


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


=== Epidemiology ===
===Epidemiology===


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


=== Life Cycle ===
===Life Cycle===


* Host ingests an '''oocyst''' (needing as few as 10 to cause disease)
*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'''
*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
*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'''
*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 type I meronts mature and release motile '''merozoites'''
* The merozoites again attach to the intestinal epithelial cells
*The merozoites again attach to the intestinal epithelial cells
* Merozoites then either reproduce asexually, as above, or sexually
*Merozoites then either reproduce asexually, as above, or sexually
** Sexual reproduction involves a '''macrogamont''' and '''microgamont''', which form a '''zygote'''
**Sexual reproduction involves a '''macrogamont''' and '''microgamont''', which form a '''zygote'''
** The zygote develops into an oocyst which contains four sporozoites
**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)
*Oocysts may be involved in auto-inoculation (if thin-walled) or environmental contamination (if thick-walled)


=== Pathophysiology ===
===Pathophysiology===


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


== Clinical Manifestations ==
==Clinical Manifestations==


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


=== Immunocompetent adults ===
===Immunocompetent adults===


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


=== Childhood diarrhea ===
===Childhood diarrhea===


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


=== People living with HIV ===
===People living with HIV===


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


=== Other immunocompromised patients ===
===Other immunocompromised patients===


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


== Diagnosis ==
==Diagnosis==


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


== Management ==
==Management==


* Supportive care, including fluids and antimotility agents like loperamide
*Supportive care, including fluids and antimotility agents like loperamide
* In immunocompetent hosts: [[Is treated by::nitazoxanide]] 500 mg po tid for 3 days
*In immunocompetent hosts: [[Is treated by::nitazoxanide]] 500 mg po tid for 3 days
* In severely immunocompromised patients, may not be curable without reversing immunosuppression
*In severely immunocompromised patients, may not be curable without reversing immunosuppression


{{DISPLAYTITLE:''Cryptosporidium hominis''}}
{{DISPLAYTITLE:''Cryptosporidium hominis''}}

Revision as of 13:57, 5 August 2020

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-ÎşB), 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

  • Supportive care, including fluids and antimotility agents like loperamide
  • In immunocompetent hosts: nitazoxanide 500 mg po tid for 3 days
  • In severely immunocompromised patients, may not be curable without reversing immunosuppression
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