Giardia lamblia: Difference between revisions
From IDWiki
Giardia lamblia
m (→: typo) |
m (Text replacement - " species]]" to "]]") |
||
(12 intermediate revisions by the same user not shown) | |||
Line 1: | Line 1: | ||
* |
*A member of the [[Giardia]] that causes intestinal disease ('''giardiasis''') in humans and animals |
||
* |
*Also known as '''beaver fever''' |
||
== |
==Background== |
||
===Microbiology=== |
|||
* Flagellated protozoan that infects the small bowel |
|||
* Host specificity related to genotype ("assemblage") |
|||
** Assemblages A & B infect humans, but also numerous non-human hosts including primates, dogs, cats, cattle, sheep, deer, rodents, horses, and beavers |
|||
** Assemblages C & D affect dogs; E affects cattle, goats, sheep, and pigs; F affects cats; G affects rodents; and H affects marine vertebrates |
|||
* Antigenic variation is determined by the variant-specific surface protein (VSP) |
|||
** Replaced every few generations |
|||
*Flagellated protozoan that infects the small bowel |
|||
== Life Cycle == |
|||
*Host specificity related to genotype ("assemblage") |
|||
**Assemblages A & B infect humans, but also numerous non-human hosts including primates, dogs, cats, cattle, sheep, deer, rodents, horses, and beavers |
|||
**Assemblages C & D affect dogs; E affects cattle, goats, sheep, and pigs; F affects cats; G affects rodents; and H affects marine vertebrates |
|||
*Antigenic variation is determined by the variant-specific surface protein (VSP) |
|||
**Replaced every few generations |
|||
===Life Cycle=== |
|||
* A cyst is ingested via fecal-oral contamination |
|||
* In the small bowel, the cyst releases two trophozoites (free-living form) via excystation |
|||
* Trophozoites multiply by binary fission |
|||
* When they reach the large bowel, they encyst |
|||
*A cyst is ingested via fecal-oral contamination |
|||
== Epidemiology == |
|||
*In the small bowel, the cyst releases two trophozoites (free-living form) via excystation |
|||
*Trophozoites multiply by binary fission |
|||
*When they reach the large bowel, they encyst |
|||
===Epidemiology=== |
|||
* Worldwide distribution |
|||
* Generally transmitted fecal-oral route (via environment), but person-to-person transmission is possible in daycares |
|||
* Numerous animal reservoirs, not fully understood how important they are |
|||
* Cysts can survive several months in cold water |
|||
* Peak prevalence occurs in children of up to 15 to 30% in poor countries |
|||
* Reinfection is common |
|||
*Worldwide distribution |
|||
== Pathophysiology == |
|||
*Generally transmitted fecal-oral route (via environment), but person-to-person transmission is possible in daycares |
|||
*Numerous animal reservoirs, not fully understood how important they are |
|||
*Cysts can survive several months in cold water |
|||
*Peak prevalence occurs in children of up to 15 to 30% in poor countries |
|||
*Reinfection is common |
|||
===Pathophysiology=== |
|||
* Infected with as few as 10 to 25 cysts |
|||
* Trophozoites colonize the upper small bowel, adhering to the mucosal enterocytes |
|||
* Host response involves B- and T-cells, including production of IgM and IgG antibodies, possibly IgA antibodies as well |
|||
*Infected with as few as 10 to 25 cysts |
|||
== Clinical Presentation == |
|||
*Trophozoites colonize the upper small bowel, adhering to the mucosal enterocytes |
|||
*Host response involves B- and T-cells, including production of IgM and IgG antibodies, possibly IgA antibodies as well |
|||
*Causes villous atrophy, which can contribute to malabsorption |
|||
*Inhibits disaccharidases, which contributes to lactose intolerance |
|||
==Clinical Manifestations== |
|||
* Can have '''asymptomatic cyst passage''' (5 to 15%) |
|||
** Can last up to 6 months in children |
|||
* Most common syndrome is '''acute diarrhea''' (25 to 50%) |
|||
** Incubation period 1 to 2 weeks |
|||
** Malaise, flatulence, cramps, bloating, nausea, anorexia, vomiting, and malabsorption |
|||
** '''Sulfuric belching''' is classic |
|||
** Fevers are uncommon but possible |
|||
* Can also cause '''chronic diarrhea''' |
|||
** Malaise, occasional headache, diffuse abdominal and epigastric pain worse with food |
|||
** May have malabsorption, often has weight loss |
|||
** Symptoms can wx and wane, with periods of remission or constipation |
|||
* '''Post-''Giardia'' syndrome''' with irritable bowel syndrome and chronic fatigue may last for years |
|||
** Can have significant malabsorption |
|||
* Also, can have '''post-''Giardia'' lactose intolerance''' lasting several weeks |
|||
*Can have '''asymptomatic cyst passage''' (5 to 15%) |
|||
== Diagnosis == |
|||
**Can last up to 6 months in children |
|||
*Most common syndrome is '''acute diarrhea''' (25 to 50%) |
|||
**Incubation period [[Usual incubation period::1 to 2 weeks]] |
|||
**Usually presents after 7 to 10 days |
|||
**Malaise, flatulence, cramps, bloating, nausea, anorexia, vomiting, and malabsorption |
|||
**'''Sulfuric belching''' is classic |
|||
**Fevers are uncommon but possible |
|||
*Can also cause '''chronic diarrhea''' |
|||
**More common in [[CVID]], [[X-linked agammaglobulinemia]], and [[AIDS]] |
|||
**Malaise, occasional headache, diffuse abdominal and epigastric pain worse with food |
|||
**May have malabsorption, often has weight loss |
|||
**Symptoms can wax and wane, with periods of remission or constipation |
|||
*'''Post-''Giardia'' syndrome''' with irritable bowel syndrome and chronic fatigue may last for years |
|||
**Can have significant malabsorption |
|||
*Also, can have '''post-''Giardia'' lactose intolerance''' lasting several weeks |
|||
==Diagnosis== |
|||
* Stool microscopy |
|||
** May see active trophozoites in saline wet prep |
|||
** Look for cysts after iodine staining |
|||
** Sensitivity 60-80% with one stool sample, up to 90% with three |
|||
* Antigen assays are sometimes used during outbreaks or for screening |
|||
** Sensitivity 85-98% and specificity 90-100% |
|||
* PCR is becoming more common |
|||
* String test |
|||
** Put a string down into small bowel and then pull it back; it should have bile |
|||
** Look with a microscope |
|||
** Done when there is high suspicion but O&P negative |
|||
*Stool microscopy |
|||
== Management == |
|||
**May see active trophozoites in saline wet prep |
|||
**Look for cysts after iodine staining |
|||
**Sensitivity 60-80% with one stool sample, up to 90% with three |
|||
*Antigen assays are sometimes used during outbreaks or for screening |
|||
**Sensitivity 85-98% and specificity 90-100% |
|||
*PCR is becoming more common |
|||
*String test |
|||
**Put a string down into small bowel and then pull it back; it should have bile |
|||
**Look with a microscope |
|||
**Done when there is high suspicion but O&P negative |
|||
==Management== |
|||
* Tinidazole 2 g po once |
|||
* Metronidazole 250 mg po tid for 5 to 7 days |
|||
*[[Is treated by::Tinidazole]] 2 g po once, which is the gold standard |
|||
* Alternatives: nitazoxanide, albendazole, paromomycin, quinacrine, furazolidone |
|||
*[[Is treated by::Metronidazole]] 250 mg po tid for 5 to 7 days, but has a higher failure rate |
|||
*Alternatives: [[Is treated by::nitazoxanide]], [[Is treated by::albendazole]], [[Is treated by::paromomycin]], [[Is treated by::quinacrine]], and [[Is treated by::furazolidone]] |
|||
*Avoid caffeine, lactose, and smoking |
|||
*Can consider [[Saccharomyces boulardii]] probiotics (Florastor) |
|||
{{DISPLAYTITLE:''Giardia lamblia''}} |
{{DISPLAYTITLE:''Giardia lamblia''}} |
||
[[Category:Protozoa]] |
|||
[[Category:Gastrointestinal infections]] |
[[Category:Gastrointestinal infections]] |
||
[[Category:Flagellates]] |
|||
[[Category:Infectious diseases]] |
Latest revision as of 17:07, 1 February 2022
- A member of the Giardia that causes intestinal disease (giardiasis) in humans and animals
- Also known as beaver fever
Background
Microbiology
- Flagellated protozoan that infects the small bowel
- Host specificity related to genotype ("assemblage")
- Assemblages A & B infect humans, but also numerous non-human hosts including primates, dogs, cats, cattle, sheep, deer, rodents, horses, and beavers
- Assemblages C & D affect dogs; E affects cattle, goats, sheep, and pigs; F affects cats; G affects rodents; and H affects marine vertebrates
- Antigenic variation is determined by the variant-specific surface protein (VSP)
- Replaced every few generations
Life Cycle
- A cyst is ingested via fecal-oral contamination
- In the small bowel, the cyst releases two trophozoites (free-living form) via excystation
- Trophozoites multiply by binary fission
- When they reach the large bowel, they encyst
Epidemiology
- Worldwide distribution
- Generally transmitted fecal-oral route (via environment), but person-to-person transmission is possible in daycares
- Numerous animal reservoirs, not fully understood how important they are
- Cysts can survive several months in cold water
- Peak prevalence occurs in children of up to 15 to 30% in poor countries
- Reinfection is common
Pathophysiology
- Infected with as few as 10 to 25 cysts
- Trophozoites colonize the upper small bowel, adhering to the mucosal enterocytes
- Host response involves B- and T-cells, including production of IgM and IgG antibodies, possibly IgA antibodies as well
- Causes villous atrophy, which can contribute to malabsorption
- Inhibits disaccharidases, which contributes to lactose intolerance
Clinical Manifestations
- Can have asymptomatic cyst passage (5 to 15%)
- Can last up to 6 months in children
- Most common syndrome is acute diarrhea (25 to 50%)
- Incubation period 1 to 2 weeks
- Usually presents after 7 to 10 days
- Malaise, flatulence, cramps, bloating, nausea, anorexia, vomiting, and malabsorption
- Sulfuric belching is classic
- Fevers are uncommon but possible
- Can also cause chronic diarrhea
- More common in CVID, X-linked agammaglobulinemia, and AIDS
- Malaise, occasional headache, diffuse abdominal and epigastric pain worse with food
- May have malabsorption, often has weight loss
- Symptoms can wax and wane, with periods of remission or constipation
- Post-Giardia syndrome with irritable bowel syndrome and chronic fatigue may last for years
- Can have significant malabsorption
- Also, can have post-Giardia lactose intolerance lasting several weeks
Diagnosis
- Stool microscopy
- May see active trophozoites in saline wet prep
- Look for cysts after iodine staining
- Sensitivity 60-80% with one stool sample, up to 90% with three
- Antigen assays are sometimes used during outbreaks or for screening
- Sensitivity 85-98% and specificity 90-100%
- PCR is becoming more common
- String test
- Put a string down into small bowel and then pull it back; it should have bile
- Look with a microscope
- Done when there is high suspicion but O&P negative
Management
- Tinidazole 2 g po once, which is the gold standard
- Metronidazole 250 mg po tid for 5 to 7 days, but has a higher failure rate
- Alternatives: nitazoxanide, albendazole, paromomycin, quinacrine, and furazolidone
- Avoid caffeine, lactose, and smoking
- Can consider Saccharomyces boulardii probiotics (Florastor)