Protozoal infections - Coccidia, Toxoplasma, Giardia, Amoeba Flashcards
What is giardia? Appearance? Lifecycle
- Flagellate protozoan
- Pear shaped 15um long
- Attaches to small intestine with sucker but does not invade -> not bloody diarrhoea
- Produces a small 4 nucleus cyst (expelled in stool)
Giardia incubation? Who has high risk?
7-10 days (occasionally months)
Children
MSM
Giardia Rx completed and test negative but ongoing diarrhoea probably due to?
Lactose intolerance
Giardia dx?
- Stool microscopy for Characteristic small 4 nuclei cyst (may require 3 samples)
- Also now ELISA / EIA and point of care tests
String test is used for? How does jt work
Giardia / stronglyotides
- Patient shallows some string which is attached to cheek with gelatin on end. Left overnight and then examined for trophozoites
Giardia small bowel biopsy?
Villlous flattening, crypt deepening and inflam infiltrate in lamina propria
Giardia rx? 2nd line (especially in HIV)
tinidazole
[Metronidazole / albendazole ]
Nitazoxanide
Prevention giardia
Boil water, sedimentation, flocculation
Prevention giardia
Boil or filter water, chlorination, flocculation, sedimentation
Main protective factor against giardia
IgA
Amoeba most common presentation? Geography
- Dysentery
- Then liver abscess
[Only 4-10% of infected with E histolytica develop sx]
Found throughout tropics
Entamoeba which one causes issues? Which is much more common but doesn’t cause significant disease?
- E Histolytica
- E dispar - more common
- Issue is that both cysts look the same on microscopy but no need to treat dispar
Confirm dx of amoebic dysentery? Stain? Differentiate from dispar?
- Amoebic trophozoites containing ingested RBCs in a fresh Stool sample
- Should be within 15 minutes of sample
-iron haematoxylin / trichrome stain
Non-virulent Eg E Dispar would not have ingested RBCs
E histolytica life cycle
- Four-nucleated cyst ingested following consumption of contaminated food / water
- -> digested by gut releasing 8 trophozoites which continue to replicate through fission
- Produce cysts which are excreted in stool and can survive weeks in water
Incubation of amoeba?
Few days to several years
Most common location amoebic abscess? What’s often seen on CXR? LFTs
- Single one in right lobe of liver in 70%
- Raised right hemidiaphragm or effusion (communication with abscess)
- LFTs often unremarkable bar raised ALP
Stool microscopy makes mainstay of dx for Amoeba in resource poor settings - what about in richer? GOld standard?
[Egg microscopy]
- ELISA Stool antigen testing - most common
- PCR - gold standard
-Serum IgG - does not differentiate from past infection - Enzyme immunoassay (EIA)
What does amoebic colitis look like on endoscopy?
- Mimicks IBD with ulcers
- Can take biopsies of these if other tests inconclusive
Amoeba rx?
Metronidazole for 5-10 days or single dose tinidazole (2g)
Followed by a course of luminal amoebicides to eradicate cysts
- Eg diloxanide furoate, paromomycin, iodoquinol
Prevention amobea
- Improved hygiene/ sanitation and clean drinking water
- Boil / peel / cook food and water
amoebic cysts resistant to?
Chlorination
Sensitive to iodine
How many people infected with amoeba develop the disease when infected?
4-10% in first year
Describe entamoeba
Non-flagellate protozoan
2 Main parts of life cycle entamoeba
Noninvasive, infective cysts
Invasive trophozoite
Which receptor allows amoeba to attach to the intestinal mucosa
Galactose lectin
[Can test for this]
amoebic colitis usual incubation? sx? risk of progression to?
sx after 1-2 weeks and lasts 4-6 weeks
The pain is usually the worst LLQ
Bloody diarrhoea
Risk of fulminant colitis/NEC/Megacolon in risk groups (Immunosupressed, malnourished, pregnant)
Mass in caecum in amoeba is?
Ameoboma- inflammatory reaction in cecum
Ameoboma differentials
Intestinal TB, typhoid fever, appendiceal mass and colonic cancer
72 yo with AML
Hx of chronic diarrhea
develops bloody diarrhea
on day 12 of chemotherapy
multiple ulcers plus a
4cm mass in the ascending
colon =
Ameboma
Which LFT most derranged in amebic liver abcess
ALP
Women or men more likely to have an amebic liver abscess
Men make up 90%
25 yo male from Lima
Hx: 3 week history of fever,
weight loss, RUQ pain
no diarrhea
PE: T 39C, pulse 120
chronically ill, pale
no jaundice, tenderness
over RUQ
Labs: mild anemia, leukocytosis
elevated alkaline phosphatase
Amebic liver abscess
2 complications of amebic liver abscess spread
Pericarditis
Empyema
Where do you get cutaneous amoeba histolytica lesions? Due to? What does it look like?
ano-genital, perianal region
▪ direct inoculation from cysts in the stools
▪ well-demarcated, round-oval ulcer
with heaped-up borders
Only way to diagnose ameoboma
Colonoscopy + biopsy
Ix gold standard for amebic liver abscess
PCR + imaging (US fine)
Positive amoeba but no dystentery or liver abscess Rx
Luminal agent - paromomycin,
[ diloxanide furoate, iodoquinol]
Appearance of aspirate from amoebic abscess
Yellow-brown’
‘anchovy paste’
Name 3 situations you would perform diagnostic tap amebic abscess
-Left lobe - risk of pericardial spread
->10cm
-Not responding to medical therapy
-Unclear diagnosis ?pyogenic
▪ 18 yo female from rural Trujillo
▪ 3 week history of diarrhea
▪ admitted with acute abdomen and sepsis
▪ multiple colonic perforations?
What is it?
Usual host?
Dx?
RX?
Balantidiasis
-Balantidium coli is the largest intestinal protozoan of humans and the only ciliate
[Massive oval with fluffy edge kidney-shaped nuclei]
-Pigs usual hosts (humans accidental)
-trophozoites in a fresh stool sample or in scrapings from a colonic ulcer
Tetracycline or Metronidazole
TROPHOZOITE OF ENTAMOEBA HISTOLYTICA
CYST OF ENTAMOEBA HISTOLYTICA
-one to four nuclei identical to that of trophozoites
Abscess in right lobe of liver + dysentery and now this on colonoscopy
Amoebic colitis
multiple flask-shaped ulcers; extensive areas of hemorrhage and necrosis
Cryptosporidium which type for humans? Animals and humans? Life cycle.
- C hominis
- C parvum
Feacal oral - oocyst releases 4 sporozoites which invades epithelium
- Can either produce thin-walled oocysts which auto-infect same host. Or thick walled which are excreted
Cryptosporidiosis dx? Stain that can be used?
Acid fast oocysts in faeces/ luminal aspirate using kinyoun acid fast stain
[I was fucKinyoun when I had it]
Most have PCR assays now
Unusual finding of eosinophilia in which protozoan infection? Rx?
cystoisospora infection
Co-trimoxazole
[CystoEYEsospora - egg looks like eye and has Eosinopholia]
Cryptosporidiosis rx?
- Usually self limiting
- Nitazoxide
Cyclospora rx?
Co-trimox
[or cipro]
2 main stages of protazoa? Which are infective? which are feeding?
Trophozoite : feeding/vegetative stage. May cause damage
Cyst: non replicative, resistance stage. Spherical shape. Infective stage
Compare nucleus of histolytica vs dispar vs E coli
Compare Chromatid bars of histolytica vs dispar vs E coli
Histolytica and dispar - the blunt bois
Entamoeba histolytica Life cycle
Infective vs diagnostic stage
Infective stage : mature cyst.
Diagnostic stage : cysts, trophozoites.
Dispar / histolytica
Histolytica trophozoite
Hitolytica / dispar trophozoite
even peripheral chromatin , central karyosome
ingested RBCs - E. histolytica nucleus (1),
even peripheral chromatin , central karyosome
Ingested RBCs - E. histolytica nucleus (1),
even peripheral chromatin , central karyosome
Ingested RBCs - E. histolytica nucleus (1),
even peripheral chromatin , central karyosome
ingested RBCs - E. histolytica nucleus (1),
even peripheral chromatin , central karyosome
E. histolytica / E. dispar - Pre cyst
nucleus (1), even peripheral chromatin , central karyosome,
chromatid bars ( blunt ends