Protozoans Flashcards
What is the species?
E. histolytica trophozoite
pseudopods, vacuoles, cytoplasm, ingested RBCs (E. histolytica), nucleus even peripheral chromatin, central karyosome.
How do you Rx cystoisospora?
Co-trimoxazole
What is this?
Acid fast variability on staining
Cyclospora
Some stain in their entirety, some do not
What is the species?
E. histolytica / E. dispar trophozoite
Cyst
cytoplasm, nuclei (2-3), even peripheral chromatin, central karyosome,
chromatoidal bars (blunt ends).
What is the organism for cyclospora?
Cyclospora Cayetenesis
Transmission of cryptosporidium?
Person-to-person - main!
Drinking water
Recreational water
Swimming pools, water parks, lakes and streams
Contaminated food
Animals
What do you get from raspberries?
Cyclospora cayetensis
Requires environmental maturation
What is the smallest of the intestinal protozoans?
Cryptosporidium
4-5 microns
How may cryptosporidium present differently if CD4 <50?
Cholera like diarrhoea with volume depletion
Biliary tract infection - cholangitis
Chronic diarrhoea
What is the cryptosporidium that infects cattle?
C. parvum
What is the most common flagellated parasite to cause human disease?
Giardia lamblia
Name the species
Chilomastix mesnili (non pathogenic to humans)
Cyst
Flagellate
Lemon shaped
1 nucleus
Eccentric karyosome
Anterior hyaline protuberance
What blood test is useful for cystoisospora?
Eosinophilia - mild
What is the treatment of chagas disease?
benznidazole for 60 days or nifurimox for 90 days
How do you Rx microsporidia?
Albendazole E. intestinalis
Fumagillin E bieneusi
What is the route of transmission of chagas disease?
by vector-faeces into skin break or oral, also by blood transfusion, organ transplant, vertical transmission
What size are cyclospora?
8-10 microns
What is this organism?
Chagas (Trypanosoma cruzi)
amastigotes inside cardiomyocytes
What type of organisms are coccidia?
Intracellular with an apical complex
Name the species
Balantioides coli
Trophozoite
Ciliated
ovoid, macronucleus (kidney-shaped), micronucleus, contractile vacuole, cytostome.
What is an ameoboma?
Inflammatory reaction in the caecum
Palpable LIF mass (DD: intestinal TB, typhoid, appendix max, Ca, Crohns)
Histology: Marked granulation tissue
What is this organism?
Stool miscroscopy - Giardia
x3 fresh samples – identifies Giardia in 90%
Trophozoites: Saline wet mount - need to be fast
Cysts: Zinc sulfate flotation + iodine staining
Name the species
Cystoisospora belli
Immature oocysts with sporoblasts
What is unique about the way cryptosporidium infects the gut?
Apical complex forms complex with cell membrane of epithelial cells
What are the main classes of intestinal protozoans?
Pseudopods (use ecto and endoplasm to move)
Flagella
Cilia
Apical complex/intracellular
What is the clinical presentation of cystoisospora?
Diarrhea usually chronic
Frequent assoc biliary disease
How do you treat giardiasis?
Tinidazole one dose
Metronidazole (5-7 days)
Name the species
Giardia lamblia
Cyst
axostyle - long stick centrally
Are the immature oocysts that are shed in faeces immediately infective for cystoisospora?
No!
No auto infection
How do you treat E.Histolytica?
have to Rx cyst and trophozoite - treat trophozoite first!
Need non-absorbable luminal agents to kill the cysts (no systemic activity) - Iodoquinol, paramomycin
Metronidazole to kill trophozoite
What is the value of immunity from cryptosporidium?
Cannot be reinfected
Rx of cryptosporidiosis?
Most infections self limiting with fluids and electrolytes
Rx of choice - Nitazoxanide
Always start ARVs or optimise immunosuppression
What is the infective/diagnostic stage of cyclospora?
Mature oocysts - infective
Immature oocysts in stool - diagnostic
What is the infectious stage of the life cycle of ameobiasis (entamoeba histolytica)
Cysts
Amoebic cysts are resistant to chlorination, but sensitive to iodine solutions
Which patients with Chagas disease warrant treatment?
Indications for treatment
Acute Chagas
Reactivated Chagas (mostly those with HIV)
Congenital Chagas
All children with Chagas (acute or chronic)
Adult <50y old, without advanced cardiomyopathy
What is the vector/reservoir/infective stage of chagas disease?
Vector: triatomine insects 3 important genera: Triatoma, Panstrongylus, Rhodnius
Infectious stage: metacyclic trypomastigotes
Reservoir: domestic animals - dogs
What is this organism?
Trophozoite and cyst of E.Histolytica
Well demarcated single nucleus with central nucleolus, peripheral chromatin
Ingests erythrocytes - visible inside trophozoite
Symptoms of giardia?
Diarrhoea
Prolonged duration of diarrhoea >1wk
Bloating, flatulence
Steatorrhoea, foul smelling greasy
Weight loss
Malaise
What is pathogenesis of giardia?
Disrupts the brush border, mucosal invasion, secretion of enterotoxin, induces inflammatory reaction
Is foodborne/waterborne the only way of transmitting giardia?
No - sexual transmission - msm
What is the infective stage of giardiasis?
Cysts
Name the species
Giardia lamblia
How does cryptosporidium present?
Diarrhoea, watery.
Travellers diarrhoea in particular (endemic areas ppl have immunity)
Often prolonged or persistent
Causes malnutrition, may cause cognitive and developmental delay in children
What is the treatment for giardiasis?
Single-dose tinidazole (or metronidazole 5-7d)
Microsporidium - interesting points re: life cycle?
Live inside body within cells
Transmitted as spores
Coiled microtubular structure
∆ of cryptosporidium?
Microscopy
Also immunoassay antigen detection and PCR
Name the species
Iodamoeba butschlii (non pathogenic to humans)
Cyst
5-20um
1 nucleus
Big eccentric karyosome
Big glycogen vacuole
What is the species?
E. histolytica / trophozoite
pseudopods, vacuoles, cytoplasm, ingested RBCs (E. histolytica), nucleus even peripheral chromatin, central karyosome.
Name the species
Balantioides coli
Cyst
cyst wall, macronucleus (kidney-shaped), micronucleus, vacuole.
Cilia get taken up inside cyst wall
How do you treat cryptosporidium?
Nitazoxanide
What is the Rx for cyclospora?
Co-trimoxazole
What is the species?
Entamoeba coli (non pathogenic to humans)
Trophozoite
pseudopods, vacuoles, cytoplasm, nucleus (1), uneven peripheral chromatin,
eccentric karyosome.
What are the predictors of mortality in chagas disease?
NYHA status 3 or 4
Cardiomegaly on CXR
Impaired LV function on echo
NSVT on holter
What is this?
Cystoisospora Belli
Name the species
Endolimax nana (non pathogenic to humans)
Cyst
5-10um
1-4 nuclei
Big central karyosome
No peripheral chromatin
Like 4 on dice
What stages of intracellular protozoan may be found in stool culture?
Trophozoite or cyst
Trophozoite: long, 1 nucleus, has pseudopods
Cyst: circular, multinuclear
What is the most common intestinal protozoa causing diarrhoea in resource poor settings?
Cryptosporidium hominis
What organism causes chagas disease?
Trypanosoma cruzi
What are the most common microsporidia?
Enterocytozoon bieneusi (1)
Encephalitozoon intestinalis (2)
What is the name of organism for cryptosporidium?
Cryptosporidium hominus
(Most common protozoa in HIV)
What is the transmission of Entamoeba histolytica?
faeco-oral, water, foodbourne
What is this?
Cryptosporidium hominus
How does cryptosporidium cause auto infection?
1 mature oocyst = 4 sporozoites
Name the species
Blastocystis spp (hominus)
Vacuolar form
central vacuole, annular cytoplasm, peripheral nuclei (2-6).
What stain do you need for the Coccidia species for ∆?
Acid fast (Ziehl Neelson) - some
What is the best diagnostic test for Chagas disease?
serology for IgG (chronic), (blood smear / serum PCR for acute)
What is the only protozoa to cause eosinophilia?
Cystiospora Belli
How does microsporidia present?
Main 2 species - AIDS patients causing diarrhoea and biliary disease
Rarer subtypes cause myositis, keratoconjuncitivitis
What are the key tests to diagnose ameobiasis?
Stool samples - identifying trophozoites and cysts
Need to examine quickly as trophozoites inactivate quickly. Fresh sample - 30mins, 3 samples to improve sensitivity
Antigen in stool and serum
ELISA against galactose-lectin antigen
PCR gold standard, often not available
What is the mode of transmission for giardia?
Waterborne and foodborne - drink untreated surface water
What size are cystoisospora on acid fast?
20-30 microns
What proportion of people infected with entamoeba histolytica are symptomatic, and what is the main presentation of invasive disease?
Bloody diarrhoea: amoebic dysentery
Abdo pain - usually left lower quadrant
How do you treat balantoides coli?
Tetracycline
Largest protozoan.
Only ciliated parasite that infects humans.
Dysentery, perforation.
Name the species
Cyclospora cayetanensis
Acid fast variability
Transmission of cyclospora?
Foodborne - berries, herbs
Waterborne
What are the pathogenic ameobas?
Free-living amoebas
- Naegleria
- Acanthamoeba
- Ballamuthia
Entamoeba histolytica
How do you do microscopy for microsporidia?
modified trichrome,
hot Gram, UV2 - not typical stains!
What is this?
Cryptosporidium.
Some of the cells stain acid fast to different degrees - lots of heterogeneity
What is the species?
Entamoeba coli (non pathogenic to humans)
Mature cyst
cytoplasm, nuclei (8, rarely 16), uneven peripheral chromatin, eccentric
karyosome, chromatoidal bars (sharp ends).
Which is the most common amoeba to cause human disease?
Entamoeba histolytica
Presentation of cyclospora?
Diarrhoea, abdo cramps, weight loss, nausea
For >2 weeks
Why does auto infection not occur with cyclospora?
Sporogony
At least 1-2 weeks in environment
How do you diagnose cyclospora?
Microscopy
Where else in the body can be affected by ameoba?
Liver abscess, splenic abscess, lung abscess, GU infection, Pericarditis
Cutaneous amebiasis – very rare,
What is the best diagnostic test for giardiasis?
Antigen test of stool – ELISA for cyst wall glycoprotein
How do you treat cystoisospora and cyclospora?
Co-trimoxazole
What is the classical presentation of chagas disease?
Acute disease - not common
Febrile disorder lasting 1-2 months (1wk incubation) with Romana’s sign - periorbital unilateral oedema
Chronic disease – determinate form 10-30y after exposure: Cardiomyopathy (CHD – Chagas heart disease), Heart failure, Conduction defects – heart block
Arrhythmia – NSVT, RBBB – frequent ECG finding
Also:
Mega-oesophagus
Dysphagia, oodynophagia, regurgitation
Mega-colon
Sigmoid colon
Constipation
What are the names of the organisms for giardia?
Giardia lamblia, duodenalis, intestinalis
What is the most common presentation of ameobiasis?
Self-limiting asymptomatic infection – 90%
What is the species?
E. histolytica trophozoite
pseudopods, vacuoles, cytoplasm, ingested RBCs (E. histolytica), nucleus even peripheral chromatin, central karyosome.
What Is the infective/diagnostic stage of cystoisospora/cyclospora?
Infective: mature oocysts with sporozoites
Diagnostic: immature oocysts
What is the most common parasitic cause of diarrhoea?
Giardia
What is the drug of choice for Rx of balantioides?
Tetracycline
What is the largest protozoan?
Balantidium Coli
Which protozoan commonly affects pigs? Causes dysentery and perforation.
Balantidium Coli
What do you commonly see in aspirate from an entamoeba histolytica liver cyst?
No organisms
What is infective stage of most intestinal protozoan?
Cyst
Trophozoite would be destroyed by stomach
(diagnostic stage - trophozoite or cyst)
How many people are asymptomatic of E.Histolytica?
90%
What non pathogenic Entamoebas may you see on stool sample?
Endolimax nana
Iodamoeba butschlii
How would you differentiate E.histolytica and E.Dispar?
PCR, ELISA
Who gets severe infections with E.histolytica?
Kids, pregnant, immunosuppressed
Key features of amebiasis colitis?
Onset - 1-2 weeks, lasting for 6 weeks
Abdo pain- LEFT SIDE
Bloody diarrhoea
Wt loss
Can progress to fulminant colitis/toxic megacolon in 0.5%
What are the GI complications of amebiasis?
Ameoboma - inflammatory reaction in the caecum
Colitis
Non GI complications of amebiasis?
Liver abscess - 1-4 weeks
Fever, weight loss, abdo pain, hepatomegaly, jaundice occasionally
Also pleural and pericardiac spread
What bloods would be suspicious of an ameobic liver abscess?
ALP rise, WCC rise, mild elevation of liver enzymes
Presentation of amoebic abscess in children?
High mortality, multiple abscess, present with diarrhoea, HM common
Imaging of amoebic liver abscess?
Raised hemidiaphragm on right CXR
∆∆ of ameobic abscess
Pyogenic abscess - septic pt, purulent material
Hydatid cyst
Cancer
Spread of ameoba to perianal region presents as?
Perianal abscess from direct inoculation
Infective stage of amebiasis?
Cyst
Diagnosis of ameobic liver cyst?
E.histolytica in the stool - wet mount cyst or trophozoite
Other tests for amebiasis?
ELISA against galactose lectin antigen. Only + in first 7 days
Antibodies
PCR - gold standard!!!
Non serology tests for E.Histolytica?
Endoscopy - multiple ulcers, exudate, in caecum and ascending colon
When would you do an endoscopy for E.Histolytica?
If stool negative but high clinical suspicion
If suspicion of an ameboma
What do you see on endoscopy for E.histolytica?
Multiple flask shaped ulcers
What is this?
Flask shaped ulcer, E.Histolytica
Where would you find trophozoites in a colonic ulcer?
At margin
What tests can you do on the liver abscess?
sterile, odorless, brown fluid, trophozoites are hardly found, antigen positive. Anchovy paste fluid!
PCR of fluid
Mx of liver abscess with ameoba?
Metronidazole plus paramomycin (luminal) same as colonic
Which ameobic liver abscesses do you manage with drainage?
Not responding to med Rx, large, left lobe
Presentation of balantidium coli?
Dysentery
Definitive host for balantidium?
Pigs
Giardia organism?
Giardia lamblia, duodenalis, intestinalis
Infective stage of Giardia?
Cyst
Difference between ameobiasis and giardiasis anatomically?
Giardia affects small bowel
3 presenting syndromes of giardia?
Acute diarrhoea
Chronic diarrhoea
Malabsorption - can lead to vitamin deficiencies
Key features in the hx for giardia?
Prolonged diarrhoea
Bloating and flatulence
Foul smelling greasy stools
Weight loss
Test of choice for Giardia?
Antigen detection ELISA - detects a cell wall glycoprotein of giardia and cryptosporidium
Stool exam - 3 samples increases sensitivity
Rx of giardiasis
Metronidazole 7/7
