GIS W5 Parasitology Flashcards
Name the Protozoan (unicellular eukaryote) parasites
i) Giardia
ii) Cryptosporidium
iii) Entamoeba
Name the Helminths (multicellular eukaryote)
i) Ascaris
ii) Trichuris
iii) Enterobius
iv) Ancylostoma/Necator
v) Strongyloides …and Schistosoma, a fluke
vi) Diphyllobothrium
vii) Echinococcus
viii) Taenia
Often not treated with antiparasitics but __________ is especially important
Fluid replacement
most common intestinal parasite in US
11) Giardia lamblia (intestinalis)
e) Mechanism: presence of parasite causes loss of epithelial absorptive surface area. Other factors may play a role, not well understood.
11) Giardia lamblia (intestinalis)
g) Symptoms useful for diagnosis:
i) Foul-smelling diarrhea
ii) Flatulance
iii) Stools are greasy, tend to float (fatty)
iv) Malabsorption of fat, lipids, some vitamins
11) Giardia lamblia (intestinalis)
b) Often seen when a sanitation system fails
i) Pool/waterpark chlorination/UV treatment
ii) Storms or issues with drinking water
c) Diarrhea symptoms for 1-2 weeks to ~30 days, may seem to resolve and then come back
12) Cryptosporidium parvum
d) Mechanism: Absorption impaired and secretion enhanced when intestinal epithelial cells are infected by Cryptosporidium
12) Cryptosporidium parvum
a) Causes Amebiasis
i) AKA Amebic Dysentery, Amebic liver abscesses
b) More prevalent in tropical/subtropical climates
c) Only 10-20% of infected individuals will become ill
13) Entamoeba histolytica
i) Bloody, mucus-ey loose stool
ii) Relatively mild symptoms but
iii) Can invade the liver and form an abcess
iv) X-ray/ultrasound to detect abscess or tissue damage
13) Entamoeba histolytica
iv) Blood vessel invasion:
(1) Amebic hepatitis = single abscess in right lobe; should present with right upper quadrant pain, fever, weight loss
v) Mucosal cell invasion:
(1) Results in replication,
(2) Cysts in feces
13) Entamoeba histolytica
i) Class: Nitroimidazoles
ii) Distribution: Tissue antiparasitic- low concentration in intestine, oral dose almost completely absorbed with high bioavailability
(1) Despite this, it is the drug of choice to treat symptomatic Giardia infection, even though organism that does not penetrate the epithelium!!
a) Metronidazole, Tinidazole
iv) Mechanism of action:
(1) Drug breakdown toxic metabolites that generate free radicals induce DNA strand breakage
v) Toxicity:
(1) Disulfiram reaction, avoid alcohol
(2) Disturb normal GI flora
a) Metronidazole, Tinidazole
i) Mechanism: Essential to anaerobic energy metabolism -interferes with pyruvate::ferredoxin oxidoreductase enzyme dependent electron transfer
ii) Selectivity: Species difference in electron transfer
b) Nitazoxanide
iii) Distribution: Rapidly metabolized to tizoxanide. Parent compound is not detected in plasma
b) Nitazoxanide
i) Mechanism: Unknown
ii) Toxicity:
iii) loss of visual acuity
iv) Use with caution in patients with thyroid disease – its use interferes with certain thyroid tests
v) Distribution: only 10% of the drug is absorbed so it works locally on the protozoa including cysts in the GI tract, luminal antiparasitic (amebicide)
c) Iodoquinol
i) Mechanism: Aminoglycoside- targets ribosomal 30S subunit
ii) Toxicity: Diarrhea, other GI effects including issues with intestinal flora because it has activity against some bacteria.
iii) Distribution: Luminal antiparasitic- Minimal absorption after oral administration
d) Paromomycin
a) Spectrum: Broad spectrum, many bacteria, but also effective against apicomplexans including Toxoplasma and Cystoisospora (formerly Isospora), and Cyclospora
16) TMP-SMX (Trimethoprim Sulfamethoxazole) “Co-trimoxazole”, “Bactrim”
(1) Staple-sized worms
ii) Worldwide distribution, most common helminth infection in US
iii) Symptom: perianal pruritis
a) Enterobius vermicularis
22) Soil-transmitted roundworms
i) a few mm
- Skin penetration
b) Strongyloides
22) Soil-transmitted roundworms
i) 9-11 mm (small staple size)
- skin penetration
a) Necator
22) Soil-transmitted roundworms
i) 3-5 cm
- egg ingestion
c) Trichuris
22) Soil-transmitted roundworms
i) 15-35 cm (spaghetti, a ruler)
- egg ingestion
d) Ascaris
formed from the breakdown of eosinophils and may be seen in the stool or sputum of patients with parasitic diseases. Cause may or may not be a parasitic infection, may be asthma.
ii) Charcot-Leyden crystals
