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Protozoa - GI infections
- Giardia lamblia
- Entamoeba histolytica
- Cryptosporidium
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Giardia lamblia
- Disease:
- Giardiasis: bloating, flatulence, foul-smelling, fatty diarrhea (often seen in campers and hikers)
Think fat rich Ghirardelli chocolates for fatty stools of Giardia
Transmission: Cysts in water
Dx: Trophozoits or cysts in stool
Tx: Metronidazole
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Entamoeba histolytica
Disease: Amebiasis: bloody diarrhea (dyssentery), liver abscess (reddish brown), RUQ pain (histology shows flask-shaped ulcer if submucosal abscess of colon rputures
Transmission: Cysts in water
Dx: Serology and/or trophozoites with RBCs in the cytoplasm or cysts (with multiple nuclei) in the stool
Tx: Metronidazole and iodoquinol
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Entamoeba histolica
- C. trophozoites (with RBCs in the cytoplasm)
- D. cyst (with multiple nuclei)
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- Disease: Severe diarrhea in AIDS
- -Mild disease (watery diarrhea) in non-immunocompromised
Transmission: Cysts in water
Dx: Cysts on acid-fast stain
Tx: Prevention (by filtering city water supplies); no treatment
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Protozoa - CNS infections
- Toxoplasma gondii
- Naegleria fowleri
- Trypanosoma brucei
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- Disease: Brain abscess in HIV (seen as ring-enhancing brain lesions on CT/MRI)
- -congenital toxoplasmosis = "classic triad" of chorioretinitis, hydrocephalus, and intracranial calcifications
Transmission: cysts in meat or cat feces; crosses placenta (pregnant women should avoid cats)
Dx: serology, biopsy
Tx: Sulfadiazine + pyrimethamine
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Naegleria fowleri
Disease: rapidly fatal meningoencephalitis
Transmission: Swimming in freshwater lakes (Think Nalgene bottle filled with freshwater containing Naelgeria); enter via cribiform plate
Dx: Amoebas in spinal fluid
Tx: Amphotericin has been effective for a few survivors
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Trypanosoma brucei
- T. gambienseT. rhodesiense
Disease: African sleeping sickness: enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma
Transmission: Tsetse fly, a painful bite
Dx: Blood smear
Tx: Suramin for blood-borne disease or melarsoprol for CNS penetration (it SURe is nice to go to sleep; MELAtonin helps with sleep)
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Trypanosoma on blood smear
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Protozoa - Hematologic infections
- Plasmodium-P. vivax/ovale
- -P. falciparum
- -P. malariae
Babesia
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Plasmodium
Disease: Malaria: fever, headache, anemia, splenomegaly
- -P. vivax/ovale
- Presentation: 48-hr cycle (tertian; includes fever on first day and third day);
- - dominant form in liver
- -P. falciparum
- Presentation: severe; irregular fever patterns
- - parasitized RBCs occlude capillaries in brain (cerebral malaria), kidneys, lungs
- -P. malariae
- Presentation: 72-hr cycle (quartan)
Transmission: Mosquito (Anopheles)
Dx: blood smear, trophozoite ring form, RBC shizont with merozoites
- Tx: Chloroquine (blocks plasmodium heme polymerase); if resistant, use mefloquine
- -vivax/ovale - add primaquine for dominant form in liver (hypnozoite)
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Plasmodium (malaria)
- A. blood smear, trophozoite ring form
- B. RBC schizont with merozoites
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Babesia
Disease: fever and hemolytic anemia; predominantly in northeastern US; asplenia pts have increase risk for severe disease
Transmission: Ixodes tick (same as Borrelia burgdorferi of Lyme disease; may often co-infect humans)
Dx: Blood smear, ring form, "Maltese cross"
Tx: Quinine, clindamyacin
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Babesia
Blood smear - 1. ring form
- 2. "Maltese cross"
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Protozoa - other
- Trypanosoma cruzi
- Leishmania donovani
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Trypanosoma cruzi
Disease: Chagas' disease (dilated cardiomyopathy, megacolon, megaesophagus); predominantly in South America
Transmission: Reduviid bug ("kissing bug"), a painless bite (much like a kiss)
Tx: Nifurtimox
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Leishmania donovani
Disease: Visceral leishmaniasis (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia
Transmission: Sandfly
Dx: Macrophages containing "amastigotes"
- Tx: Sodium stibogluconate
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STDs
(parasites)
Trichomonas vaginalis
Disease: Vaginitis: foul-smelling, greenish discharge; itching and burning; do not confuse with Gardnerella vaginalis, a gram-negative bacterium that causes bacterial vaginosis
Transmission: Sexual (cannot exist outside human - cannot form cysts)
Dx: Trophozoites (motile) on wet mount
Tx: Metronidazole for pts and partner
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Nematodes (roundworms)
types
Routes of infection
- Ingestion - Enterobius, Ascaris, Trichinella
- Cutaneus - Strongyloides, Ancylostoma, Necator
- You'll get sick if you EAT these!
- These get into your feet from the SANd.
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Nematodes
intestinal
- Enterobius vermicularis (pinworm)
- Ascaris lumhricoides (giant roundworm)
- Trichinella spiralis
- Strongyloides stercoralis
- Ancylostoma duodenale, Necator americanus (hookworms)
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Enterobius vermicularis
(pinworm)
Food contaminated with eggs; intestinal infection; causes anal pruritis (the Scotch tape test)
Tx: bendazoles or pyrantel pamoate (worms are BENDy; treat with meBENDazole)
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Ascaris lumbricoides
(giant roundworm)
Eggs are visible in feces; intestinal infection
Tx: bendazoles or pyrantel pamoate
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Trichinella spiralis
Undercooked meat, usually pork; inflammation of muscle (larvae encyst in muscle); periorbital edema
Tx: bendazoles
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Strongyloides stercoralis
Larvae in soil penetrate the skin; intestinal infection; causes vomiting, diarrhea, and anemia
Tx: bendazoles or ivermectin
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Ancylostoma duodenale,
Necator americanus
(hoodworms)
Larvae penetrate skin of feet; intestinal infection causes anemia (sucks blood from intestinal walls)
Tx: bendazoles or pyrantel pamoate
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Nematodes - tissue
- Dracunculus medinensis
- Onchocerca volvulus
- Loa loa
- Wuchereria hancrofti
- Toxocara canis
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Dracunculus medinensis
In drinking water; skin inflammation and ulceration
Tx: Niridazole, prolonged extraction
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Onchocerca volvulus
Transmitted by female blackflies; causes hyperpigmented skin and river blindness (remember black flies, black skin nodules, "black sight"). Can have allergic reaction to microfilaria
Tx: Ivermectin (IVERmectin for rIVER blindness)
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Loa loa
Transmitted by deer fly, horse fly, and mango fly; causes swelling in skin (can see worm crawling in conjunctiva)
Tx: Diethylcarbamazine
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Wuchereria bancrofti
Female mosquito; causes blockage of lymphatic vessels (elephantiasis). Takes 9 months - 1 year after bite to get elephantiasis sx.
Tx: Diethylcarbamazine
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Toxocara canis
Food contamination with eggs; causes granulomas (if in retina --> blindness) and visceral larva migrans
Tx: Albendazole or mebendazole
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Cestodes (tapeworms)
- Taenia solium
- Diphyllobothrium latum
- Echinococcus granulosus
- Treat most with Praziquantel
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Taenia solium
- Ingestion of larvae encysted in undercooked pork leads to intestinal tapeworm.
- Ingestion of eggs causes cysticercosis and neurocysticercosis, mass lesions in brain ("swiss cheese"" appearance)
Tx: Praziquantel (use -bendazoles for neurocysticercosis)
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Diphyllobothrium latum
Ingestion of larvae in raw freshwater fish. Causes vit B12 deficiency, results in anemia
Tx: Praziquantel
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Echinococcus granulosus
Eggs in dog feces when ingested can cause cysts in liver; causes anaphylaxis if echinococcal antigens are released from cyst (surgeons inject ethanol before removal to kill daughter cysts)
Tx: Bendazoles
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Trematodes (flukes)
- Schistosoma
- Clonorchis sinensis
- Paragonimus westermani
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Schistosoma
Snails are host; cercariae penetrate skin of humans
- Causes granulomas, fibrosis, and inflammation of the spleen and liver.
- Chronic infection with S. haematobium can lead to squamous cell carcinoma of the bladder
Tx: Praziquantel
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Clonorchis sinensis
- Undercooked fish
- causes inflammation of the biliary tract --> pigmented gallstones
- Also associated with cholangiocarcinomas
Tx: Praziquantel
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Paragonimus westermani
- Undercooked crab meat
- Causes inflammation and secondary bacterial infections of the lung, causing hemoptysis
Tx: Praziquantel
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Parasite hints
Findings --> organism
- Brain cysts, seizures - Taenia solium (cysticercosis)
- Liver cysts - Echinococcus granulosus
- B12 deficiency - Diphyllobothrium latumBiliary tract disease, cholangiocarcinoma - Clonorchis sinensis
- Hemoptysis - Paragonimus westermani
- Portal hypertension - Schistosoma mansoniHematuria, bladder cancer - Schistosoma haematobiumMicrocytic anemia - Ancylostoma, Necator
- Perianal pruritis - Enterobius (pinworm)
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