USMLE - Micro Parasites

Anaerobic parasitic protozoan

Giardiasis: bloating flatulence, foul-smelling, fatty diarrhea

Campers/Hikers

Cysts in water

Trophozoite or cyst in stool

Metronidazole

Anaerobic parasitic protozoan
Amebiasis: bloody diarrhea, Liver abscess (anchovy paste exudate), RUQ pain
Flask-shaped ulcer if submucosal abscess of colon ruptures
Cysts in water
Serology +/or trophozoites (w/ RBCs in cyto) or cysts (w/ multiple nuclei) in stool
Metronidazole. Iodoquinol for asymptomatic cyst passers

Parasitic protozoan

AIDS pts

Severe diarrhea. Watery diarrhea in non-immunocompromised

Cysts in water

Cysts on acid fast stain

Prevention (filtering water). Nitazoxanide in immunocompetent hosts

Obligate, intracellular, parasitic protozoan
HIV pts
Brain abscess. Seen as ring-enhancing brain lesions on CT/MRI
Congenital toxoplasmosis = classic triad of Chorioretinitis (eye), Hydrocephalus, Intracranial calcification
Cysts in meat or oocysts in cat feces (crosses placenta)
Serology, Biopsy
Sulfadiazine, Pyrimethamine

Protists parasite
Rapidly fatal meningeoencephalitis
Swimming in freshwater lakes. Enters via cribiform plate
“Nalgene bottle filled with freshwater containing Naegleria”
Amoebas in spinal fluid
Amphotericin

T. gambiense and T. rhodesiense
Protozoan
Africa sleeping sickness
Enlarged lymph nodes, recurring fever (antigenic variation), Somnolence, Coma
Tsetse fly (a painful bite)
Blood smear
Suramin for blood borne disease. Melarsoprol for CNS penetration

P vivax/ovale, P falciparum, P. malariae
Protists
Malaria: fever, headache, anemia, splenomegaly
Mosquito (Anopheles)
Blood smear, Trophozoite ring form, RBC schizont with merozoites
Begin w/ Chloroquine (blocks plasmodium heme polymerase). If resistent use Mefloquine. If life threatening use IV quinidine and test for G6PD deficiency

48 hour cycle (fever on 1st and 3rd day - tertian)

Dormant form (hypnozoite) in liver

Add primaquine for hypnozoite and test for G6PD deficiency)

Severe, irregular fever pattern.
Parasitized RBCs occlude capillaries in brain (cerebral malaria), Kidney, and Lungs
Banana shaped

72 hour cycle (quartan)

Protozoan parasite

Babesiosis: fever and hemolytic anemia

NE USA

Asplenia --> risk of severe disease

Ixodes tick (same as Lyme disease)

Blood smear, ring form, "Maltese cross," PCR

Atovaquone + Azithromycin

Protozoan parasite

Chagas' Disease: Dialted cardiomyopathy, Megacolon, Megaesophagus

South America

Reduviib bug (painless bite)

Blood smear

Nifurtimox

Protozoa

Visceral Leishmaniasis: Spiking fever, HSM, Pancytopenia

Sandfly

Macrophages containing amastigotes

Sodium Stibogluconate

Anaerobic flagellated protozoan
Vaginitis: Foul smelling greenish discharge, itching and burning
Sexual (does not form cysts)
Trophozoites on wet mount
Metronidazole for pt and partners (prophylaxis)

Nematode (roundworm). Pinworm

Contaminated eggs

Intestinal infection causing anal pruritus

Scotch tape test

Bendazoles or Pyrantel Pamoate

"worms are BENDy, treat with meBENDzole"

Nematode (roundworm). Giant Roundworm

Fecal-to-oral

Intestinal infection

Eggs visible in feces under microscope

Bendazoles or Pyrantel Pamoate

Nematode (roundworm)
Larvae in soil penetrate skin
Intestinal infection causing vomiting, diarrhea, anemia
Ivermectin or Albenazole

Nematode (roundworm). Hookworm
Larvae penetrate skin
Intestinal infection causing anemia by sucking blood from intestinal walls
Bendazoles or Pyrantel Pamoate

Nematode (roundworm)
Drinking water
Skin inflammation and ulceration
Slow extraction of worms

Nematode (roundworm)
Female blackfly bite
Hyperpigmentated skin and river blindness
“Black flies, Black skin nodules, Block sight”
Allergic reaction to microfilaria posible
Ivermectin
“IVERmectin for rIVER blindness”

Nematode (roundworm)
Deer, horse, or mango flies
Swelling in skin, worms in conjunctiva
Diethylcarbamazine

Nematode (roundworm)
Female mosquito
Blocks lymphatic vessels –> elephantiasis ~1 year after bite
Diethylcarbamazine

Nematode (roundworm)
Eggs
Visceral larva migrans
Albendazole or mebendazole

“get sick if EAT these”
Enterobius, Ascaris, Trichinella
“Get these in your feet from SANd”
Strongyloides, Ancylostoma, Necator

Cestodes (tapeworm)
Larvae or eggs ingested in undercooked pork
Larvae: Intestinal infection, Praziquantel
Egg: Cysticercosis, Neurocysticercosis
Goes to Brain, Muscles, Heart, and Skin
Praziquantel, -bendazoles for neurocysticercosis

Cestodes (tapeworm)
Ingestion of larvae from raw freshwater fish
VitB12 deficiency --> anemia
Praziquantel

Echinococcus granulosus

What kind of organism?

Transmission

Disease

Treatment

Trematodes (flukes)
Snails
Cercariae (larva) penetrate skin
Liver and spleen granulomas, fibrosis and inflammation
Chronic infection with S haematobium can lead to squamous cell carcinoma of the bladder d
Praziquantel

Trematodes (flukes)

Undercooked fish

Biliary tract inflammation --> pigmented gallstones

Cholangiocarcinoma

Praziquantel

Trematodes (flukes)
Undercooked crab meat
Lung inflammation and secondary bacterial infection with hemoptysis
Praziquantel

Taenia solium (Cysticercosis)

Echinococcus granulosus

Diphyllobothrium latum

Clonorchis sinensis

Paragonimus westermani

Schistosoma mansoni

Schistosoma haematobium

Ancylostoma duodenale, Necator americanus

Enterobius

Cestodes, Trematodes, Nematodes